Removal of micropollutants in drinking water using UV-LED/chlorine advanced oxidation process followed by activated carbon adsorption

Water Research, Journal Year: 2020, Volume and Issue: 185, P. 116297 - 116297

Published: Aug. 13, 2020

Language: Английский

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Rate Constants and Mechanisms for Reactions of Bromine Radicals with Trace Organic Contaminants

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(15), P. 10502 - 10513

Published: July 23, 2021

Bromine radicals can pose great impacts on the photochemical transformation of trace organic contaminants in natural and engineered waters. However, reaction kinetics mechanisms involved are barely known. In this work, second-order rate constants with Br• Br2•– were determined for 70 common 17 model compounds using laser flash photolysis steady-state competition kinetics. The kBr• values ranged from <108 to (2.86 ± 0.31) × 1010 M–1 s–1 kBr2•– <105 (1.18 0.09) 109 at pH 7.0. Six quantitative structure–activity relationships developed, which allow predicting additional unknown values. Single-electron transfer was shown be a favored pathway reactions contaminants, supported by transient spectroscopy quantum chemical calculations. This study is essential advancing scientific understanding halogen radical-involved chemistry contaminant transformation.

Language: Английский

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Mechanistic and Kinetic Understanding of the UV₂₅₄ Photolysis of Chlorine and Bromine Species in Water and Formation of Oxyhalides

Environmental Science & Technology, Journal Year: 2020, Volume and Issue: 54(18), P. 11546 - 11555

Published: Aug. 7, 2020

This study investigated the UV254 photolysis of free available chlorine and bromine species in water. The intrinsic quantum yields for •OH X• (X = Cl or Br) generation were determined by model fitting formaldehyde formation using a tert-butanol assay to be 0.61/0.45 HOCl/OCl- 0.32/0.43 HOBr/OBr-. steady-state concentration UV/HOX was higher than that UV/OX- factor 23.3 7.8 Br, respectively. attributed different consumption rate HOCl versus OCl-, while HOBr/OBr-, both rates implied. supported k 1.4 × 108 M-1 s-1 reaction with HOCl, which >14 times less reactions HOBr, OBr-. Formation ClO3- BrO3- found significant apparent 0.12-0.23. A detailed mechanistic on XO3- including new pathway involving XO• is presented, has important implications as level can exceed regulation (BrO3-) guideline (ClO3-) values during UV/halogen oxidant water treatment. Our kinetic models well simulate experimental results halogen decomposition, probe compound degradation, BrO3-.

Language: Английский

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Selective Reactivity and Oxidation of Dissolved Organic Matter by Manganese Oxides

Environmental Science & Technology, Journal Year: 2021, Volume and Issue: 55(17), P. 12084 - 12094

Published: Aug. 25, 2021

Dissolved organic matter (DOM) varies widely across natural and engineered systems, but little is known about the influence of DOM composition on its reactivity with manganese oxides. Here, we investigate bulk molecular transformations 30 diverse samples after reaction acid birnessite (MnO2), a strong oxidant that may react in Mn-rich environments or treatment systems. The reduces Mn forms generally more aliphatic lower apparent weight. However, extent depends water type (e.g., wastewater, rivers) highly aromatic undergoes greater changes. Despite variability due to composition, aqueous products attributable oxidation phenolic precursors are identified waters analyzed by high-resolution mass spectrometry. number matched product formulas correlates significantly indicators aromaticity, such as double-bond equivalents (p = 2.43 × 10–4). At level, aromatic, lignin-like carbon reacts selectively all despite initial resulting formation wide range products. These findings demonstrate occurs also suggest pool composition-dependent linked source aromaticity.

Language: Английский

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Multi-angle comparison of UV/chlorine, UV/monochloramine, and UV/chlorine dioxide processes for water treatment and reuse

Water Research, Journal Year: 2022, Volume and Issue: 217, P. 118414 - 118414

Published: April 6, 2022

Language: Английский

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