Preparation of Titanium Dioxide Anatase Pigment from Rosetta Ilmenite Concentrate Via the Sulfate Route

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Full Paper CTAIJ 10(5) 2015 [193-199] Preparation of titanium dioxide anatase pigment from Rosetta ilmenite concentrate via the sulfate route

N.A.Abdelfattah Nuclear Materials Authority, P.O. Box: 530 El Maadi, Cairo, (EGYPT) ABSTRACT

The sulfate rout for the processing of Rosetta ilmenite concentrate for the preparation of pigment grade titanium

dioxide is studied The working concentrate is assaying 39.89%TiO2 while the FeO and Fe2O3 assay 31.51 and 24.65% respectively. After optimizing the digestion factors, the obtaind sulfate liquor was subjected to reduction followed

by crystallization of copperas (FeSO4.7H2O). To this point, the process is in the black stage. The solution of the remaining titanyl sulfate is then subjected to Hydrolysis and the resultant solids are subjected to bleaching followed by calcinations to produce a product in which the TiO percent exceeds 98%. The obtained, XRD pattern of  2 the latter has shown its anatase structure. 2015 Trade Science Inc. - INDIA

INTRODUCTION ored TiO2 pigment which has extensive application in paints, plastic, paper and rubber besides printing inks, ‘s crust Titanium is relatively abundant in the earth cosmetics, soap and pharmaceutical industries. where its assay amounts to 0.44%. Its minerals are usu- Two main processes are used to manufacture pig- ally found in igneous and metamorphic rocks and are ment grade TiO2 and titanium metal; namely the sulphate mainly represented by ilmenite (FeO-TiO2), rutile (TiO2) process and the chloride process. The two processes

and titanomagnetite (Fe2TiO4-Fe2O4). Other minerals differ in both their chemistry and raw materials require- [3] include anatase (TiO2) which is formed on joint planes ments . Because the chloride process has some ad- and in veins in schists and gneisses as well as leucoxene vantages over the traditional sulphate process in both which is a weathered form ilmenite and assays up to cost and waste management, however, in the sulphate – grade titanium raw materials are accept- 85% TiO2. Ilmenite supplies about 91% of the worlds process low demand for titanium minerals and the worlds ilmenite able. According to Harben (2002), the two routes can production reached 5.19 million metric tons in 2009[1,2]. be summarized as follows. Thus, the sulfate route, fine World titanium sponge metal production reached grained ilmenite concentrate (minimum 44% TiO2) or 166.000 metric tons in 2008(Gambogi, 2010). Tita- sulfatable titanium slag (78% TiO2) is digested in sulfu- nium minerals are not only found in hard rock but also ric acid at 150-180 C and the digested cake is dis- in beach sands, and their world reserves are attaining solved in cold water followed by filtering the residual about 1300 million tons. Due to the highly extensive ferrous sulfate (FeSO4.7H2O). The titanyl sulfate in the consumption of rutile, there is no doubt that ilmenite as filtrate is then heated with stream at 95-110C in the the most important titanium resource will continue to presence of TiO2 seed crystals to yield sulfuric acid dominate the titanium industry in the future. A survey on – 96% TiO (waste/regenerated acid) together with 93 2 the use of titanium in its various forms indicate that al- as an intermediate product. The latter is then washed, – 1000 to produce ana- most 95% of its use is for the production of white col- treated and calcined at 800 194 Preparation of titanium dioxide anatase pigment from Rosetta ilmenite concentrate CTAIJ, 10(5) 2015

