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Algal organic matter (AOM) from seasonal algal blooms may be an important precursor of disinfection byproducts (DBPs) in drinking water. This paper presents the effect of ferrate(VI) treatment on two blue-green algae, Chlorella sp. and Pseudanabaena limnetica, in eutrophic water. The results demonstrated that Fe(VI) removed the algal cells by causing cell death, apoptosis, and lost integrity, and decreased AOM (in terms of total organic carbon) in water via oxidation and coagulation. Chlorination of the Fe(VI) pre-oxidized algal water samples generated halogenated DBPs (including trihalomethanes, haloacetic acids, haloketones, chloral hydrate, haloacetonitriles, and trichloronitromethane), but the concentrations of DBPs were lower than those formed in the chlorinated samples without pre-treatment by Fe(VI). Higher Fe(VI) dose, longer oxidation time, and alkaline pH were beneficial in controlling DBPs. In bromide-containing algal solutions, negligible amount of bromo-DBPs were generated in the Fe(VI) pre-oxidation, and halogenated DBPs were mainly formed in the subsequent chlorination., (Copyright © 2019 The Authors. Published by Elsevier Ltd.. All rights reserved.)

2,4,6-Trichloroanisole (TCA) is an odorous compound that is often detected in tap water and is difficult to be removed via water treatment. In this study, the transformation efficiency of TCA in the presence of persulfate (PS) activated by iron (Fe 2+ , Fe 0 , and Fe 3+ ) was investigated for the first time. The effects of the activator dosage, oxidant dosage, pH, dosing method, chelating agents, humic acid, and temperature were evaluated. The degradation rate of TCA increased with increasing PS dosages (0.12-0.48 mM) and initial Fe 2+ concentrations (0.12-0.96 mM), while it decreased with higher Fe 2+ concentrations. Fe 2+ /PS and Fe 0 /PS systems achieved their best TCA removal efficiency at pH 7 and 2.5, respectively. According to the results of electron paramagnetic resonance (EPR), the contribution of SO 4 - • to TCA degradation was much higher than that of •OH. Gradual addition of Fe 2+ improved TCA degradation compared to single addition. Citric acid (CA) promoted TCA degradation under Fe 2+ /PS at the beginning of the reaction, but inhibited it after 10 min. Ethylenediaminetetraacetic acid (EDTA) improved the TCA removal rate with an EDTA/Fe 2+ molar ratio of 0.5:1, while it decreased it at higher EDTA/Fe 2+ molar ratios. Oxalic acid (OA) negatively affected TCA degradation with increasing OA/Fe 2+ molar ratios. Among all of the chelating agents, only CA increased TCA degradation by Fe 0 /PS. Humic acid promoted TCA degradation by Fe 2+ /PS at the proper dosage (1 mg/L). Under our specific conditions and over the temperature ranging from 10 to 25 °C, no change was observed in the reaction kinetics. It was found that 2,4,6-trichlorophenol (TCP) was the only detected oxidation product. The presence of an Fe 2+ redox cycle in iron-activated PS systems was confirmed by TCA degradation under the Fe 3+ redox cycle in iron-activated PS systems was confirmed by TCA degradation under the Fe 3+ /PS system.

The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization.

The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization. [ABSTRACT FROM AUTHOR]

Abstract: Electrocoagulation (EC) using electrodes made from iron scrap is a novel and promising strategy for arsenic (As) contaminated ground water remediation. In synthetic groundwater, amorphous hydrous ferric oxide (HFO) precipitates formed by the rapid dissolution of a sacrificial iron scrap anode adsorbed As very effectively. A competitive adsorption model developed in this study with parameters fitted for As and other coexisting anions (phosphate and silicate) was in good agreement with the observed results. It is indicated that the maximum adsorption capacity of HFO generated in the EC system was ∼0.70mol/mol. Reducing the As concentration in water from 500μg/L As(V) and As(III) to below 50μg/L (local drinking water standard in Bangladesh) required ∼8mg/L and ∼32mg/L iron respectively (pH=7.1±0.1, charge dosage rate=3 coulomb/L/min). It was found that coexisting cations (Ca2+ and Mg2+) neutralized the HFO surface charge, promoted aggregation and resulted in greater As removal. The presence of humic acid exhibited a negligible effect on As removal and HFO precipitate settling. Jar tests showed that the turbidity of the solution could be reduced to <1 NTU with the addition of 2mg/L Al3+. [Copyright &y& Elsevier]