Effect of rice-straw biochar on selective biodegradation of nonylphenols in isomer specificity

In a previous study, we found that rice-straw biochar degraded and removed hydrophobic organic contaminants (HOCs) through coupled adsorption-biodegradation. However, few studies have determined whether biochar affects HOC isomer degradation and isomer-selective biodegradation or whether biochar can alter HOC isomer features, resulting in changes to HOC isomer residues in water environments. In this study, the effects of biochar at two dosages (0.001 and 0.01 g) on the biodegradation of ten isomers of a typical xenoestrogen of nonylphenol (NP) were evaluated. The results revealed that there were no effects of biochar on the adsorption of NP isomers. However, biochar addition affected the biodegradation of a specific isomer without altering the features of the NP isomers. The treatment of NP isomers with Pseudoxanthomonas sp. yielded degradation ratios ranging from 60.7 to 100%. At 0.001 g biochar treatment, the degradation of eight NP isomers was enhanced (except for NP₁₉₄ and NP_193a+b) due to their bulky structures. The degradation of the ten NP isomers was inhibited when 0.01 g biochar was added. These findings characterized the effects of biochar on NP isomer contaminants and provided basic information for the application of biochar for the remediation of NP isomer contaminants.