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3 ABSTRACf Three major types of solution chemical equilibria involving flotagents (i.e. flotation reagents such as collectors, frothers and modifiers), minerals and solution playa crucial role in determining the behavior of complex flotation systerm. Minerals of phosphates (apatite and francolite), tungsten (wolframite and scbeelite) and associated carbonates (calcite and dolomite) are sparingly soluble in aqueous solution and form dissolved mineral species in bulk solution. Such dissolved species interact with mineral solids, often resulting in surface conversion of the minerals. In addition, they can interact with various flotagents and lead to surface or bulk precipitation and loss of selectivity in the flotation. Relevant solution equilibria of such sparingly soluble minerals and their interactions with oleic acid and structurally modified reagents were determined in this study using a multi-pronged experimental approach. Methods to manipulate and control the solution chemical equilibria and thus achieve selectivity in flotation systems are discussed. Introduction Pbysico-chemical interactions which have a governing role in flotation systems are detennined by properties of a number of system components including minerals, flotagents (surfactants, inorganic/organic/polymeric additives), water and air bubbles/oil droplets. Most of these components have their own characteristic chemical equilibria in aqueous solution which often become exceedingly complex in the presence of one another. These reactions include self association of surfactants, dissolution of the solids, hydrolysis/ complexation/precipitation of dissolved mineral species and their interactions with various flotagent species in the solution. In addition to adsorption of various species. several reactions similar to the above bulk reactions can occur at the solid-liquid interface and can have a governing role in determining the ultimate flotagent adsorption and flotation. Specifically surface chemical alterations resulting from adsorption or surface precipitation of flotagents and the orientation of such species at the solid-liquid interface will determine the hydrophobicity of the mineral surface. A considerable amount of work has been done in the past on the flotation of complex phosphate rocks containing carbonaceous gangues such as calcite, magnesite and dolomite [Moudgil and Somasundaran, 1986; Hanna and Somasundaran, 1976; Lawver et al, 1982]. The flotation process in these cases is complicated due to similarities in the chemical composition and the semi-soluble nature of the constituent minerals. Poor selectivity is often obtained in many of these flotation schemes. Our previous work has shown that surface conversion and dissolved mineral species-flotagent interactions are two major reasons for the poor selectivity in phosphate flotation separation [Somasundaran et ai, 1985; Somasundaran and Ananthapadmanabhan, 1986; Xiao et al, 1987]. It is, therefore, helpful to understand various solution chemical equilibria in these systems in order to improve the selectivity in flotation. In this paper, three types of solution chemical equilibria of flotagents and minerals and implications to flotation are examined. 1. Solution Equilibria of Flotagents In general. both anionic and cationic type surfactants are widely used in flotation. These include carboxylates, alkyl sulfonates. alkyl sulfates, alkyl amines and chelating agents such as xanthates and oximes. Most minerals. with the exception of sulfides, require long chain surfactants for their flotation. The behavior of long chain surfactants in solution is detennined by the properties of the polar heads and hydrophobic tails and the resultant tendency of the solvent to accommodate them under various conditions. Hydrolyzable surfactants such as oleic acid and amine can undergo special association interactions that can influence their adsorption and flotation properties. For example, oleic acid undergoes dissociation to form ions (R-) at high ph values and exist as neutral molealles (RH) at low ph values [Somasundaran, 1976; Ananthapadmanabhan and Somasundaran, 198). In the intermediate region. the ions and neutral molecules can associate to form ion-molecule complexes. As the collector concentration is increased, micellization or precipitation of the collector can occur in the solution. In addition, surfactant species can associate to form other aggregates such as dimers (R;-) in premiceuar solutions. Since the surface activities of these species

