(731f) Upgrading Biochar Via Co-Pyrolysis of Agricultural Biomass and Spent Tires/Sulfur Wastes for Environmental Remediation

This study was carried out to use 5 biochars (woochip (WC) biochar, raw sulfur/rice straw (RS) biochar, modified sulfur/RS biochar, spent tire/RS biochar, and CO₂-activated biochar) as sorbents for explosive (2,4-dinitrotoluene (DNT)), halogenated phenol (2,4-dichlorophenol (DCP)), toxic metals (Pb and Ba) and toxic anions (Cr and Se). RS biochar was also evaluated as control material. Spent tire/RS biochar was the most effective sorbent for DNT, showing the maximum sorption capacities of 23.4 mg/g. Statistical analysis indicates that BET surface area and hydrophobic may be involved in the sorption of DNT to biochar. Compared to RS biochar, WC biochar samples effectively remove DCP considering maximum sorption capacity and properties of sorbents and sorbates, it appears that the sorption capacity of biochar for DCP is related to the pH, pK_a of DCP to biochar. Raw sulfur/RS biochar and CO₂-activated RS biochar had the highest sorption capacities for Pb, showing 126.6 and 132.2 mg/g, respectively. In the case of Ba, CO₂-activated RS biochar was the most effective (23.98 mg/g). Correlation analysis between biochar properties and maximum sorption capacities suggests that surface functional groups and CEC may affect the sorption of cationic heavy metals to biochar. Microtox^® bioassay and TCLP tests did not show any toxic effects of the synthesized biochar. Our results suggest that co-pyrolysis of spent tires with biomass wastes may be a viable option to dispose spent tires by decreasing mobility and toxicity of metals as well as increasing sorption capacity of biochar for some contaminants.