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.