4 k can be marketedly different from those of each other, flotation of minerals in their presence can be expected to be dependent upon solution conditions such as ph. The solution equilibria of oleic acid are shown as below [Ananthapadmanabhan and Somasundaran, 1988): HOl(l) = H1(aq) PKsol = 7.6; HOl(aq) = H PKa = 4.95; 21- = (1>22- p = -3.7; HOl + 1- = (Ol>2H- PKad = The species distribution of oleic acid as a function of ph based on the above equilibria is shown in Fig.!. It can be seen from this figure that (a) ph of precipitation of oleic acid at the given concentration is 7.45; (b) activities of oleate monomer and dimer remain almost constant above the ph of precipitation and decreases sharply below it; (c) the activity of the acid-soap (R2H-) exhibits a maximum in the neutral ph range. It was found from surface tension experiments (Fig.2) that oleate solutions exhibit a minimum in surface tension in the neutral ph range, suggesting increased surface activities of acid-soap species in this range. S91ution equilibria of cationic collectors such as dodecylamine are similar to that of oleate [Ananthapadmanabhan et ai, 198]. The species distribution of dodecylamine at a concentration of I.Ox1-5 M is shown in Fig.3. In this case the neutral molecule (RNHz) precipitates in the high ph range and ionic species, RNH3 + and (RNH3)j+, dominate in the acidic ph range. Again, ion-molecule complex exhibits a maximum as ph of the solution is changed. Strongly ionizable surfactants such as dodecylsulfonate may not form acid-soap in significant amounts, but can be expected to form dimers (Rj-). The calculated distribution of various sulfonate species shown in Fig.4 indicates the presence of Rj- throughout the ph region, but acid - soap and neutral acid are present in comparable proportions only at very low ph values [Ananthapadmanabhan, 198]. 2. Mineral - solution Equilibria When mineral particles are contacted with water, they will undergo dissolution, the extent of which is dependent upon the type and concentration of chemicals in solution. The dissolved mineral species can undergo further reactions such as hydrolysis, complexation, adsorption and even surface or bulk precipitation. The complex equilibria involving all such reactions can be expected to determine the interfacial properties of the particles and their flotation behavior. For example, in the case of phosphate minerals such as apatite, calcite and dolomite under atmospheric condition, the dissolution of these minerals in water will be followed by ph-dependent hydrolysis and complexation of the dissolved species (Somasundaran et ai. 1985; Xiao et al., 1989]. The species distnbution diagrams calculated from various solution equilioria and stoichiometric restrictions are shown in Fig.5 a-c. For both calcite and apatite, (Fig.5 a-b), Ca2+ is the most predominant species in the acidic ph range while carbonate species of CO32- and HCO3- predominate in the basic ph range. The major phosphate species from apatite are H2PO4.' HPO42- and PO43- depending on ph. For dolomite, Ca2+ and Mg2+ species are the dominant species below ph 1 while carbonate and hydroxyl species of Ca and Mg become predominant above ph 1. The solubility of dolomite in water decreases with increase in ph. For the above sparingly soluble minerals. the effect of dissolved species on interfacial properties can be marked, as seen in Fig.6 for zeta-potential data obtained for calcite-apatite in water and in the supernatants of each other [Amankonah and Somasundaran, 1985]. When apatite is contacted with calcite supernatant, zeta-potential of it is seen to shift to that of calcite in water and vice verse, suggesting surface conversion of apatite to calcite and calcite to apatite respectively. Implications of such conversion on selective flotation is to be noted. In flotation, the presence of flotagents such as oleate or other collectors actually complicates the system behavior even further and this aspect is discussed in a subsequent section. Surface conversion due to reactions of the dissolved species with the mineral surface can be predicted using thermodynamic stability diagram for heterogeneous mineral systems based on relevant mineral dissociation equilibria. This is illustrated in Fig.7 for the calcite / apatite / dolomite system. The activity of Ca2 + species in equilibrium with various solid phases shows that the singular point for calcite and apatite is 9.3. Above this ph. apatite is less stable than calcite and hence conversion of apatite surface to that of calcite can be expected in calcite. apatite system. Similarly, the calcite-dolomite and apatite-dolomite singular points occur at ph 8.2 and 8.8, respectively.

