Biochar enhanced the degradation of organic pollutants through a Fenton process using trace aqueous iron

Abstract The Fenton process is among the most popular technique for oxidation of organic pollutants, but faces the challenges of slow Fe(III)/Fe(II) cycling, limited OH production, and the by-production of hazardous iron-containing sludge. In this work, two biochars (LB700 and LB500) were added in a Fenton process using trace aqueous iron (0.2–1.8 mg/L), so as to enhance the degradation of organic pollutants while minimizing the production of iron-containing sludge. The results indicate that the addition of biochar in the Fenton process accelerated the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP). The pseudo-first order rate constants (kobs) for 2,4-D degradation in the combined biochar and Fe(II)/H2O2 systems are enhanced to 3.09–4.97 times that in the homogenous Fe(II)/H2O2 system and 4.61–5.80 times that in the biochar/H2O2 systems. The mechanism investigations using electron spin resonance (ESR) and a chemical probe method indicate that addition of biochar increased the cumulative production of OH in Fenton system, and the high temperature biochar LB700 led to more OH production and consequently quicker 2,4-D degradation. The biochar can also facilitate the Fe(III)/Fe(II) cycling and initiate the Fenton-like oxidation of 2,4-D using trace aqueous Fe(III). This research work suggests a facile and environmentally friendly way to enhance the efficiency of advanced oxidation of refractory pollutants.