[Extraction of Pb from sewage sludge with PESA].

Poly-epoxy-succinic acid (PESA), as a novel biodegradable chelant, was used to remove the heavy metals from the sewage sludge based on chemical extraction technology. For the sewage sludge from Shanghai Taopu Municipal Wastewater Plant, the influence factors including pH and the concentration of PESA on the extraction efficiency was investigated. It is found that PESA had a higher efficiency for the extraction of Pb from sludge than that of other heavy metals. The analysis of species distribution shows that the extracted Pb mainly comes from the following states, water soluble, acid soluble, reducible and oxidizable fractions. The extraction efficiency of Pb reached 73% when the molar ratio of PESA to total heavy metals was 4:1 and system pH was 4. The concentration of PESA and system pH have a significant effect on the extraction efficiency of Pb. The extraction efficiency of Pb decreases gradually with pH increasing, and the dependence of the extraction efficiency on pH decreases with the molar ratio increasing.