Extraction of Nickel from Garnierite Laterite Ore Using Roasting and Magnetic Separation with Calcium Chloride and Iron Concentrate

Article Extraction of Nickel from Garnierite Laterite Ore Using Roasting and Magnetic Separation with Calcium Chloride and Iron Concentrate

Junhui Xiao 1,2,3,* , Wei Ding 1,3, Yang Peng 1,3, Tao Chen 1,3, Kai Zou 1,3 and Zhen Wang 1,3

1 Sichuan Engineering Lab of Non-Metallic Mineral Powder Modiﬁcation and High-Value Utilization, Southwest University of Science and Technology, Mianyang 621010, China; [email protected] (W.D.); [email protected] (Y.P.); [email protected] (T.C.); [email protected] (K.Z.); [email protected] (Z.W.) 2 Key Laboratory of Sichuan Province for Comprehensive Utilization of Vanadium and Titanium Resources, Panzhihua University, Panzhihua 61700, China 3 Key Laboratory of Ministry of Education for Solid Waste Treatment and Resource Recycle, Southwest University of Science and Technology, Mianyang 621010, China * Correspondence: [email protected]; Tel.: +86-139-9019-0544

Received: 20 March 2020; Accepted: 14 April 2020; Published: 15 April 2020

Abstract: In this study, segregation roasting and magnetic separation are used to extract nickel from a garnierite laterite ore. The garnierite laterite ore containing 0.72% Ni, 0.029% Co, 8.65% Fe, 29.66% MgO, and 37.86% SiO2 was collected in the Mojiang area of China. Garnierite was the Ni-bearing mineral; the other main minerals were potash feldspar, forsterite, tremolite, halloysite, quartz, and kaolinite in the garnierite laterite ore. The iron phase transformations show that nickel is transformed from (Ni,Mg)O SiO nH O to a new nickel mineral phase dominated by [Ni]Fe solid solution; and · 2· 2 iron changed from Fe2O3 and FeOOH to a new iron mineral phase dominated by metal Fe and Fe3O4 after segregation roasting. Ferronickel concentrate with Ni of 16.16%, Fe of 73.67%, and nickel recovery of 90.33% was obtained under the comprehensive conditions used: A roasting temperature of 1100 ◦C, a roasting time of 90 min, a calcium chloride dosage of 15%, an iron concentrate dosage of 30%, a coke dosage of 15%, a coke size of 1 + 0.5 mm, a magnetic separation grinding ﬁneness of − <45 µm occupying 90%, and a magnetic separation magnetic ﬁeld intensity of H = 0.10 T. The main minerals in ferronickel concentrate are Fe, [Ni]Fe, Fe3O4, and a small amount of gangue minerals, such as CaO SiO and CaO Al O SiO . · 2 · 2 3· 2 Keywords: nickel; garnierite laterite ore; segregation roasting; magnetic separation

1. Introduction Nickel, as a national strategic reserve metal, is not only a threat to the sustainable development of the national economy but also a potential major threat to the national defense. As an important metal, nickel is widely used in stainless steel and new material industries. According to marketing observations, 66.2% of the total metal nickel is consumed by the stainless-steel industry. Rapid expansion of these industries, especially stainless-steel manufacture, has dramatically increased the demand for nickel in recent years. Of all the land nickel reserves, 30% exist as sulfide ores, with the balance comprised of oxide ores [1]. Because of the low grade of nickel ore mined from mines, most of the nickel concentrate can be obtained after the beneficiation process before smelting. Nickel ores are usually divided into three types: Nickel sulfide, nickel oxide, and nickel arsenide. Nickel arsenide contains minerals, such as red nickel NiAs, arsenic NiAs2, and nickel arsenide NiAsS. Only a small amount of these minerals are produced in Morocco, North Africa, and nickel extraction from nickel

Minerals 2020, 10, 352; doi:10.3390/min10040352 www.mdpi.com/journal/minerals Minerals 2020, 10, 352 2 of 13 arsenide is currently limited to individual countries. About 70% of the world’s nickel production comes from nickel sulfide and 30% from nickel oxide. There are more than 60 known nickel minerals, and the following six kinds of sulfide minerals (Ni 1.0–2.5%) and three kinds of oxidized minerals (Ni 0.5–1.5%) have industrial value, including: Nickel-bearing laterite, (Fe,Ni)O(OH) nH O, genthite · 2 (Ni,Mg) 3SiO 6H O, garnierite H (Ni,Mg)SiO xH O, pentlandite (Fe,Ni) S , Ni-bearing pyrrhotite 4· 2· 2 2 4· 2 9 8 (Ni,Fe) S , millerite NiS, violarite (Fe,Ni) S , polydymite 3NiS FeS , and hengleinite (Ni,Co) S [2,3]. 7 8 2 4 · 2 3 4 Laterite nickel deposit is formed by the weathering and leaching of nickel-bearing peridotite in tropical or subtropical regions. As a nickel ore, it was discovered by Garnier in New Caledonia in 1863, so the ore is called “garnierite”—a magnesium-based nickel silicate. Because the ore is red due to the oxidation of iron after weathering, it is called laterite. In fact, in the upper part of the deposit, as a result of weathering and leaching, more iron, and slightly higher cobalt as compared to lesser silicon, magnesium, and nickel, it appears red; in the lower part of the deposit, as a result of weathering and enrichment, nickel ore is more silicon, more magnesium, lesser iron, higher nickel, and lower cobalt, which is called magnesium garnierite laterite ore. Both ores, relative to nickel sulfide deposits, are called nickel oxide ores [4–6]. Laterite nickel ore is the most abundant nickel ore resource in the world. The nickel in laterite is in the state of a disseminated structure, and the effect of traditional mineral processing is quite poor. Only the large gangue minerals with a low nickel content and low rate of decay can be removed by wet or dry beneficiation. So far, no effective physical beneficiation method has been found to enrich laterite nickel ore. Laterite ore can be divided into two types: One is the limonite type, which is contained in the surface of laterite ore, in which nickel occurs mainly in the solid melt state of nickel oxide and iron oxide, such as (Fe,Ni)O(OH) nH O; and the other type is the silicate-type nickel · 2 oxide, in which Ni, Fe,t and Co replace part of magnesium oxide in different proportions, especially serpentine Mg6[Si4O10](OH)8 [7–10]. At present, the pyrometallurgy process, hydrometallurgy process, and combination of the hydrometallurgy and pyrometallurgy processes are the three processing technologies of laterite nickel ore in the world. The pyrometallurgy process can also be divided into the process of producing ferro-nickel by reduction melting and the process of producing nickel-matte by reduction sulfurization melting. The hydrometallurgical process can be divided into the ammonia leaching process and acid leaching process according to the different leaching solutions. According to the different dressing methods after roasting, the combined process of hydrometallurgy and pyrometallurgy can be divided into reduction roasting–magnetic separation and reduction roasting–flotation. In the process of pyrometallurgy, it is difficult to prevent the reduction of iron oxides into metallic iron, so the products of pyrometallurgy are usually ferro-nickel alloys, also known as ferro-nickel. To purify nickel from ferronickel, it is very expensive to obtain pure metallic nickel. Nickel and iron are the main components of stainless steel. Therefore, the production of ferro-nickel in the form of nickel and iron has no impact on the stainless-steel industry [11–16]. In traditional nickel industries, about 60% of the metal nickel was produced from sulfide ores about 10 years ago. However, miners of nickel sulfide ores have been confronted with increasing challenges due to much deeper drilling requirements, higher production costs, and greater depletion of reserves. Therefore, nickel laterite ore has attracted greater attention in recent years, leading to about 50% of metal nickel being produced from laterite currently. China has become the largest nickel consumer in the world due to the soaring production of stainless steel. Laterite ores are imported into China because of the depletion of domestic nickel sulfide resources. Consequently, it is of great importance to the Chinese economy to effectively utilize low-grade nickel laterite ore [17]. There are abundant nickel oxide ore resources in the Yuanjiang, Mojiang, and Mangshi areas of Yunnan Province in China, among which the nickel oxide ore in Mojiang area contained about 0.7% nickel, which is the nickel ore resource with the lowest grade among the three areas. Mojiang nickel ore belongs to the magnesium serpentine-type nickel silicate ore type. Due to the lower nickel grade, higher magnesium content, complex mineral composition of the ore, and fine-grained dissemination, Minerals 2020, 10, 352 3 of 13 it has not been properly developed and utilized up to now. Therefore, in this paper, the magnesium garnierite laterite ore in Mojiang area was taken as the object of study, and the valuable metal nickel in the ores was extracted by segregation roasting and magnetic separation, thus providing great practical significanceMinerals 2020 for, 10 the, x FOR development PEER REVIEW of nickel oxide ores in this area. 3 of 13