Full Paper tase or rutile titanium dioxide (TiO2). tase form and hydrolysis from chloride solutions (sul-  fate- free) yields the rutile form. These normal products FeTiO3 +5H2O+ 2H2SO4 TiOSO4 + FeSO4.7 H2O  can be reversed in either case by special techniques TiOSO4 + 2H2O TiO (OH)2 + H2SO4  such as e.g. seeding with nuclei of the other form or by TiO (OH)2 TiO2 + H2O On the other hand, in the chloride route, natural addition of chemical additives. – 98% TiO In recent years, hydrometallurgical processes have rutile (94 2) or synthetic rutile (92-95% TiO ), anatase (90-95% TiO2), leucoxene (> 86% been developed where direct hydrochloric acid leach- 2 – 90% TiO TiO ) chlorinatable titanium slag (80 ) to- ing and solvent extraction are used to produce pigment 2 2 grade TiO of a purity exceeding 99.5% and titanium gether with oil coke and chlorine are treated in fluid 2 metal through conventional fused electrolysis[6-12]. Im- bed reactors at 925 - 1000 to give raw TiCl4 (tickle) mixed with a reducing agent and distilled. Combustion proved sulphate processes have also been developed of the purified tickle with pure oxygen at 985 would and become more and more important due to its low result in anatase or rutile titanium dioxide. energy requirement compared to the conventional  thermo and electro chemical processes. 2TiO2 + 3C + 4Cl2 2CO + CO2 +2 TiCl4  The present work is concerned with the direct TiCl4 + O2 TiO2 + 2Cl2 preparation of anatase grade TiO2 pigment from Rosetta As a matter of fact two main grades (crystal phases) ilmenite concentrate using the sulphate process. In this of TiO pigment could be produced; viz rutile or ana- 2 process, the ore containing titanium is dissolved in sul- tase. Rutile has a more closely packed crystal structure furic acid, yielding a solution of titanium, iron and other making it denser than anatase, with its higher refractive metal sulfates. Then, through a series of steps including index (2.8 with an optimum particle size in organic binder chemical reduction, purification, precipitation, washing of 0.19um) and chemical stability (outdoor paints, plas- and calcination, pigmentary-size intermediate TiO2 is tics, printing ink, cosmetics). On the other hand, ana- produced. The crystal structure, anatase or rutile, is tase has a bluer tone (refractive index 2.55 with an op- controlled by proper nucleation conditions besides those timum particle size in organic binder of 0.24um) and is of calcination. To realize this purpose, the provided less abrasive (indoor paints, paper, tixtiles rubber, soap Rosetta ilmenite concentrate was first subjected to di- and pharmaceutical) gestion using concentrated sulphuric acid under differ- Rutile TiO has a relative scattering ppwer of up to 2 ent condtions in order to determine their optimum val- 800 whereas anatase TiO its 600, both of which com- 2 ues. Before hydrolyzing the titanyl sulfate solution, proper pare favorably with zinc sulfide (ZnS) at 360 and barite separation of ferrous sulfate (Copperas) was under- at 25. As a pigment, titanium dioxide is indeed the pre- – 2.80 (pro- taken. mier white pigment with a high R.I. of 2.55 vide good pacifying strength or hiding power) and EXPERIMENTAL reflectivity (generates brightness and whiteness or light- ening power); inertness and chemical stability (being Material essentially insoluble in acids, bases, and other solvents including air pollutants); resistance to UV degradation A technological sample of Rosetta beach ilmenite (color retention); tinting strength; nontoxicity; thermal concentrate was kindly provided by the Black Sands stability over a wide range of temperature; and a favor- Project of the Nuclear Materials Authority (NMA). In able price / effect ratio (paper, paint, plastics, rubber, TABLE 1 the chemical composition of this concentrate [14] ceramic, textiles and cosmetics). is shown . Presence of Fe O is due to partial oxidation of the According to Harjne and Call (1984), the titanium 2 3 dioxide is generally prepared commercially by hydro- FeO in the ilmenite mineral the ferric state besides pos- lytic precipitation from solution of titanium sulfate or sible solid solution. On the other hand, it is interesting to refer to the presence of 0.42% Cr O and 0.21% of vapor phase oxidation of titanium tetrachloride. Nor- 2 3 V O which might be present as minor chromite and mally, hydrolysis from sulfate solutions yields the ana- 2 5 chemical technology An Indian Journal CTAIJ, 10(5) 2015 N.A.Abdelfattah 195

