Magnetic ball-milled FeS@biochar as persulfate activator for degradation of tetracycline

In this study, composite of iron sulfide and biochar ([email protected]) was synthesized successfully via physical ball milling and applied to the oxidative removal of tetracycline (TC) in the presence of persulfate (PS). Characterization results showed that [email protected], which has a small particle size, can be synthesized at a preset FeS-BC mass ratio. In addition, the ball-milled [email protected] showed sufficient ferromagnetism. The effects of pH, dosages of [email protected] and PS, and co-existing anions on TC degradation were investigated. Our results showed that TC degradation efficiency was enhanced at low pH and high dosages of PS and [email protected] Under optimal conditions (pH = 3.6, [[email protected]] = 0.3 g/L and [PS] = 10 mM), a TC removal efficiency of 87.4% could be achieved after 30 min. Nevertheless, the TC removal rate was slightly inhibited by inorganic anions in the order of CO32− > Cl− > NO3−. Surface-bound Fe(Ⅱ) and S(Ⅱ) acted as electron donors in the activation process and generated SO4− and OH at the surface of [email protected] In addition, S(Ⅱ) also participated in Fe(III) reduction. BC not only reduced the agglomeration of FeS, serving as a continuous source of effective Fe, but also acted as an electron shuttle and a suitable carbon-based adsorption material, facilitating fast electron transfer among PS, electron donors, and pollutants. Moreover, non-radical degradation processes might also exist in the [email protected]/PS/TC system. The [email protected] could be a promising effective activator for the remediation of other emerging organic contaminants.