2. Materialsin the ores and was Methods extracted by segregation roasting and magnetic separation, thus providing great practical significance for the development of nickel oxide ores in this area. 2.1. Sampling 2.The Materials garnierite and laterite Methods ore was collected as the test research sample in the Mojiang area of China. The samples2.1. Sampling taken this time were powdery, most of which had a particle size of less than 10 mm. Meanwhile, the samples were relatively moist. Therefore, after the samples were dried by natural drying, theThe samples garnierite of laterite garnierite ore was were collected crushed as the by test the research jaw crusher sampleand in the finely Mojiang ground area of by China. theroller The samples taken this time were powdery, most of which had a particle size of less than 10 mm. crusher, and then the disk crusher was used for dry grinding until the particle size was less than Meanwhile, the samples were relatively moist. Therefore, after the samples were dried by natural 0.1 mm,drying, and the fully samples mixed of garnierite evenly. Thewere garnieritecrushed by lateritethe jaw crusher ore contained and finely Ni ground 0.72%, by Cothe roller 0.029%, crusher, Fe 8.65%, MgO 29.66%, and SiO 37.86%. Garnierite (Ni,Mg)O SiO nH O, potash feldspar K O Al O 6SiO , and then the disk crusher2 was used for dry grinding until· the2· particle2 size was less than 20.1mm,· 2 and3· 2 forsteritefully mixed Mg2Si evenly.2O6, tremolite The garnierite Ca2Mg laterite5Si8O ore22 (OH)contained2, halloysite Ni 0.72%, Al Co2 O0.029%,3 2SiO Fe2 4H 8.65%,2O, MgO quartz 29.66%, SiO2 , and · · kaoliniteand SiO Al22 Si37.86%.2O5(OH) Garnierite4 were (Ni,Mg)O·SiO the main minerals2·nH2O, potash in the feldspar garnierite K2O·Al laterite2O3·6SiO ores.2, forsterite The iron Mg concentrate2Si2O6, containingtremolite Fe Ca 61.22%2Mg5Si8O was22(OH) collected2, halloysite as the Al2O additive3·2SiO2·4H from2O, quartz a dressing SiO2, and pant kaolinite by magnetic Al2Si2O5 separation(OH)4 and floatationwere the main in Dahongshangminerals in the garnierite area of China. laterite Theores. main The iron minerals concentrate were containing goethite Fe FeOOH, 61.22% flogopitewas collected as the additive from a dressing pant by magnetic separation and floatation in Dahongshang KMg3[AlSi3O10] [F,OH]2, sodaclase Na2O Al2O3 6SiO2, and quartz SiO2. area of China.· The main minerals were goethite· FeOOH,· flogopite KMg3[AlSi3O10]·[F,OH]2, sodaclase The main chemical composition analysis of the silicate nickel and iron concentrate is shown in Na2O·Al2O3·6SiO2, and quartz SiO2. Tables1 and2, respectively. The nickel phase of the garnierite laterite ore is shown in Table3, and the The main chemical composition analysis of the silicate nickel and iron concentrate is shown in X-rayTables diffraction 1 and 2, (XRD) respectively. analysis The of thenickel silicate phase nickel of the andgarnierite iron concentratelaterite ore is is shown shown in inTable Figure 3, and1. the X-ray diffraction (XRD) analysis of the silicate nickel and iron concentrate is shown in Figure 1. Table 1. Main chemical composition of garnierite laterite ore (%). Table 1. Main chemical composition of garnierite laterite ore (%). Ni Fe Co MgO SiO2 Al2O3 CaO 0.72Ni 8.65 Fe 0.029 Co MgO 29.66 SiO 37.862 Al2O3 10.05 CaO 5.22 0.72 8.65 0.029 29.66 37.86 10.05 5.22

Table 2. Main chemical composition of iron concentrate (%). Table 2. Main chemical composition of iron concentrate (%). Fe P S MgO SiO Al O CaO Fe P S MgO SiO2 2 Al2O3 2 CaO3 61.2261.22 0.09 0.09 0.0320.032 4.11 9.22 9.22 7.12 7.12 6.78 6.78

TableTable 3. 3.Nickel Nickel phase phase analysisanalysis of of ga garnieriternierite laterite laterite ore ore (%). (%).

NickelNickel in in NickelNickel in in NickelNickel in in NickelNickel in in NickelNickel Sulfate Sulfate NickelNickel Sulﬁde Sulfide NickelNickel Oxide Oxide NickelNickel Silicate Silicate 0.0020.002 0.0010.001 0.031 0.031 0.686 0.686

1500 9000 △-Fe O (a) 1-Ca2Mg5Si8O22(OH)2 (b) 2 3 1350 2 △ ○-SiO 1 2-(Ni,Mg)O·SiO2·nH2O 8000 2 ☆ 1200 3-Mg2Si2O6 - Na2O·Al2O3·6SiO2 7000 4-K O·Al O ·6SiO ◇-KMg [AlSi O ]·[F,OH] 1050 2 2 3 2 3 3 10 2 6000 5-Al2Si2O5(OH)4 900 6-Al2O3·2SiO2·4H2O 5000 750 7-FeOOH 4000 600 ○

2 Intensity(a.u.) Intensity (a.u.) 3000 ☆ ◇ 450 4 3 7 5 2000 3 6 300 6 4 4 6 1000 150 0 0 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 5 10152025303540 2θ (°) 2θ (°)

FigureFigure 1. XRD 1. XRD di ﬀdiffractogramsractograms of ofthe the garnieritegarnierite laterite laterite ore ore (a) ( aand) and iron iron concentrate concentrate (b). (b).

Minerals 2020, 10, 352 4 of 13

2.2. Chemical Reagent and Equipment The main chemical reagent used in this test was calcium chloride with analytical purity from Guangzhou Chemical Regent, Co., Ltd., Guangzhou, China. The coke from Shanxi Coking Coal Group Co. Ltd. (Taiyuan, China) was crushed and divided into six particle sizes of 3 + 2.5 mm, 2.5 + 2 mm, − − 2 + 1.5 mm, 1.5 + 1 mm, 1 + 0.5 mm, and 0.5 + 0 mm as reducing agents in the process of − − − − segregation roasting. The main equipment used in the experiment included a muﬄe furnace ( 1300 C, Shanghai Shiyan ≤ ◦ Electric Furnace Co., Ltd. Shanghai, China), cone ball mill (XMQ—Φ240 90 mm, Jilin Exploration × Machinery Plant, Changchun, China), disc grinder (Φ300 150 mm, Jilin Exploration Machinery Plant), × drying box (Southwest Chengdu Experimental Equipment Co., Ltd. Chengdu, China), and vacuum ﬁlter (Φ300, Southwest Chengdu Experimental Equipment Co., Ltd.).

2.3. Roasting–Magnetic Separation Test The garnierite laterite ores, calcium, hematite concentrate, and coke were mixed and put into the roasting furnace. These mixtures were heated to a certain temperature (950–1200 ◦C) under a neutral or weak reducing atmosphere, where the chlorinating agent was used to form volatile metal chlorides. For each magnetic separation test, segregation roasting ores were put into a 6.25 dm3 Φ240 90 conical × ball mill. The grinding density was set at 60%. The pulp was then placed in a XCGS 13 (Φ50, overall − dimensions 1000 800 500 mm) Davis Magnetic Tube (Jilin Exploration Machinery Plant) with × × a special magnetic ﬁeld intensity. The products were ﬁltered, dried, weighed, sampled, and tested for further evaluation based on the grade and recovery of nickel and iron in the magnetic products. The calculation formulas of nickel recovery and iron recovery are shown in Equations (1) and (2):

Nickel recovery = Q β /Q α 100%, (1) 1 × Ni 0 × Ni × Iron recovery = Q β /Q α 100%, (2) 1 × Fe 0 × Fe × where Q1 is the weight of nickel concentrate, g; Q0 is the weight of segregation roasting ores, g; βNi is the nickel grade of nickel concentrate, %; βFe is the iron grade of nickel concentrate, %; αNi is the nickel grade of segregation roasting ores, %; and αFe is the iron grade of segregation roasting ores, %.

