Cerium oxide /Co-Co Prussian blue analogue composite catalyst for enhanced peroxymonosulfate activation for effective removal of tetracycline hydrochloride from water.

In this paper, a novel CeO2/Co3[Co(CN)6]2 (CeO2/PBACo-Co) composite was prepared with co-precipitation and utilized to activate peroxymonosulfate (PMS) to eliminate tetracycline hydrochloride (TCH). Catalyst screening showed that the composite with a CeO2:PBACo-Co mass ratio of 1:5 (namely, 0.2-CeO2/PBACo-Co) had the best performance. The degradation efficiency of TCH in 0.2-CeO2/PBACo-Co/Oxone system was investigated. The experimental results illustrated that 98% of 50 mg/L TCH and 48.5% of TOC were degraded by 50 mg/L 0.2-CeO2/PBACo-Co and 400 mg/L Oxone within 120 min at 25 °C and initial pH 5.3. Recycling studies showed that the elimination rate of TCH can still achieve 85.8% after five cycles, suggesting that 0.2-CeO2/PBACo-Co composite processes good reusability. Trapping experiments and EPR tests revealed that the reaction system produced multiple active species (1O2, O2•-, SO4•-, and •OH). We proposed the catalytic mechanism of 0.2-CeO2/PBACo-Co for PMS activation, which mainly involves the promoted Co3+/Co2+ cycle by Ce3+ donated electrons. These results indicate that CeO2/PBACo-Co composite is an effective catalyst for wastewater remediation.

Constructing core-shell structured Co3O4-MnWO4 composite photoelectrode with superior PEC water purification performance.

Semiconductor photoelectrocatalytic (PEC) technology is one of the most effective methods for removing organic pollutants from wastewater in advanced oxidation processes(AOPs). The selection of suitable semiconductor materials as photoanodes is a crucial factor for achieving superior PEC performance. Here, a core-shell structured Co3O4-MnWO4 architecture is created by enveloping MnWO4 nanoparticles onto the surface of Co3O4 nanowires through a two-step hydrothermal process. The optimized Co3O4-MnWO4-5 photoelectrode showed superior PEC degradation efficiency for KN-R (∼91.2% in 2 h) and durable stability (the accelerated lifetime reached ∼9100 s at a current density of 50 mA cm-2). Three actual wastewaters were also collected to verify the practical applicability of the photoelectrode.The energy consumption was measured at 4.48 kWhm-3, with a COD removal efficiency of 83% and a decolorization rate of 98%. These results demonstrate the excellent performance and promising application of the photoelectrode. The enhancement of PEC performance for the core-shell structured Co3O4-MnWO4 architecture can be attributed to the suitable energy band structure of the Co3O4-MnWO4 composite, higher OEP, larger electrochemical active surface area, accelerated transport of interface carriers, and lower charge transfer resistance. The energy band structure of the Co3O4-MnWO4 composite showed a strong redox ability to induce electrons/holes (e-/h+), which enhances the generation of intermediate active species (hydroxyl radical ·OH and superoxide radicals ·O2-). Therefore, the rationally designed core-shell structured Co3O4-MnWO4 architecture exhibited excellent practical applicability in the degradation of organic pollutants.

Peroxymonosulfate activation by magnetic CoNi-MOF catalyst for degradation of organic dye.

In this work, Fe3O4/CoNi-MOF was synthesized by a simple solvothermal method. The catalytic performance of 0.2-Fe3O4/CoNi-MOF toward PMS activation was studied by degradation of 20 mg/L methylene blue (MB). The results indicated that 0.2-Fe3O4/CoNi-MOF had good catalytic ability, the removal rate of MB was 99.4% within 60 min with 125 mg/L PMS and 150 mg/L catalyst. Quenching experiment and electron paramagnetic resonance (EPR) analysis revealed that the singlet oxygen (1O2), superoxide radical (•O2-) and sulfate radical (SO4•-) played a crucial role in the catalytic degradation process. Meantime, mechanism of PMS activation by 0.2-Fe3O4/CoNi-MOF was proposed, the electrons donated by Fe2+ can also enhance the Co-Ni cycles. In conclusion, Fe3O4/CoNi-MOF composite catalyst has the advantages of simple preparation, excellent catalytic activity and reusability, which is an effective catalyst for water pollution control.

Peroxymonosulfate activation through ferromagnetic bimetallic spinel sulfide composite (Fe3O4/NiCo2S4) for organic pollutant degradation.

