Abstract: Dechlorane plus (DP) is a class of widely used chlorinated flame retardants that are persistent, long-range migratory and bioaccumulative, posing serious harm to the ecological environment and human health. It has been included in the list of key new pollutants for control in China in 2023. Currently, most of the research on DP focuses on its environmental distribution and toxicity effects, but less on the related remediation techniques and mechanisms. In this study, biochar (BC) and rhamnolipid (RL) were used to modify nano zero-valent iron (nZVI) to obtain modified nZVI composites (RL/nZVI@BC), aiming to examine the removal effect of DP under different conditions and to investigate the removal mechanism of DP by this remediation material in combination with the change of morphology and structure properties of RL/nZVI@BC. The results showed that the modified nZVI composites enhanced DP removal from water. The removal rate of syn-DP and anti-DP in water by RL/nZVI@BC reached 98.4% and 97.6% under the conditions of nZVI:RL:BC=1:0.01:2, the material dosage of 2 g·L^-1, the DP initial concentration of 500 μg·L^-1, the pH of 3, the temperature of 45 ℃ and the concentration humic acid (HA) of 0 mg·L^-1. Kinetic analysis showed that the removal of DP by RL/nZVI@BC was consistent with pseudo-secondary degradation and adsorption kinetics (R² of 0.86-0.90 and 0.93-0.98, respectively), through the synergistic combination of π-π chemical bond binding adsorption of biochar, physical adsorption of specific surface energy, and reductive dechlorination of nZVI.

Key words: biochar, nano-zero-valent iron (nZVI), rhamnolipid, dechlorane plus