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Synergistic removal of ammonium by monochloramine photolysis
摘要： The presence of ammonium (NH4+) in drinking water treatment results in inhibition of disinfection efficiency and formation of nitrogenous disinfection by-products. Our previous study found monochloramine (NH2Cl) photolysis under 254 nm UV irradiation can be effective for removal of NH4+; however, the mechanisms of NH4+ degradation in this process were unknown. The kinetics and fundamental radical chemistry responsible for NH4+ removal in the UV/NH2Cl process were investigated in this study. The results showed that the pseudo first-order rate constant for NH4+ degradation in the UV/NH2Cl process ranged between 3.6 × 10?4 to 1.8 × 10?3 s?1. Solution pH affected radical conversion and a higher NH4+ degradation efficiency was achieved under acidic conditions. The effects of chloride were limited; however, the presence of either bicarbonate or natural organic matter scavenged radicals and inhibited NH4+ removal. NH2Cl photolysis generated an aminyl radical (NH2?) that further transformed to a chlorine dimer (Cl2??) and a hydroxyl radical (HO?). The second-order rate constants for Cl?, Cl2??, and HO? reacting with NH4+ were estimated as 2.59 × 108 M?1s?1, 3.45 × 105 M?1s?1, and 1.4 × 107 M?1s?1 at pH 3.9, respectively. Cl?, Cl2??, and HO? contributed 95.2%, 3.5%, and 1.3% to NH4+ removal, respectively, at the condition of 3 mM NH2Cl and pH 7.5. Major products included nitrite and nitrate, possibly accompanied by nitrogen-containing gases. This investigation provides insight into the photochemistry of NH4+ degradation in the UV/NH2Cl process and offers an alternative method for drinking water production.
关键词： Ammonium,Reactive chlorine radicals,UV/NH2Cl process,Kinetic model
更新于2025-09-19 17:15:36
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Chlorine Vacancy Passivation in Mixed Halide Perovskite Quantum Dots by Organic Pseudohalides Enables Efficient Rec. 2020 Blue Light-Emitting Diodes
摘要： Blue-emitting perovskites are easily attainable by precisely tuning the halide ratio of mixed halide (Br/Cl) perovskites (MHPs). However, the adjustable halide ratio also hinders the passivation of Cl vacancies – the main source of trap states leading to inferior performance blue MHP light-emitting diodes (LEDs). Here, we report a strategy to passivate Cl vacancies in MHP quantum dots (QDs) using non-polar-solvent-soluble organic pseudohalide (n-dodecylammonium thiocyanate (DAT)), enabling blue MHP LEDs with greatly enhanced efficiency. Density-functional-theory calculations reveal that the thiocyanate (SCN-) groups fill in the Cl vacancies and remove electron traps within the bandgap. DAT-treated CsPb(BrxCl1-x)3 QDs exhibit near unity (~100%) photoluminescence quantum yields; and their blue (~470 nm) LEDs are spectrally stable with an external quantum efficiency (EQE) of 6.3% – a record for perovskite LEDs emitting in the 460-480 nm range relevant to Rec. 2020 display standards – and a half-lifetime of ~99 s.
关键词： light-emitting diodes,organic pseudohalides,blue emission,perovskite,chlorine vacancy passivation,quantum dots
更新于2025-09-19 17:13:59
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Energy dependence of Cl emission lines in CO <sub/>2</sub> laser induced breakdown spectroscopy
摘要： Chlorine (Cl) detection using laser induced breakdown spectroscopy (LIBS) techniques in geology and environment samples is still challenging since the experimental conditions greatly influence the analytical performance of LIBS. Cl emission in LIBS must be studied carefully to find the optimum condition to allow Cl detection. In the present study, Cl emission was studied from polyvinyl chloride (PVC) sample containing Cl as major element. A Transversely Excited Atmosphere (TEA) carbon dioxide (CO2) laser was used for inducing plasma from the sample. Cl emission was investigated by varying the experimental conditions, especially energy of the laser pulse. The emission spectrum from the consequent plasma was detected using an Optical Multichannel Analyzer (OMA) system. It was found that Cl emission lines only can be obtained when helium was used as the surrounding gas. The strongest emission line of Cl I 837.59 nm in the infrared region cannot be detected even under helium surrounding gas. Instead, many ionic emission lines of Cl in ultraviolet regions including the strong ionic lines (Cl II 479.45 nm, Cl II 481.00 nm, Cl II 481.94 nm and the weak lines (Cl II 476. 86 nm, Cl II 478.13 nm, Cl II 489.67 nm, Cl II 490.47 nm and Cl II 491.77 nm) can unequivocally be detected. It was also found that the intensity of Cl emission lines critically depends on the energy of the laser pulse, namely the emission intensity of Cl lines increases sharply with energy. In present work, the highest intensity of Cl emission lines was obtained when the energy of the laser pulse was about 2500 mJ, giving strong and clear Cl emission lines with low background and relatively high signal to background ratio of more than 3.
