Study on adsorption characteristics of biochar on heavy metals in soil

Three kinds of biochars (called poplar branch biochar (PBC), water hyacinth biochar (WHC), and corn straw biochar (CSC)) were prepared in a fixed-bed pyrolyzer at different pyrolysis temperature of 300-700 degrees C. The effects of biochar species, pyrolysis temperature and biochar addition on adsorption characteristics of typical heavy metals (HMs) of Pb and Zn in vegetable soil (collected from lead-zinc-silver mining area, Nanjing, China) were investigated. The obtained results indicate that WHC presents the best adsorption ability at the same experimental conditions, whose adsorption efficiency on HMs of Zn and Pb is 21.83% and 44.57%, and the relative adsorption capacity of Zn and Pb is 227.65 mu g/g and 363.76 mu g/g, respectively. The adsorption efficiency of biochar on HMs of Zn and Pb in soil increases gradually with the increasing of pyrolysis temperature. The increasing of biochar addition is beneficial to increase adsorption efficiency of soil HMs, but unhelpful for adsorption capacity.