5 Solution conditions for the conversion of apatite to calcite by dissolved species can be more readily identified by considering the chemical reaction responsible for the process: Cal (PO4)6(OH)2 (s) + 1 CO32- = 1 Caco3 (s) + 6PO H- It can be seen that. depending on the ph of the solution, apatite can be converted to calcite if the total carbonate in solution is above a certain critical level. In fact. the amount of dissolved carbonate from atmospheric does exceed that required to convert apatite to calcite under high ph conditions. Although the kinetics of such transformations is not known. such reactions can be important in determining the surface characteristics of minerals. The presence of surface converted layer on apatite or calcite has been supported by the electrokinetic results given in Fig.6 and surface analysis (Somasundaran et al. 1985). Tungstun minerals such as wolframite and scheelite are other examples of sparingly soluble mineral Systems. The major solution equilibria of wolframite (Mn. Fe)WO4 and scheelite CaWO4 are shown as follows (Wang et ai., 1989): a) MnWO"s,.,..Mn'. WO:- K.., = 1-'." Mn'. +OH-MnOH. K, -1'.'. Mn'. +ZOH-Mn(OH)1 c,.) K: -1'.' Mnl. +3H-,..a=.Mn(OH); K.-IO'.' Mn" + 4H-Mn(OH)- K.. -1'" 2Mn'. +OH-MnIOHI' K. -1'." 2Mn:. +31-(-Mn.(OH). K. -1,..a. Mn(OH):.o,Mn:...2J(- K, = 1-1., J{. + 'VO-HWO; K\' - 1'.' H'.;.HWO-;:.-*-H.WO".,) K-lO WO.(,.+H,O2H'+WOi- Km-IO-'' b) P8W'.,.)..Fe'. + WO:- K - 1-t I Fe'. + OH-FeOHo K - to..' Fo'. +2OH-Fc(OH),(.,) K; * 1". Fel.+31{-Fe(Off). K.-lo,t., Fe"+.Ol{-Fc(OJf}- K: 8 JO".. Fe(Off)I,.,Fc" +21{- K.. = 1-'." c) CaWO",..Ca:' +\,"Oi- K IO-" Ca:o+OH-..CaOH-' Ca:- +ZOH-C.(OIf): K;-IO'..' (' K = 1'." Ca(OH)"olCa'o +OH- Ko... 1-"" The species distribution diagrams callat-rl from these equilibria are shown in Fig.8 a-c. For wolframite, both Mn2+ and Fe2+ are dominant species for ph < 2.8. The mineral surface is positive due to the presence of more MnOH+ and FeOH+ than HWO4- till both become equal around ph = 2.8 (i.e. PZC). When ph increases to 4.8, both HWO4" and WO42- will predominate and the surface exhibits a negative potential. It is interesting to note that there is a "near PZC region" (slightly negative) where predominant species Mn2+, Fe2+ and WO42- become equal to, each other in the ph range between 6. and 93. Regardless of the change in the Mn/Fe ratio, the "near PZC region" remains around neutral ph. When ph is > 93, WO42- sharply increases and makes surface more negative. Experimental results obtained (Fig.9) are in good agreement with the above theoretical prediction. It is evident from this discussion that dissolution equilibria of sparingly soluble minerals can play a major role in determining the surface properties of mineral particles. Selective hydrophobization of such particles using surfactants is the key to flotation separation. Hence, interactions between dissolved mineral and flotagent species and their role in flotation are discussed next. 3. Minerai - flotagent Equilibria Chemical equilibria in aqueous solutions containing both minerals and flotagents can be expected to be rtluch more complex than in either of the individual systems. In addition to flotagent adsorption at the solidliquid interface. interactions of the dissolved mineral species with various flotagent species in solution can be expected. It may be noted that the process of adsorption in many cases shows several similarities to bulk interactions. Also in a number of cases, the solution conditions for the so-called chemisorption correspond to that for the precipitation of the surfactant in the interfacial region. suggesting that chemisorption may in fact be a surface precipitation phenomenon. For example, depletion isotherms of oleic acid on, francolite and dolomite are shown in Fig.l (Xiao et al, 1988; Xiao et at. 1989). Both francolite and dolomite show two-region linear isotherms with a change in the slope at a concentration of about 1-4 kmol/m3. At a concentration higher than 1.7 x 1-4 kmol/m3, slopes of both curves are higher indicating that more oleate species is depleted from the mineral slurries. Simultaneous analysis of dissolved mineral species in the supernatants of samples used in adsorption experiments (Fig.ll a-b) shows that there is a sharp decrease in the concentration of both Ca and Mg species in solution when oleate concentration exceeds

