Froth Flotation in Saline Water†

S. Castro* Department of Metallurgical Engineering, University of Concepcion1 J. S. Laskowski Department on Mining Engineering, University of British Columbia2

Abstract The use of seawater in mining/metallurgical operations seems to be the only sustainable solution in many zones with limited resources of fresh water. This requires new flotation technologies for processes which are to be carried out in highly concentrated electrolyte solutions. This paper reviews fundamental aspects of flotation in aqueous solutions with high concentration of inorganic electrolytes. Salt flotation, the process of flotation of inherently hydrophobic solids in concentrated electrolyte solutions, is especially suitable for theoretical analysis since no other organic agents are used in it. Starting from this example, the case of flotation of sulfide ores (chalcocite, chalcopyrite, pyrite and molybdenite) is discussed. The flotation of Cu-Mo sulfide ores requires the use of flotation agents, which are different for the inherently hydrophobic molybdenite and hydrophilic copper sulfides. The process is commonly carried out in alkaline pH adjusted with lime to depress pyrite, but in seawater depressing effect of Ca ions on molybdenite flotation is augmented, and different pyrite depressants are needed. Keywords: Froth flotation, Salt flotation, Cu sulfides flotation; saline water; seawater flotation

Closed water circuits in flotation plants result in a 1. Introduction high electrolyte concentration in the process water. Water is a medium in which flotation takes place Hence, the question arises how the ionic strength and flotation efficiency is highly dependent on wa- of the process water affects flotation. Many differ- ter quality. In general, water is becoming a scarce ent chemical additives (e.g. collectors which may resource for mineral processing plants, and in arid be weak or strong electrolytes, either low molecular regions the need of saving freshwater for communi- weight polymers used as dispersants or high mo- ties is imperative. Rivers and groundwater are being lecular weight polymers used as flocculants, etc.) increasingly depleted at an alarming rate in many dry are utilized in flotation processes. The properties of places. Hence, the use of water with a high concentra- aqueous solutions of some of these compounds are tion of inorganic electrolytes in flotation plants is be- strongly affected by ionic strength. At the same time ing increasingly important. The use of seawater could ionic strength affects directly particle-particle (co- be a sustainable solution for many dry zones located agulation/flocculation) and particle-bubble (flotation) close to sea. The oceans represent the earth’s major interactions. The simplest flotation system in which water reservoir. About 96.5-97% of the earth’s water is only inorganic compounds, for instance NaCl, are uti- seawater, while another 1.7%-2% is locked in icecaps lized as flotation agent is so-called salt flotation. and glaciers. Fresh water accounts for only around The aim of this paper is to review fundamental 0.5%-0.8% of the earth’s total water supply1). aspects of flotation in aqueous solutions with substan- tial concentration of inorganic salts, and to discuss † Accepted: July 8th, 2011 available information on the use of seawater in com- 1 Concepción, Chile mercial flotation operations. We limit the scope of 2 Vancouver, B.C., Canada this paper to the range of electrolyte concentrations * Corresponding author Ｅ-mail: [email protected] comparable with concentration of seawater that is TEL: (+56) 41-2204956 FAX: (+56) 41-2243418 to the range up to 1 M NaCl. This eliminates from

ⓒ 2011 Hosokawa Powder Technology Foundation 4 KONA Powder and Particle Journal No.29 (2011) our discussion the case of potash ore flotation, the results cannot be ascribed to a changing coalescence flotation process which is carried out in saturated of bubbles and is clearly a function of hydrophobicity NaCl-KCl brine (at 20 ℃，1,450 kg of the NaCl-KCl of the floated particles. But since small inorganic ions saturated aqueous solution contains about 0.300 kg cannot change solid wettability these results show of NaCl, 0.150 kg of KCl and 1 kg of water2); thus, the what could be expected, namely that only very hydro- saturated brine is about 6-7 mole/L solution of NaCl phobic particles can float under such conditions. and KCl). In order to study these effects further, a model was needed for which electrical charge and hydrophobic- 2. Salt Flotation Process ity could be independently maintained, and meth- 2.1 Flotation of inherently hydrophobic miner- ylated silica was used as a model of hydrophobic als in salty water surface6,7). Surface properties of this model system Klassen and Mokrousov3) in their monograph on are characterized in Fig. 2 6). The surface of silica fundamentals of flotation dedicated one chapter to the is completely hydrophilic but it can be made hydro- phenomenon of “salt flotation”; the term coined to de- phobic by reaction with trimethyl chlorosilane. The scribe the flotation of inherently hydrophobic miner- hydrophobicity depends on the number of surface als in concentrated electrolyte solutions without any hydroxyls that actually reacts with silane. Since quite organic agents. As demonstrated by Klassen4), this a large number of the surface hydroxyls do not react process may be quite efficient if the floated mineral with silane, the zeta potential values for both methyl- is highly hydrophobic; very hydrophobic bituminous ated hydrophobic silica and hydrophilic silica – as coals were shown to float in 0.3-0.5 M NaCl solutions demonstrated by the bottom (b) part of Fig. 2 - are quite well, while less hydrophobic low rank coals did the same. not. Fig. 1 taken from the publication that appeared Fig. 3 shows the results of the flotation tests in in 19835) confirms such a relationship quite clearly. which methylated quartz particles were floated in Fig. 1 shows the flotation rate constants obtained aqueous solutions of KCl at a constant pH of 6.1-6.5 8). from batch flotation tests in which coals varying in Flotation rate does not only depend on hydrophobic- rank were floated in 0.5 MNaCl. Moisture content in ity of the particles but also - since these particles coal is a function of its rank; it is very low for very hydrophobic bituminous coals, and is much higher for lower-rank coals which are much more hydrophilic. Since all these experiments were carried out at the same electrolyte concentration (0.5 MNaCl) these

