Search

Graphical abstract Highlights • The influence of water matrix on the efficiency of AOTs is overviewed. • Photolysis, photocatalysis, UV/H 2 O 2 -, Fenton-, and O 3 -based processes are reviewed. • Dissolved organic matter and inorganics can act as inhibitors and/or promoters. • The effect results from the interplay of the co-existing substances. • The knowledge on the role of matrix constituents is crucial for installation of AOTs. Abstract Micropollutants (MPs) in the aquatic compartments are originated from many sources and particularly from the effluents of urban wastewater treatment plants (UWWTPs). Advanced oxidation technologies (AOTs) usually applied after biological processes, have recently emerged as effective tertiary treatments for the removal of MPs, but the oxidation rates of the single compounds may be largely affected by the constituent species of the water matrix. These species include dissolved organic matter and inorganic species (e.g., carbonate, bicarbonate, nitrite, sulphate, chloride). This review analyses the impact of such substances on common AOTs including photolysis, UV/H 2 O 2 , Fenton, photocatalysis, and ozone-based processes. The degradation efficiency of single MPs by AOTs results from the combined impact of the water matrix constituents, which can have neutral, inhibiting or promoting effect, depending on the process and the mechanism by which these water components react. Organic species can be either inhibitors (by light attenuation; scavenging effects; or adsorption to catalyst) or promoters (by originating reactive oxygen species (ROS) which enhance indirect photolysis; or by regenerating the catalyst). Inorganic species can also be either inhibitors (by scavenging effects; formation of radicals less active than hydroxyl radicals; iron complexation; adsorption to catalyst or decrease of its effective surface area) or promoters (e.g., nitrate ions by formation of ROS; iron ions as additional source of catalyst). The available data reviewed here is limited and the role and mechanisms of individual water components are still not completely understood. Further studies are needed to elucidate the wide spectrum of reactions occurring in complex wastewaters and to increase the adoption of AOTs in UWWTPs. [ABSTRACT FROM AUTHOR]

• N-doped reduced graphene oxide was synthesized using melamine (M) as N source (rGO-M). • A rGO-M-PVDF composite membrane was prepared by including rGO-M in a PVDF matrix. • rGO-M-PVDF promoted the activation of persulfate in continuous mode. • Conversions of micropollutants in the range 54–91% were obtained. • rGO-M-PVDF showed resistance towards fouling phenomena. Metal-free carbon-based polymer nanocomposite membranes were employed for the first time for activated persulfate oxidation in continuous mode of operation. For that purpose, reduced graphene oxide doped with nitrogen by using melamine as source (rGO-M) was included as catalytic active phase in a poly(vinylidene fluoride) matrix (PVDF). The performance of the resulting composite membrane (rGO-M-PVDF) was compared against that obtained with supported membranes prepared by simple filtration of rGO-M into a PTFE substrate. The uniform distribution of rGO-M within both the surface pores and cross-sectional channels of the composite rGO-M-PVDF membrane (with a thickness of 292 ± 20 μm) was confirmed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while its main structural features were studied by X-ray diffraction (XRD) and Raman spectroscopy. The quite good performance of this composite membrane was demonstrated by the degradation of three fluoroquinolone antibiotics at ppb level in ultrapure water (100 μg L−1 each), leading to average pollutant mass removal rates in the range 2.05–2.73 mg m−2 h−1. Conversions of the pharmaceuticals in the range 54–91% were obtained even after 24 h of operation in full continuous mode. Persulfate conversion was confirmed and high resistance to fouling was observed with this novel catalytic membrane. Average pollutant mass removal rates in the range 0.34–0.77 mg m−2 h−1 were obtained in preliminary experiments performed with surface water instead of ultrapure water, highlighting the need for additional studies on both water matrix effects and process optimization. [ABSTRACT FROM AUTHOR]