Abstract:
Objective Biomass ash (BA) can effectively adsorb heavy metals since it has amounts of micro-pores and functional groups. Meanwhile, the phosphorus-based materials could decrease the availability of heavy metals through the formation of metal-phosphate precipitation. In this study, phosphorus-containing materials were combined with biomass ash so as to further improve the immobilization effect of heavy metals in soil.
Method The immobilization effects of Cu and Pb in contaminated soil were studied after the application of biomass ash combined with potassium dihydrogen phosphate (KH2PO4) with a 10:4 ratio under the dosages of 0.2 ~ 0.6%.
Result Soil pH in biomass ash combined with phosphate (BAP) treatments was effectively increased than that of single biomass ash (BA) treatments. After 45 d of incubation, the available Cu in the BA and BAP treatments decreased by 57.0% and 93.0%, respectively, and the available Pb decreased by 64.6% and 99.6%, compared with the control. While the soil available phosphorus was increased by 388% than the control. Compared with the BA treatment, the combination treatments were more effective to transform the Cu from active fraction to moderately active fraction, and from active fraction to moderate active and stable fractions for Pb.
Conclusion Phosphate was facilitated to the immobilization of soil Cu and Pb by biomass ash, and the phosphate combined with biomass ash could be used to immobilize the heavy metals in soils.