Comparative OH radical oxidation using UV-Cl2 and UV-H2O2 processes

Watts, Michael J.; Rosenfeldt, Erik J.; Linden, Karl G.

doi:10.2166/aqua.2007.028

Cited by 58 publications

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“…The predicted k 1 for TCEP and TBEP is the product of their derived second-order •OH reaction rates and [OH] SS . However, in UV-irradiated free chlorine solutions, the total •OH-scavenging can be significantly affected by pH; as the ratio of OCl - to HOCl increases with pH so does the fraction of [OH] ss that reacts with unphotolyzed free chlorine hypochlorite ion (25). Modifying the conventional equation for [OH] ss to account for free chlorine speciation yields Equation 2.…”

Section: Resultsmentioning

confidence: 99%

“…In surface water spiked with TCEP, little to no TCEP degradation was observed in the range of applied UV fluences (up to 1000 mJ/cm 2 ) regardless of how much NaOCl was added prior to UV irradiation. It has been previously demonstrated that at neutral pH, increasing the initial concentration of free chlorine leads to a decrease in the first-order, fluence-based rate constant for oxidation of an organic with a slower rate of reaction with •OH than OCl - (25), as OCl - accounts for an increasing majority of •OH-scavenging. For UV-H 2 O 2 to be an effective process for oxidation of TCEP, a significant increase in the initial oxidant concentration and subsequent fraction of the applied UV light absorbed by H 2 O 2 is required.…”

Section: Resultsmentioning

confidence: 99%

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Advanced Oxidation Kinetics of Aqueous Trialkyl Phosphate Flame Retardants and Plasticizers

Watts

Linden

2009

Environ. Sci. Technol.

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Tri alkyl phosphate esters are a class of anthropogenic organics commonly found in surface waters of Europe and North America, due to their frequent application as flame retardants, plasticizers, and solvents. Four tri alkyl phosphate esters were evaluated to determine second-order rates of reaction with ultraviolet- and ozone-generated •OH in water. In competition with nitrobenzene in UV irradiated hydrogen peroxide solutions tris(2-butoxyethyl) phosphate (TBEP) was fastest to react with •OH (kOH,TBEP=1.03×1010 M-1s-1), followed sequentially by tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), and tris(2-chloroisopropyl) phosphate (TCPP) (kOH,TBEP=6.40×109, kOH,TBEP=5.60×108, & kOH,TBEP=1.98×10 M-1s-1). A two-stage process was used to test the validity of the determined kOH for TBEP and the fastest reacting halogenated alkyl phosphate, TCEP. First, •OH oxidation of TCEP and TBEP, in competition with nitrobenzene, was measured in ozonated hydrogen peroxide solutions. Applying multiple regression analysis, it was determined that the UV-H2O2 and O3-H2O2 data sets were statistically identical for each compound. The subsequent validated kOH were used to predict TCEP and TBEP photodegradation in neutral pH, model surface water after chemical oxidant addition and UV irradiation (up to 1000 mJ/cm2). The insignificant difference, between the predicted TBEP and TCEP photodegradation and a best-fit of the first-order exponential decay function to the observed TBEP and TCEP concentrations with increasing UV fluence, was further evidence of the validity of the determined kOH. TBEP oxidation rates were similar in the surface waters tested. Substantial TCEP oxidation in the model surface water required a significant increase in H2O2.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Advanced Oxidation Kinetics of Aqueous Trialkyl Phosphate Flame Retardants and Plasticizers

Watts

Linden

2009

Environ. Sci. Technol.

