Chemical leaching of typical heavy metals from desulfurisation sludge in a coal-fired power plant

The issue of excessive heavy metal content in desulfurised sludge from coal-fired power plants is addressed by conducting a study on samples collected from four coal-fired power plants in northern China. In this study, we focus on analysing the physicochemical properties of the sludge and the concentrations of heavy metals such as Cr, Ni, Zn, Pb, and Cu. Various leaching agents, including citric acid, oxalic acid, tartaric acid, lactic acid, and deionised water, were tested for their effectiveness for removing Cr and Ni heavy metals, and oxalic acid showed the best leaching performance. The optimal leaching conditions were determined to be a concentration of 0.3 mol/l, a 6-h leaching time, and a solid-to-liquid ratio of 1:20, resulting in significant removal rates of Cr and Ni. The study also analysed the distribution characteristics of Cr and Ni using the Community Bureau of Reference sequential extraction method and investigated the removal mechanism of these heavy metals in oxalic acid leaching desulfurisation sludge. These findings offer valuable insights for resource utilisation and environmentally safe disposal of desulfurised sludge, particularly to mitigate environmental risks associated with Cr and Ni combined pollution.