Preliminary Study On Enhanced Reduction Of Tetrabromobisphenol A By Sulfidized Nanoscale Zerovalent Iron With Surfactant

Sulfidized nanoscale zerovalent iron（S-nZVI）has enhanced reactivity and selectivity,which can effectively reduce various organohalogenated contaminants（OHCs）,such as tetrabromobisphenol A（TBBPA）.Surfactants can stabilize S-nZVI particles,increase the solubility of OHCs,and leach out halogenated organic compounds from contaminated soil.Therefore,the joint use of surfactant and S-nZVI is significant for remediating OHCs contaminated groundwater and soil.In this work,we studied the effects of three surfactants on the reactivity and selectivity of S-nZVI with TBBPA,found that Triton X-100（TX-100）had the best enhanced effect,elucidated the enhanced mechanism of TBBPA reduction by S-nZVI in the presence of Triton X-100（TX-100）,and discussed the feasibility of combining surfactant leaching and S-nZVI reduction technology to remediate TBBPA contaminated soil.The main findings are as follows:（1）TX-100 could significantly enhance the reduction of TBBPA by S-nZVI,and the enhancement was affected by the S/Fe molar ratio and TX-100 concentration.Under the optimal S/Fe molar ratio（0.050）,the rate constant and electron efficiency of TBBPA reduction by S-nZVI were 16 and 42 times higher than those of nanoscale zerovalent iron,respectively.TX-100 could further improve the reduction of TBBPA by S-nZVI.Under the optimal TX-100 concentration(0.20 g L^-1),the rate constant and electron efficiency of TBBPA reduction by S-nZVI were 21 and 7 times higher than those of the control group（S-nZVI only）,respectively,which were 326 and 277 times higher than those by nanoscale zerovalent iron.（2）The sorption of TX-100 on S-nZVI surface was the main reason for the enhanced reduction of TBBPA.TX-100 could improve the stability and reactivity of S-nZVI material by inhibiting the agglomeration of S-nZVI.Meanwhile,TX-100 could promote the dissolution of TBBPA and the sorption of TBBPA on S-nZVI surface,which improved the reactivity and selectivity of S-nZVI with TBBPA.Moreover,the reusability of S-nZVI material was also greatly improved by TX-100.TBBPA reduction efficiency was slightly reduced to 92.4%after 7 consecutive experiments in the presence of TX-100,while the S-nZVI was almost unreactive with TBBPA after 4consecutive experiments without TX-100.These results indicate that the combined technology of TX-100（leaching out TBBPA from contaminated soil）and S-nZVI（degrading TBBPA in the washing solution）could be applied to remediate TBBPA contaminated soil.The leaching efficiency was 90.0%and more than 99.5%of the TBBPA in leaching solution could be reduced by S-nZVI.