Abstract:
GLDA was used as the elution agent to leach industrial sewage sludge, and the optimal leaching parameters were determined to provide a reference for the treatment of industrial sludge. A batch sludge washing experiment was conducted to investigate the washing efficiencies of heavy metals by GLDA under the conditions of GLDA concentration of 0.5%-20%, pH of 2-10, liquid-solid ratio of 10∶1-80∶1 and leaching time of 0-24 h. The experimental data were fitted by kinetic equation. The results showed that the heavy metals removal efficiencies could be improved by decreasing pH, increasing liquid-solid ratio and prolonging leaching time. The highest removal efficiencies of Zn, Ni, Cd and Cr were 91.21%, 76.34%, 69.56% and 65.01%, respectively, under the conditions of pH by 2, concentration of 5%,
L/S ratio of 60: 1, and leaching time of 480 mins. The study of the desorption kinetics showed that the four heavy metals were well-fitted to the pattern of the pseudo second-order model, indicating that the leaching process of heavy metals in sludge was dominated by chemical leaching. The results suggested that GLDA was suitable for the leaching and removal of heavy metals from industrial sludge under optimum conditions.