(a)

Fig. 2 Effect of pH and pre-treatment on contact angle of methylated silica. (A) Silica coated in 0.04 M trimethyl chlorosilane solution; (B) Silica coated in 0.001 M solution; (C) Silica heated at 450℃ for 20 hrs before coating in 0.001 M solution. Fig. 1 Maximum flotation rate constants (salt flotation Bottom part: (o) Methylated hydrophobic silica; in 0.5M NaCl) versus moisture content for U.S. (+) Pure hydrophilic silica [after Laskowski and western coals (after Fuertenau et al., 1983)5). Kitchener (1969)6)]. (b)

KONA Powder and Particle Journal No.29 (2011) 5 carry electrical charge - the particle-to-bubble attach- enon. ment which depends on the energy barrier opposing the attachment (equivalent of activation energy in 2.2 Effect of electrolytes on bubble coalescence chemical reactions)8,9). The particles used in these ex- Flotation requires small bubbles and the flotation periments were hydrophobic (θ = 53 deg.), however rate constant is proportional to the bubble surface the tests were carried out over the pH range (6.1- area flux, Sb; (Sb depends not only on the amount of 6.5) where the zeta potential of the methylated quartz air pumped into a cell, it increases with decreasing particles is in the range of -35 – -40 mV. As seen from the size of bubbles). Dispersion of gas into bubbles Fig. 3, the rate of the flotation process carried out is the heart of the flotation process. In conventional under such conditions clearly depends on electrolyte flotation process the size of bubbles is determined by concentration and the correlation of the flotation rate bubble coalescence which can be entirely prevented and the energy barrier is quite good (Fig. 4)8). These by a frother10,11). findings explain very well the salt flotation phenom- Frothers are best characterized by their critical co-

100

40 Recovery, % Recovery, KCl, 10-3 M 20 KCl, 10-2 M KCl, 10-1 M KCl, 10º M 0 0 50 100 150 200 250 Time, sec

Fig. 3 The effect of KCl concentration on flotation of the methylated quartz particles (θ=53°) at pH 6.1 to 6.5 (after Laskowski et al., 1991)8).

0.1 30

25 2 1

- Rate constant Energy barrier 20

15 0.01 10

5 Rate constant (k), sec 0 Energy barrier, erg/cm

0.001 0.0001 0.001 0.01 0.1 1 KCl concentration, mole/l Fig. 4 The effect of KCl concentration on the flotation rate constant and the energy barrier; θ=53° at pH 6.1 to 6.5 (after Laskowski et al., 1991)8).

6 KONA Powder and Particle Journal No.29 (2011) alescence concentration (Cho and Laskowski10,11). As cess requirements: Fig. 5 shows, the critical coalescence concentration of MIBC in water is about 10 p.p.m. At the concen- (i) In the environment of high ionic strength, the trations higher then that the bubbles generated in energy barrier opposing attachment of the MIBC solutions are stable and do not coalesce. Bub- hydrophobic particles to bubbles is reduced ble coalescence can also be prevented by increasing making attachment possible; electrolyte concentration. As Fig. 5 shows, in con- (ii) At the same time, fine bubbles are generated centrated electrolyte systems the bubbles are stable under such conditions. and do not coalesce even in the absence of a frother. This is further illustrated in Fig. 6 13) which shows The quoted results explain satisfactorily the salt the results obtained while working with seawater. flotation phenomenon, the process in which inher- It is quite obvious that bubbles do not coalesce in ently hydrophobic particles are floated without the seawater and thus fine bubbles can be produced in use of any organic agents (we will return to the prob- seawater without addition of a frother. lem of flotation of anisotropic hydrophobic minerals The salt flotation then meets all the flotation pro- in salt solutions at the end of this publication).

