Effect of Water Composition on Flotation of Lead and Zinc Sulphide Ore

ABSTRACT 533 Effect of Water Composition on Flotation of Lead and Zinc Sulphide Ore Ünzile Yenial*, Gülay Bulut Mineral Processing Engineering Department, Mining Faculty, Istanbul Technical University, İstanbul, Turkey, Professor, +902122856173, gbulut@itu.edu.tr ABSTRACT Water composition has a significant effect on flotation. A better understand the role of water composition in flotation is very important for process quality and performance. Based on source of process water, the concentrations of the dissolved ions, hardness, contaminants and residual composition of reagents can varied in the process water. The various water resources employed during lead and zinc flotation caused activation, depression or selectivity effects on minerals due to the presence of different ions in solution. Metal ions in these water resources were adsorbed on the ore, whilst ions associated with gangue minerals were released into the flotation pulp. This paper includes a research for the effect of different water compositions on lead and zinc sulphide flotation. Experiments were carried out five types of water such as tap water, recycling water, tailing dam water, underground mine water and sea water. The ore sample was obtained from Esan Balıkesir-Balya mine. The mineralogical study of ore sample shows that it contains mainly galena, sphalerite, pyrite, hematite, quartz, diopside, epidote, calcite, and chlorite. It is found that recycling water and tailing dam water has a positive effect on recovery of lead and zinc minerals and detrimental effect on content of both minerals. This result may explain with remaining reagents in these waters. Underground mine water and tap water gave nearly the same recoveries of zinc. Sea water affects the recovery lead and zinc negatively. *Corresponding author: Mineral Processing Engineering Department, Mining Faculty, Istanbul Technical University, İstanbul, Turkey, Research Assistant, +902122857360, yenial@itu.edu.tr

INTRODUCTION Water is an important issue in mining and mineral processing. Mining consumes large quantities of water. Only copper mining industry consumed over 1.3 billion m 3 of water in 2006. If a plant not re use or recycle any water, requires 1.9-3.0 m 3 of water per tonne of ore processed (Gunson et al., 2012). Many parts of mineral processing such as grinding, flotation, dense medium separation, gravity concentration and hydrometallurgical operations use large volumes of water (Schumann, Levay & Ametov, 2009). Increasing water demand and lack of fresh water cause water recycling and finding new water resources. Underground water, sea water and acid rock drainage water can be possible alternatives for new water sources but their chemical composition is different than fresh water, and may also have some side effects. Reusing process water is an alternative and also the most probably chosen way to decrease fresh water demand. Recycling water can be obtained from tailing dams, thickeners, dewatering units (Schumann et al., 2009). Using recycled water or poor quality water can have some detrimental effects on process water quality due to accumulation of certain chemical species (Schumann, Levay & Ametov, 2009). The use of recycle water in flotation has a significant effect on selectivity and recovery. Recycling water may contain some residual reagents and their oxidation products, metallic ions, alkaline earth metal ions (Rao & Finch, 1989). Closed water circuits in flotation plants result in a high electrolyte concentration in the process water (Ramos, Castro & Laskowski, 2011). Water has a direct impact on flotation process quality and has to be examined how it effects. It is claimed that detergents, organic carbons, dissolved solids, reagents and dissolved oxygen in recycling water affect the hydrophobicity of gangue minerals thus floated with concentrate (Muzenda, 2010). This study presents a research results for the effect of water composition on flotation lead and zinc sulphide ore. Experiments were carried out with five different types of water, such as tap water, tailing dam water, underground water, recycling water and sea water. METHODOLOGY Ore Sample: The ore sample used in tests was obtained from Esan-Balya Lead and Zinc sulphide mine which is located in Balıkesir-Turkey. The mineralogical study of ore sample shows that it contains mainly galena, sphalerite, pyrite, hematite, quartz, diopside, epidote, calcite, and chlorite. The ore mainly contains 33.4% SiO2, 10.1% Fe2O3, 2.79% PbO and 4.36 ZnO as it shown in Table 1. Water Samples: Water samples used in flotation tests were taken from several points. Tailing dam water was obtained from Balya Plant Tailing dam, underground water was obtained from Balya Plant natural underground water, settled and used after settling in flotation circuit. Sea water was taken from The Agean Sea and recycling water was obtained from dewatering of concentrates and tailing after laboratory scale flotation experiment. Table 2 presents the chemical analysis of water samples. Water samples were used in laboratory tests by adding it into the ball mill while milling which is followed by separate flotation tests for each one of the water samples.

