Qualitative and quantitative investigation on adsorption mechanisms of Cd(II) on modified biochar derived from co-pyrolysis of straw and sodium phytate

Developing effective modification methods and obtaining a comprehensive understanding of adsorption mechanisms are essential for the practical application of biochars for the removal of heavy metals from solutions. In this study, rice straw was impregnated with sodium phytate and pyrolyzed at 350 °C, 450 °C, and 550 °C to synthesize modified biochars (i.e., MBC350, MBC450, and MBC550). The Cd(II) adsorption capacities and contributions of different mechanisms, including the effects of biochar-derived dissolved organic matter (BDOM), were investigated using batch sorption experiments and characterization analyses. The modification of sodium phytate promoted the pyrolysis of biomass, thereby increasing the BDOM content and aromatic structures at low and high pyrolysis temperatures, respectively. Moreover, the modification also increased the exchangeable Na