Degradation of phenol by Cu-Ni bimetallic-doped sludge biochar as a fenton-like catalyst: Mechanistic study and practical application

In this study, the sewage sludge was converted into sludge biochar (SBC) and doped with Cu-Ni bimetal to synthesize a novel composite catalyst (Cu-Ni@SBC) for the activation of H2O2 for phenol degradation. Characterization results showed that the Cu-Ni bimetal was successfully doped into the SBC and led to the formation of a porous structure with abundant cavities, resulting in a larger specific surface area and higher adsorbed oxygen content. Mechanism analysis revealed a valence state conversion cycle between Cu0-Cu(II), Ni(III)-Ni(II) and Cu-Ni which made Cu-Ni@SBC have higher electron transfer performance. Response surface methodology was applied to determine the optimal preparation and reaction conditions, under which the Fenton-like system composed of Cu-Ni@SBC and H2O2 removed 100 % of phenol and mineralized 69.1 % of TOC from simulated wastewater. In addition, the experimental results showed that the Cu-Ni@SBC material had a relatively wide pH adaptation range (4–8), and the removal efficiency of phenol could reach 76.4 % after 5 cycles of experiments, and the catalytic inhibition rates of the two common coexisting anions, HCO3– and Cl-, were 17.1 % and 0 %, respectively. The results of practical application revealed that the phenol removal efficiency reached 90.44 % and the pollutant mineralization rate could reach 58.5 % within 90 min, which proved that the catalyst was suitable for the advanced degradation of organic matter in coal chemical wastewater. Therefore, Cu-Ni@SBC can be considered as a promising Fenton-like catalyst, and the process method is also of some guiding significance for the treatment of coal chemical wastewater.