Bicarbonate enhanced heterogeneous activation of peroxymonosulfate by copper ferrite nanoparticles for the efficient degradation of refractory organic contaminants in water.

Nowadays, the treatment of residual refractory organic contaminants (ROCs) is a huge challenge for environmental remediation. In this study, a potential process is provided by copper ferrite catalyst (CuFe2O4) activated peroxymonosulfate (PMS, HSO5-) in the bicarbonate (HCO3-) enhanced system for efficient removal of Acid Orange 7 (AO7), 2,4-dichlorophenol, phenol and methyl orange (MO) in water. The impact of key reaction parameters, water quality components, main reactive oxygen species (ROS), probable degradation mechanism, rational degradation pathways and catalyst stability were systematically investigated. A 95.0% AO7 (C0 = 100 mg L-1) removal was achieved at initial pH (pH0) of 5.9 ± 0.1 (natural pH), CuFe2O4 dosage of 0.15 g L-1, PMS concentration of 0.98 mM, HCO3- concentration of 2 mM, and reaction time of 30 min. Both sulfate radical (SO4-•) and hydroxyl radical (•OH) on the surface of catalyst were proved as the predominant radical species through radical quenching experiments and electron paramagnetic resonance (EPR) analysis. The buffer nature of HCO3- was partially contributed for the enhanced degradation of AO7 under CuFe2O4/PMS/HCO3- system. Importantly, according to 13C nuclear magnetic resonance (NMR) and EPR analysis, the positive effect of bicarbonate may be mainly attributed to the formation of peroxymonocarbonate (HCO4-), which may enhance the generation of •OH. The magnetic CuFe2O4 particles can be well recycled and the leaching concentration of Cu was acceptable (<1 mg L-1). Considering the widespread presence of bicarbonate in water environment, this work may provide a safe, efficient, and sustainable technique for the elimination of ROCs from practical complex wastewater.

Efficient degradation of clofibric acid by heterogeneous catalytic ozonation using CoFe2O4 catalyst in water.

CoFe2O4 (Cobalt ferrite, CF) nanoparticles were prepared, well characterized and applied as efficient solid catalyst in catalytic ozonation, named CF/O3 process, for the removal of emerging organic contaminants (EOCs). The degradation and mineralization of clofibric acid (CA) in CF/O3 process were dramatically enhanced in comparison with those under the O3 system. Surface hydroxyl groups (HGs) were considered as an important factor for ozone decomposition and the reactive oxygen species (ROS) on the catalyst surface were mainly responsible for CA elimination. The contribution and formation of ROS, including hydroxyl radicals (•OH), especially superoxide radicals (O2•-), singlet oxygen (1O2), and hydrogen peroxide (H2O2) were evaluated, and a rational mechanism was elucidated accordingly. Probable degradation pathway of CA was proposed according to the organic intermediates identified. The acute toxicity of the treated solution increased during the first 15 min and then declined rapidly and nearly disappeared as the reaction proceeded. In addition, acceptable catalytic performance of CF/O3 can be obtained for the treatment of other EOCs and the treatment of natural surface water spiked with CA. This work presents an efficient and promising catalytic ozonation technique for the elimination of EOCs in complex water matrices.

Efficient degradation of bisphenol A in water by heterogeneous activation of peroxymonosulfate using highly active cobalt ferrite nanoparticles.

Cobalt ferrite CoFe2O4 catalyst was fabricated and systematically investigated as an efficient peroxymonosulfate (PMS, HSO5-) activator for the degradation of recalcitrant organic contaminants (ROCs) in water treatment. Both SO4- and OH on the surface of catalyst were unveiled to be primarily responsible for bisphenol A (BPA) degradation by a comprehensive study using electron paramagnetic resonance (EPR), radical scavengers and quantification of SO4-, and the negligible contribution of singlet oxygen (1O2) was also observed. BPA degradation was accelerated in the presence of humic acid, and it increased first but then decreased with the further addition of fulvic acid. Moreover, the presence of chloride and bicarbonate ions can enhance both BPA and TOC removal. The toxicity of the target aqueous solution ascended slowly at the early stage but then declined dramatically and almost vanished as the reaction proceeded. The removal efficiencies of other typical ROCs (clofibric acid, 2,4-dichlorophenol, etc.) and the decontamination of natural surface water spiked with BPA were also evaluated. This CoFe2O4/PMS process could be well applied as a safe, efficient, and sustainable approach for ROCs remediation in complex wastewater matrix.

Ultrasound-assisted heterogeneous peroxymonosulfate activation with Co/SBA-15 for the efficient degradation of organic contaminant in water.

A potential advanced oxidation process is provided by SBA-15 supported cobalt (Co/SBA-15) activated peroxymonosulfate (PMS, HSO5-) in the ultrasound (US) enhanced system, named Co/SBA-15/PMS/US process, for the elimination of refractory organic contaminants (ROCs) in water. This process exhibited favorable behavior with 95.5 % C.I. Acid Orange 7 (AO7) degradation using 5 mM PMS, 0.5 g/L Co/SBA-15 catalyst, 190 W US power at initial pH of 6.0 after 90 min reaction. Co/SBA-15 particles remained satisfied catalytic activity and stability with very low level of cobalt release in 10 successive cycles. The scavenge tests and electron paramagnetic resonance (EPR) result as well as the cobalt leaching concentration revealed that the reactive radicals (SO4- and OH) on catalyst surface were primarily responsible for AO7 oxidation, and a rational mechanism was elucidated accordingly. The presence of chloride ions and bicarbonate could improve AO7 removal. The probable pathway of AO7 degradation was proposed based on the intermediates identified. This Co/SBA-15/PMS/US process could be well applied for the destruction of other typical ROCs (bisphenol A, clofibric acid, and rhodamine B) and the treatment of lake and river water spiked with AO7, and this study may provide an efficient PMS technique for the remediation of ROCs in water.