Hydrothermal Enhanced Nanoscale Zero-Valent Iron Activated Peroxydisulfate Oxidation of Chloramphenicol in Aqueous Solutions: Fe-Speciation Analysis and Modeling Optimization

Mechanism insight into efficient peroxydisulfate activation by novel nano zero-valent iron anchored yCo3O4 (nZVI/yCo3O4) composites

Novel nano zero-valent iron anchored bio-matrix supported Co₃O₄ (nZVI/yCo₃O₄) composites were fabricated for tetracycline (TC) efficient degradation by activating peroxydisulfate (PS). The systematical characterizations verified that the nZVI/yCo₃O₄ composites with magnetism have higher surface area than yCo₃O₄ and pure Co₃O₄, contributing to more accessible active sites. Various catalytic parameters (nZVI mass ratio, leached ions, initial pH, catalyst dosage, PS concentration and coexisting anions) were thoroughly investigated. In nZVI/yCo₃O₄/PS system, 97.6 %, 93.4 % and 77.3 % TC were degraded within 15 min at pH 3.0, 6.0 and 9.0, respectively. Based on four successive degradation runs, the excellent mineralization rate and reusability of nZVI/yCo₃O₄ composites were mainly benefited from the suppressed metals leaching. The PS activated mechanisms were proposed as non-radicals (¹O₂) dominated pattern at acidic conditions and radicals (SO₄-) predominant pattern at alkaline environment, which may be highly related to the electron donating capacity of nZVI at different pH and the M^(n + 1)+/Mⁿ⁺ redox cycling between Fe or Co metal. The plausible degradation routes of TC were presented based on the detected intermediates. Overall, the synthesized heterogeneous nZVI/yCo₃O₄ composites can efficiently active PS at a wide pH range, and further broaden the application of Co-based catalysts in PS activation.