2.5

Distilled water 2.0 50% saturated brine 100% saturated brine

1.5

1.0

0.5

0.0

Sauter mean bubble diameter, mm bubble diameter, mean Sauter 0 10 20 30 40 50 60 MIBC Concentration, ppm Fig. 5 Sauter mean bubble diameter as a function of MIBC concentration and electrolyte concentration (after Laskowski et al., 2003)12).[the term “brine” used here stands for saturated solution of KCl +NaCl (about 6 mole/L)].

1.6

0 ppm 2 ppm 1.4 4 ppm 6 ppm 8 ppm 10 ppm 15 ppm 1.2 30 ppm 50 ppm 100 ppm

1.0

0.8 Sauter mean bubble diameter, mm diameter, bubble mean Sauter

0.6 0 20 40 60 80 100 Seawater, % (v/v)

Fig. 6 Effect of MIBC frother on bubble size in seawater (Castro et al., 2010)13)

KONA Powder and Particle Journal No.29 (2011) 7 flotation of copper sulfides. In this area both the re- 3. Flotation with non-thio collectors sults of small scale flotation tests with pure minerals, In this section we are going to use the results as well as batch flotation tests with copper ores are published by Onoda and Fuerstenau14) and Yousef et available. al.15). The first paper is on the effect of inorganic ions Lekki and Laskowski in 197216) published a paper on flotation of quartz with cationic collector (dodecy- on the effect of saline mine water (14-17g/L NaCl) on lammonium acetate), and the second one is on flota- flotation of chalcocite, and on the flotation of copper tion of phosphate ore with anionic collector (sodium ores from the mines in Poland containing chalcocite oleate) in seawater. Both papers show that the flota- and different gangue. They showed that NaCl de- tion is possible in electrolyte solutions. presses flotation of chalcocite in a Hallimond tube Onoda and Fuerstenau14) demonstrated that the if the process is carried out without any frother. As influence of electrolyte concentration depends upon Fig. 7 demonstrates, in the presence of α-terpineol collector concentration. At low collector concentra- (frother) the trend is reversed and the flotation in tions the depressing effect of inorganic ions was salty water is better than in distilled water. clear, however at high collector concentrations where Alvarez and Castro17) studied in 1976 the flotation of the collector is strongly adsorbed through hydrocar- chalcocite, chalcopyrite, and pyrite in NaCl solutions bon chain interactions (hemi-micellisation), inorganic (0.5M), and in seawater. A pure sample of chalcocite ions were shown to have little effect on quartz flota- was floated with isopropyl xanthate and a significant- tion. ly lower floatability was observed in NaCl solutions in Yousef at al15) studied flotation in seawater of a neutral and acid pH range (Fig. 8). A narrow peak of calcareous phosphate ore, composed of francolite, recovery was observed in seawater with a maximum calcite and dolomite. It could be expected that in around pH 9, showing a poorer floatability compared the environment of seawater, the environment that with sodium chloride in the entire range of pH. Chal- contains both Ca2+ and Mg2+ ions, the use of anionic copyrite was more resistant to the effect of salinity. surfactant will require prior removal of these ions. It On the other hand pyrite was strongly depressed in was demonstrated that the use of sodium carbonate NaCl solutions and seawater by pH regulated with (soda ash) in combination with sodium silicate could HCl/NaOH, as is shown in Fig. 9. overcome the harmful effect of such bivalent cations The tests shown in Fig. 7 were conducted at pH of in the flotation of the phosphate ore with fatty acids 9.7. As Fig. 8 implies, this is the best pH for flotation in seawater. of chalcocite under such conditions. Fig. 7 indicates that the effect of NaCl strongly depends on α-terpineol concentration (a very strong frother); at α-ter- 4. Flotation of sulfides with thio-collectors pineol concentrations lower than about 10 mg/L the Quite a few papers have been published on the flotation in the presence of NaCl was worse than in

100 % 80

60 e recovery,

it 40 coc l Without NaCl a 20 NaCl, 5 g/L NaCl, 40 g/L Ch

0 0 20 40 60 80 100 Dterpineol concentration, mg/l Fig. 7 Flotation of chalcocite as a function of α-terpineol in NaCl solutions (EtX=3mg/g; pH=9.7).(Lekki and Laskowski, 1972)16).

