Direct Photolysis of Chlorophenols In Aqueous Solution By Ultraviolet Excilamps

Matafonova, Galina; Philippova, Natalya; Batoev, Valeriy; Ao, Sio-Iong

doi:10.1063/1.3627208

Cited by 4 publications

(6 citation statements)

References 25 publications

(38 reference statements)

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“…Chlorophenols are weak acids and can be partially dissociated in water . Thus, 2,5‐DCP (p K a 2,5‐DCP =7.51) is a phenol at pH 3 and 4, a phenolate at pH 11, and a phenol/phenolate equilibrium at pH 7; this can be appreciated in the UV/Vis absorption spectra of 2,5‐DCP shown in Figure and Figure S12 in the Supporting Information.…”

Section: Resultsmentioning

confidence: 94%

“…[28] Thus,2 ,5-DCP (pKa 2,5-DCP = 7.51) is ap henol at pH 3 and 4, ap henolate at pH 11,a nd ap henol/phenolate equilibrium at pH 7; this can be appreciated in the UV/Vis absorption spectra of 2,5-DCP shown in Figure 6 andF igureS12 in the Supporting Information. [28] Thus,2 ,5-DCP (pKa 2,5-DCP = 7.51) is ap henol at pH 3 and 4, ap henolate at pH 11,a nd ap henol/phenolate equilibrium at pH 7; this can be appreciated in the UV/Vis absorption spectra of 2,5-DCP shown in Figure 6 andF igureS12 in the Supporting Information.…”

Section: Solar Photodegradationo F25-dcpmentioning

confidence: 87%

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A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

Irigoyen-Campuzano

González‐Béjar

Pino

et al. 2017

Chemistry A European J

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Heterogeneous catalysts that can absorb light over the solar range are ideal for green photocatalysis. Recently, attention has been directed towards the generation of novel solar-light photocatalysts, in particular, metal-free polymers. Herein, it is demonstrated that a metal-free, nonconjugated, anthraquinone-based copolymer (poly[1,4-diamine-9,10-dioxoanthracene-alt-(benzene-1,4-dioic acid)] (COP)) with a strong absorption in the visible region is effective as a sunlight heterogeneous photocatalyst. As a proof of concept, it has been used to mineralize 2,5-dichlorophenol (2,5-DCP) in water under air and sunlight irradiation. The photocatalytic efficiency of COP compares well with that of TiO -P25 when the reaction is carried out in a solar photoreactor in acid medium. Steady-state and time-resolved (absorption and emission) studies performed on COP suspended in 6:4 DMF/H O have provided valuable information about the COP species generated under different pH conditions. Steady-state absorption and fluorescence data are consistent with the existence of a tautomeric equilibrium between the 9,10-keto and 1,10-iminoketo quinoid forms for the anthraquinone in the ground state. Moreover, in basic media, transient absorption measurements showed the presence of two bands ascribed to the tautomeric triplet excited states, whereas only one of the triplets was observed in acid medium. A mechanism for the photocatalyzed degradation of 2,5-DCP by COP is proposed on the basis of these observations.

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Section: Resultsmentioning

confidence: 94%

Section: Solar Photodegradationo F25-dcpmentioning

confidence: 87%

A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

Irigoyen-Campuzano

González‐Béjar

Pino

et al. 2017

Chemistry A European J

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“…Krypton chloride excimer (KrCl*) lamps, with an emission peak centered at 222 nm (UV 222 ), have emerged as a promising far-UVC radiation source for air and surface disinfection during the COVID-19 pandemic. , KrCl* lamps contain no mercury, require short stabilization time (15 s), and have a reasonably high wall-plug efficiency (5–15%). , UV 222 is highly effective for inactivation of pathogens and safer for humans than conventional UV 254. ,− However, the use of UV 222 in treating aqueous micropollutants remains scarce in the literature. − KrCl* lamps are promising alternatives to LP-UV lamps to drive UV-AOPs, because many oxidant precursors (e.g., H 2 O 2 , hypochlorous acid, and peroxydisulfate) have higher molar absorption coefficients at 222 nm than 254 nm. ,, The comparison of (innate) quantum yields of these oxidant precursors at 222 and 254 nm remains unaddressed in the literature; nonetheless, the higher molar absorption coefficients suggest higher radical yields of these oxidant precursors at 222 nm than 254 nm. This hypothesis can be supported by a recent study which reports that the steady-state concentration of hydroxyl radical (HO • ) normalized by the incident fluence rate in the UV/H 2 O 2 AOP is 9.4 times higher at 222 nm than 254 nm in deionized water and 3.7 times higher in groundwater …”

Section: Introductionmentioning

confidence: 99%

A High-Radical-Yield Advanced Oxidation Process Coupling Far-UVC Radiation with Chlorinated Cyanurates for Micropollutant Degradation in Water

Zhao

Shang

Yin

2023

Environ. Sci. Technol.

