Electrochemical oxidation process (EOP) is promising for micropollutant degradation in water treatment, where chloride ions (Cl) are inevitable in aqueous systems, leading to the EOP/Cl system. The oxidation of Cl at anodes generates reactive chlorine species (RCS), including heterogeneous chlorine species (Cl), homogeneous free available chlorine (FAC), chlorine dioxide (ClO), and chlorine radicals (CRs). This study developed a method to differentiate various RCS responsible for the removal of carbamazepine in EOP/Cl using the RuO/IrO-Ti anode.
View Article and Find Full Text PDFThe UV/monochloramine (UV/NHCl) process, while efficiently eliminating micropollutants, produces toxic byproducts. This study utilized Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to investigate molecular-level changes in natural organic matter (NOM) and to disclose formation pathways of nitro(so) and chloro byproducts in the UV/NHCl process. The UV/NHCl process significantly increased the saturation and oxidation levels and altered the elemental composition of NOM.
View Article and Find Full Text PDFNatural organic matter (NOM) is a major sink of radicals in advanced oxidation processes (AOPs) and understanding the transformation of NOM is important in water treatment. By using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in conjunction with machine learning, we comprehensively investigated the reactivity and transformation of NOM, and the formation of organosulfates during the UV/peroxydisulfate (PDS) process. After 60 min UV/PDS treatment, the CHO formula number and dissolved organic carbon concentration significantly decreased by 83.
View Article and Find Full Text PDFReactive bromine species (RBS) are gaining increasing attention in natural and engineered aqueous systems containing bromide ions (Br). However, their roles in the degradation of structurally diverse micropollutants by advanced oxidation processes (AOPs) were not differentiated. In this study, the second-order rate constants () of Br, Br, BrO, and ClBr were collected and evaluated.
View Article and Find Full Text PDFPeracetic acid (PAA) is regarded as an environmentally friendly oxidant because of its low formation of toxic byproducts. However, this study revealed the potential risk of generating disinfection byproducts (DBPs) when treating iodine-containing wastewater with PAA. The transformation efficiency of bisphenol A (BPA), a commonly detected phenolic contaminant and a surrogate for phenolic moieties in dissolved organic matter, by PAA increased rapidly in the presence of I, which was primarily attributed to the formation of active iodine (HOI/I) in the system.
View Article and Find Full Text PDFFormation of nitrogenous disinfection byproducts from aliphatic amines is a widespread concern owing to the serious health risks associated with them. However, the mechanisms of transforming aliphatic amines and forming nitro products in the UV/chlorine process have rarely been discussed, which are investigated in this work. Initially, secondary amines (RRNH) are transformed into secondary organic chloramines (RRNCl) via chlorination.
View Article and Find Full Text PDFThe ultraviolet (UV)/chlorine process has attracted increasing attention for micropollutant abatement. However, the limited hydroxyl radical (HO) generation and the formation of undesired disinfection byproducts (DBPs) are the two major issues in this process. This study investigated the roles of activated carbon (AC) in the UV/chlorine/AC-TiO process for micropollutant abatement and DBP control.
View Article and Find Full Text PDFThis study investigated the roles of diverse free available chlorine (FAC) species including HOCl/OCl, HOCl, ClO, and Cl in the degradation of micropollutants. The degradation of 5 micropollutants was significantly affected by pH, FAC dosage, and chloride (Cl) concentration. The reaction orders in FAC (n) of 5 micropollutants (acetaminophen, carbamazepine, naproxen, gemfibrozil, and mecoprop) ranged from 1.
View Article and Find Full Text PDFThe formation of disinfection byproducts (DBPs) during UV/chlorine treatment, especially nitrogenous DBPs, is not well understood. This study investigated the formation mechanisms for dichloroacetonitrile (DCAN) from typical amino compounds during UV/chlorine treatment. Compared to chlorination, the yields of DCAN increase by 88-240% during UV/chlorine treatment from real waters, while the yields of DCAN from amino compounds increase by 3.
View Article and Find Full Text PDFThe UV/monochloramine (UV/NHCl) process has attracted increasing attention in water treatment, in which hydroxyl radicals (HO), reactive chlorine species (RCS) and reactive nitrogen species (RNS) are produced. This study investigated the effects of water matrices including halides, natural organic matter (NOM), alkalinity and pH, on the degradation kinetic of a variety of micropollutants and radical chemistry in the UV/NHCl process. The presence of chloride blunted HO and Cl impacts, but enhanced Cl effect on micropollutants reactive toward Cl.