8 KONA Powder and Particle Journal No.29 (2011) 100

Distilled water NaCl 0.5 M 80 Seawater

20 Chalcocite recovery, %

0 6 8 10 12 14 pH Fig. 8 Effect of pH (adjusted by NaOH/HCl) on the flotation of chalcocite in a Hallimond tube (15 mg/L IsopX and 10 mg/L amyl alcohol) (Alvarez and Castro, 1976)17).

100

Distilled water 60 NaCl, 0.5M Seawater

40 Recovery, % Recovery,

0 4 6 8 10 12 14 pH Fig. 9 Effect of pH (adjusted by NaOH/HCl) on the flotation of pyrite in a Hallimond tube (15 mg/L IsopX and 10 mg/L amyl alcohol). (Alvarez and Castro, 1976)17). distilled water, but it was better than in distilled water The presence of ions dissolved from Cu and Fe sul- at the higher α-terpineol concentrations. Different fides during conditioning with seawater and NaCl so- (weaker) frother was used in the other tests (Fig. 8 lutions was significant. The flotation of chalcocite was and 9) and the concentration utilized in these tests decreased when it was floated in NaCl solutions pre- was 10 mg/L. These concentrations are too close to viously conditioned with pyrite, suggesting the effect the border line and so these results do not lend them- of dissolved ions. The tests carried out with different selves to ready analysis. Interesting are the results ions revealed that Cu2+ ions were able to depress py- of the flotation tests with pyrite in Fig. 9. They show rite and chalcocite in 0.5 M NaCl , but the flotation of much poorer flotation of pyrite in seawater when chalcopyrite was not affected. See Fig. 10. compared with the flotation results in distilled water. It must be borne in mind, however, that the electro- 5. Flotation plant practice with the use of saline chemical conditions (galvanic effects) play a very water and seawater important role in the flotation of real sulfide ores, and that the single-mineral tests in such cases may be In the 1930’, small mills in Chile (e.g. Tocopilla) very different from those carried out with an ore. floated a chalcopyrite ore in seawater18). In 1975, pilot

KONA Powder and Particle Journal No.29 (2011) 9 100

Recovery, % Recovery, Cc in distilled water CPy in distilled water 20 Cpy in NaCl 0.5M Cc in NaCl 0.5M Py in NaCl 0.5M 0 0 1 2 3 4 5 6

Concentration of Cu2+, mg/l

Fig. 10 Effect of Cu2+ ions on the flotation of chalcocite, chalcopyrite and pyrite in distilled water and NaCl 0.5M solutions with IsopX and MIBC (for chalcopyrite α-terpineol was used as frother).

plant tests were reported for the flotation of a copper A very stable flotation was reported with the use sulfide ore in seawater from the Andacollo deposit. of seawater at a natural pH of 8 at Texada Mill (iron It was found that due to the frothing properties of operation with Cu, Au, Ag by-products) and also a seawater at pH 9.5, the rougher circuit operated well reduced consumption of reagents was reported by even without a frother19). Haig-Smillie (1974)23). At the Raglan concentrator At present, in a small mill (Planta Las Luces-Minera (Quebec, Canada), which processes a copper-nickel Las Cenizas S.A.-Taltal, Chile) a copper sulfide ore ore in salty water (30,000 p.p.m.), a frother is not em- (mainly chalcocite) is successfully floated with sea- ployed at all24). In Australia, at the Mt Keith operation, water by using around 36% of fresh seawater and 64% a low grade nickel ore is floated in hyper-saline pro- of recycled seawater from the tailings dam20). cess water, at 60,000–80,000 ppm of salts25, 24, 26)). Simi- Recently, a new large flotation plant (95,000 tpd) is larly, at Batu Hijau, a copper-gold ore concentrator in operating with seawater in Chile. It is the Esperanza Indonesia, the seawater usage was also accompanied plant (Antofagasta Minerals S.A.), which is producing by a reduction in reagent consumption when floating a bulk Cu-Au concentrate21). It is planned to use 70% at pH 8.5-9.015). of recycled seawater, as the pilot plant tests showed that this is better for Mo and Au recovery. 6. Flotation of inherently hydrophobic anisotro- Other base metal sulfide ores (Cu-Pb-Zn; Pb-Zn) pic minerals in salt solutions can also be successfully floated by xanthates22) in seawater and in water with increased electrolyte con- In case of isotropic minerals, all sides of the crystal centrations. In seawater and in salty water, a lower are created by breaking the same type of bonds with consumption of reagents in bulk flotation – particu- resulting mineral surfaces being homogeneous and larly frother- was noted. However, experiments car- having identical electrical charge. For instance, in ried out with synthetic seawater, showed that certain the case of quartz, new surfaces formed when larger frothers increased the volume of the froth (Dowfroth pieces of quartz are crushed are created by breaking type), and others decreased it (Flotol). At the same identical Si-O bonds. As a result all the new quartz time, the froth produced in seawater and polymetallic surfaces have the same composition. ores, easily carries gangue slimes, and much atten- The sides of anisotropic mineral crystals are cre- tion must be paid to cleaning stages. Lime is often ated by breaking different bonds – one, which is necessary for froth control. However, with excess of formed by the rupture of van der Waals bonds and lime the froth could be too heavily loaded and of in- the other, which is formed by rupture of strong ei- sufficient volume. Fresh water is often used as wash ther ionic or covalent bonds. The minerals like mo- water in the concentrate filters to remove excess of lybdenite and graphite belong to this group. Fig. 11 chloride ions from the concentrates. shows their crystallo-chemical structure. These min-