Spinel sulfides are a good candidate as heterogeneous catalysts for wastewater treatment through peroxymonosulfate (PMS) activation. In this paper, magnetic Fe3O4/NiCo2S4 composite was successfully synthesized by hydrothermal method. Catalyst screening displayed that the composite catalyst with a Fe3O4:NiCo2S4 molar ratio of 1:3 (i.e.,0.33-Fe3O4/NiCo2S4) is the most optimal. The results showed that 0.33-Fe3O4/NiCo2S4 composite catalyst had superior catalytic activity, achieving 99.8%,65.1% and 40.7% of RhB, COD and TOC removals within 30 min with 180 m g/L PMS and 75 mg/L catalyst. We proposed a potential catalytic mechanism of PMS activation by Fe3O4/NiCo2S4 in two aspects. On the one hand, sulfur species such as S2- and S22- enhance the Co3+/Co2+, Ni3+/Ni2+ and Fe3+/Fe2+ cycles on Fe3O4/NiCo2S4 surface. On the other hand, there is the synergistic effect of Co3+/Co2+, Ni3+/Ni2+ and Fe3+/Fe2+ cycles in activating PMS. Overall, owing to its excellent catalytic activity, reusability, and easy recovery, Fe3O4/NiCo2S4 is a potentially useful catalyst for remediation of contaminated water.

Degradation of organic dye wastewater by H2O2-enhanced aluminum carbon micro-electrolysis.

In this research, the treatment of methylene blue (MB) dye wastewater by a novel system that combines H2O2 with an aluminum-carbon micro-electrolysis (ACE) was explored. The effects of the H2O2 amount, initial pH, aluminum to carbon ratio, total aluminum-carbon mass, dye concentration, and reaction temperature on degradation of MB were investigated. The findings revealed that under the following conditions: H2O2 34.0 mg/L, initial pH of 3.0, aluminum-to-carbon ratio of 2:1, total aluminum-carbon mass of 2.0 g/L, MB concentration of 20 mg/L, and 20 °C, the degradation rate of MB could reach 99.3% after 180 min, which is 18.4% more compared with ACE at the same conditions without H2O2. Through the quenching experiments, it was proved that the efficient free radicals produced during degradation are •OH and •O2-. Finally, a possible mechanism of H2O2 enhanced aluminum carbon micro-electrolysis (HP-ACE) for MB degradation was discussed.

Activation of peroxymonosulfate by CoFe2O4 loaded on metal-organic framework for the degradation of organic dye.

The magnetic composite CoFe2O4/ZIF-8 based on metal organic framework (MOF) with high specific surface area and high activity was synthesized by solvothermal method. The prepared catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), vibration sample magnetometer (VSM) and N2 adsorption-desorption isotherms, respectively. After characterization, CoFe2O4/ZIF-8 was applied to heterogeneous activation of peroxymonosulfate (PMS) for degrading methylene blue (MB). The result showed that the 0.075-CoFe2O4/ZIF-8 sample had the excellent catalytic activity. After catalytic reaction for 60 min, the degradation efficiency of MB (20 mg/L) reached about 97.9% at room temperature of 20 °C. The quenching experiment and electron paramagnetic resonance (EPR) analysis indicated that SO4- and OH radicals were the main active species in MB degradation. Meanwhile, the possible MB degradation mechanism was proposed. After four catalytic cycles, the degradation efficiency of MB has not been greatly reduced, indicating the practical application potential of CoFe2O4/ZIF-8 in water pollution cleanup.

Sewage sludge pretreatment by microwave irradiation combined with activated carbon fibre at alkaline pH for anaerobic digestion.

This research focuses on the effects of microwave-assisted activated carbon fibre (ACF) (MW-ACF) treatment on sewage sludge at alkaline pH. The disintegration and biodegradability of sewage sludge were studied. It was found that the MW-ACF process at alkaline pH provided a rapid and efficient process to disrupt the microbial cells in the sludge. The results suggested that when irradiated at 800 W MW for 110 s with a dose of 1.0 g ACF/g solid concentration (SS) at pH 10.5, the MW-ACF pretreatment achieved 55% SS disintegration, 23% greater than the value of MW alone (32%). The concentration of total nitrogen, total phosphorus, supernatant soluble chemical oxygen demand, protein, and polysaccharide increased by 60%, 144%, 145%, 74%, and 77%, respectively. An increase in biogas production by 63.7% was achieved after 20 days of anaerobic digestion (AD), compared to the control. The results indicated that the MW-ACF pretreatment process at alkaline pH provides novel sludge management options in disintegration of sewage sludge for further AD.