Persulfate

Recently there is vigorous growth of reports on persulfate (PS)-based advanced oxidation processes (AOPs), inclining to development of newfangled catalysts and treatment of a wide range of organic pollutants. PS-related non-radical oxidation pathways are lately proposed, whereas there still exist debatable observations and explanation on these issues. While non-radical reactions in heterogeneous systems have been well commented, this review focuses on the latest discovery of non-radical oxidation in homogeneous persulfate (especially peroxymonosulfate (PMS)) systems. The application of direct oxidation process is firstly summarized and the roles of PMS distal oxygen in attack on organic pollutants like antibiotics are highlighted. Besides, the effects of exogenic and endogenic halogen on the reactivity and mechanisms of HOX in PS activation are discussed. Then the formation and reaction pathways of singlet oxygen (1 O 2) triggered by phenol/carbonyl compounds and nucleophiles are elaborated. Recent discovery on formation of high valent metal species by PS activation and their reactivity is reviewed lastly. By sorting out a large number of cutting-edge research reports, this review conducts a detailed and critical analysis and overview on the homogeneous PS non-radical mechanisms, and points out the controversies and challenges so as to better understand the reaction mechanism and further improve their treatment performance.

Pyrite mine waste was used as a non-toxic and natural catalyst for the activation of peroxydisulfate (PDS) and peroxymonosulfate (PMS) to oxidize tetracycline (TTC), one of the most extensively used antibiotics worldwide, in contaminated water. The results demonstrated that PMS was activated more effectively than PDS by using pyrite. Scavenging experiments indicated that both OH • and SO 4 • − were the main oxidative species in the pyrite/ PMS process, while SO 4 • − was more dominant. A high degradation of 98.3 % and significant mineralization (up to 46 %) of TTC (50 mg/L) were achieved using pyrite activated PMS at a reaction time of 30 and 60 min, respectively. In-vivo toxicity of raw and pyrite/PMS treated TTC solutions was evaluated using biochemical and histopathological assays. The results revealed that the pyrite/PMS process significantly decreased the nephro-toxicity (90 %) and hepatotoxicity (85 %) effect of TTC. Catalyst reusability was evaluated under cycling conditions. No significant decrease in process efficiency was measured between the first and fourth cycle (<3% decrease in TTC removal). In conclusion, mine waste pyrite nanoparticles can be considered as a non-toxic and clean catalyst to activate PMS for an effective detoxification, degradation, and intermediate mineralization of TTC, as a refractory water pollutant.

The objective of this study was to investigate the performance of employing H2O2 reagent in persulfate activation to treat stabilized landfill leachate. A central composite design (CCD) with response surface methodology (RSM) was applied to evaluate the relationships between operating variables, such as persulfate and H2O2 dosages, pH, and reaction time, to identify the optimum operating conditions. Quadratic models for the following two responses proved to be significant with very low probabilities (&lt;0.0001): chemical oxygen demand (COD) and NH3-N removal. The obtained optimum conditions included a reaction time of 116 min, 4.97 g S2O82−, 7.29 g H2O2 dosage and pH 11. The experimental results were corresponding well with predicted models (COD and NH3-N removal rates of 81% and 83%, respectively). The results obtained in the stabilized leachate treatment were compared with those from other treatment processes, such as persulfate only and H2O2 only, to evaluate its effectiveness. ...