6 4. 1. x 1-5 kmol/m3 in the case of francolite (Fig.lla) and 3. x 1-5 kmol/m3 in the case of dolomite (Fig.11b). This suggests that bulk precipitation of calcium and magnesium species with oleate can occur under such conditions. As seen from these results. in the low concentration range «1-4 kmol/m3), the linear rise in the isotherm suggests that oleate adsorption on both minerals may occur predominantly due to chemical bonding on surfaces without forming any precipitation. At an intermediate concentration around 1-4 kmol/m3, the solubility limit of Ca and Mg oleates can be reached in the interfacial region but not in the bulk solution. suggesting the occurrence of surface precipitation on both the minerals. In the high concentration range (> 5 x 1-4 kmol/m3), oleate depletion in the case of both the minerals may be predominated by the precipitation of Ca and Mg species with oleate, both on the mineral surface and in the bulk solution (Xiao. et ai, 1989; Xiao, 199). Major chemical equilibria for the precipitation of Ca and Mg species and oleate can be described as follows [Somasundaran and Wang, 1984; Leja, 1982]: Ca = Ca(Olh l2 = 3.81xl-13; Mg = Mg(1)2 KMgol2 = 158xl-11. Formation of Ca and Mg oleates on the mineral surfaces as well as in the bulk solution can lead to surface and bulk precipitation. The onsets of the precipitation of CaOl2 and MgOl2 are calculated from their solubility products in dolomite/oleate and francolite/oleate systems and are marked in Fig.11 a-b. The oleate concentration at the onset of precipitation calculated from the solubility data for CaOl2 and MgOl2 and that obtained by dissolved species analyses are in good agreement with each other. The role of surface and bulk precipitates in mineral flotation can be elucidated by correlating onsets of flotation and surface precipitation in dolomite/francolite systems. Preferential partitioning of the surfactant in the bulk precipitate as opposed to surface precipitate appears to deleteriously affect the flotation of dolomite and francolite. Flotation behavior of francolite and dolomite was studied as a function of oleate concentrations (Fig.l2a) and ph (Fig.12b). It appears from Fig.l2a that the floatability of both dolomite and francolite is quite similar and very sensitive to the oleate concentration. It can be also observed from Fig.12b that selective flotation of francolite is possible above ph 9. or dolomite below ph 5.. However, selective flotation was absent in the case of flotation of a binary mixture of dolomite md francolite (Table 1). A major problem in oleate flotation is the low solubility of oleic acid and its poor tolerance for multivalent cations. It has been found that such precipitation can be avoided by using ethoxylated sulfonates as collectors in the case of flotation of dolomite and francolite [Xiao et ai, 1987]. Adsorption isotherms of octylbenzenesulfonate (as a reference) and ethoxylated sulfonate on dolomite and francolite are shown in Fig. 13 a-b. The isotherms of octylbenzenesulfonate on both minerals are S shaped with four regions and those of ethoxylated sulfonate are typical Langmuir type with only rising part and plateau region. The comparison of the adsorption isotherms of the two surfactants shows that ethoxylated sulfonate adsorbs more than octylbenzenesulfonate on the minerals before the plateau is reached, but there is a significant reduction of its adsorption in the plateau region of the isothemt. The reduced plateau adsorption may be due to specific interaction of ethoxyl groups with the surface, or steric effects (interference of bulky hydrated ethoxyl groups with close packing of the alkyl chains ). Analysis of dissolved Ca and Mg species in the supernatant (Figs.I4 and 15) shows that there precipitation of Ca disulfonate above a concentration of 1. x 1.3 M octylbenzenesulfonate and not that of Mg disulfonate (Fig.14 a-b). Redissolution of Ca disulfonate precipitates occurs around 3 to 4 x 1.3 M octylbenzenesulfonate. Redissolution is attributed to solubilization of Ca disulfonate by micelles [Somasundaran et ai, 1984]. However, the levels of Ca and Mg species in dolomite and francolite / ethoxylated sulfonate systems remain constant over the tested concentration range, indicating the absence of any precipitation (Fig.I5 a-b). This is attributed to the increased salt tolerance of the surfactant due to the addition of ethoxyl groups into the alkyl chain of the sulfonate. With a mixture of oleic acid and ethoxylated sulfonate as collector, the level of oleate (7.Oxl-6 M) was selected in such a manner that Ca oleate precipitation was avoided (see Fig.II). Dolomite (77 % grade and 92 % recovery) can be floated selectively but only in the acidic range from a binary mixture of dolomite and francolite (1:1) (Table 1). The reagent consumption is

