H2O2 treatment enhanced the heavy metals removal by manure biochar in aqueous solutions

The physicochemical properties and adsorption capacities of yak manure biochar (SP350-YMB) and modified yak manure biochar by H2O2 (AC-YMB) were investigated. Results showed the oxygen content and the carboxyl group content of manure biochar increased by 63.4% and 101%, and the ash content decreased 42% after modification, respectively. Compared to SP350-YMB, the adsorption capacities of heavy metal ions (Pb2+, Cu2+, Cd2+ and Zn2+) were enhanced by AC-YMB in single-metal and multi-metal solutions. The maximum adsorption capacity of Pb2+ increased from 76.41mgg-1 by SP350-YMB to 169.57mgg-1 by AC-YMB based on Langmuir-Freundlich model in single-metal solutions. Pseudo-first and Pseudo-second-order model were used to predict the Pb2+ adsorption kinetics by AC-YMB. H2O2 modification reduced ash content and increased carboxyl content resulting in the major mechanism of heavy metal sorption shifting from precipitation with carbonate/phosphate to complexation with carboxyl. Results from this study indicated that H2O2 modified biochar could act as effective surface sorbent to remove heavy metals, but its ability to remove multi-metal ions needs to be carefully evaluated on an individual basis.