2.4. Experiment Procedure The garnierite laterite ores were crushed into <3.0 mm by a roll crusher and further ground to <0.1 mm by a disc mill as the segregation roasting sample. Garnierite laterite ores (a mass of 50 g for each test), calcium chloride, hematite concentrate, and coke were mixed and put into the muﬄe furnace for segregation roasting, which turned nickel into a new metal nickel mineral phase and iron into a new metal iron mineral phase. Metal nickel and metal iron are ferromagnetic metals. The speciﬁc magnetic susceptibility of nickel metal is greater than the magnetic susceptibility of magnetite. Nickel was recovered from segregation roasting ores after grinding with a magnetic separator. The process of segregation roasting–magnetic separation is shown in Figure2.

2.5. Analysis and Characterization The chemical composition of solid materials was analyzed by a Z-2000 atomic absorption spectrophotometer (Hitachi Co., Ltd., Tokyo, Japan), the diffraction grating was Zenier-tana Type, 1800 lines/mm, the flash wavelength was 200 nm, the wavelength range was 190~900 nm, the automatic peak seeking setting, and the spectral bandwidth was divided into 4 grades (0.2, 0.4, 1.3, and 2.6 nm) for the analysis of the mineral chemical composition. The phase composition of solid substances was analyzed by X-ray diffraction (XRD, X Pert pro, Panaco, The Netherlands). The microstructure of the solid products was observed by SEM (S440, Hirschmann Laborgerate GmbH & Co. KG, Eberstadt, Minerals 2020, 10, 352 5 of 13

MineralsGermany) 2020 equipped, 10, x FOR PEER with REVIEW an energy dispersive X-ray spectroscopy (EDS) detector (UItra55, Carlzeiss5 of 13 NTSMinerals GmbH, 2020, 10 Hirschmann, x FOR PEER REVIEW Laborgerate GmbH & Co. KG, Eberstadt, Germany). 5 of 13

Figure 2. Scheme of the nickel extraction process from nickel silicate ore. Figure 2. Scheme of the nickel extraction process from nickel silicate ore. Figure 2. Scheme of the nickel extraction process from nickel silicate ore. 3. Results and Discussion 3.3. Results and Discussion 3.1. Effect of Calcium Chloride Dosage 3.1.3.1. EEffectffect of Calcium Chloride DosageDosage The effect of different calcium chloride dosages on the extraction of nickel is shown in Figure 3a. The nickelTheThe eeffectff ectgrade ofof didifferentinff erentferric calciumcalciumnickel decreased chloridechloride dosagesdosages and the onon nickel the extraction recovery of increased nickel is shown when in the Figure calcium 33a.a. ThechlorideThe nickelnickel dosage grade grade increased. in in ferric ferric nickel When nickel decreased the decreased calcium and chloride theand nickel the dosage nickel recovery exceededrecovery increased 15%, increased when the nickel the when calcium grade the decrease chloridecalcium wasdosagechloride more increased. dosage noticeable increased. When in nickel the When calcium iron, the calciumand chloride the chlorideincrease dosage dosage exceededof nickel exceeded 15%,recovery the15%, nickelas the smaller, nickel grade gradewhich decrease decrease further was showsmorewas more noticeable that thenoticeable amount in nickel in of hydrogen iron,nickel and iron, thechloride and increase the is advantag increase of nickeleous of recovery nickel to the asnickelrecovery smaller, chloride as which smaller, increase further which by shows increasing further that theshows amountappropriate that the of hydrogenamount calcium of hydrogen chloride isdosage chloride advantageous. Atis advantag the same to theeous time, nickel to the other chloridenickel elements, chloride increase suchincrease by as increasing magnesium,by increasing the aluminum,appropriatethe appropriate iron, calcium potassium, calcium chloride chloride sodium, dosage. dosage etc., At thecan. sameAt also the react time, same with other time, hydrochloric elements, other elements, such gas as and magnesium, suchgenerate as magnesium, magnesium aluminum, chloride,iron,aluminum, potassium, ferric iron, chloride, potassium, sodium, potassium etc., sodium, can also chloride,etc., react can withalso and hydrochloricreactsodium with chloride. hydrochloric gas and This generate gasleads and to magnesium generatethe consumption magnesium chloride, of aferricchloride, lot of chloride, calcium ferric potassiumchloride,chloride andpotassium chloride, an increase chloride, and of sodium the and chlorination chloride.sodium chloride. Thisagent leads cost. This to Therefore, leads the consumption to the a calcium consumption of chloride a lot ofof dosagecalciuma lot of calciumof chloride 15% ischloride and more an increase appropriate;and an increase of the a chlorination ferronickel of the chlorination agent concentrate cost. agent Therefore, with cost. a Therefore,nickel a calcium grade a chloride calcium of 4.01%, dosage chloride iron of 15%contentdosage is more ofof 12.16%,15% appropriate; is andmore nickel aappropriate; ferronickel recovery concentrate aof ferronickel 51.82% was with concentrate obtained. a nickel grade with of a4.01%, nickeliron grade content of 4.01%, of 12.16%, iron andcontent nickel of 12.16%, recovery and of 51.82%nickel recovery was obtained. of 51.82% was obtained.

20 90 30 100 (a) Ni grade Ni recovery Ni grade Ni recovery 18 (b) 20 Fe grade Fe recovery 8090 2530 Fe grade Fe recovery 90100 16 (a) Ni grade Ni recovery Ni grade Ni recovery 18 70 (b) 80 80 25 90 14 Fe grade Fe recovery 20 Fe grade Fe recovery 16 6070 7080 12 1520 14 50 60 10 60 70 12 1015 8 4050 5060 10 6 30 105 40 8 40 50 4 6 2030 05 3040 Grade(%) Grade (%) Grade 2 4 10 20

30 Recovery (%) 20 Recovery (%) -50 0 Roasting temperature: 950 ℃ Roasting temperature: 950 ℃ Grade(%) Grade (%) Grade 2 010 1020 Recovery (%) -2 Roasting time: 60 min Recovery (%) -10-5 Roasting time: 60 min 0 Roasting temperature: 950 ℃ -10 Roasting temperature: 950 ℃ 0 -4 Coke dosage: 10% 0 Calcium chloride dosage: 15% 10 -2 Roasting time: 60 min -15-10 Roasting time: 60 min Coke size: －2+1.5 mm -20 Coke size: －2+1.5 mm -10 -6 Coke dosage: 10% -10 Calcium chloride dosage: 15% 0 -4 Grinding fineness: ＜0.074 mm occupying 90% -20-15 Grinding fineness: ＜0.074 mm occupying 90% -8 Coke size: －2+1.5 mm -30-20 Coke size: －2+1.5 mm -20-10 -6 Magnetic filed intensity: H=0.08 T Magnetic filed: H=0.08 T -10 Grinding fineness: ＜0.074 mm occupying 90% -40 -25-20 Grinding fineness: ＜0.074 mm occupying 90% -30 -8 -30 -20 0 5 10Magnetic 15 filed intensity: 20 H=0.08 25 T 30 35 0 5 10Magnetic 15 filed: H=0.08 20 T 25 30 35 -10 -40 -25 -30 0 5Calcium 10 chloride 15 dosage 20 (%) 25 30 35 0 5 10Coke 15 dosage 20 (%) 25 30 35 Calcium chloride dosage (%) Coke dosage (%) Figure 3. EffectEﬀect of calcium chloride dosage ( a) and coke dosage ( b) on nickel extraction.