关键词： LIBS,PVC,helium surrounding gas,TEA CO2 laser,Chlorine detection
更新于2025-09-16 10:30:52
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Rhenium diselenide as the broadband saturable absorber for the nanosecond passively Q-switched thulium solid-state lasers
摘要： Although the solar cells based on the α-CsPbI3 presents very impressive power conversion efficiency, it suffers from insufficient crystalline structure stability even in ambient condition. Herein, the black orthorhombic γ phase based CsPbI3 is successfully fabricated with its performance further optimized by doping chlorine ions. It is found that the chlorine incorporation improves crystallization dynamics for favorable surface morphology and crystalline orientation. In particular by doping 3 mol% chlorine into the γ-CsPbI3 film, its trap density is minimized with enhanced black phase stability and much improved thin film characteristics, including conductivities, electron and hole mobilities. Consequently, the solar cell efficiency is increased to as high as 16.07%. More importantly, the PCE of the optimized device shows only 0.45% degradation after continuous light soaking for 200 h. It retains as much as 94% of its initial PCE even after being exposed in air (relative humidity of 20–30% at 25 °C) for 60 days.
关键词： Chlorine,Solar cells,Efficiency,Stability,γ-CsPbI3
更新于2025-09-11 14:15:04
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Structure–Activity/Stability Correlations from the Electrochemical Dynamic Responses of Titanium Anode Coatings Formed of Ordered TiO <sub/>2</sub> @RuO <sub/>2</sub> Microspheres
摘要： Spherical TiO2/RuO2 particles were synthesized by ultrasonic spray pyrolysis (USP) at 200 and 800?C. The activity for the oxygen and chlorine evolution reactions (OER and CER, respectively) and the dynamic responses from electrochemical impedance spectroscopy (EIS) of the USP powders, as well as of the corresponding coatings on Ti, were analyzed and are discussed. The loss of coating activity is discussed with respect to the differences in the EIS and cyclic voltammetry responses of the coatings in their active and inactive states. The 800?C-USP sample was found to be more active than the 200?C-USP sample for both the CER and the OER, whereas the stability of the former was considerably lower. The correlation between the structure, composition and morphology of the powder and the coating with the registered electrochemical properties is discussed. The EIS analysis of the coating resistance distributions induced by the thermal treatment of the powder indicated a complex combination of the pore resistance and the pseudocapacitive charge transfer resistance. An additional coating resistance, due to loose grain boundaries, was introduced into the coatings in their active and inactive state. The EIS analysis indicated the changes in TiO2-enriched core/RuO2-enriched shell structure, caused by the USP temperature.
关键词： TiO2/RuO2,cyclic voltammetry,electrochemical impedance spectroscopy,oxygen evolution reaction,chlorine evolution reaction,ultrasonic spray pyrolysis,coating stability
更新于2025-09-11 14:15:04
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Ciprofloxacin degradation in UV/chlorine advanced oxidation process: Influencing factors, mechanisms and degradation pathways
摘要： Ciprofloxacin (CIP) is a widely used third generation fluoroquinolone antibiotics, and has been often detected in wastewater treatment plants. Finding an effective way to remove them from wastewater is of great concern. Ultraviolet (UV)/chlorine advanced oxidation process (AOP) has many advantages in micropollutant removal. In this study, CIP degradation in UV/chlorine process was investigated. Only 41.2% of CIP was degraded by UV photolysis and 30.5% by dark chlorination in 30 min, while 98.5% of CIP was degraded by UV/chlorine process in 9 min. HCO3- had markedly inhibition, NO3- and SO42- had slight inhibition, and Cl- had a marginal inhibition on the CIP degradation in UV/chlorine system. The degradation of CIP in UV/chlorine process was mainly attributed to the attack of reactive species. The relative contributions of hydrated electrons (eaq-), hydroxyl radicals (HO.), chlorine atoms (Cl.), and UV photolysis were investigated. Under neutral condition in aqueous solution, CIP degradation had highest pseudo first-order reaction rate constants, in which eaq- followed by Cl., HO., and UV photolysis. The intermediates and byproducts were identified and the degradation pathway was proposed. The total organic chlorine (TOCl) and biotoxicity were further assessed. CIP and natural organic matters (NOMs) were removed efficiently in real water. UV/chlorine showed the potential for the wastewater treatment containing CIP.
