Heterogeneous activation of persulfate by a novel nano-magnetite/ZnO/activated carbon nanohybrid for carbofuran degradation: Toxicity assessment, water matrices, degradation mechanism and radical and non-radical pathways

We investigated for the first-time the fabrication of zinc oxide/water hyacinth-based activated carbon (ZnO/AC) and nano-magnetite (NM) (NM/ZnO/AC) nanohybrid for the utilization in photo-Fenton-like system. Response surface analysis showed that the optimal operating conditions for complete carbofuran degradation were pH 3, initial carbofuran concentration of 5.0 mg/L, PS concentration of 0.0923 mM and NM/ZnO/AC catalyst dose of 0.9 g/L. The degradation efficiencies declined to 46% and 28.8% after adding hydroxyl and sulfate radicals' quenchers, respectively compared to 92.8% in the case of no scavenger confirming the major role of sulfate and hydroxyl radicals. The degradation percentages of carbofuran were 100%, 95.7%, 51.8%, 67.8% and 21.6% for distilled, tap, sea, lake and drain water matrices showing the inhibitory effect of dissolved organic matter, turbidity and inorganic ions on the degradation performance. The degradation efficiencies and mineralization ratios of carbofuran in the case of suspended NM/ZnO/AC were higher than that of immobilized mode in five succeeding runs. The by-products generated after carbofuran degradation were primarily produced by cleavage and attack of reactive radicals. The efficient degradation of carbofuran, as well as the reduction of the toxicity of the generated intermediates affirmed the viability of using the synthesized composite for industrial effluents treatment.