10 KONA Powder and Particle Journal No.29 (2011) erals have a sheet-structure (which is also referred such conditions. Because inherently hydrophobic to as laminar crystal structure). The van der Waals minerals are anisotropic the salt flotation of these bonds between subsequent layers are weak, and they minerals is not a clear cut case. are easily broken during crushing/grinding with It has been reported that the ores of native sulfur, the newly exposed surfaces being hydrophobic. The and also talc, can be floated in salt solutions29). The edges of such minerals are, however, hydrophilic. So, salt flotation of molybdenite has not been extensively the properties of such particles are different at the studied but this topic is extremely important if seawa- basal planes (faces) and at the edges, also electrical ter is to be used in processing of Cu-Mo ores. Molyb- charge at these surfaces differs. Since the ratio of denite response to increasing salt concentration will planes-to-edges changes with the particle size (it de- be here discussed using Castro et al’s30) unpublished creases with decreasing particle size) these particles, results. depending on particles size, exhibit different prop- Flotation tests were carried out in a Partridge- erties27,28); finer particles are more hydrophilic than Smith micro-flotation cell with a sample of cleaned coarse particles. Therefore, the surface properties molybdenite concentrate, in the presence of 10 mg/ measured on large polished specimens may be very L isopropyl xanthate and 10 mg/L MIBC, and pH ad- different from the properties of fine particles. justed either by NaOH or CaO. These results reveal As it is has been shown in the first part of this pa- that while low concentrations of NaCl (below 0.1 M) per, hydrophobic particles of bituminous coal float do not affect floatability of molybdenite, over the 0.1 quite well in concentrated electrolyte solutions (salt – 1 M concentration range depression is appreciable. flotation). This flotation, however, depends on wet- The loss of molybdenite floatability in alkaline solu- tability of the floated particles, and low rank coals tions is strongly increased by NaCl addition. The de- which are not that hydrophobic float poorly under pressant effect of CaO is greatly increased by NaCl.

Fig. 11 Crystallo-chemical structure of graphite and molybdenite.

100

70 pH 9, NaOH

Molybdenite recovery, % recovery, Molybdenite pH 9, CaO

60 1e-5 1e-4 1e-3 1e-2 1e-1 1e+0 NaCl concentration, M Fig. 12 Effect of NaCl concentration on the flotation of molybdenite at pH 9 adjusted either by NaOH or CaO30).

KONA Powder and Particle Journal No.29 (2011) 11 100

60 pH 10, NaOH Molybdenite recovery, % recovery, Molybdenite pH 10, CaO

50 1e-5 1e-4 1e-3 1e-2 1e-1 1e+0 NaCl concentration, M Fig. 13 Effect of NaCl concentration on the flotation of molybdenite at a pH of 10 adjusted either by NaOH or CaO30).

50 (º) e, e,

l 40

Edge without CaCl2

ang 30 t Face without CaCl2

ac Face with 0.001 M of CaCl2 t 20 Face with 0.15 M of CaCl2 on

C 10

-10 4 6 8 10 12 14 pH

31) Fig. 14 Effect of pH on contact angle measured on faces and edges of MoS2 crystal (López-Valdivieso et al., 2006) .

