Synthesis of superparamagnetic MnFe2O4/mSiO2 nanomaterial for degradation of perfluorooctanoic acid by activated persulfate

Recent advances in the application of magnetic materials for the management of perfluoroalkyl substances in aqueous phases

Perfluoroalkyl substances (PFASs) are a class of artificially synthesised organic compounds extensively used in both industrial and consumer products owing to their unique characteristics. However, their persistence in the environment and potential risk to health have raised serious global concerns. Therefore, developing effective techniques to identify, eliminate, and degrade these pollutants in water are crucial. Owing to their high surface area, magnetic responsiveness, redox sensitivity, and ease of separation, magnetic materials have been considered for the treatment of PFASs from water in recent years. This review provides a comprehensive overview of the recent use of magnetic materials for the detection, removal, and degradation of PFASs in aqueous solutions. First, the use of magnetic materials for sensitive and precise detection of PFASs is addressed. Second, the adsorption of PFASs using magnetic materials is discussed. Several magnetic materials, including iron oxides, ferrites, and magnetic carbon composites, have been explored as efficient adsorbents for PFASs removal from water. Surface modification, functionalization, and composite fabrication have been employed to improve the adsorption effectiveness and selectivity of magnetic materials for PFASs. The final section of this review focuses on the advanced oxidation for PFASs using magnetic materials. This review suggests that magnetic materials have demonstrated considerable potential for use in various environmental remediation applications, as well as in the treatment of PFASs-contaminated water.

Research Updates on the Mechanism and Influencing Factors of the Photocatalytic Degradation of Perfluorooctanoic Acid (PFOA) in Water Environments

Perfluorooctanoic acid is ubiquitous in water bodies and is detrimental to the health of organisms. Effectively removing perfluorooctanoic acid (PFOA), a persistent organic pollutant, has been a hot topic around the world. With traditional physical, chemical, and biological methods, it is difficult to effectively and completely remove PFOA, the costs are high, and it is easy to cause secondary pollution. There are difficulties in applying some technologies. Therefore, more efficient and green degradation technologies have been sought. Photochemical degradation has been shown to be a low-cost, efficient, and sustainable technique for PFOA removal from water. Photocatalytic degradation technology offers great potential and prospects for the efficient degradation of PFOA. Most studies on PFOA have been conducted under ideal laboratory conditions at concentrations that are higher than those detected in real wastewater. This paper summarizes the research status of the photo-oxidative degradation of PFOA, and it summarizes the mechanism and kinetics of PFOA degradation in different systems, as well as the influence of key factors on the photo-oxidative degradation and defluoridation process, such as system pH, photocatalyst concentration, etc. PFOA photodegradation technology's existing problems and future work directions are also presented. This review provides a useful reference for future research on PFOA pollution control technology.

Utility and mechanism of magnetic nano-MnFe2O4/MWNT activation for oxidative degradation of tetracycline by persulfate

A magnetic MnFe₂O₄/MWNT nanocomposite activated with sodium persulfate (PDS) was investigated for the removal of the widely used antibiotic tetracycline (TC). The best-performing 80 wt.% MnFe₂O₄/MWNT nanocomposite was screened for catalytic degradation of TC by comparing the catalytic and adsorption processes. The nanocomposite was evaluated using a series of physical characterizations. The effects of catalyst dosage, PDS dosage, temperature, initial pH, and initial concentration of TC on TC removal were investigated. After the reaction for 90 min, the addition of 4 mM PDS to the 80 wt.% MnFe₂O₄/CNT catalyst at 0.5 g/L degraded 78.85% of TC and 51.97% of TOC at an initial TC concentration of 40 mg/L. The reusability of MnFe₂O₄/MWNT nanocomposite was evaluated and the structural stability of the material was verified. It was demonstrated that multiple active species (SO₄^-, ·OH, ·O₂^-, ¹O₂) were produced in the MnFe₂O₄/MWNT/PDS system. The catalytic mechanism was analyzed based on the XPS results. Total organic carbon (TOC) measurement indicated partial TC had completely mineralized. The presumable degradation pathway of TC was proposed according to intermediate products by the LC-MS method.

Surface facet Fe2O3-based visible light photocatalytic activation of persulfate for the removal of RR120 dye: nonlinear modeling and optimization

Photocatalytic activation of persulfate (PS) is recently emerged as an energy-efficient and environmentally sustainable approach for pollutants degradation, which enables to leverage the strengths of low-cost solar energy and heterogeneous catalysis. Herein, we investigated the photocatalytic decomposition of reactive red 120 (RR120) dye using PS-activated Fe₂O₃ nanoparticles and elucidated the effect of their facets, α-Fe₂O₃ (001), β-Fe₂O₃ (100), and γ-Fe₂O₃ (111). β-Fe₂O₃ not only boosted the charge carrier separation but also provided more active sites for PS activation resulting in 6- and 3.5-fold higher photocatalytic activities compared to α-Fe₂O₃ and γ-Fe₂O₃, respectively. Response surface methodology and artificial neural network coupled with genetic algorithm models were utilized to optimize and foresee Fe₂O₃/PS system under visible light. Almost 100% color removal and 82% organic removal were observed under the optimum conditions at 20 mg/L RR120, 22 mg/L β-Fe₂O₃, 18 mg/L PS, and pH: 3. Scavenger test indicated that both sulfate and hydroxyl radicals are responsible for the observed RR120 removal. Although cell viability test indicated that cytotoxicity of wastewater is not significantly reduced after treatment. All the results proposed that β-Fe₂O₃/PS at relatively low doses has a great potential to decompose and mineralize recalcitrant dyes in wastewater under invisible light.