View Article and Find Full Text PDFBromide (Br) is a typical scavenger to sulfate radical (SO) and hydroxyl radical (HO), which simultaneously forms secondary reactive bromine species (RBS) such as Br and Br. This study investigated the effects of Br at fresh water levels (~μM) on the radical chemistry in the UV/peroxydisulfate (UV/PDS) process by combining the degradation kinetics of probe compounds (nitrobenzene, metronidazole, and benzoate) with kinetic model. Br at 1 - 50 μM promoted the conversion from SO to HO and RBS in the UV/PDS process.
View Article and Find Full Text PDFThe UV/chlorine process is efficient for the abatement of micropollutants; yet, the formation of disinfection by-products (DBPs) and the toxicity can be altered during the treatment. This study investigated effluent organic matter characterization, DBP formation and toxicity alteration after the UV/chlorine treatment of wastewater; particularly, typical water matrix components in wastewater, namely, ammonia and bromide, were studied. The raw wastewater contained low levels of ammonia (3 µM) and bromide (0.
View Article and Find Full Text PDFThe carbonate radical (CO) is a typical secondary radical observed in engineering and natural aquatic systems. This study investigated the degradation kinetics of 20 pharmaceuticals and personal care products (PPCPs) by CO and the transformation pathways of a typical PPCP (naproxen) that is susceptible to CO. CO is highly selective for compounds containing aniline and phenolic hydroxyl groups as well as naphthalene rings, such as sulfamethoxazole, sulfamethazine, salbutamol, propranolol, naproxen, and macrolide antibiotics such as azithromycin, for which the second-order rate constants range from 5.
View Article and Find Full Text PDFThe solar/chlorine process is an energy-efficient advanced oxidation process that can produce reactive species such as hydroxyl radical, reactive chlorine species and ozone. This study investigated the process' ability to detoxify the typical herbicides atrazine and mecoprop (methylchlorophenoxypropionic acid). Both herbicides are resistant to direct solar photolysis or chlorination alone, but they can be degraded by the solar/chlorine process effectively.
View Article and Find Full Text PDFThe UV/persulfate process is an effective advanced oxidation process (AOP) for the abatement of a variety of micropollutants via producing sulfate radicals (SO). However, when this technology is used to reduce target pollutants, the precursors of disinfection byproducts (DBPs), such as natural organic matter (NOM) and organic nitrogen compounds, can be altered. This study systematically investigated the DBP formation from NOM and five model compounds after UV/HO and UV/persulfate treatments followed with 24 h chlorination.
View Article and Find Full Text PDFThis work investigated the feasibility and mechanisms of solar/chlorine process in the removal of a kind of emerging contaminants, lipid regulators (gemfibrozil (GFRZ), benzafibrate (BZF), and clofibric acid (CA)), in simulated and real waters. These lipid regulators could be effectively removed by solar/chlorine treatment, and their corresponding pseudo-first-order rate constants (k') increased with increasing chlorine dosage. The degradation of GFRZ and BZF was primarily ascribed to reactive chlorine species (RCS) and ozone, while that of CA was mainly attributable to hydroxyl radical (HO) and ozone.
View Article and Find Full Text PDFThe solar/chlorine process produces multiple reactive species by solar photolysis of chlorine, which can be used as an energy-efficient technology for water treatment. This study investigated the effects of pH and dissolved oxygen (DO) on the degradation of pharmaceuticals and personal care products (PPCPs) and on the formation of disinfection byproducts (DBPs) in the solar/chlorine system. The degradation of 24 structurally diverse PPCPs was enhanced appreciably in the solar/chlorine system compared to solar irradiation and dark chlorination.
View Article and Find Full Text PDFThe degradation of pharmaceuticals and personal care products (PPCPs) by the UV/HO and UV/chlorine processes was compared at practical concentrations in simulated drinking water and wastewater. In pure water, the UV/chlorine process performed better than the UV/HO process for the degradation of 16 PPCPs among the investigated 28 PPCPs under neutral conditions. Interestingly, the UV/chlorine approach was superior to the UV/HO approach for the removal of all PPCPs in simulated drinking water and wastewater at the same molar oxidant dosage.
View Article and Find Full Text PDFDegradation of three lipid regulators, i.e., gemfibrozil, bezafibrate and clofibric acid, by a UV/chlorine treatment was systematically investigated.
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