Catalytic oxidation of biorefractory cyanide-containing coking wastewater by deconjugation effect of bimetal copper-loaded activated carbon

Abstract

Due to the strong complexation and conjugation of various metal ions, the biorefractory low-concentration total cyanides (TCNs) remain stable and tenacious in wastewater after physicochemical-biological treatment. This study proposes a copper-loaded activated carbon (AC/Cu) mechanism to effectively remove TCN in the complex system, where the bimetallic synergy of AC/Cu/Zn can enhance the cyanide removal capacity up to 24.78 mg-TCN/g-AC, which is superior to most as-reported technologies in thermodynamics and kinetics. This result can be attributed to the weakening conjugated effect of less-coordinated cuprous cyanide with a lower barrier of transition and ground state calculated by density functional theory (DFT). Then, the presence of coupled metal ions (such as Zn2+) exposes more free cyanide through complexation competition which is reflected in the further reduction of the transition state barrier. More importantly, the orbital hybridization is of general significance for the conjugate recombination and deconjugation of conjugated pollutants, which will provide a new direction for the removal of refractory pollutants.