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a b s t r a c tMicrowave (MW)-activated H 2 O 2 and persulfate (PS)-induced ZnO-catalyzed purification of water contaminated with the cationic dye Rhodamine B (RhB) is investigated. The degradation is much faster compared with that under identical conventional heating (CH) conditions thus suggesting that the MW effect is not just thermal. PS is more efficient for the oxidation and eventual mineralization of RhB compared with H 2 O 2 . Combination of H 2 O 2 and PS does not have either synergic effect or even additive effect thereby demonstrating the mutual destruction of the oxidants in the presence of one another at least to a limited extent. The enhanced MW degradation in the presence of oxidants is attributed to increased formation of reactive free radicals and their interaction with the dye. ZnO, which enhances the degradation of many organic chemical pollutants under advanced oxidation process (AOP) conditions, inhibits the degradation in the presence of MW/PS and CH/PS. The activation energy of the degradation is reduced by MW in comparison with CH under identical reaction conditions. The effect of different reaction parameters, namely, oxidant dosage, concentration of the dye, pH, MW power, dosage of catalyst, temperature, and reaction volume on the degradation/mineralization rate is evaluated and optimum conditions are determined. The identity of many of the intermediates formed during the degradation is confirmed by LC/MS.

Photo-driven advanced oxidation process (AOP) with pharmaceutical wastewater has been poorly investigated so far. This paper presents the results of an experimental investigation on the photocatalytic degradation of emerging pharmaceutical contaminant chloroquine (CLQ) in water using zinc oxide (ZnO) nanoparticles as the catalyst and solar light (SL) as the source of energy. The catalyst was characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDAX), and transmission electron microscopy (TEM). The effect of various operating parameters such as catalyst loading, the concentration of target substrate, pH, and the effect of oxidants and anions (salts) on the efficiency of degradation was tested. The degradation follows pseudo-first-order kinetics. Surprisingly, contrary to the observation in most photocatalytic studies, the degradation is more efficient under solar radiation, with 77% under solar (SL) irradiation and 65% under UV light in 60 min. The degradation leads to slow and complete COD removal through several intermediates identified by the liquid chromatography–mass spectrometry (LC-MS) technique. The results suggest the possibility of using inexpensive natural, non-renewable solar energy for the purification of CLQ-contaminated water, thereby enabling the reuse of scarce water resources. Graphical Abstract

Microplastic pollution has rapidly become one of the major global environmental concerns because of its low biodegradability rate and threat to biota. Although many treatment methods are reported, the advanced oxidation process (AOP) is recommended because of its capacity to completely mineralize organic pollutants into carbon dioxide and water. This review gathers published investigations on recent AOP techniques (UV/solar photolysis and photocatalysis (PC), UV/H2O2, Fenton reaction, sonolysis, heat‐activated persulphate and peroxymonosulphate) tested for the degradation of microplastics from water and wastewater. The review lists 54 studies, by far the most comprehensive collection on the AOP‐driven treatment of microplastics, and is also the first to explain the methods related to the ultrasonic degradation of microplastics. We found that all the reviewed AOP techniques achieved satisfying performance in the degradation of microplastics. This paper proposes recommendations for future research based on the review.