Table 1. The chemical analysis of Ore Sample. Elements Amount, % MgO 1.95 Al2O3 6.76 SiO2 33.4 K2O 2.18 CaO 20.0 Fe2O3 10.1 CuO 0.36 ZnO 4.36 As2O3 0.231 PbO 2.79 Sb2O3 0.0884 Others 17.78 Table 2. The chemical analysis of water samples. Elements Tap Water Tailing Dam Recycling Underground Sea Water Water Water Water Calcium 56.52 ppm 826 ppm 555.9 ppm 339.30 ppm 441 ppm Magnesium *n.d n.d n.d n.d 1300 ppm Lead 0.0220 ppm 0.2903 ppm 3.44 ppm 0.1020 ppm 0.0185 ppm Iron 0.0050 ppm 0.0150 ppm 0.0091 ppm 0.0047 ppm 0.0117 ppm Copper 0.0022 ppm 0.0091 ppm 0.0160 ppm 0.0022 ppm 0.0045 ppm Zinc 0.8022 ppm 1.3290 ppm 0.0620 ppm 0.8192 pmm 0.0457 ppm Arsenic 0.0005 ppm 0.05 ppm 0.0243 ppm 0.0409 ppm 0.0043 ppm Flour 36 ppm 88 ppm 38 ppm 0.1104% 20 ppm Chlor 200 ppm 155 ppm 87 ppm 1.6508% 1.93% Nitrate - 105 ppm - 211 ppm 28 ppm Sulphate 59 ppm 1206 ppm 730 ppm 40.9508 % 2800 ppm ph 8 12.4 11.5 7.3 8.2 Eh +165 mv +210 mv -15 mv +135 mv +190 mv *n.d: no data. Flotation Test Conditions: The crushed ore sample was ground as 30 min and the d80 of flotation sample was under 0.212 mm. 1000 grams of ore sample subjected to the flotation tests. The flotation machine that is used for the laboratory tests was Denver with 2.5L cell volume for rougher flotation. Lead and zinc cleaner flotation experiments were carried out employing 1.7L cell. The flowsheet used in the flotation tests given on Figure 1. Reagent types are compatible with those in Balya Flotation Plant and doses were

determined with previous laboratory tests. Tables 3, 4 and 5 present rougher and cleaner flotation conditions of lead and zinc, respectively. Lime and sulfuric acid were employed as ph regulators. Pb Rougher Concentrate Pb Rough Flotation Cleaning -1 Zn Rough Flotation Zn Rougher Concentrate Pb Middling Cleaning -2 Cleaning -3 Tailing Cleaning -1 Pb Concentrate Cleaning -2 Cleaning -3 Zn Middling Cleaning -4 Zn Concentrate Figure 1 The flowsheet of Flotation Tests. Table 3 Rougher flotation conditions of Pb and Zn. Pb-Rougher Flotation Zn Rougher Flotation ph:10.5(with lime) ph:12 (with lime) Na2SiO3: 500+0 g/t CuSO4 : 1500 g/t ZnSO4 : 2000+1000 g/t Conditioning Time: 45 min. FeSO4 : 2000+2000 g/t KAX:50 g/t Conditioning Time: 15+5 min. Ethyl Hegzogonal: 60 g/t KEX: 10+0 g/t Conditioning Time: 10 min. A242: 0+10 g/t Flotation Time:5 min. B. Glycol: 20+0 g/t Conditioning Time: 5+5 min. Flotation Time: 3+3 min.

