Differentiating reactive chlorine species for micropollutant abatement in chloride containing water by electrochemical oxidation process.

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.

Probing nitro(so) and chloro byproducts and their precursors in natural organic matter during UV/NHCl treatment by FT-ICR MS with machine learning insights.

The 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.

Insights into the transformation of natural organic matter during UV/peroxydisulfate treatment by FT-ICR MS and machine learning: Non-negligible formation of organosulfates.

Natural 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.

Comprehensive Assessment of Reactive Bromine Species in Advanced Oxidation Processes: Differential Roles in Micropollutant Abatement in Bromide-Containing Water.

Reactive 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.

pH-dependent bisphenol A transformation and iodine disinfection byproduct generation by peracetic acid: Kinetic and mechanistic explorations.

Peracetic 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.

Formation Mechanisms of Nitro Products from Transformation of Aliphatic Amines by UV/Chlorine Treatment.

Formation 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.

Roles of Activated Carbon in UV/Chlorine/Activated Carbon-TiO Process for Micropollutant Abatement and DBP Control.

The 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.

Overlooked roles of ClO and Cl in micropollutant abatement and DBP formation by chlorination.

This 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.

Exploring Pathways and Mechanisms for Dichloroacetonitrile Formation from Typical Amino Compounds during UV/Chlorine Treatment.

The 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.

Mechanistic and kinetic understanding of micropollutant degradation by the UV/NHCl process in simulated drinking water.

The 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.

Insights into the effects of bromide at fresh water levels on the radical chemistry in the UV/peroxydisulfate process.

Bromide (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.

DBP formation and toxicity alteration during UV/chlorine treatment of wastewater and the effects of ammonia and bromide.

The 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.

Kinetics and pathways of the degradation of PPCPs by carbonate radicals in advanced oxidation processes.

The 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.

Solar irradiation combined with chlorine can detoxify herbicides.

The 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.

DBP alteration from NOM and model compounds after UV/persulfate treatment with post chlorination.

The 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.

Feasibility of the solar/chlorine treatment for lipid regulator degradation in simulated and real waters: The oxidation chemistry and affecting factors.

This 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.

PPCP degradation and DBP formation in the solar/free chlorine system: Effects of pH and dissolved oxygen.

The 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.

Comparison of the UV/chlorine and UV/HO processes in the degradation of PPCPs in simulated drinking water and wastewater: Kinetics, radical mechanism and energy requirements.

The 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.

Degradation of lipid regulators by the UV/chlorine process: Radical mechanisms, chlorine oxide radical (ClO)-mediated transformation pathways and toxicity changes.

Degradation of three lipid regulators, i.e., gemfibrozil, bezafibrate and clofibric acid, by a UV/chlorine treatment was systematically investigated.