Efficient degradation of organic phosphorus in glyphosate wastewater by catalytic wet oxidation using modified activated carbon as a catalyst

Glyphosate (PMG) wastewater, which is an organic phosphorus (OP) wastewater containing 200-3000mg/L PMG, was treated via catalytic wet oxidation (CWO) to degrade PMG to orthophosphate . The catalysts were activated carbons (ACs) modified by H2O2 oxidation and thermal treatment with ammonia or melamine. The catalysts were characterized using N-2 adsorption/desorption, Boehm titration, and X-ray photoelectron spectroscopy. The CWO experiments were performed in a co-current upflow fixed-bed reactor at 110-130 degrees C and under 1.0MPa. The AC modified by H2O2 and melamine had the highest catalytic activity and had excellent stability in the continuous 55-day test: 100% PMG removal and over 93% OP removal for different samples of real PMG wastewater. More pyrrolic nitrogen, pyridinic nitrogen, and graphitic nitrogen along with quinone oxygen functional groups on the surface of the AC showed higher catalytic activity according to linear fitting results. The identification and quantification of critical reaction intermediaries and the main end products of PMG degradation were possible, and a degradation pathway was proposed.