3.2. Effect ofFigure Coke Dosage3. Effect of calcium chloride dosage (a) and coke dosage (b) on nickel extraction. 3.2. Effect of Coke Dosage 3.2. EffectThe eofff ectCoke of Dosage different coke chloride dosages on the extraction of nickel is shown in Figure3b. In theThe process effect of different segregation coke roasting, chloride ifdosages the amount on the of extraction reductant of added nickel increases,is shown in the Figure water–gas 3b. In thereaction processThe willeffect of easily ofsegregation different occur, andcoke roasting, then chloride the if in thedosages situ amount reduction on th ofe extractionreductant of metal oxides, ofadded nickel thusincreases, is shown affecting inthe Figure the water–gas eff ect3b. ofIn reactionthe process will ofeasily segregation occur, and roasting, then the if in the situ amount reduction of reductantof metal oxides, added thus increases, affecting the the water–gas effect of segregationreaction will roasting. easily occur, It is knownand then from the Figurein situ reduction3b that when of metal the coke oxides, dosage thus increased affecting theto 20%, effect the of nickelsegregation grade roasting.of ferronickel It is knowndecreased from to Figure 2.76%. 3bCompared that when with the thecoke coke dosage dosage increased of 15%, to the 20%, nickel the gradenickel decreasedgrade of ferronickel by 0.92% anddecreased the nickel to 2.76%. recovery Compared increased with by the3.1%. coke This dosage indicates of 15%, that thethe nickel coke grade decreased by 0.92% and the nickel recovery increased by 3.1%. This indicates that the coke

Minerals 2020, 10, 352 6 of 13

segregation roasting. It is known from Figure3b that when the coke dosage increased to 20%, the nickel Minerals 2020, 10, x FOR PEER REVIEW 6 of 13 grade of ferronickel decreased to 2.76%. Compared with the coke dosage of 15%, the nickel grade dosagedecreased of 15% by 0.92% is optimal; and the a nickelferronickel recovery concentrate increased with by 3.1%.a nickel This grade indicates of 3.68%, that theiron coke content dosage of 16.22%,of 15% isand optimal; nickel arecovery ferronickel of 70.01% concentrate was obtained. with a nickel grade of 3.68%, iron content of 16.22%, and nickel recovery of 70.01% was obtained. 3.3. Effect of Roasting Temperature 3.3. Effect of Roasting Temperature The effect of different segregation roasting temperatures on the extraction of nickel is shown in The effect of different segregation roasting temperatures on the extraction of nickel is shown in Figure 4a. The segregation roasting temperature is one of the key factors to determine whether the Figure4a. The segregation roasting temperature is one of the key factors to determine whether the chlorination agent can decompose and whether the valuable metal iron can be chlorinated to form chlorination agent can decompose and whether the valuable metal iron can be chlorinated to form volatile metal chloride. Under the condition of the same surface tension, the vapor pressure of particles volatile metal chloride. Under the condition of the same surface tension, the vapor pressure of particles with a smaller radius of curvature is larger, so the process of particles growing up is the process of with a smaller radius of curvature is larger, so the process of particles growing up is the process of particles with a smaller radius of curvature melting and evaporating to the surface of particles with particles with a smaller radius of curvature melting and evaporating to the surface of particles with a a larger radius of curvature condensation. larger radius of curvature condensation. It is conducive to gradually increase the particles of ferronickel by increasing the roasting It is conducive to gradually increase the particles of ferronickel by increasing the roasting temperature, but the higher temperature will cause part of the ferronickel to re-enter the olivine temperature, but the higher temperature will cause part of the ferronickel to re-enter the olivine lattice, lattice, reducing the yield of ferronickel. Upgrading the roasting temperature can improve the nickel reducing the yield of ferronickel. Upgrading the roasting temperature can improve the nickel iron iron nickel grade and nickel recovery. When the temperature exceeds 1100 °C, the nickel grade and nickel grade and nickel recovery. When the temperature exceeds 1100 C, the nickel grade and recovery recovery of a smaller increase in temperature may cause the energy costs◦ to increase at the same time. of a smaller increase in temperature may cause the energy costs to increase at the same time. In the testing process, we found that the materials were partially melted at a temperature of 1100 °C, In the testing process, we found that the materials were partially melted at a temperature of and the material was already in the melted state at a temperature of 1200 °C. Furthermore, the 1100 C, and the material was already in the melted state at a temperature of 1200 C. Furthermore, segregation◦ roasting ores will be difficult to grind and affect the recovery of nickel◦ and iron in the the segregation roasting ores will be difficult to grind and affect the recovery of nickel and iron in the magnetic separation process. Therefore, the roasting temperature of 1100 °C is suitable; a ferronickel magnetic separation process. Therefore, the roasting temperature of 1100 C is suitable; a ferronickel concentrate with a nickel grade of 4.52%, iron content of 19.22%, and nickel◦ recovery of 70.01% was concentrate with a nickel grade of 4.52%, iron content of 19.22%, and nickel recovery of 70.01% obtained. was obtained.

80 24 100 (a) 28 (b) Ni grade Ni recovery 70 Fe grade Fe recovery 90 20 24 60 80 16 20 70 Ni grade Ni recovery 50 16 12 Fe grade Fe recovery 60 40 12 8 50 30 8 4 4 40 20 30 Grade (%) Grade Grade (%) Grade 0

0 Recovery (%) Roasting time: 60 min 10 Recovery (%) Roasting temperature: 950 ℃ 20 Calcium chloride dosage: 15% -4 -4 0 Roasting time: 60 min Coke dosage: 15% 10 -8 Calcium chloride dosage: 15% Coke size: －2+1.5 mm -8 -10 Coke size: －2+1.5 mm 0 Grinding fineness: ＜0.074 mm occupying 90% -12 Grinding fineness: ＜0.074 mm occupying 90% Magnetic filed: H=0.08 T -20 -16 -10 -12 Magnetic filed: H=0.08 T -30 -20 -20 900 950 1000 1050 1100 1150 1200 1250 40 50 60 70 80 90 100 110 120 Roasting temperature (℃) Roasting time (min)

FigureFigure 4. 4. EffectEﬀect of ofsegregation segregation roasting roasting temperature temperature (a) and (a) segregation and segregation roasting roasting time (b time) on (nickelb) on extraction.nickel extraction.

3.4. E ect of Roasting Time 3.4. Effectff of Roasting time TheThe eeffectffect ofof di differentfferent roasting roasting times times on theon extractionthe extraction of nickel of nickel is shown is shown in Figure in4 b.Figure The chemical4b. The chemicalreactions reactions in the process in the process of segregation of segregation roasting roasting are are mainly mainly divided divided into into decomposition decomposition reaction, chlorinationchlorination reaction, reaction, and and reduction reduction reaction. reaction. Howeve However,r, the the reactions reactions of of decomposition, decomposition, chlorination, chlorination, andand reduction reduction are are not not only only successive chemical chemical re reactionsactions but but also also involve involve a a complex phase phase change change process.process. The The segregation segregation roasting roasting time time mainly mainly affects affects the the degree degree of ofthe the ch chemicalemical reaction reaction in the in the process process of segregationof segregation roasting. roasting. If the If theroasting roasting time time is too is tooshor short,t, the theeffective effective chemical chemical reaction reaction is not is not enough enough to achieveto achieve a better a better segregation segregation effect. effect. The The results results in Figure4b in Figure 4confirmb confirm that that a roasting a roasting time time of of90 90min min is suitable; a ferronickel concentrate with a nickel grade of 4.13%, iron content of 16.11%, and nickel recovery of 79.63% was obtained.

Minerals 2020, 10, x FOR PEER REVIEW 7 of 13

3.5.Minerals Effect2020 of, 10Coke, 352 Size 7 of 13 The effect of the coke size on the extraction of nickel is shown in Figure 5a. During the segregation and roasting test, the particle size of the nickel silicate sample after crushing and dry is suitable; a ferronickel concentrate with a nickel grade of 4.13%, iron content of 16.11%, and nickel grinding was <0.100 mm. In order to better promote the segregation and roasting effect, it is necessary recovery of 79.63% was obtained. to determine a reasonable coke particle size to match the particle size of the ore sample. 3.5. EOnffect the of one Coke hand, Size coke plays the role of atmosphere adjustment in the segregation roasting process. On the other hand, it also acts as an adsorption carrier for metal particles reduced by volatile chloride The effect of the coke size on the extraction of nickel is shown in Figure5a. During the segregation by hydrogen. Therefore, when coke is involved in the generation of hydrogen and carbon monoxide and roasting test, the particle size of the nickel silicate sample after crushing and dry grinding was gas, it also needs to have a certain amount of surplus after achieving the segregation roasting reaction <0.100 mm. In order to better promote the segregation and roasting effect, it is necessary to determine time. a reasonable coke particle size to match the particle size of the ore sample.