These experiments were carried out in the absence later picture may well explain why the salt flotation of of a non-polar collector (diesel oil or kerosene), and it molybdenite is so different from the salt flotation of is reasonable to expect an improvement of floatability bituminous coal. when such a collector is used. Fig. 14 shows that the hydrophobicity of basal As more recent tests on the surface properties of planes further decreases in alkaline solutions, and molybdenite carried out with the use of Atomic Force especially in the presence of Ca2+ ions. Based on the Microscopy revealed31), the common interpretations AFM picture which indicates that the molybdenite may be too simplified in the case of this mineral. We basal surfaces are very heterogeneous it is possible are used to depict the basal planes of anisotropic to explain these phenomena. If thiomolybdate species minerals as hydrophobic and homogenous. The AFM are responsible for the electrical charge at the edges, picture of molybdenite surface obtained by cleaving these edges also exist on the “planes” and the effect confirmed Komiyama et al’s findings32) that molybde- of Ca2+ ions can be explained by formation of calcium nite faces are not fully hydrophobic and have terraces thiomolybdate33). and rims of nanometric size. Therefore, the basal planes are not really planes, because these are highly 7. Conclusions heterogeneous surfaces with a lot of nano-size topo- graphic structures (e.g., crater structures). And such 1．Because hydrophobic surfaces usually carry elec- a surface is not very hydrophobic (Fig. 14). This trical charge, the attachment of the hydrophobic

12 KONA Powder and Particle Journal No.29 (2011) particles to bubbles is opposed by an energy , Moscow, (Russian text). barrier. With increasing ionic strength such a 5) Fuerstenau, D.W., Rosenbaum, J.M. and Laskowski, barrier is reduced and flotation of hydrophobic J.S. (1983): Effect of surface functional groups on the flotation of coal. Coll. & Surf., Vol. 8, pp. 153-164. solids (e.g. bituminous coal) is very good in 0.3 – 6) Laskowski, J.S. and Kitchener, J.A. (1969): The hydro- 0.5 M NaCl solutions. Bubble coalescence, which philic-hydrophobic transition on silica, J. Coll. Interf. determines bubble size in flotation systems, is Sci., Vol. 29, pp. 670-679. prevented at such salt concentrations, reducing 7) Lamb, R.N. and Furlong, D.N. (1982): Controlled the bubble size (similarly to a frother). These are wettability of quartz surfaces, J. Chem. Soc., Faraday the principles on which the so-called salt flotation Transactions I, Vol. 78, pp. 61-73. process is based. 8) Laskowski, J.S., Xu, Z. and Yoon, R.H. (1991): Energy 2．In salt solutions, flotation of molybdenite is not as barrier in particle to bubble attachment and its effect on flotation kinetics, Proc. 17th Int. Mineral Process- good as flotation of bituminous coal. This may be ing Congress, Dresden, pp. 237-249. explained by anisotropic properties of molybde- 9) Laskowski, J.S. (1986): The relationship between float- nite and heterogeneous nature of the plane sur- ability and hydrophobicity, “Advances in Mineral Pro- faces, as revealed by recent AFM studies. cessing” (P. Somasundaran, ed.), SME, Littleton, pp. 3．Flotation of quartz with cationic collector (dodecy- 189-208. lamine) in not affected in concentrated electrolyte 10) Cho, Y.S. and Laskowski, J.S. (2002): Effect of flotation solutions at high collector dosages that is over frothers on bubbles size and foam stability, Int. J. Min- the concentration range over which this collector eral Processing, Vol. 64, pp. 69-80. 11) Cho, Y.S. and Laskowski, J.S. (2002): Bubble coales- adsorbs in the form of hemi-micelles. cence and its effect on dynamic foam stability, Can. J. 4．Flotation of phosphate ores with fatty acids (an- Chemical Engineering, Vol. 80, pp. 299-305. 2+ 2+ ionic collector) requires removal of Ca and Mg 12) Laskowski, J.S., Cho, Y.S. and Ding, K. (2003): Effect ions, if seawater is used in the flotation. of frothers on bubble size and foam stability in potash 5．The detrimental effect of lime (calcium ions) on ore flotation systems. Can. J. Chemical Engineering, floatability of molybdenite is higher in sodium Vol. 81, pp. 63-69. chloride solutions and seawater than in fresh wa- 13) Castro, S., Venegas, I., Landero, A. and Laskowski, J.S. (2010): Frothing in seawater flotation systems, Proc. ter. XXV Int. Mineral Processing Congress, Brisbane, pp. 6 Copper sulfide minerals, such as, chalcocite and ． 4039-4047. chalcopyrite float well, both in salty water and 14) Onoda, G.Y. and Fuerstenau, D.W. (1964): Amine seawater in the pH range of 8.0-9.5; however, the flotation of quartz in the presence of inorganic electro- flotation recovery abruptly decreases at pH high- lytes. Proc. 7th Int. Mineral Processing Congress (N. er than 10, particularly in the case of chalcocite. Arbiter, ed.), Gordon and Breach, pp. 301-306. 7．The flotation of pyrite in sodium chloride solu- 15) Yousaf, A.A., Arafa, M.A., Ibrahim, S.S. and Abdel tions and seawater decreases with increasing Khadek, M.A. (2003): Seawater usage in flotation for minerals beneficiation in arid regions, Proc.22nd Int. pH more than in fresh water. However, when Mineral Processing Congress (Lorenzen and Brad- molybdenite is present in a sufide ore, it is rec- shaw, eds.), Cape Town, Vol. 2, pp. 1023-1033. ommended that lime be replaced by other pyrite 16) Lekki, J. and Laskowski, J.S. (1972): Influencia del depressant, able to operate at lower pH, in order NaCl sobre la flotación de minerales sulfurados de co- to prevent Mo losses. bre, Minerales, Vol. 27, No. 118, pp. 3-7 (Spanish text). 17) Alvarez, J. and Castro, S. (1976): Flotation of chalcocite and chalcopyrite in seawater and salty water, Proc. References IV EncontroNacional de Tratamento de Minerios, São José Dos Campos, Brazil, Anais Vol. 1, pp. 39-44 (Span- 1) Greenlee, L. F., Lawlerb, D.F., Freeman, B.D., Mar- ish text). rotc, B. and Moulinc (2009): Reverse osmosis desali- 18) Burn, A.K. (1930): The flotation of chalcopyrite in sea- nation: water sources, technology, and today’s chal- water, Bulletin Institution of Mining and Metallurgy, lenges. Water Research, Vol. 43, pp. 2317–2348. Nº 314. 2) Gaska, R.A., Goodenough, R.D. and Stuart, G.A. 19) Morales, J.E. (1975): Flotation of the Andacollo’s ore (1965): Ammonia as a solvent, Chem. Eng. Progress, in pilot plant by using seawater. Minerales, nº 130, Vol. 61, pp. 139-144. Vol.30, pp. 16-22. 3) Klassen, V.I. and Mokrousov, V.A. (1963): “An Intro- 20) Monardes, A. (2009): Use of seawater in grinding- duction to the theory of flotation”, Butterworths, Lon- flotation and tailing dam operations at Las Luces plant don. (Minera Las Cenizas-Taltal), Proc. XI Simposium on 4) Klassen, V.I. (1963): “Coal flotation. Gosgortiekhizdat”

