Degradation of BTEXS with stable and pH-insensitive iron-manganese modified biochar from post pyrolysis

An efficient iron-manganese modified biochar (FMBC) was successfully synthesized as a heterogeneous Fenton-like catalyst through easy post-modification and applied for degradation of benzene, toluene, ethylbenzene, xylene isomers (ortho, para, and meta), and styrene (BTEXS) in the presence of H2O2. The catalyst was characterized by Brunauer–Emmett–Teller method, scanning electron microscopy, and X-ray photoelectron spectrometry. The effects of H2O2 concentration, FMBC dose, and initial pH on BTEXS degradation were also investigated. Results showed that degradation efficiency of FMBC for individual BTEXS varied from 83.05% to 94.12% in 3 h. Kinetic analysis showed that a first-order kinetic model with respect to BTEXS concentration could be used to explain the BTEXS degradation for FMBC/H2O2 system. The degradation reaction was more suitable in a wide pH range (3–10) than those in previous studies, thereby overcoming the low-efficiency problem of conventional Fenton reaction at high pH. Moreover, the doses of FMBC and H2O2 are a crucial factor affecting BTEXS degradation. Radical scavenger experiments revealed that ∙OH, ∙O2−, and 1O2 participated in the degradation process, and ∙OH was the major contributor. The synthesized catalyst is durable with stable BTEXS removal efficiency after seven consecutive cycles. The removal efficiency of BTEXS by FMBC in produced water reached 93.23% in 12 h, indicating FMBC has practical value.