The simplest and ultrafast microwave-mediated solid-state construction of cobalt oxide/carbon hybrid as an efficient peroxymonosulfate activator for ciprofloxacin degradation

Activation of peroxymonosulfate with ZIF-67-derived Co/N-doped porous carbon nanocubes for the degradation of Congo red dye

In this study, porous carbon nanocubes encapsulated magnetic metallic Co nanoparticles (denoted as Co@N-PCNC) was prepared via pyrolyzing ZIF-67 nanocubes precursor at 600 °C and characterized by various technologies. It was used to activate peroxymonosulfate (PMS) to degrade Congo red (CR) dye efficiently. Over 98.45% of 50 mg L-1 CR was degraded using 0.033 mM PMS activated by 75 mg L-1 Co@N-PCNC within 12 min. The free radical quenching experiments were performed to reveal the nature of the reactive oxygen species radicals generated throughout the catalytic oxidation of CR. The effects of common inorganic anions and the water matrix on CR removal were studied. Moreover, the results of the kinetic study revealed the suitability of the pseudo-first-order and Langmuir-Hinshelwood kinetic models for illustrating CR degradation using the Co@N-PCNC/PMS system. Ultimately, the Co@N-PCNC displayed good operational stability, and after five cycles, the CR removal rate can still maintain over 90% after 12 min.

Mechanism of peroxymonosulfate activation by nanoparticle Co@N-C: Experimental investigation and theoretical calculation

The release of organic dyes, such as Rhodamine B (RhB), into industrial wastewater has led to significant issues with color pollution in aquatic environments. Herein, we prepared a cobalt nanoparticles (NPs)-based catalyst with the nitrogen-doped carbon-support (Co@N-C) for effective PMS activation. The Co@N-C/PMS system demonstrated the excellent catalytic activity of Co@N-C for activating PMS, achieving nearly 100% degradation of RhB. Singlet oxygen (1O2) and sulfate radicals (SO4•-) were dominant reactive oxygen species for RhB degradation. Density functional theory (DFT) calculations substantiated that the production of 1O2 commenced with the initial generation of *OH through hydrogen abstraction from PMS, culminating in the direct release of oxygen to form 1O2 (PMS→*OH→O*→1O2). The generation of SO4•- was attributed to electron transfer to PMS from the surface of Co NPs (Co0→Co2+→Co3+) and the C-N shell (Co2+→Co3+). The research findings provided new insights into the development of Co-based heterogeneous catalysis for advanced oxidation of refractory organic pollutants in wastewater treatment.

Iron-loading N and S heteroatom doped porous carbon derived from chitosan and CdS-Tetrahymena thermophila for peroxymonosulfate activation

Transforming waste into resources is an important strategy to enhance the economic efficiency and reduce the waste entering the environment. In this work, iron-loading N and S co-doped porous carbon materials, as peroxymonosulfate (PMS) activator for pollutants degradation, were prepared by pyrolysis of the mixture of iron loading chitosan and CdS-Tetrahymena thermophila under N2 flow. Chitosan is mainly derived from the shell waste of shrimp and crab, and CdS-Tetrahymena thermophila is produced in the removing process of Cd2+ pollution bioremediation using Tetrahymena thermophila. The synergistic effects of iron related species and heteroatoms (S/N) co-doped porous carbon in the obtained carbon materials improved the performance for activating PMS. The prepared Fe-S-CS-1-900 exhibited high performance for the degradation of Rhodamine B (RhB) by activating PMS. Radical quenching tests and electron paramagnetic resonance measurements suggested that superoxide radical (O2-) and singlet oxygen (1O2) were the primary reactive oxygen species in RhB degradation. These results propose new insights of using biomass waste to derive Fe-loading N and S heteroatom co-doping carbon as PMS activator applied in the removal of organic pollutants.

Catalytic Degradation of Organic Contaminants by Microwave-Assisted Persulfate Activation System: Performance and Mechanism

In this study, a nickel ferrite (NiFe2O4) system was constructed to purify a phenol solution in water. During the process, the influences of several critical operating parameters including the NiFe2O4 amount, PS dosage, MW power, initial pH value, and different natural water anions were systematically studied. The results indicated that the constructed system performed excellently regarding the removal efficiency (97.74%) of phenol within 30 min. Meanwhile, the influence of co-existing anions such as Cl−, NO3−, H2PO4−, and HCO3− was also studied, which displayed an inhibiting action on phenol degradation, while HA facilitated it. To explore the reaction mechanism of this system, major free radical quenching experiments were conducted, and it was confirmed that both SO4•− and HO• were primary radicals. Moreover, stability experiments confirmed the apt stability of the NiFe2O4 system. Besides, the mineralization and toxicity analysis performed during phenol degradation also confirmed the superiority of the as-constructed system. Furthermore, the possible degradation mechanism of phenol was proposed. Hence, this system could be applied in advanced wastewater treatment.