KONA Powder and Particle Journal No.29 (2011) 13 Mineral processing (MOLY-COP 2009), Puyehue, R.B. Grieves, eds.), AIChE Symposium Series, 150, Chile, (Spanish text). Vol. 71, pp. 183-188. 21) Parraguez, L., Bernal, L. and Cartagena, G. (2009): 28) Castro, S.H. and Correa, A. (1995): The effect of Chemical study for selectivity and recovery of metal particle size on the surface energy and wettability of sulfides by flotation using seawater. Proc. VI Inter- molybdenite, Proc. 1st UBC-McGill Int. Symposium national Mineral Processing Seminar (PROCEMIN on Processing of Hydrophobic Minerals and Fine Coal 2009), Santiago, pp. 323-333. (J.S. Laskowski and G.W. Poling, eds.), Met. Soc. of 22) Rey, M. and Raffinot, P. (1966): Flotation of ores in CIM, pp. 43-57. sea water: High frothing; soluble xanthate collecting, 29) Laskowski, J.S. (1966): Flotation of inherently hydro- World Mining, June, pp. 18-21. phobic minerals in concentrated solutions of inorganic 23) Haig-Smillie, L.D. (1974): Sea water flotation, Proc. 6th salts, Trans. of Silesian University of Technology, Min- Annual Meeting of Canadian Mineral Processors, pp. ing, Issue no. 16, (Polish text). 263-281. 30) Castro, S., Jara, C., Muñoz, M. and Laskowski, J.S., 24) Quinn, J.J., Kracht, W., Gomez, C.O., Gagnon, C. and Floatability of molybdenite in aqueous sodium chlo- Finch, J.A. (2007): Comparing the effect of salts and ride solutions (Unpublished). frother (MIBC) on gas dispersion and froth proper- 31) López-Valdivieso, A., Madrid-Ortega, I., Reyes-Bahena, ties, Minerals Engineering, 20, pp. 1296-1302. J.L., Sánchez-López, A.A. and Song, S. (2006): Propie- 25) Senior, G.D., and Thomas S.A. (2005): Development dades de la interface molibdenita/solución acuosa and implementation of a new flowsheet for the flota- y su relación con la flotabilidad del mineral. Proc. tion of a low grade nickel ore, International Journal of 16thCongreso Int. de MetalurgiaExtractiva, Saltillo, Mineral Processing, 78, pp. 49-61. Mexico, pp. 299-310. 26) George, C.W. (1996): The Mt. Keith operation, Proc. 32) Komiyama, M., Koyohara, K., Fujikawa, T., Ebihara, Nickel ́96 Mineral to Market (E.J. Grimsey and I. T., Kubota, T. and Okamoto, Y. (2004): Crater struc- Neuss, eds.), Austral. Institution of Mining and Metal- ture on a molybdenite basal plane observed by ultra- lurgy, Melbourne, pp. 19-23. high vacuum tuneling microscopy and its implication 27) Chander, S., Wie, J.M. and Fuerstenau, D.W. (1975): to hydrotreating, J. Molecular Catalysis A:Chemical, On the native floatability and surface properties of Vol. 215, pp. 143-147. naturally hydrophobic solids, Advances in Interfacial 33) Fuerstenau, D.W. and Chander, S. (1972): On the natu- Phenomena of Particulate/Solution/Gas Systems; Ap- ral floatability of molybdenite. Trans. SME, Vol. 255, plications to Flotation Research (P. Somasundaran and pp. 62-69.