关键词： advance oxidation process,UV/chlorine process,UV photolysis,reactive species,wastewater,Ciprofloxacin
更新于2025-09-10 09:29:36
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STM and DFT Study of Chlorine Adsorption on the Ag(111)- <i>p</i> (4x4)-O Surface
摘要： Coadsorption of chlorine and oxygen on the Ag(111) surface has been studied with low-temperature scanning tunneling microscopy (LT-STM) in a combination with density functional theory (DFT) calculations. Room temperature adsorption of chlorine onto the Ag(111)-p(4×4)-O surface leads to the appearance of new bright objects located between protrusions of the 4×4 reconstruction. As chlorine adsorbs, objects form "rosettes" around corner holes. This configuration coincides with the configuration of the chlorine atoms in the Ag(111)-(3×3)-Cl reconstruction structure. We conclude that the adsorption of chlorine on the Ag(111)-p(4×4)-O surface occurs dissociatively, with chlorine atoms displacing oxygen atoms from the fourfold positions. Adsorption of chlorine at 77 K results in the formation of the mixed Cl–O species on the Ag6 triangles of the p(4×4) reconstruction. Both scenarios of chlorine adsorption are unexpected and cannot be explained within a commonly accepted Ag6 model of the p(4×4) reconstruction.
关键词： STM,DFT,Chlorine adsorption,Ag6 model,Ag(111)-p(4×4)-O surface
更新于2025-09-10 09:29:36
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Highly efficient total nitrogen and simultaneous total organic carbon removal for urine based on the photoelectrochemical cycle reaction of chlorine and hydroxyl radicals
摘要： Urine is a major nitrogen and COD source and threatens the aqueous environment, leading to eutrophication and energy consumption. However, the conventional technologies encounter the bottleneck due to the high load of nitrogen and organics in urine. Here we propose an innovative idea for complete transformation of urea-nitrogen to N2 and simultaneous degradation of organics to CO2 with the assistance of chlorine and hydroxyls radicals (Cl? and HO?) in photoelectrochemical cell system. This idea reveals circulation process of these two radicals: photoexcited holes from WO3 anode oxidize chloride and hydroxyl ions to Cl? and HO? radicals under illumination, these radicals convert urea-nitrogen to N2 or slight nitrate, and then slight nitrate is selectively reduced to N2 on a novel Pd/Au modified porous metallic sheet. TN analysis of a simulated urea solution of 30 mg L-1 demonstrated that N2 and CO2 are the primary oxidation products of the urea, and the urea-N was completely stripped (99.45%) in 90 min. Meanwhile, with the detection of EPR spectrum, organics can be transformed to CO2 by OH? in this cyclic system. Significantly, the feasibility of actual urine treatment was also investigated, indicating great denitrification efficiency (99.37%) and TOC removal efficiency (50.91%), respectively. This work sheds light upon a new economical, efficient, and environment-friendly means of urine sewage treatment.
关键词： urine,hydroxyl radicals,denitrification,chlorine radicals,photoelectrochemical
更新于2025-09-09 09:28:46
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Degradation of Paracetamol by an UV/Chlorine Advanced Oxidation Process: Influencing Factors, Factorial Design, and Intermediates Identification
摘要： The combination of a low-pressure mercury lamp and chlorine (UV/chlorine) was applied as an emerging advanced oxidation process (AOP), to examine paracetamol (PRC) degradation under different operational conditions. The results indicated that the UV/chlorine process exhibited a much faster PRC removal than the UV/H2O2 process or chlorination alone because of the great contribution of highly reactive species (?OH, ?Cl, and ClO?). The PRC degradation rate constant (kobs) was accurately determined by pseudo-first-order kinetics. The kobs values were strongly affected by the operational conditions, such as chlorine dosage, solution pH, UV intensity, and coexisting natural organic matter. Response surface methodology was used for the optimization of four independent variables (NaOCl, UV, pH, and DOM). A mathematical model was established to predict and optimize the operational conditions for PRC removal in the UV/chlorine process. The main transformation products (twenty compound structures) were detected by liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS).
关键词： paracetamol,response surface methodology,UV/chlorine,transformation products,reaction kinetics
更新于2025-09-09 09:28:46
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Phosphorus and chlorine co-doped carbon dots with strong photoluminescence as a fluorescent probe for ferric ions
摘要： Usually, carbon dots (CDs) display a relatively weak fluorescence quantum yield (QY). In order to obtain brighter CDs, phosphorus and chlorine co-doped CDs (P,Cl-CDs) were prepared via hydrothermal treatment of maltose in the presence of phosphoric and hydrochloric acids. The new CDs are highly monodispersed in water solution, have high fractions of P (14.4 atomic%) and Cl (8.9 atomic%), and exhibited yellow fluorescence with a QY of 15%. This is higher than that of monoatomic doped CDs (8.7 and 9.3% for P-CDs and Cl-CDs, respectively). The P,Cl-CDs are highly photostable, and fluorescence is strongly (statically) quenched by Fe(III). Fluorescence decreases with increasing concentration of Fe(III) in the range from 0.1–8.0 μmol?L-1, with a 60 nmol?L-1 detection limit. The doped CDs are shown to be a viable nanoprobe for the fluorometric determination of Fe(III) in spiked serum and water samples.
关键词： Quantum yield,Phosphorus,Fluorescent probe,Chlorine,Co-doped carbon dots
更新于2025-09-04 15:30:14