100 100 100 28 Ni grade Ni recovery Ni grade Ni recovery (a) 90 (b) 24 Fe grade Fe recovery 90 Fe grade Fe recovery 90 80 20 80 80 70 16 70 70 12 60 Roasting temperature: 950 ℃ 60 8 50 60 Roasting time: 60 min 40 50 4 50 Calcium chloride: 15% 0 30 Coke dosage: 10% 40 40 － -4 20 Coke size: 1+0.5 mm 30 Grade (%) Grade (%) Grinding fineness: ＜0.074 mm occupying 90% Recovery (%) -8 10 Recovery (%) 30 Roasting temperature: 950 ℃ Magnetic filed: H=0.08 T 20 -12 0 20 Roasting time: 60 min 10 -16 Calcium chloride dosage: 15% -10 10 -20 0 Coke dosage: 15% -20 -24 Grinding fineness: ＜0.074 mm occupying 90% 0 -30 -10 -28 Magnetic filed: H=0.08 T -40 -10 -20 －3+2.5 －2.5+2 －2+1.5 －1.5+1 －1+0.5 －0.5+0 5 101520253035404550556065 Coke size (mm) Iron concentrate dosage (%)

FigureFigure 5. 5. EffectEffect of of coke coke size size ( (aa)) and and iron iron concentrate concentrate dosage dosage ( (b)) on on nickel nickel extraction. extraction. On the one hand, coke plays the role of atmosphere adjustment in the segregation roasting process. As can be seen from Figure 5a, the reduced coke size is conducive to the improvement of the On the other hand, it also acts as an adsorption carrier for metal particles reduced by volatile chloride by nickel grade and recovery of nickel iron. However, when the coke size decreased to −0.5 + 0 mm, the hydrogen. Therefore, when coke is involved in the generation of hydrogen and carbon monoxide gas, recovery rate of nickel decreased to 78.13%. Compared with the coke size of −1 + 0.5 mm, the nickel it also needs to have a certain amount of surplus after achieving the segregation roasting reaction time. grade increased by 0.23% and the recovery rate decreased by 3.9%. It is further indicated that the coke As can be seen from Figure5a, the reduced coke size is conducive to the improvement of the size of −1+0.5 mm is more suitable; a ferronickel concentrate with a nickel grade of 4.25%, iron content nickel grade and recovery of nickel iron. However, when the coke size decreased to 0.5 + 0 mm, of 17.02%, and nickel recovery of 82.03% was obtained. − the recovery rate of nickel decreased to 78.13%. Compared with the coke size of 1 + 0.5 mm, the nickel − 3.6.grade Effect increased of Iron byConcentrate 0.23% and Dosage the recovery rate decreased by 3.9%. It is further indicated that the coke size of 1 + 0.5 mm is more suitable; a ferronickel concentrate with a nickel grade of 4.25%, iron content − of 17.02%,A certain and amount nickel recovery of activator of 82.03% can be was added obtained. in the roasting process to promote the favorable chemical reaction in the direction of the forward reaction and improve the metallurgical efficiency. In3.6. the E ffsegregationect of Iron Concentrate roasting process, Dosage the purpose of adding activator is to promote the conversion rate of valuableA certain metal amount nickel, of so activatoras to realize can the be effectiv addede in separation the roasting of nickel. process Nick toel promote and iron the have favorable strong magneticchemical properties. reaction in At the higher direction temperatures, of the forward nickel reaction is easily and dissolved improve in the iron metallurgical oxides to form effi aciency. solid solution.In the segregation Different roastingtypes of process,iron oxides the have purpose different of adding solubility activator in nickel is to promote[18–20]. the conversion rate In the iron-oxygen system, there are three oxides FeO, Fe3O4, and Fe2O3, and the theoretical of valuable metal nickel, so as to realize the effective separation of nickel. Nickel and iron have strong oxygen content is 22.8%, 27.64%, and 30.06%, respectively. In the process of iron ore smelting, when magnetic properties. At higher temperatures, nickel is easily dissolved in iron oxides to form a solid the temperature is higher than 570 °C, according to the state phase diagram of the Fe-O system, FeO solution. Different types of iron oxides have different solubility in nickel [18–20]. will be produced. Relevant studies believe that Fe3O4 is the solid solution in FeO. Fe3O4 is a molten In the iron-oxygen system, there are three oxides FeO, Fe3O4, and Fe2O3, and the theoretical compound with a melting point of 1597 °C. When the temperature is below 1100 °C, it is a pure substance, oxygen content is 22.8%, 27.64%, and 30.06%, respectively. In the process of iron ore smelting, when the and at higher temperatures, the oxygen content changes. Before the temperature is higher than 1452 temperature is higher than 570 ◦C, according to the state phase diagram of the Fe-O system, FeO will be °C, as the temperature increases, the amount of dissolved Fe2O3 increases, so the oxygen content in produced. Relevant studies believe that Fe3O4 is the solid solution in FeO. Fe3O4 is a molten compound the solid solution increases. Therefore, hematite concentrate was added as an activator in this with a melting point of 1597 ◦C. When the temperature is below 1100 ◦C, it is a pure substance, and experiment to investigate the extraction effect of nickel with different dosages [21–26]. at higher temperatures, the oxygen content changes. Before the temperature is higher than 1452 ◦C, The results in Figure 5b reveal that the addition of iron concentrate has a very significant effect as the temperature increases, the amount of dissolved Fe2O3 increases, so the oxygen content in the on the extraction of nickel, as the nickel grade of nickel iron can be significantly improved, and the solid solution increases. Therefore, hematite concentrate was added as an activator in this experiment to investigate the extraction effect of nickel with different dosages [21–26]. Minerals 2020, 10, 352 8 of 13

Minerals 2020, 10, x FOR PEER REVIEW 8 of 13 The results in Figure5b reveal that the addition of iron concentrate has a very significant e ffect on ironthe extraction content in of nickel nickel, iron as theis also nickel greatly grade increa of nickelsed. ironWhen can 30% be significantly hematite concentrate improved, is and added, the ironthe highestcontent innickel nickel grade iron isof alsoferronickel greatly increased.is 15.26% Whenand the 30% iron hematite content concentrate is 72.65%. is The added, 30% the hematite highest concentratenickel grade was of ferronickel found to be is the 15.26% optimum and the condition iron content for a isbetter 72.65%. Ni grade The 30% and hematite recovery concentrate rates. This wasshows found that to30% be hematite the optimum concentrate condition is ideal; for a bettera ferro Ninickel grade concentrate and recovery with rates. a nickel This grade shows of that 15.26%, 30% ironhematite content concentrate of 72.65%, is and ideal; nickel a ferronickel recovery concentrateof 80.45% was with obtained. a nickel grade of 15.26%, iron content of 72.65%, and nickel recovery of 80.45% was obtained. 3.7. Effect of Magnetic Separation Conditions of Roasting Ores 3.7. Effect of Magnetic Separation Conditions of Roasting Ores 3.7.1. Effect of Grinding Fineness 3.7.1. Effect of Grinding Fineness The effects of the grinding fineness of segregation roasting ores on the extraction of nickel are The effects of the grinding fineness of segregation roasting ores on the extraction of nickel are shown in Figure 6a. Nickel silicate ore was processed by segregation roasting, and the valuable metal shown in Figure6a. Nickel silicate ore was processed by segregation roasting, and the valuable metal nickel was absorbed on the surface of coke by a chlorination reduction and the metal particles were nickel was absorbed on the surface of coke by a chlorination reduction and the metal particles were small. It is necessary to basically dissociate the mineral after grinding before magnetic separation, and the small. It is necessary to basically dissociate the mineral after grinding before magnetic separation, fineness of grinding is an important index of the dissociation of the monomer. Improving the fineness and the fineness of grinding is an important index of the dissociation of the monomer. Improving the of grinding and the degree of mineral dissociation is beneficial to the separation of nickel and iron in fineness of grinding and the degree of mineral dissociation is beneficial to the separation of nickel and the magnetic separation process. However, it is easy to produce an over-grinding phenomenon when iron in the magnetic separation process. However, it is easy to produce an over-grinding phenomenon the grinding is too fine, and the energy consumption is said to be increased, which is not conducive when the grinding is too fine, and the energy consumption is said to be increased, which is not to the recovery of nickel and iron. conducive to the recovery of nickel and iron. Minerals are more affected by the mechanical external forces in the magnetic separation process Minerals are more affected by the mechanical external forces in the magnetic separation process with the decrease of the particle size. It is necessary to change the magnetic field strength to overcome with the decrease of the particle size. It is necessary to change the magnetic field strength to overcome the mechanical external forces. Taking all things into consideration, the grinding fineness of <0.045 the mechanical external forces. Taking all things into consideration, the grinding fineness of <0.045 mm mm occupying 90% is suitable; a ferronickel concentrate with a nickel grade of 18.23%, iron content occupying 90% is suitable; a ferronickel concentrate with a nickel grade of 18.23%, iron content of of 75.22%, and nickel recovery of 78.91% was obtained. 75.22%, and nickel recovery of 78.91% was obtained. 3.7.2. Effect of Magnetic Field Intensity 3.7.2. Effect of Magnetic Field Intensity In order to further improve the separation index of ferronickel concentrate, it is necessary to In order to further improve the separation index of ferronickel concentrate, it is necessary to investigate the extraction and separation effect of ferronickel with a different magnetic field intensity. investigate the extraction and separation effect of ferronickel with a different magnetic field intensity. The results in Figure 6b show that the nickel grade decreases, and the nickel recovery increases with The results in Figure6b show that the nickel grade decreases, and the nickel recovery increases with the magnetic field intensity increasing. The magnetic field intensity of H = 0.10 T was selected, and a the magnetic field intensity increasing. The magnetic field intensity of H = 0.10 T was selected, and a ferronickel concentrate with nickel grade of 15.56%, iron content of 73.22%, and nickel recovery of ferronickel concentrate with nickel grade of 15.56%, iron content of 73.22%, and nickel recovery of 89.52% was obtained. 89.52% was obtained.