14 KONA Powder and Particle Journal No.29 (2011) Author’s short biography

Sergio Castro Sergio Castro is a Professor of mineral processing (flotation and surface chemistry) in the Department of Metallurgical Engineering at the University of Concep- ción-Chile. He received a B. Sc. degree in Chemistry from the University of Chile in 1972, with subsequent graduate studies on colloid and surface chemistry in mineral processing. He joined the Engineering Faculty of the University of Concep- cion in 1974. Visiting scientist in the Department of Mining and Mineral Process Engineering, at the University of British Columbia-Canada, in 1985. His research interests are in fundamentals and applied research on copper and molybdenum flotation. His research has lead to over 100 technical papers and, as editor, 8 technical books. In 2008 he was elected as a member of the Council of the International Mineral Processing Congress (IMPC).

Janusz S. Laskowski Professor Janusz Laskowski obtained all his degrees, including Ph. D. in 1963, from the Silesian University of Technology, Gliwice, Poland. His education also included one year stay as a postgraduate student with Department of Colloid Chemistry, Lo- monosov University, Moscow, and one year stay as a post-doctoral fellow with Dr. J.A. Kitchener at Imperial College, London. He was associate professor of mineral processing at Silesian University of Technol- ogy until 1972, and then was appointed professor at Wroclaw Technical University. In 1979, he chaired the 13th Int. Mineral Processing Congress in Warsaw. Since 1982 until 2001 (when he retired) he was professor of mineral processing at the Depart- ment of Mining Engineering, University of British Columbia, Vancouver, Canada. He spent sabbatical leaves with Departamento de Minas, Universidad de Chile, Santiago (1971/72); Department of Materials Science and Mineral Engineering, University of California, Berkeley (1981); Surface Chemistry Group at Ecole Natio- nale Superiéure de Géologie, Nancy, France (1988/89) and Department of Chemi- cal Engineering, University of Cape Town, South Africa (1996). After retiring in 2001, Janusz Laskowski remains active in academic research and teaching. He currently pursues collaborative research with the Universidad de Concepcion in Chile, Universidad Autónoma de San Luis Potosi, Mexico, CSIRO Institute in Melbourne, and University of Cape Town in South Africa. He has au- thored 260 papers in journals and conference proceedings, two books, “Coal Flota- tion and Fine Coal Utilization” (Elsevier 2001) and “Physical Chemistry in Mineral Processing” (Slask, Poland, 1969) which updated was translated into Spanish in 1974 “Fundamentos Fisicoquimicos de la Mineralurgia” (Universidad de Concep- cion, 1974). Edited and co-edited several volumes including the Proceedings of the 13th Int. Mineral Processing Congress, Warsaw, 1979. Over the period from 1984 to 2005 was Editor-in-Chief of Coal Preparation international journal. Dr. Laskowski was elected a Fellow of Canadian Institute of Mining in 1995. He has been the recipient of many professional awards: the Arthur F. Taggart Award from the Society of Mining Engineers in 2000; the Alcan Award of the Metallurgical Soci- ety of CIM in 2004; the Lifetime Achievement Award in 2008 at the 24th International Mineral Processing Congress, Beijing; and the Antoine Gaudin Award of SME/ AIME in 2010. On December 4, 2009, he received the Medalla Rectoral and was deco- rated as a Distinguished University Visitor by Chile’s Universidad de Concepción.

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