Advanced treatment of biologically treated coking wastewater by persulfate oxidation with magnetic activated carbon composite as a catalyst.

Advanced treatment of biologically treated coking wastewater (BTCW) using persulfate (PS) oxidation with magnetic activated carbon composite (CuFe2O4:AC w/w ratio of 1:1.5, denoted as 1.5-MACC) as a green catalyst was evaluated at ambient temperature (30 °C). Effects of PS (K2S2O8) and 1.5-MACC doses on PS decomposition and total organic carbon (TOC) removal in BTCW were also studied during 360 min. The results showed that the 1.5-MACC/PS system has a much better performance on TOC removal in BTCW than only 1.5-MACC or PS system. PS decomposition and TOC removal follow first-order kinetics in the 1.5-MACC/PS system. The optimum condition of the 1.5-MACC/PS system to treat BTCW is with a K2S2O8 dose of 4 g L-1 and 1.5-MACC dose of 5 g L-1. Under this condition, TOC in the PS oxidation effluent is 20.4 mg L-1 with a removal efficiency of 85.4%. TOC removal is a synergistic effect of adsorption and oxidation. TOC oxidation is due to the generation of ·SO4- via the activation of PS by CuFe2O4 impregnated AC. The gas chromatography-mass spectrometry (GC-MS) analysis revealed that phenol compounds and esters were removed significantly by the 1.5-MACC/PS system. When 1.5-MACC was used for the fourth time in the 1.5-MACC/PS system, the removal ratio of TOC was still over 62.2% in 360 min reaction. Thus, the 1.5-MACC/PS system has a potential practical application in treatment of BTCW.