Coordination-driven Cu-based Fenton-like process for humic acid treatment in wastewater

Fenton oxidation process is effective in organic pollutant degradation during wastewater treatment, but subject to narrow pH range and secondary pollution. In this work, an application-promising alternative, i.e., coordination-driven Cu-based Fenton-like process, was proposed for wastewater treatment using humic-acid (HA) as the target contaminant. The results showed that the removal of HA through Cu-based Fenton-like process can reach 70% under the condition of pH 8.0, 146.8 mmol/L H₂O₂, 146.8 μmol/L Cu (II), 50 °C, and 4 h. Addition of Cl^- could significantly accelerate the reaction process through coordination with copper ions, while HCO₃^- and P₂O₇^4- exhibited opposite effects. Increasing temperature is also beneficial for advancing the reaction, and the removal of HA followed pseudo-first-order kinetics. Fluorescence spectroscopic analyses showed that the removal of HA experienced a two-stage process, i.e., oxidation followed by degradation, which is dependent of the presence of coordination ions. Parallel factor analysis was used to characterize the change of fluorescence components. Three fluorescent components, i.e., terrestrial humic-like, UV/visible terrestrial humic-like and protein-like component were identified, all of which were effectively removed. This study deepens our understanding on Cu-based Fenton-like process, and may provide a promising technology for refractory wastewater treatment.