Table 4 Cleaner flotation conditions of Pb. Pb-Cleaning -1 Pb-Cleaning -2 Pb-Cleaning -3 ph: 10,5 ph: 10,5 ph: 10,5 FeSO4 : 1000 g/t FeSO4 : 250+100 g/t FeSO4 : 100 g/t Conditioning Time: 5 min. Conditioning Time: 5+3 min. Conditioning Time: 5 min. A242: 2.5 g/t A242: 5+5 g/t A242: 2.5 g/t B. Glycol: 2.5 g/t B. Glycol: 5+5 g/t B. Glycol: 5 g/t Conditioning Time: 3 min. Conditioning Time: 3+2 min. Conditioning Time: 3 min. Flotation Time: 5 min. Flotation Time: 3+2 min. Flotation Time: 3 min. Table 5 Cleaner flotation conditions of Zn. Zn-Cleaning -1 Zn-Cleaning -2 Zn-Cleaning -3 Zn-Cleaning -4 ph: 12 ph: 12 ph: 12 ph: 12.2 Hegzogonal: 10 g/t Hegzogonal: 10 g/t Hegzogonal: 10 g/t Hegzogonal: 10 g/t Cond. Time: 2 min. Flotation Time: 5 min. Cond.Time: 2 min. Flotation Time: 5 min. Cond.Time: 2 min. Flotation Time: 5 min. Cond. Time: 2 min. Flotation Time: 3 min. RESULTS AND DISCUSSION In order to investigate effect of water composition on lead and zinc ore, rougher and cleaner flotation were valuated separately. Effect of water composition on rougher flotation In order to investigate the effect of water composition on lead and zinc flotation, the ore sample subjected to different waters, with the same reagent regime and conditions. The effect of water composition on rougher flotation is shown on Figure 4 (a) and (b). In rougher flotation stage lead was floated 23.84% content and 89.4% recovery using tap water. The highest recovery was obtained with tailing dam water as 93.4% and the lowest recovery was obtained with sea water as 88.2%. The recovery has not changed so much but the content of the rougher concentrates were varied. The highest content was obtained with tap water and the lowest content was obtained sea water. Thus, sea water has a negative effect on lead flotation by means of content and grade. Zinc was floated with 20.95% content and 87.6% recovery with tap water. When water composition changes, both content and recovery decreased. While recycling water and underground water have similar tendency, sea water dramatically decreased zinc content of the rougher concentrate.

Recovery, % Content, % 30 25 23,84 20 15 20,95 19,36 18,42 18,25 15,36 20,3 16,53 11,62 19,9 10 5 0 Pb Content, % Zn Content, % Figure 4 (a) Effect of water composition on lead and zinc content at rougher flotation. 100 93,4 89,4 90,5 90,6 87,6 88,2 90 84,9 86,5 82,1 78,7 80 70 60 50 40 30 20 10 0 Pb Recovery, % Zn Recovery, % Figure 4 (b) Effect of water compositions on lead and zinc recovery at rougher flotation.

Effect of water composition on cleaner flotation Cleaner flotation stages were employed to investigate effect of water composition. Lead was floated with 55.24% content and 56.4% recovery with tap water. The highest recovery was obtained with tailing dam water which has good agreement with rougher stage. Underground water and recycling water have nearly the same effect on lead recovery. 14.57% content of lead was floated using sea water and very low recovery was obtained as 8.8%. The sharp decrease in lead recovery and content was occurred in 3 rd stage of cleaner stage. Zinc was floated with 39.21% content and 83.6% recovery with tap water. Zinc recovery was not influenced by water type except sea water but zinc grade was changed with type of the water. The lowest zinc grade was obtained with recycling water which may arise from residual reagents especially xanthates were activated pyrite since grinding. The highest zinc content (40.89%) was obtained with sea water due to ionic strength of the sea water affected the bubble size and entrainment of the gangue minerals (Manono, Wiese & Corin, 2013). As Kurniawan et al. (2011) mentioned that increased electrolyte solutions to the flotation system can be considered as promoters in the absence of frother as they produce smaller bubble sizes in the froth. The enhancement in the flotation performance depends on the type of and concentration of the salt. Zinc and Lead recoveries decreased with sea water due to the different and high concentration of ions. Sea water contains approximately 1300 ppm Mg +2, and over ph 9, magnesium ions forms as magnesium hydroxide and this may result precipitation of Mg(OH)2. Ramos, Castro and Laskowski (2013) showed that the flotation of molybdenite is very sensitive to magnesium hydroxylcomplexes and colloidal magnesium hydroxide. The main depression mechanism of sea water was explained by Mg(OH)2. The subsequent formation of colloidal magnesium ions may coats molybdenite particles and makes them hydrophilic. Underground water has been previously experienced in Mufulira flotation plant and found that the low ph of the underground water caused galvanic interaction in grinding stage and adversely effected flotation. The addition of lime on grinding stage solved this problem and the recoveries were increased (Ng andu, 2001). The low content of the lead concentrates could be increased with rearrangement of reagent regime. The residual reagents in tailing dam water and recycling water activated the gangue minerals, especially pyrite and excessive amount of these reagents has a big influence on froth thickness and stability. Recycling water and tailing dam water contains residual reagents from the flotation circuit, therefore the improvement of recoveries depends on excessive amount of reagents. Although underground water does not contain any reagent, obtained similar recovery due to high content of sulphate (40.95%). In addition, the phs of waters are different from each other. Tailing dam water, recycling water has the high phs as 12.4 and 11.5; underground water has the lowest ph as 7.2. The grinding ph of media may also influenced flotation of these minerals. The flotation tests were applied at ph 10.5 and 12 that means there are some colloidal hydroxides precipitate and this importance were explained well in some papers (Ramos, Castro & Laskowski, 2013; ). It is understood that a water composition such as ion concentration, ph, and residual reagents are responsible for flotation performance together.

