Excellent treatment effect of actual wastewater from a pesticide plant using electro-Fenton process catalyzed by natural pyrite

The experiment used natural pyrite as catalyst for electro-Fenton process to treat actual wastewater containing high concentrations of chlorine salts from a pesticide factory in Guangdong province, China. It revealed that under the optimized conditions of initial pH of 3, electrode spacing of 4 cm, and current density of 40 mA/cm(2), excellent treatment effect was achieved using 3 g/L pyrite as catalyst with graphite cathode and Ti/RuO2-IrO2-SnO2 anode after a duration of 3 h. Specifically, the removal efficiencies of chemical oxygen demand (COD), absorbance at 478 nm (I-478), ammonia nitrogen (AN) and total nitrogen (TN) reached 99.1 %, 99.8 %, 98.9 % and 46.0 % respectively, and instantaneous current efficiency (ICE) at 3 h and energy consumption (EC) were 48.16 % and 97 kWh/kgCOD. Pyrite exhibited good reusability, mainly due to its proper dissolution capacity to renew surface active sites. It was speculated that the nitrogen removal of pesticide wastewater might mainly owe to the oxidation of NH4+ by chlorine/hypochlorite which were based on anode discharge reaction of contained Cl-. The electro-Fenton process catalyzed by natural pyrite showed good potential for efficiently treating the actual pesticide processing plant wastewater with high contents of chlorine salts.