100 100 110 110 Ni recovery (a) Ni grade (b) Ni grade Ni recovery Fe recovery 90 Fe Grade 90 100 Fe grade Fe recovery 100

80 80 90 90

70 70 80 80 70 70 60 Roasting temperature: 950 ℃ 60 Roasting temperature: 950 ℃ 60 60 Roasting time: 60 min Roasting time: 60 min 50 Calcium chloride: 15% 50 50 Calcium chloride: 15% 50 Iron concentrate dosage: 30% Iron concentrate dosage: 30% Grade (%) Grade

40 40 Grade (%) Recovery (%) Coke dosage: 10% 40 Coke dosage: 10% 40 Recovery (%) 30 Coke size: －1+0.5 mm 30 Coke size: －1+0.5 mm Magnetic field intensity: H=0.08T 30 Grinding fineness: －0.074 mm occupying 90% 30 20 20 20 20

10 10 10 10

0 0 0 0 ＜0.154 ＜0.100 ＜0.074 ＜0.045 ＜0.038 ＜0.019 0.04 0.06 0.08 0.10 0.12 0.14 Grinding fineness (occupying 90%) Magnetic filed intensity H (T)

Figure 6. EffectEffect of grinding fineness fineness ( a) and magnetic field field intensity (b) on nickel extraction.

3.8. Scale-up Test of Roasting–Magnetic Separation

To further investigate the process conditions for repeatability, a scale-up test was carried out under the comprehensive condition used: Segregation roasting temperature of 1100 °C, segregation roasting time of 90 min, calcium chloride dosage of 15%, iron concentrate dosage of 30%, coke dosage

Minerals 2020, 10, 352 9 of 13

3.8. Scale-Up Test of Roasting–Magnetic Separation To further investigate the process conditions for repeatability, a scale-up test was carried out under the comprehensive condition used: Segregation roasting temperature of 1100 ◦C, segregation roasting time of 90 min, calcium chloride dosage of 15%, iron concentrate dosage of 30%, coke dosage of 15%, coke size of 1 + 0.5 mm, magnetic separation grinding ﬁneness of <45 µm occupying 90%, − and magnetic separation magnetic ﬁeld intensity of H = 0.10 T. A mass of 500 g was used for each scale-up repeat test, and the results are shown in Table4. These results show that the index of the repeated experiments is superior to the conditions of the results of the extraction index of nickel is better than the condition test index. Main element analysis also reports the ferronickel concentrate (Table5), and the valuable cobalt was enriched to 0.42% in the nickel iron product. Nickel, iron, and cobalt will be respectively extracted by a subsequent smelting process.

Table 4. Repeated scale-up test results of extraction from the garnierite laterite ore by roasting– magnetic separation.

Grades in the Segregation Grades in Ferronickel Recovery Repeat Roasting Ores (wt %) Concentrate (wt %) (wt %) Ni Fe Ni Fe Ni Fe 1 0.56 20.81 16.15 73.72 90.32 11.09 2 0.55 20.79 16.13 73.69 90.35 10.92 3 0.53 20.75 16.21 73.45 90.31 10.44 4 0.58 20.83 16.32 73.92 90.36 11.39 5 0.56 20.68 16.08 73.75 90.38 11.23 6 0.54 20.86 16.07 73.49 90.26 10.67 Average 0.55 20.79 16.16 73.67 90.33 10.96

Range (R = Emax E ) 0.15 0.43 0.12 0.95 − min PN di i=1| | 16.16 73.67 90.33 10.96 Arithmetic mean error (δ = N ) N N 2 = P 2 = P ( ) Sum square variation (SS di Ei E ) 0.04 0.15 0.01 0.63 i=1 i=1 − SS Average deviation (MS = f ) 0.008 0.03 0.002 0.13 r P 2 (Ei E) √ 0.09 0.17 0.04 0.36 Standard deviation (s = N −1 = MS) −

Table 5. Average main element analysis of ferronickel concentrate (wt %).

Ni Fe Co MgO SiO2 Al2O3 CaO 16.16 73.67 0.42 1.05 3.66 0.15 3.12

3.9. Nickel and Iron Phase Transformation Mechanism in the Roasting Process According to the mineral analysis of the garnierite laterite ore, the main mineral phases in the garnierite laterite ores were K O Al O 6SiO , Mg Si O , Al O 2SiO 4H O, Al Si O (OH) , FeOOH, 2 · 2 3· 2 2 2 6 2 3· 2· 2 2 2 5 4 Ca Mg Si O (OH) , and (Ni,Mg)O SiO nH O. The main mineral phases in the iron concentrate were 2 5 8 22 2 · 2· 2 Fe2O3 and SiO2, The main chemical reactions that may occur in the segregation roasting system are shown in Equations (3)–(19):

(Ni,Mg)O SiO nH O (Ni,Mg)O SiO + nH O (3) · 2· 2 (s) → · 2(s) 2 (g), Ca Mg Si O (OH) Ca Mg SiO + H O (4) 2 5 8 22 2(s) → 2 5 23(s) 2 (g), Al O 2SiO 4H O Al O 2SiO + 4H O (5) 2 3· 2· 2 (s) → 2 3· 2(s) 2 (g), Al Si O (OH) Al Si O + 2H O (6) 2 2 5 4(s) → 2 2 7(s) 2 (g), Minerals 2020, 10, 352 10 of 13

FeOOH Fe O + H O (7) (s) → 2 3(s) 2 (g), C + H O CO + H (8) (s) 2 (g) → (g) 2(g), C + 2H O CO + 2H (9) (s) 2 (g) → 2(g) 2(g), Minerals 2020, 10, x FOR PEER CaClREVIEW + SiO + H O CaO SiO + 2HCl 10 of(10) 13 2(s) 2(s) 2 (g) → · 2(s) (g), CaCl2(s) + Al2O3 2SiO2(s) + H2O(g) CaO Al2O3 2SiO2(s) + 2HCl(g), (11) CaCl2(s) + SiO· 2(s) + H2O(g) → CaO·SiO→ 2(s)· + 2HCl· (g), (10)