Full Paper TABLE 1 : Chemical composition of the working Rosetta il- TABLE 2 : Effect of sulfuric acid / ilmenite weight ratio upon menite concentrate the efficiency of Rosetta ilmenite breakdown

Oxides Wt.% H2SO4/Ilmenite Wt. Ratio Breakdown efficiency, %

TiO2 39.89 1/1 35 FeO 31.51 1.5/1 40

Fe2O3 24.65 2/1 47 MnO 1.35 2.5/1 55

Al2O3 0.88 3/1 57 MgO 0.61 TABLE 3 : Effect of digestion temperature upon the efficiency CaO 0.12 of Rosetta ilmenite breakdown SiO2 0.30 Temperature C0 Breakdown efficiency, % Total 99.31 150 55 vanadferous titanomagnetite respectively. 200 85 Experimental procedures 250 90 300 95 (a) Ilmenite digestion TABLE 4 : Effect of digestion time upon the efficiency of Several dissolution experiments of the provided il- Rosetta ilmenite breakdown menite concentrate sample was perfomed under differ- ent conditions in a manner to determine their optimum Digestion time, hr Breakdown efficiency, % conditions. Thus the effects of sulfuric acid / ilmenite 1 30 ratio, digestion temperature and time have been stud- 2 62 ied. In these experiments the ore size used ranged from 3 90 (-100 to +150 mesh). After digestion, the leaching il- 4 95 menite values were dissolved by water during 1hr fol- 5 98 µg Ti/ml, was mixed with lowed by adding 35 kg/ton iron powder to reduce the ume, assaying not more than 2 leached ferric iron to the ferrous state. These steps were 5 ml of 2% tiron solution, 5 ml of 0.05 M EDTA solu- then followed by filtration and washing for separation tion, 10 ml of the buffer solution (pH 4.5) and 50 mg of of iron, the prepared solution was subjected to evapo- sodium dithionite. Each mixture was shaken well, com- ration in a manner to crystallize FeSO 7H O by proper ë 4. 2 pleted up to a suitable volume and measured at max=430 cooling down -5C. nm within 15 min[15].

(b) TiO2 hydrolysis (b) Product analysis An aqueous solution of titanyl sulphate after sepa- A semi-quantitative of ESEM analysis was used for ration of ferrous sulfate and containing the equivalent of identifiying the purity of the final product. The final prod-

250 grams TiO2 per liter and an acid to titanium weight uct pigment anatase was subjected to X-ray diffraction ratio of 1.8 was hydrolysed by water addition in pro- analysis to determine its pattern and crystal structure. portion of 20 parts water per 100 parts of titanyl sul- Also for this purpose a Philips PW-3710 with genera- fate solution at 90 over a period of 15 minutes. The tor PW-1830, Cu target tube and Ni filter at KV and obtained slurry was then maintained at a temperature 30 mA. Instrument of the Nuclear Material Authority of 100 for about 3hr where in order to attain complete was used. hydrolysis. Analytical procedures RESULTS AND DISCUSSION (a) Ti control analysis Optimization of the sulfate route breakdown fac- For titanium control analysis, a suitable sample vol- tors chemical technology An Indian Journal 196 Preparation of titanium dioxide anatase pigment from Rosetta ilmenite concentrate CTAIJ, 10(5) 2015

Full Paper

Figure 1 : Hydrate of TiO2 before bleaching

Figure 2 : Hydrate of TiO2 after bleaching

Figure 3 : XRD of TiO2 pigment product

(a) Effect of acid/ilmenite mass ratio efficiency of ilmenite was determined by TiO2analysis To study the effect of sulfuric acid / ilmenite mass in the obtained solution after its proper dissolution in ratio on the breakdown of Rosetta ilmenite concen- water and filtration. From these data TABLE 2, it is trate, several experiments were performed using ratios clearly evident that the dissolution efficiency has ranged varying from 1:1, to 3:1 ratio at 150 for a curing time of from 35 to 57% by increasing the acid / ilmenite ratio 3hrs. The grain size of the working ilmenite concentrate from 1/1 to 3/1 resppectively. These relatively low effi- was fixed in all experiments to range from (-100 to +150 ciencies are most probably due to the relatively low mesh) in closed system. The results for the breakdown digestion temperature. Therefore, the work was then oriented towards increasing the digestion temperature chemical technology An Indian Journal CTAIJ, 10(5) 2015 N.A.Abdelfattah 197

