Role of Ash Content in Biochar for Copper Immobilization
Abstract Sorption of various contaminants on biochar has been investigated extensively in the literature. However, ash content was generally removed through weak acid or deionized water washing. The objective of this study was to investigate the role of biochar ash content in Cu(II) removal. Twenty four biochars were prepared from pine chips (PCs) and peanut shells (PSs) at 200 500degC. All the biochars were washed with deionized water or HCl/HF to remove ash contents. Treated and untreated biochar particles were then compared for their physical chemical properties as well as sorption characteristics for Cu(II) Cation exchange was an important mechanism controlling Cu(II) sorption on biochars. Precipitation was not important for most biochars, but contributed up to 20% for biochars produced from PSs at 500degC. Removal of ash content increased Cu(II) sorption on PC biochars. A significantly positive relationship was observed between ash content and sorption coefficients for Cu(II) for PS biochars. Thus, the