CaCl(Ni,Mg)O2(s) + AlSiO2O2(s)3·2SiO+ 4HCl2(s) + H(g)2O(g)MgCl → CaO·Al2(g) + 2NiClO3·2SiO2(g) 2(s)+ SiO+ 2HCl2(s) +(g),2H 2O(g), (11)(12) · → (Ni,Mg)O·SiO2(s)Fe + 4HClO (g)+ 6HCl→ MgCl2(g)2FeCl + NiCl2(g)g ++ 3HSiO2(s)O + 2H2O(g), (12)(13) 2 3(s) (g) → 3( ) 2 (g), → Fe2O3Fe3(s) +O 6HCl+(g)CO 2FeCl2Fe3(g) + O3H2+OCO(g), (13)(14) 2 3(s) (g) → 3 4 2(g), 3Fe2O3(s) + CO(g) → 2Fe3O4 + CO2(g), (14) 3Fe2O3(s) + H2(g) 2Fe3O4 + H2O(g), (15) 3Fe2O3(s) + H2(g) → 2Fe→3O4 + H2O(g), (15) 2FeCl3(g) + 3H2(g) 2Fe(s) + 6HCl(g), (16) 2FeCl3(g) + 3H2(g) → 2Fe→(s) + 6HCl(g), (16) NiCl + H→ Ni + 2HCl (17) NiCl2(g)2(g) + H2(g) 2(g) Ni→(s) + 2HCl(s) (g), (g), (17) 4Fe4Fe2O3(s)O + Fe+(s) Fe→ 3Fe3O3Fe4(s), O (18)(18) 2 3(s) (s) → 3 4(s), → NiClNiCl2(g) + Fe+(s)Fe + H2(g)+ H [Ni]Fe[Ni]Fe + 2HCl+ (g).2HCl (19)(19) 2(g) (s) 2(g) → (g). X-rayX-ray diffraction diﬀraction (XRD), (XRD), scanning scanning electron electron microscopy microscopy (S (SEM),EM), and and energy energy dispersive dispersive X-ray X-ray spectroscopyspectroscopy (EDS) (EDS) were were used used to ch toaracterize characterize the segregation the segregation roasting roasting ores and ores ferronickel, and ferronickel, and analyzing and theanalyzing phase transformation the phase transformation of nickel and ofnickel iron in and the iron segregation in the segregation roasting process. roasting The process. XRD Theanalysis XRD resultsanalysis of results the segregation of the segregation roasting roasting ores and ores ferroni and ferronickelckel concentrate concentrate are shown are shown in Figure in Figure 7, and7, andthe SEM-EDSthe SEM-EDS analysis analysis results results of the of segregation the segregation roasting roasting ores ores and andferronickel ferronickel are areshown shown in Figure in Figure 8. 8.

8000 (a) 1 1-CaO·Al O ·2SiO 2400 (b) 2 3 2 1 1-Fe 7000 2-Fe 2200 2-[Ni]Fe

3-[Ni]Fe 2000 3-Fe3O4 6000 4-CaO·SiO 2 1800 4-CaO·SiO2 5-Fe O 5000 3 4 1600 5-CaO·Al2O3·SiO2 1400 4000 1200 2 2 2 1000 3000 800 Intensity (a.u.) 3 Intensity (a.u.) 2000 3 600 400 3 1000 5 4 5 5 4 1 4 5 4 200 0 0 -200 5 101520253035404550 5 101520253035404550 2θ (°) 2θ(°)

FigureFigure 7. 7. XRDXRD diffractograms diﬀractograms of of the the segregation segregation roasting roasting ores ores ( (aa)) and and ferronickel ferronickel ( (bb).).

TheThe results results in in Figures Figures 7 and8 8 show show thatthat afterafter thethe segregationsegregation roastingroasting ofof garnieritegarnierite lateritelaterite ore,ore, nickelnickel changes changes from from (Ni,Mg)O·SiO (Ni,Mg)O SiO2·nnHH2OO to to a a new new nickel nickel mineral mineral phase phase dominated dominated by by an an [Ni]Fe [Ni]Fe solid solid · 2· 2 solution;solution; and and iron iron changes changes from from Fe Fe22OO33 andand FeOOH FeOOH to to a a new new iron iron mineral mineral phase phase dominated dominated by by metal metal FeFe and and Fe Fe33OO44. .Nickel Nickel and and iron iron belong belong to to ferromagnetic ferromagnetic metals. metals. Magnetite Magnetite belongs belongs to to strong strong magnetic magnetic minerals,minerals, and and their their specific specific magneti magnetizationzation coefficients coefficients are are different different to some extent. The The main main minerals minerals inin the the ferronickel ferronickel concentrate concentrate obtained obtained from from the the segr segregationegation roasting roasting ore ore after after grinding grinding were were Fe, Fe, [Ni]Fe, [Ni]Fe, FeFe33OO4,4 ,and and SiO SiO2. 2In. Inthe the process process of ofmagnetic magnetic separation, separation, a small a small amount amount of gangue of gangue minerals, minerals, such such as CaO·SiOas CaO SiO2 andand CaO·Al CaO 2AlO3·SiOO SiO2, entered, entered into into the the ferronickel ferronickel concentrate concentrate as as a aresult result of of mechanical mechanical · 2 · 2 3· 2 entrainment.entrainment. In Inthe the segregation segregation roasting roasting system, system, the relation the relationshipship between between the difficulties the di inffi cultiesthe reduction in the ofreduction metal nickel of metal and nickel metal and iron metal chloride iron is chloride FeCl3 < is NiCl FeCl2,3 and< NiCl nickel2, and is nickela kind is of a kindiron-soluble of iron-soluble oxide. FeCloxide.3 itself FeCl is3 itselfa kind is of a kindchlorinating of chlorinating agent, agent,promoting promoting the chlorination the chlorination and segregation and segregation of nickel, of nickel, and formsand forms the solid the solidsolution solution of [Ni]Fe. of [Ni]Fe.

Minerals 2020, 10, 352 11 of 13

Minerals 2020, 10, x FOR PEER REVIEW 11 of 13

6000

(a) Si 5000 (c) Mg 4000 O

3000

2000 Fe Intensity (cps)

1000 Al Ca Ni 0

-1000 -10123456 Binding energy (keV) 12000 Fe (b) 11000 10000 (d) 9000 8000 7000 6000 5000 4000 Intensity (cps) Ni O 3000 2000 Si 1000 Al Ca 0 -1000 -10123456 Binding energy (keV)

FigureFigure 8. 8.SEM SEM imagesimages ofof thethesegregation segregation roastingroasting oresores( a(a)) and and ferronickel ferronickel ( b(g);); -EDS -EDS images images of of the the segregationsegregation roasting roasting ores ores (c ()b and) and ferronickel ferronickel (d (h).).

4.4. Conclusions Conclusions BasedBased on on the the results results obtained obtained in in this this work, work, we we drew drew the the following following conclusions: conclusions: (1) The garnierite laterite ore sample was collected in the Mojiang area of China. The garnierite (1) The garnierite laterite ore sample was collected in the Mojiang area of China. The garnierite laterite ore contained Ni 0.72%, Co 0.029%, Fe 8.65%, MgO 29.66%, and SiO2 37.86%. Garnierite was the laterite ore contained Ni 0.72%, Co 0.029%, Fe 8.65%, MgO 29.66%, and SiO2 37.86%. Garnierite was Ni-bearing nickel mineral in the garnierite laterite ore. Potash feldspar, forsterite, tremolite, halloysite, the Ni-bearing nickel mineral in the garnierite laterite ore. Potash feldspar, forsterite, tremolite, quartz, and kaolinite are the other gangue minerals in the garnierite laterite ore. halloysite, quartz, and kaolinite are the other gangue minerals in the garnierite laterite ore. (2) A process of segregation roasting–magnetic separation was used to process the garnierite (2) A process of segregation roasting–magnetic separation was used to process the garnierite laterite ore. The ferronickel concentrate with Ni of 16.16%, Fe 73.67%, and nickel recovery of 90.33% laterite ore. The ferronickel concentrate with Ni of 16.16%, Fe 73.67%, and nickel recovery of 90.33% was obtained under the conditions used: A segregation roasting temperature of 1100 C, a segregation was obtained under the conditions used: A segregation roasting temperature of 1100◦ °C, a segregation roasting time of 90 min, a calcium chloride dosage of 15%, an iron concentrate dosage of 30%, a coke roasting time of 90 min, a calcium chloride dosage of 15%, an iron concentrate dosage of 30%, a coke dosage of 15%, a coke size of 1 + 0.5 mm, a magnetic separation grinding ﬁneness of <45 µm dosage of 15%, a coke size of− −1 + 0.5 mm, a magnetic separation grinding fineness of <45 μm occupying 90%, and a magnetic separation magnetic ﬁeld intensity of H = 0.10 T. occupying 90%, and a magnetic separation magnetic field intensity of H = 0.10 T. (3) The results of the nickel and iron phase transformations show that nickel is transformed (3) The results of the nickel and iron phase transformations show that nickel is transformed from from (Ni,Mg)O SiO2 nH2O to a new nickel mineral phase dominated by the [Ni]Fe solid solution. (Ni,Mg)O·SiO2·nH2O· to a new nickel mineral phase dominated by the [Ni]Fe solid solution. Iron Iron changed from Fe2O3 and FeOOH to a new iron mineral phase dominated by metal Fe and Fe3O4 changed from Fe2O3 and FeOOH to a new iron mineral phase dominated by metal Fe and Fe3O4 after after segregation roasting. segregation roasting. (4) XRD, SEM, and EDS analysis of the segregation roasting ores and ferronickel concentrate show (4) XRD, SEM, and EDS analysis of the segregation roasting ores and ferronickel concentrate that the main minerals in ferronickel concentrate are Fe, [Ni]Fe, and a small amount of Fe3O4; a small show that the main minerals in ferronickel concentrate are Fe, [Ni]Fe, and a small amount of Fe3O4; a amount of gangue minerals, such as CaO SiO2 and CaO Al2O3 SiO2, are present in the ferronickel small amount of gangue minerals, such as ·CaO·SiO2 and CaO·Al· 2·O3·SiO2, are present in the ferronickel concentrate because of mechanical entrainment in the magnetic separation process. concentrate because of mechanical entrainment in the magnetic separation process.

