ABSTRACT
The current study investigates a novel redox technology based on synthetic franklinite-like zinc-ferrite nanomaterial with magnetic properties and redox nature for potential use in water treatment. Physicochemical characterization revealed the nanoscale size and AB2O4 spinel configuration of the zinc-ferrite nanomaterial. The redox activity of nanoparticles was tested for degradation of diclofenac (DCF) pharmaceutical in water, without any added external oxidants and under dark experimental conditions. Results revealed ~90% degradation in DCF (10 µM) within 2 min of reaction using 0.17 g/L Zn1.0Fe2.0O4. Degradation of DCF was due to chemical reduction by surface electrons on zinc-ferrite and oxidation by oxygen-based radicals. Three byproducts from reduction route and eight from oxidation pathways were identified in the reaction system. Reaction pathways were suggested based on the identified byproducts. Results demonstrated the magnetic zinc-ferrite is a standalone technology that has a great promise for rapid degradation of organic contaminants, such as DCF in water.
ABSTRACT
The photochemical degradation and mineralization of tyrosol (TSL), a model phenolic compound present in olive mill wastewater, were studied by UV-254â¯nm irradiated peroxymonosulfate (PMS), hydrogen peroxide (H2O2) and persulfate (PS). Effects of initial TSL concentration, UV fluence, pH, phosphate buffer and presence of inorganic anions (i.e., Cl-, SO42- and NO3-) were also investigated. Sulfate and hydroxyl radicals were demonstrated to be responsible for TSL degradation and mineralization. Regardless of the treatment conditions, pseudo-first-order kinetics could be obtained, with the efficiencies following UV/PSâ¯>â¯UV/H2O2 > UV/PMS. The better removal of TSL by UV/PS correlated with the quantum yield and concentration of sulfate radical in the system. Albeit acidic condition slightly enhanced the performance of the AOPs, complete oxidation of TSL was achieved at pH 6.8 by both UV/PS and UV/H2O2. Though, inorganic anions or different concentrations of phosphate buffer did not affect TSL degradation kinetics, presence of inorganic ions decreased significantly the TOC removal for both UV/PMS and UV/H2O2 processes. Meanwhile, UV/PS process was the least influenced by inorganic ions and showed the highest TOC removal of â¼35%. Overall, UV/PS process was the most effective for TSL degradation and mineralization in the presence or absence of common water constituents.
ABSTRACT
Various studies have revealed the non-biodegradable and endocrine disrupting properties of sulfonated organic UV absorbers, directing people's attention toward their risks on ecological and human health and hence their removal from water. In this study, UV-254nm/H2O2 advanced oxidation process (AOP) was investigated for degrading a model UV absorber compound 2-phenylbenzimidazole-5-sulfonic acid (PBSA) and a structurally similar compound 1H-benzimidazole-2-sulfonic acid (BSA), with a specific focus on their mineralization. At 4.0mM [H2O2]0, a complete removal of 40.0µM parent PBSA and 25% decrease in TOC were achieved with 190min of UV irradiation; SO4(2-) was formed and reached its maximum level while the release of nitrogen as NH4(+) was much lower (around 50%) at 190min. Sulfate removal was strongly enhanced by increasing [H2O2]0 in the range of 0-4.0mM, with slight inhibition in 4.0-12.0mM. Faster and earlier ammonia formation was observed at higher [H2O2]0. The presence of Br(-) slowed down the degradation and mineralization of both compounds while a negligible effect on the degradation was observed in the presence of Cl(-). Our study provides important technical and fundamental results on the HO based degradation and mineralization of SO3H and N-containing UV absorber compounds.