7 s. found to be reduced by half when oleate and ethoxylated sulfonate mixtures are used (total concentration of 8.OxlO-5 M). Factors which can be manipulated to further enhance selectivity include ph, flotagent concentration. ionic strength. temperature and conditioning. The role of chemicals can be different in different systems and it may include alterations of surface properties of solids and complexation of ions/species which causes unintentional activation of the solid or precipitation of the surfactant. Conclusions Solution chemistry of sparingly soluble minerals and flotagents in flotation systems is complex. and governs the flotation behavior of minerals in mixed systems. Dissolution of phosphate minerals such as apatite and francolite. tungsten minerals such as wolframite and scheelite and associated minerals such as calcite and dolomite mainly depends upon the solution conditions such as ph and ionic strength. forming dissolved mineral species. The resultant dissolved species can interact with mineral solids leading to surface conversion of the minerals and can also interact with oleate leading to surface or bulk precipitation. An examination of adsorption and flotation in a number of systems such as oleate or sulfonate/francolite or dolomite shows that such precipitation can be controlled by selecting appropriate flotagents and solution conditions to achieve better selectivity in the flotation. Acknowledgement The authors acknowledge the support of the Florida Institute of Phosphate Research and the National Science Foundation. References Ananthapadmanabhan, K.P. and Somasundaran. P., 198, Interfacial Phenomena in Mineral Processing (B. Yarar ed.), Engineering Foundation. N. Y., Ananthapadmanabhan. K.P. and Somasundaran. P. 1988, J. Colloid & Interface Sci., Vol.22(1), Hanna. H.S. and Somsundaran. P Flotation AM.Gaudin Memorial Volume (M.C.Fuerstenau ed. Vol. 1. AlME. N.Y., Lawver, J.E., Wiegel, R.L, Snow, R.E. and Huang, C.L, 1982, Proceedings of XIVth Int. Miner. Process. Congress, Session IV-Flotation, Paper IV-2O, Toronto. Leja. J., Surface Chemistry of Froth Flotation, Plenum Press, New York, 295. Moudgil, 8.M. and Somasundaran. P., 1986, Advances in Mineral Processing (P. Somasundaran ed.), SME/ AIME, Colorado, Somasundaran, p , Int. J. Miner. Process., Vol.3, Somasundaran, P. and Wang, Y.H., 1984, Adsorption and Surface Chemistry of Hydroxyapatite (D.N. Mishra ed.),plenum. N.Y., Somasundaran. P., Anathapadmanabhan. KP., Celik, M.S. and Manev, E.D., 1984, Soc. Petroleum Eng. J., Dec Somasundaran, P., Amankonah. J.O. and Anathapadmanabhan, KP., 1985, Colloids and Surfaces, Vol. IS, Somasundaran. P. and Anathapadmanabhan. K.P., 1986, Advances in Mineral Processing (P. Somasundaran ed.), SME/AIME, Colorado, Wang, D. and Hu, Y., 1989, Solution Chemistry of Flotation, Hunan Scientific Press, Changsha (in Chinese ). Xiao. L. Viswanathan. K. V. and Somasundaran, P Extractive Metallurgy and Material Sci.- Proceed Inter. Sym. (S. Li et al. ed.), Changhsha. China Xiao. L, Viswanathan. K. V. and Somasundaran. P., SME pre print , 1988 Annual Meeting of AIME/SME, Pheonix, Arizona or Mineral & Metall. Process., May 1989, 1-3. Xiao. L. Somasundaran, P. and Kunjappu J.K., 1989, submitted to J. Colloid Interface Sci. Xiao. L, 199, D.E.S. Thesis. Columbia University. Amankonah. University. J.O., 1985, Ph.D. Thesis. Columbia Amankonah, J.. and Somasundaran, P., 1985, Colloids and Surfaces. VoI.l5, Ananthapadmanabhan. Columbia University. K.P.. 198, D.E.S. Thesis, Ananthapadmanabhan. K.P., Somasundaran. P. and Healy, T. W., 198, Trans. SMEj AIME. 266, 23-9.

8 6 -.,. ū CII.., l '6-! K-QL ATE 3.1O-s..V_ - I&. >- I- ;: - I- u -< - I -81 " -' -1 Figure t3 -ph Oleate species distrobution diagram as a function of ph. Total oleate concentration = 3 x 1.5 M [Ananthapadmanabhan and Somasundaran, 198]. E i 4 - :z cn 5,, I II "- Z I I.- 3! i u ' C( &a. a: :> cn Figure 2 2,. KNO,1' :mol/m1 i. - -;-... 9"-.:., 8(-OLEATE CONC. _I,,"a. 7_881-6,. /.,\,... """ '". /:" J' :..,,/ I.'.,' I.,. 1.Z _681-' 1',,., '" to ph Surface tension of potassium oleate solutions as a function of ph and oleate concentration [Ananthapadmanabhan and Somasundaran, 198]. /