Minerals 2020, 10, 352 12 of 13

Author Contributions: This is a joint work of the six authors; each author was in charge of their expertise and capability: J.X.: writing, formal analysis, and original draft preparation; W.D.: conceptualization; Y.P.: validation; T.C. and K.Z.: methodology; Z.W.: investigation. All authors have read and agreed to the published version of the manuscript. Funding: This work was supported by the Sichuan Science and Technology Program (Grant No. 2019FS0451 and No. 2018FZ0092); Key Laboratory of Sichuan Province for Comprehensive Utilization of Vanadium and Titanium Resources Foundation (2018FTSZ35); China Geological Big Survey (Grant No. DD20190694). Conﬂicts of Interest: The authors declare no conﬂict of interest. The funders had no role in the design, analyses, and interpretation of any data of the study.

References

1. Nakajima, K.; Daigo, I.; Nansai, K.; Matsubae, K.; Takayanagi, W.; Tomita, M.; Matsuno, Y. Global distribution of material consumption: Nickel, copper, and iron. Resour. Conserv. Recycl. 2018, 133, 369–374. [CrossRef] 2. Wang, C.Y.; Yin, F.; Chen, Y.Q.; Wang, Z.; Wang, J. Worldwide processing technologies and progress of nickel laterites. Chin. J. Nonferrous Met. 2008, 18, 1–8. (In Chinese) 3. Mudd, G.M. Global trends and environmental issues in nickel mining: Sulfides versus laterites. Ore Geol. Rev. 2010, 38, 9–26. [CrossRef] 4. Seo, J.; Kim, K.S.; Bae, I.K.; Lee, J.Y.; Kim, H.S. A Study on Classification of Limonite and Saprolite from Nickel Laterite Ores. J. Korean Inst. Resour. Recycl. 2016, 25, 40–47. 5. Pintowantoro, S.; Abdul, F. Selective Reduction of Laterite Nickel Ore. Mater. Trans. 2019, 60, 2245–2254. [CrossRef] 6. Meshram, P.; Abhilash Pandey, B.D. Advanced Review on Extraction of Nickel from Primary and Secondary Sources. Miner. Process. Extr. Metall. Rev. 2019, 40, 157–193. [CrossRef] 7. De Bakker, J.; Peacey, J.; Davis, B. Thermal decomposition studies on magnesium hydroxychlorides. Can. Metall. Q. 2012, 51, 419–423. [CrossRef] 8. Xiao, J.H.; Zou, K.; Ding, W.; Peng, Y.; Chen, T. Extraction of Lead and Zinc from a Rotary Kiln Oxidizing Roasting Cinder. Metals 2020, 10, 465. [CrossRef] 9. Sharikov, Y.V.; Feng, L.Z. Mathematical Simulation of the Process of Nickel Oxide Recovery in a Tube-Type Rotary Kiln. Metallurgist 2018, 62, 634–641. [CrossRef] 10. Mongelli, G.; Taghipour, B.; Sinisi, R.; Khadivar, S. Mineralization and element redistribution in the Chah-Gheib Ni-laterite ore zone, Bavanat, Zagros Belt, Iran. Ore Geol. Rev. 2019, 111, 102990. [CrossRef] 11. Dong, J.C.; Wei, Y.G.; Zhou, S.W.; Li, B.; Yang, Y.D.; Mclean, A. The Effect of Additives on Extraction of Ni, Fe and Co from Nickel Laterite Ores. JOM 2018, 70, 2365–2377. [CrossRef] 12. Ilyas, S.; Srivastava, R.R.; Kim, H.; Ilyas, N.; Sattar, R. Extraction of nickel and cobalt from a laterite ore using the carbothermic reduction roasting-ammoniacal leaching process. Sep. Purif. Technol. 2020, 232, 115971. [CrossRef] 13. Oliveira, V.D.; dos Santos, C.G.; Brocchi, E.D. Assessing the Influence of NaCl on the Reduction of a Siliceous Laterite Nickel Ore Under Caron Process Conditions. Metall. Mater. Trans. B 2019, 50, 1309–1321. [CrossRef] 14. Xiao, J.H.; Zhou, L.L. Increasing Iron and Reducing Phosphorus Grades of Magnetic-Roasted High-Phosphorus Oolitic Iron Ore by Low-Intensity Magnetic Separation–Reverse Flotation. Processes 2019, 7, 388. [CrossRef] 15. Ugwu, I.M.; Sherman, D.M. The solubility of goethite with structurally incorporated nickel and cobalt: Implication for laterites. Chem. Geol. 2019, 518, 1–8. [CrossRef] 16. Farrokhpay, S.; Cathelineau, M.; Blancher, S.B.; Laugier, O.; Filippov, L. Characterization of Weda Bay nickel laterite ore from Indonesia. J. Geochem. Explor. 2019, 196, 270–281. [CrossRef] 17. Zhu, D.Q.; Cui, Y.; Pan, J.; Qiu, G.Z.; Li, Q.H. Investigation on manufacture of ferronickel from low grade nickel laterite by pre-reducing–magnetic separation-smelting process. In Proceeding of XXIV Internationl Mineral Processing Congress; Science Press: Beijing, China, 2008; pp. 1622–1633. 18. Ding, W.; Xiao, J.H.; Peng, Y.; Shen, S.Y.; Chen, T. Iron Extraction from Red Mud using Roasting with Sodium Salt. Miner. Process. Extr. Metall. Rev. 2019.[CrossRef] 19. Garces-Granda, A.; Lapidus, G.T.; Restrepo-Baena, O.J. The effect of calcination as pretreatment to enhance the nickel extraction from low-grade laterites. Miner. Eng. 2018, 120, 127–131. [CrossRef] Minerals 2020, 10, 352 13 of 13

20. Xiao, J.H.; Zhang, Y.S. Recovering Cobalt and Sulfur in Low Grade Cobalt-Bearing V–Ti Magnetite Tailings Using Flotation Process. Processes 2019, 7, 536. [CrossRef] 21. Laranjo, R.; Anacleto, N. Direct smelting process for stainless steel crude alloy recovery from mixed low-grade chromite, nickel laterite and manganese ores. J. Iron Steel Res. Int. 2018, 25, 515–523. [CrossRef] 22. Xiao, J.H.; Ding, W.; Peng, Y.; Wu, Q.; Chen, Z.Q.; Wang, Z.; Wang, J.M.; Peng, T.F. Upgrading iron and removing phosphorus of high phosphorus Oolitic iron ore by segregation roasting with Calcium chloride and Calcium hypochlorite. J. Min. Metall. Sect. B 2019, 55, 305–314. [CrossRef] 23. Elliott, R.; Pickles, C.A. Thermodynamic Analysis of the Selective Reduction of a Nickeliferous Limonitic Laterite Ore by Hydrogen. High Temp. Mater. Process. 2017, 36, 835–846. [CrossRef] 24. Xiao, J.H.; Zhang, Y.S. Extraction of Cobalt and Iron from Refractory Co-Bearing Sulfur Concentrate. Processes 2020, 8, 200. [CrossRef] 25. Farrokhpay, S.; Filippov, L. Aggregation of nickel laterite ore particles using polyacrylamide homo and copolymers with diﬀerent charge densities. Powder Technol. 2017, 318, 206–213. [CrossRef] 26. Quast, K.; Addai-Mensah, J.; Skinner, W. Preconcentration strategies in the processing of nickel laterite ores Part 5: Eﬀect of mineralogy. Miner. Eng. 2017, 110, 31–39. [CrossRef]

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).