A stable biochar supported S-nZVI to activate persulfate for effective dichlorination of atrazine

Abstract

Sulfidation of nano-zero valent iron (nZVI) has attracted extensive attention because it can improve the reactivity of nZVI. Here, a type of catalyst, biochar supported sulfurized nZVI (S-nZVI@BC) was designed by a sample one-pot method, in which biochar was dispersed into Fe3+ solution under the flowing stream of N2 condition, subsequently, NaBH4 and Na2S2O4 solution were added dropwise at a constant speed. The as-prepared catalyst possessed obvious irregular shape and sulphur had been successfully doped. The most suitable ratio of sulphur to iron (S/Fe = 0.15) and the optimum dosages of S-nZVI@BC (0.1 g/L) and persulfate (PS, 1 mM) were determined. After three consecutive cycles, the removal rates of atrazine in the systems of nZVI-PS, S-nZVI-PS and S-nZVI@BC-PS maintained at 55.5%, 87.1% and 96.8%, respectively, implying that the stability of nZVI was enhanced by S doping and BC support. In addition, the S-nZVI@BC could keep good activity in a wide pH range of 2.86–10.53, and could effectively reduce the activation energy of reaction. And the catalyst retained relatively good catalytic performance in actual natural water. The identification of active substances was achieved by electron spin resonance test, including •OH and SO4•−, 1O2 and PFRs. According to the law of Cl− conservation, the Cl element in atrazine molecule was completely removed. This study could provide an effective catalyst preparation method to promote PS activation for degradation of organic pollutants.