Abstract: 【Objective】 The degradation of 2,4-D with a combination of nanoscale Fe3O4 and microorganism in solution was studied. The research will provide a basis for remediation of pesticide pollution. 【Method】 Nanoscale Fe3O4 would eliminate the toxicity by reductively transform the electron-withdrawing chlorine groups to chloride, then the bacteria was employed to combine with nanoscale Fe3O4 to degrade 2,4-D. The combination mechanism was revealed by analysis of the relationship between   bacteria and nanoscale Fe3O4. 【Result】 The results showed that the residual rates of 2,4-D decreased from 100% to 52.0% in 48 h   in the presence of 300 mg•L-1 Fe3O4 nanoparticles. Meanwhile, the concentration of chloride ion was increased to 85 μmol•L-1,   and the degradation of 2,4-D was a preliminary reductive dechlorination process. 2,4-D could provide carbon sources for  promoting microbial growth, and the residual rates of 2,4-D was 57.0% in 5 days by the microorganism treatments. The  combination of nanoscale Fe3O4 with microorganism had significantly increased degradation of 2,4-D, and the residual rates of  2,4-D decreased to 35.7% in 7 days, which was much lower than the single treatment of nanoscale Fe3O4 or microorganism. Additionally, microorganisms was also used to degrade 2,4-DCP which was the reductive degradation products of 2,4-D, the residual rates of 2,4-DCP was 50.1% in 5 days, accordingly, the growth OD600 value of microorganisms was 3.29. 【Conclusion】 The degradation rate of 2,4-D by combination treatment was much higher than that separate nanoscale Fe3O4 or microorganism. Nanoscale Fe3O4 could stimulate the growth of microorganisms and reductive degradation product 2,4-DCP was more apt to degradation than 2,4-D.

Key words: Nanoscale Fe3O4, Microorganism, 2,4-D, Combination degradation