Recovery, % Content, % 60 55,24 50 40 44,19 39,21 38,48 37,13 40,10 37,52 40,89 32,30 30 20 14,57 10 0 Pb Content, % 100 Zn Content, % Figure 5 (a) Effect of water compositions on lead and zinc content at cleaner flotation. 80 83,6 83,3 79,7 74,5 82,4 83,5 76,4 60 56,4 44,1 40 20 8,8 0 Pb Recovery, % Zn Recovery, % Figure 5 (b) Effect of water compositions on lead and zinc recovery at cleaner flotation.

CONCLUSION A series of batch scale flotation tests were performed using the Balıkesir Balya Lead and Zinc Sulphide ore to investigate the influence of water composition on flotation performance. The results of the flotation tests revealed that the dissolved metal ions and residual reagents influenced both the froth stability and flotation recovery. The tests showed the variation of the water composition directly affects the flotation performance. Therefore the origin of the water or the mixture of different water sources must be taken account. The laboratory tests were showed that lead recovery is better when using tailing dam water, underground water and recycling water, respectively. Zinc recovery remains same with tap water when using underground water. The flotation results show different tendency depending on ion concentration of flotation solution. It can be understood from this results that high ion concentration have negative effect on flotation recovery as sea water however, certain amounts of ion concentration and residual reagents enhanced flotation performance as recycling water and tailing dam water. Nevertheless more research should be done to give elaborate explanations. ACKNOWLEDGEMENTS The authors are grateful for the support provided by Eczacıbaşı Esan Company in chemical analysis. REFERENCES Gunson, A.J, Klein, B. Veiga, M. Dunbar, S. (2012) Reducing Mine Water Requirements, Journal of Cleaner Production, 21, pp. 71-82 Kurniawan, A.U. Ozdemir, O. Nguyen, A.V. Ofor, P. Firth, B. (2011) Flotation of coal particles in MgCl2, NaCl, and NaClO3 solutions in the absence and presence of Dowfroth 250 International Journal of Mineral Processing 98, pp. 137 144. Manono, M.S. Corin, K.C. & Wiese, J.G. (2013) The effect of ionic strength of plant water on foam stability: A 2- phase flotation study Minerals Engineering 40 pp. 42 47 Muzenda, E. (2010) An Investigation into the Effect of Water Quality on Flotation Performance World Academy of Science, Engineering and Technology 70, pp. 237-241. Ng andu, D.E. (2001) The effect of underground mine water on performance of the Mufulira flotation process, The Journal of The South African Institute of Mining and Metallurgy, pp. 367-380. Ramos, O. Castro, S. & Laskowski, J.S. (2013) Copper molybdenum ores flotation in sea water: Floatability and frothability, Minerals Engineering, 53, pp. 108-112. Rao, S.R. & Finch, J.A. (1989) A review of water reuse in flotation, Minerals Engineering, 2(1), pp. 99-119 Schumann R, Levay G, Ametov I, (2009) The impact of Recycling on prcess Water Quality in mineral Processing, in Proceedings Water in Mining Conference, Perth, pp. 79-86.