Lead and Zinc Stabilization of Soil Using Sewage Sludge Biochar: Optimization through Response Surface Methodology

Abstract

In this study, the effect of biochar produced from municipal sewage sludge on the stabilization of potentially toxic elements (PTEs), including lead (Pb), and zinc (Zn) in a mining polluted soil, is investigated. Biochar is produced through the pyrolysis process at three temperatures of 300, 400, and 500 °C. The results of the biochar characterization shows that the pH and surface area of the samples increases with increasing pyrolysis temperature whereas the biochar yield decreases. Response surface methodology (RSM) is used to design and optimize the experiments. Three factors are considered, including biochar pyrolysis temperature, biochar/soil ratio, and time of incubation in the experimental design. The incubation time is the most effective parameter in the stabilization of both metals and shows a direct effect on the responses. However, the pyrolysis temperature has the lowest effect among the investigated parameters. The optimum conditions from RSM shows that biochar is able to stabilize each metal up to 70%, which presents the high potential of produced biochar to be used in the remediation of soils polluted with PTEs.