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Increasing the radical yield and reducing energy consumption would enhance the sustainability and competitiveness of advanced oxidation processes (AOPs) for micropollutant degradation in water. We herein report a novel AOP coupling far-UVC radiation at 222 nm with chlorinated cyanurates (termed the UV222/Cl-cyanurates AOP) for radical generation and micropollutant abatement in water. We experimentally determined the concentrations of HO•, Cl•, and ClO• in the UV222/Cl-cyanurates AOP in deionized water and swimming pool water. The radical concentrations are 10–27 times and 4–13 times, respectively, higher than those in the UV254/Cl-cyanurates AOP and the well-documented UV254/chlorine AOP under comparable conditions (e.g., same UV fluence and oxidant dosing). We determined the molar absorption coefficients and innate quantum yields of two chlorine species and two Cl-cyanurates at 222 nm and incorporated these parameters into a kinetic model. The model enables accurate prediction of oxidant photodecay rates as well as the pH impact on radical generation in the UV222/Cl-cyanurates AOP. We predicted the pseudo-first-order degradation rate constants of 25 micropollutants in the UV222/Cl-cyanurates AOP and demonstrated that many micropollutants can be degraded by >80% with a low UV fluence of 25 mJ cm–2. This work advances the fundamental photochemistry of chlorine and Cl-cyanurates at 222 nm and offers a highly effective engineering tool in combating micropollutants in water where Cl-cyanurates are suitable to use.

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“…For 4-CP and 2,4-DCP, the quantum yield at 222 nm was 62%–83% of that at 254 nm. A similar result was also observed previously for 4-CP. , This phenomenon was mainly due to the varied photolysis pathways among different wavelengths. For example, chlorine detachment of 4-CP is more favorable at a wavelength closer to 266–280 nm, − probably causing the low quantum yield at 222 nm.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Direct Photolysis of Organic Micropollutants by Far-UVC Light at 222 nm from KrCl* Excilamps

Huang

2023

Environ. Sci. Technol. Lett.

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Krypton chloride (KrCl*) excilamps emitting at far-UVC 222 nm represent a promising technology for microbial disinfection and advanced oxidation of organic micropollutants (OMPs) in water treatment. However, direct photolysis rates and photochemical properties at 222 nm are largely unknown for common OMPs. In this study, we evaluated photolysis for 46 OMPs by a KrCl* excilamp and compared it with a low-pressure mercury UV lamp. Generally, OMP photolysis was greatly enhanced at 222 nm with fluence rate-normalized rate constants of 0.2–21.6 cm2·μEinstein–1, regardless of whether they feature higher or lower absorbance at 222 nm than at 254 nm. The photolysis rate constants and quantum yields were 10–100 and 1.1–47 times higher, respectively, than those at 254 nm for most OMPs. The enhanced photolysis at 222 nm was mainly caused by strong light absorbance for non-nitrogenous, aniline-like, and triazine OMPs, while notably higher quantum yield (4–47 times of that at 254 nm) occurred for nitrogenous OMPs. At 222 nm, humic acid can inhibit OMP photolysis by light screening and potentially by quenching intermediates, while nitrate/nitrite may contribute more than others to screen light. Overall, KrCl* excilamps are promising in achieving effective OMP photolysis and merit further research.

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Direct Photolysis of Chlorophenols In Aqueous Solution By Ultraviolet Excilamps

Cited by 4 publications

References 25 publications

A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

A Metal‐Free, Nonconjugated Polymer for Solar Photocatalysis

A High-Radical-Yield Advanced Oxidation Process Coupling Far-UVC Radiation with Chlorinated Cyanurates for Micropollutant Degradation in Water

Enhanced Direct Photolysis of Organic Micropollutants by Far-UVC Light at 222 nm from KrCl* Excilamps

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