Recovery of Heavy Metals from Sludge

The recovery of four metal ions,to be specific,Cu2+,Pb2+,Zn2+ and Cd2+ from heavy metals sludge was investigated.Effects of acid type,acid concentration,temperature,time and ratio of solid to liquid on leaching efficiency in acid leaching process were investigated.The results show that when the sludge calcined at 750 ℃ for 3 h is treated with 4 mol/L HNO3(solid-to-liquid ratio is 1∶20) at 80 ℃ for 3 h under the rotation speed of 600 r/min,the leaching rate of Cu2+,Pb2+,Zn2+ and Cd2+ is 92.0%,99.5%,99.5%,99.3%,respectively.