CHEM-E6180 HSC exercise 13.10. Solvent extraction

Solvent extraction Organic extractant dissolved in an organic phase picks up metal ions from aqueous solution. Loaded organic phase is stripped to pure aqueous solution. Loading and stripping are controlled by pH. CHEM-E6180 SX 13.10.2016

Solvent extraction Three units in the process: Solution preparation, the filtrate (pregnant leach solution PLS) has no H+, so it has to acidified to pH = 1 to get selective extraction of copper. Loading, prepared PLS is mixed with stripped organic to extract copper, all other components from feed PLS are discharged in raffinate. Stripping, loaded organic phase is mixed with strongly acid spent electrolyte from electrowinning to strip copper from loaded extractant to fresh electrolyte. Stripped organic phase goes to loading. CHEM-E6180 SX 13.10.2016

Solvent extraction The general reaction is Higher pH to load the organic phase (few g/l acid) and low pH to strip (tens to hundred g/l acid). Hypothetic extractant has to be set up in own database Unloaded C42H2, 970 kg/ton Loaded C42Cu, 1000 kg/ton Diluent C14, 790 kg/ton 98% progress, all remaining Cu2+ goes to raffinate. CHEM-E6180 SX 13.10.2016

Solvent extraction CHEM-E6180 SX 13.10.2016

Solvent extraction CHEM-E6180 SX 13.10.2016

Loading Filtrate acidified to pH = 1 (simplify to 0.1 g/l H+). Acidified filtrate goes to loading. Inputs in loading are acidified filtrate and stripped extractant. Outputs are raffinate and loaded extractant. 98% of copper is extracted, rest goes to raffinate. Cu2+ + C42H2 = C42Cu + 2 H+ CHEM-E6180 SX 13.10.2016

Stripping Product is Pregnant electrolyte or Strong electrolyte or Fresh electrolyte containing approximately 25 g/l copper and 130 g/l sulfuric acid. The stripping medium is Spent electrolyte containing 15 g/l copper and 145 g/l sulfuric acid. Recovery from organic to Strong electrolyte is 90%. Inputs are spent electrolyte and loaded extractant, outputs are fresh electrolyte and stripped extractant. 90% of copper is stripped, rest goes with stripped extractant. C42Cu + 2 H+ = Cu2+ + C42H2 CHEM-E6180 SX 13.10.2016

Electrowinning Copper deposited in the EW is DCu * V. DCu = Cu (Fresh) – Cu (Spent) = 10 g/l. Copper taken out from stripping to fresh electrolyte must equal PLS feed – raffinate. One mole of deposited Cu produces one mole of H2SO4. CHEM-E6180 SX 13.10.2016

Solvent extraction process Prepare the units and flows. Create variable list: Aqueous phase H2O, H2SO4, H(+a), SO4(-2a), Cu(+2a), Fe(+2a), Ni(+2a), Zn(+2a) New organic phase C42H2, C42Cu No gas or solid phase CHEM-E6180 SX 13.10.2016

Solvent extraction process Filtrate input 4860 kg/h H2O 2790 kg/h SO4(-2a) 1280 kg/h Cu(+2a) 600 kg/h Fe(+2a) 130 kg/h Ni(+2a) 50 kg/h Zn(+2a) 10 kg/h Spent electrolyte input 61210 kg/h H2O 51500 kg/h Cu(+2a) 882 kg/h H2SO4 8820 kg/h CHEM-E6180 SX 13.10.2016