Synergistic adsorption and Fenton-like oxidation of neutral red by the combination of COFs and Co(OH)2 in chitosan hydrogel microspheres

Abstract

The rapid industrialization and extensive use of synthetic dyes have led to significant environmental pollution, particularly through dye wastewater, which poses severe ecological risks. Conventional single treatment methods often struggle to effectively remove complex and stable dye molecules. In this study, we developed COF-based chitosan hydrogel microspheres by combining COF-LZU1 and Co(OH)₂ via co-precipitation and self-assembly techniques. The synergistic effect between COF and Co(OH)₂ enabled simultaneous adsorption and degradation of neutral red, significantly enhancing the adsorption capacity. Under optimal conditions (15 mg of composite material, 20 min reaction time, pH = 7), the composite exhibited an adsorption capacity of 1325.48 mg/g and a degradation efficiency of 100 %, surpassing the performance of most conventional adsorbents. Furthermore, the incorporation of Co(OH)₂ into COF enhanced the stability of the composite material, as indicated by thermodynamic analysis and adsorption performance across different component ratios. Adsorption process modeling revealed that the adsorption kinetics fit well with the Elovich model, while isothermal adsorption followed the Langmuir model. Among common interfering substances, CH₃COO⁻ was found to enhance the catalytic process, whereas humic acid inhibited it. Quenching experiments and EPR analysis confirmed that superoxide anion radicals (•O₂⁻) and singlet oxygen (¹O₂) were the primary active species in the catalytic process, with hydroxyl radicals (•OH) playing a relatively minor role. This study highlights the synergistic interaction of COF and Co(OH)₂ in improving adsorption performance, stability, and catalytic efficiency, providing a novel strategy for the preparation of advanced composite materials and new insights into pollutant removal mechanisms.