A simple method for removing chelated copper from wastewaters: Ca(OH)2-based replacement-precipitation

A simple Ca(OH)2-based replacement-precipitation process was applied to the removal of EDTA-chelated copper from wastewaters. The effect of initial pH of the solution, molar ratio of Ca2+ to Cu(II), the presence of CO2 on the removal efficiency was investigated. The experimental results showed that the Ca(OH)2-based replacement-precipitation process could efficiently remove the chelated copper from wastewaters. When 12 ⩽ pH ⩽ 13 and molar ratio of Ca2+ to Cu(II) ⩾ 2, the removal efficiency could reach 99% above, also being close to the theoretically simulated results. The presence of CO2 in the air would exert negative effect on the removal efficiency, but the side effect could be effectively eliminated by the addition of flocculation agent polyacrylamide. Compared with Fe2+-based replacement-precipitation technique applied in industrial practice, the method possesses the advantages of less sludge, lower cost, higher removal efficiency and higher controllability.