9 7 (I) u a- U) X t- )- t- > u c - c -2- -! i i! RNtt; (RNHJ;+ DOCECYLAMINE HYDROCHLORIDE (RNHz'HCI) 5 KIO-' NH"Z RNH RN'RNH, "1 RNH31 4 Figure 3.,," rb-lg,jlfcmte 1-4 M WI U Go.,. : - M. > ;: u " a -' I n Figure m ph Species distrubution diagram of sodium dodecylsulfonate as a function of ph. Total sulfonate concentration = 1 x 1-4 M [Ananthapadmanabhan. 198J.

10 4 a).... ".. " J HYOROXYAPATITE (OPEN).' / z f.. E -I,.? 4f!: /' b) 4. ị -t ụ -. -, -1! -11. C) - IZ.. ii" ụ.,.. /' ;111,.. / / /:,.jo.11 )'-, ><, '. IC ,... In W- 4. u Z-CJ U) c. w > -z. -J C In -4. In -8.- '6 4. -to.m Tca OOLa-tlTE :r:.c) 2.'<1 M >" -fz.t:l "YO ;: -14.m Ca(Qi>Z(aq 'CO -- '"' 8.'8.m" ,."""""'. -J e.o 7- e.o l2.34. Figure 5 Pi 6. G.O ph l.:J Species distrubution diagrams for open systems of: a) calcite; b) hydroxyapatite; c) dolomite [Somasundaran et a). 1985; Xiao et al., 1989}. 5" c... I. I. > E..I 2 c Figure 6 ;.. I Effects of supernatants on zeta-potential of calcite and apatite [Amankonab and Somasundaran, 1985]. o N 4; r ",,3 KNO) CALtlTE IN WATEA 6 APATITE IN WATEA.. APATITE IN CALCITE Su. CALCITE IN APATITESIJP. 4.. '".&- -4. i'" " '\ t '" \, i4; :t J ", \,\ --:- '" ',...,.1, II 12 I] ph,. J I

11 9 Figure 7 t it J :"ẏi o h. I'/ X\ j Stability relations in calcite-apatite-dolomite open system at 25-C. [Mg2+) = 5. x 1-4 M [Somasundaran et ai. 1985]....;i ṿ :-.1 1 C) Figure 8 Species distrubution diagrams for open systems of: a) Mn wolframite; b) Fe wolframite; c) scheelite (Wang et ai, 1989)

12 1.-toil CGI O. Ilo Figure 9 Zeta-potential of wolframites with various Mn/Fe ratio Ne U "- a 6 - I- W &1 Q w w d INITIR.. a..e.;te cr::.? kno.ol/m:l Figure 1 Depletion isotherm of 14C labelled oleic acid on francolite and dolomite rxiao et at

13 .I.) Figure 12a Flottjnn of francolite and dolomite as a function of oleate concentration at ph 9.. Figure 12b Flotation of francolite and dolomite as a function of ph with 1.7 x 1-4 M oleate -H

14 a) 12 - i 'OJ s I,I I -. /'.IS" 1aXJ.m RESIaJR.. su.fg'i1te CC'Q.. l/m x 1.. Q l p'.,.- t.z z, c. S/ : ;jlz l/.j 3 3 CES r ig.a-=---:a. 7 RVRe- s:;:] 1.,

15 11 a).,--. :.ls I.3X1-a1/8W 3 ft X ] 1 D.!:: 11"-1.2 /L-O.J. C'c... f b) :2' - 19 c c a a c: -.c - o-3" l.m'.'. 1 1m to.:n lid.::] naz=.l AVAI-E.... k==1/m x 1 3 X, I J 6 ṣ 19 i c.,,._, AV"'"'" :-'",,. "':::;'L.'--- n. -:;.",--,,-I.. k::: I /m x 1 a Figure 15 Dissolved Ca add Mg levels in: (a) francolite, (b) dolomite suspensions as a function of ethoxylated sulfonate concentration. Table 1 Separation of binary mixture of francolite and dolomite CC'DITI'5 Z RECDVERY :: K -a..e.te I. 7XI -4 M F:H O Cdol) S6 ' ' f "\. \, ran" K-Q.BnC 7.OX1-' H Ettcxviated 7.OXI-6 H SlJle - S.O (dol)

16