Pyrolysis temperature-induced changes in the catalytic characteristics of rice husk-derived biochar during 1,3-dichloropropene degradation

Abstract

The biochar-induced catalytic degradation of contaminants produced by environmentally persistent free radicals (EPFRs) has attracted considerable attention; however, its mechanism and influential factors are poorly understood. In this study, the catalytic characteristics of rice husk-derived biochars pyrolyzed at different temperatures (300°C to 700°C, R-300 to R-700, respectively.) were investigated during soil fumigant 1,3-dichloropropene (1,3-D) degradation. Results showed that the degradation rate of 1,3-D initially decreased from 0.00152h−1 on R-300 to 0.00073h−1 on R-500 and subsequently increased from 0.00073h−1 on R-500 to 0.00305h−1 on R-700 with increasing biochar pyrolysis temperature. A U-shaped relationship was observed between biochar pyrolysis temperature and 1,3-D degradation rate. Three degradation intermediates were identified based on the National Institute of Standards and Technology database information acquired through headspace GC–MS technologies. The catalytic efficiency of biochar improved with increasing moisture content or degradation temperature. When the biochar moisture content increased from 0% to 80%, the degradation efficiency of cis- and trans-isomers on R-500 increased from 6.27% to 35.45% and from 8.48% to 36.36%. When the degradation temperature increased from 20°C to 40°C, the degradation efficiency of cis- and trans-isomers on R-500 increased from 37.50% to 49.80% and from 35.90% to 53.48%. The different effects of 1,3-D degradation rate on different biochars were attributed to the pyrolysis temperature-induced changes in the biochar pore structures, changes in the pH of biochar reaction solutions, and changes in EPFR-induced hydroxyl radicals. These results suggested that the characteristics of biochar render it suitable for the degradation of organic pollutants.