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“…Advanced oxidation processes (AOPs) are promising technologies for the removal of pharmaceutical pollutants in water, and the degradation of ATL has been studied by various oxidation processes, such as hydroxyl radicals ( • OH) formed from UV/H 2 O 2 , UV/TiO 2 , and sulfate radicals ( • SO 4 − ) formed from UV/peroxodisulfate . Among various AOPs, UV irradiation combined with chlorine (UV/chlorine) process has shown comparable efficiency with UV/H 2 O 2 for the destruction of organic pollutants in water treatment . The elementary reactions in the UV/chlorine process can be summarized as Eqs.…”

Section: Introductionmentioning

confidence: 99%

Degradation of Atenolol with Electrochemical Oxidation at Mixed Metal Oxide Electrodes Assisted by UV Photolysis

Zhu

Dong

Zhou

2018

CLEAN Soil Air Water

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Electrochemical oxidation has drawn considerable research attention for the destruction of organic contaminants. This study utilizes the combination of electrolysis and the UV photolysis process to degrade the β‐blocker atenolol (ATL). The results show that the combination of electrolysis and UV photolysis is superior to a single process alone based on the removal rates of ATL and electrical efficiency per order (EE/O). In situ electrogenerated chlorine is confirmed to be responsible for ATL degradation with NaCl electrolytes, and mixed metal oxide (MMO) anodes play a more significant role in the generation of active chlorine than platinum (Pt) anodes. Moreover, reactive species (hydroxyl radical •OH and chlorine radical •Cl) mainly contributed to ATL degradation during the photo‐electrolysis process. Increasing the concentration of NaCl electrolytes and applied current densities can enhance the ATL degradation. Finally, major intermediate products are identified, and a possible degradation pathway of ATL is proposed during the photo‐electrolysis processes. This study demonstrate that the photo‐electrolysis process can be considered as a potential technology for the destruction of pharmaceutical pollutants in water.

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“…Recently, researchers have been investigating the combination of aqueous chlorine and ultraviolet light (Cl 2 /UV) as a novel AOP method (Watts et al ; Watts and Linden, ; Sichel et al ; Chan et al ; Wang et al ). Under UV photolysis, aqueous chlorine will produce reactive radicals including hydroxyl, chlorine, and oxygen radicals (Feng et al ), all of which can be harnessed to react with and degrade organic compounds in water.…”

Section: Introductionmentioning

confidence: 99%

Pump-and-Treat Groundwater Remediation Using Chlorine/Ultraviolet Advanced Oxidation Processes

Boal¹,

Rhodes²,

Garcia³

2015

Groundwater Monit R

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Comparative studies of the use of chlorine/ultraviolet (Cl2/UV) and hydrogen peroxide/ultraviolet (H2O2/UV) Advanced oxidation processes (AOPs) to remove trichloroethylene (TCE) from groundwater in a pump‐and‐treat application were conducted for the first time at the full‐scale operational level at two water treatment facilities in Northern California. In these studies, aqueous chlorine replaced hydrogen peroxide in the AOP treatment step, where the oxidant is exposed to UV light to produce highly reactive radical species that degrade groundwater contaminants. TCE removal rates as a function of initial chlorine dose and pH were then determined. At the site where the natural pH of the water was 7.1, TCE was removed (to a concentration of less than 0.5 µg/L) for nearly every chlorine dose point tested, and pH adjustment slightly enhanced the treatment process at this facility. The second site had a high natural pH of 7.7, and here, TCE was not completely removed for any chlorine dose up to 5.7 mg/L, although TCE removal did increase when the chlorine dose increased between 0.9 and 3.6 mg/L. Residual TCE remaining in the water post‐Cl2/UV was readily removed using active carbon filtration, which is part of the overall treatment train at this facility. These studies also verified that Cl2/UV AOP did not interfere with the photolysis of N‐nitrosodimethylamine or result in an effluent acutely toxic toward Ceriodaphnia dubia. Comparative economic analysis revealed that the chemical costs associated with Cl2/UV AOP were 25 to 50% of the costs associated with in place H2O2/UV AOP treatment.

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Comparative OH radical oxidation using UV-Cl2 and UV-H2O2 processes

Cited by 58 publications

References 0 publications

Advanced Oxidation Kinetics of Aqueous Trialkyl Phosphate Flame Retardants and Plasticizers

Advanced Oxidation Kinetics of Aqueous Trialkyl Phosphate Flame Retardants and Plasticizers

Degradation of Atenolol with Electrochemical Oxidation at Mixed Metal Oxide Electrodes Assisted by UV Photolysis

Pump-and-Treat Groundwater Remediation Using Chlorine/Ultraviolet Advanced Oxidation Processes

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