Full Paper for improving the breakdown efficiency. (b) Effect of digestion temperature Another series of digestion experiments upon Rosetta ilmenite concentrate was performed at various temperaturewas ranging from 150 to 300 using an acid amount/ ilmenite weight ratio of 2.5/1 for a digestion time 3h. In these experiments, the ore size was fixed in the range from -100 to +150 mesh and the digestion time was fixed at 3hr. The obtained results shown in TABLE 3 were found to range from 55 up to 95% where the digestion temperature was raised from 150 to 300 respectively. However, to avoid excessive energy consumption,250 was chosen as the optimum digestion temperature which resulted in 90% dissolution efficiency and to investigate the effect of the digestion time. (c) Effect of digestion time A third series of breakdown experiments was performed to investigate the effect of digestion time upon the breakdown efficiency of Rosetta ilmenite concentrate. The applied digestion time was varied from only 1hr. to 5hr. In these experiments, the acid / ilmenite weight ratio was fixed at 2.5 / and the applied digestion temperature was fixed at 250 . The obtained digestion

efficiency of TiO2 TABLE 4 was found to range from only 30 to 98 % respectively. The results indicated that the magnitude of curing time of ilmenite breakdown in

increasing the leaching efficiency of TiO2 is quite rel- evant. Characteristic of the TiO2 product

For preparation of the TiO2 product, a 500g sample portion of Rosetta ilmenite concentrate was properly treated as previously mentioned. From the analysis of the reduced prepared solution shown in TABLE 5, it is

clear that it assays 140g/l TiO2 and 365g/l FeSO4 Chemical Composition of the reduced Sulfate Solu- Constituents Grams per liter TiO2 140 FeSO4 360 H2SO4 340 H2SO4/TiO2 2.42 Figure 4 : Flow sheet for treatment of ilmenite by sulfate FeSO4/TiO2 2.57 process to form white titanium anatase pigment Specific gravity 1.6 chemical technology An Indian Journal 198 Preparation of titanium dioxide anatase pigment from Rosetta ilmenite concentrate CTAIJ, 10(5) 2015

Full Paper tion of Rosetta Ilmenite Concentrate tion of H2SO4 and the production of large amount of This solution was then subjected to evaporation, sulphate wastes and high cost for the treatment. This ferrous sulfate crystallization. The titanyl sulfate solu- work has developed several improved sulphate pro- tion left behind was then properly hydrolyzed accord- cesses involving leaching strategies, bleaching step to ing to the, following equation: reduce chromophores into their soluble forms and re-  cycling acid or reusing in treatment of CaCO to CaSO TiOSO4 + 2H2O TiO (OH)2 + H2SO4 3 4 The precipitated titanium hydroxide was analyzed in cement industry. before and after its bleaching using ESEM technique REFERENCES (Figures 1 and 2). It is found that in (Figure 1) the percent of iron assay 3.64% causes problems in color and [1] J.Gambogi; Titanium mineral concentrates, US Geo- quality where the high quality of the titanium pigment logical Surv,172-173 (2009b). must contains not more than 50 ppm of iron so the [2] J.Gambogi; Titanium and titanium dioxide, mineral bleaching technique using Zn powder to eliminate any commodity summaries, US Geological Surv, 176- co-precipitated iron followed by filtration and calcina- 178 (2010). tions of the product to TiO2 at 920 for 3hrs. The ob- [3] L.Hamor; Titanium dioxide manufacture, a world tained TiO2 pigment product after analysis have an as- source of ilmenite, rutile, monazite and zircon, Con- say exceeding 98% was then subjected to XRD analy- ference Proceedings, AusIMM, perth, W, A, 143- sis where its anatase structure is confirmed. 146 (1986). [4] P.W.Harben; The industrial minerals Handy Book CONCLUSION 4th Edition, Lindsey Taylor, Pensord, U.K. (2002).

