Efficient Pretreatment of Landfill Leachate by Loading Sulfonated Cobalt Phthalocyanine Catalyst: Optimization, Regeneration and Mechanisms.

The direct biological treatment of high concentrations of toxic organics in landfill leachate represents a formidable challenge. Given the excellent performance of adsorption and catalytic oxidation of sulfonated cobalt phthalocyanine / activated carbon (CoSPc/AC), this study investigated the removal of chemical oxygen demand (COD) from landfill leachate by CoSPc/AC under different conditions of temperatures, carrier particle sizes and concentrations. The response surface model further optimized the experimental conditions. Under conditions of 60 °C temperature, 50 mesh carrier particle size, and 14,697 mg/L influent COD, the predicted COD removal efficiency reached a maximum of 79.25%. The catalysts were characterized by X-ray diffraction, transmission electron microscopy and Fourier transform infrared spectroscopy. It was revealed that the adsorption of COD in landfill leachate by activated carbon was primarily by physical adsorption, and the adsorbed organic matters were attached to a fixed point outside the activated carbon until the adsorption equilibrium was reached. The catalytic oxidation of COD mainly depends on CoSPc-O²⁻, CO³⁺ and sulfonic acid groups which had strong oxidizing properties after activation. The carrier-catalyst prepared in this study had high adsorption capacity of activated carbon as well as a good chemical oxidation capacity.Article Highlights: CoSPc/AC is more suitable for the pretreatment of landfill leachate. The adsorption mainly proceeded via physical adsorption. The catalytic oxidation mainly depended on CoSPc-O^2-, Co³⁺ and sulfonic acid groups. [ABSTRACT FROM AUTHOR]