[5] P.H.Harju, K.R.Call; Preparation of crystalline TiO2 The optimum factors of the sulfate route process- as avatase and / or rutile in porous carriers, U S ing of Rosetta ilmenite concentrate was found to in- patent 4482643 (1984). volve an acid/ ilmenite weight ratio of 2.5/1 at 250 for [6] W.Duyvesteyn, B.Sabachy, D.Verhulst, V.Edmund, 5hr. The obtained titanyl sulfate solution was subjected P.G.West-sells; Processing titaniferrous ore to tita- to ferric reduction followed by concentration through nium dioxide pigment, WO Patent 2001/00530 Al evaporation followed by copperas crystallization by (2001a). [7] V.I.Lakshmanan, R.Sridhar; Methods for separa- proper. After filtration of the latter, the titanyl sulfate tion of titanium from ore, Canadian Patent 2289967 solution was subjected to hydrolysis by water addition (2002). in the volumetric tatio of 20 parts / 100 parts at 95 for [8] V.I.Lakshmanan, R.Sridhar, M.M.Rishea, 3hr. Elimination of the co-hydrolyzed iron was achieved D.E.Joseph, R.Laat; Production of titanium metal by proper bleaching process using zinc powder. Chemi- from titanium- bearing ores involves leaching and cal analysis of the pigment product after calcinations at selective removal of iron values by solvent extrac- 925 has resulted in the pigment grade TiO2 of an assay tion, US Patent2001/007646-A1 (2001). exceeding 98%. The crystal structure of the obtained [9] V.I.Lakshmanan, R.Sridhar, D.H.Hains; A novel pigment was determined through XRD analysis where hydrometallurgical process for very high purity TiO2 its anatase structure has been revealed. Amethod for production Proceedings of 17th Industrial Minerals producing a high-quality titanium dioxide pigment hav- International Congress, Cambrian Printer, ing the crystal structure of anatase Compared to the Aberystwyth, UK, 92-95 (2004a). thermo-chemical and electro-chemical processes, di- [10] V.I.Lakshmanan, R.Sridhar, M.M.Rishea, rect hydrometallurgical leach processes are advanta- D.E.Joseph, R.Laat; Methods for separation of ti- geous in processing abundant ilmenite ores, low energy tanium from ore, US.Patent2004/6699446-B2 consumption and produce sufficiently high quality of (2004b). [11] V.I.Lakshmanan, R.Sridhar, B.G.Harris, G.Puvvada; anatase pigment TiO2 products for a wide range of application and major demand the main drawbacks of the Process for the recovery of titanium in mixed chlo- conventional sulphate processes are the high consump- ride media, WO patent 2005/049872 (2005a). chemical technology An Indian Journal CTAIJ, 10(5) 2015 N.A.Abdelfattah 199

Full Paper [12] V.I.Lakshmanan, R.Sridhar, B.G.Harris, G.Puvvada; [14] A.A.Abdou; Improved Analytical Methods for As- Process for the recovery of titanium in mixed chlo- saying Some Economic Egyptian Black Sand Min- ride media, US patent 2005/0142051 A1 (2005b). erals Concentrates, Ph.D. Thesis, Fac. Sci., Tanta [13] A.D.Stuart, J.A.Lawson, C.B.Ward, H.Peng; A Univ., Egypt (2011). sulphate process, WO Patent 2005090619-A1 [15] A.V.Moharir, V.A.K.Sarma, G.S.R.Krishna; Micro- (2010). chemical Journal, 17, 167 (1972).

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