UV/H2O2 Process Under High Intensity UV Irradiation: A Rapid and Effective Method for Methylene Blue Decolorization     

Qian Zhang  Chaolin Li  Ting Li 《洁净——土壤、空气、水》2013,41(12):1201-1207

This study examined the UV/H₂O₂ decolorization efficiency under high UV photon flux (intensity normalized by photon energy) irradiation; the incident UV was ranging from 3.13 × 10^?8 to 3.13 × 10^?6 einstein cm^?2 s^?1. The experimental results showed that complete decolorization of 20 mg L^?1 methylene blue (MB) can be achieved within 5 s and 99% decolorization of 1000 mg L^?1 MB can be achieved in 180 s under the best condition of high UV intensity UV/H₂O₂ process. To the best of our knowledge, UV/H₂O₂ decolorization process in such a short time has not been reported. The electrical energy per order of the process was 16.21 kWh m^?3 order^?1 and it is relatively economical compared with other advanced oxidation processes. The kinetics of decolorization follows pseudo‐first order. There is a linear relationship between rate constant and UV intensity, which indicates that increasing UV intensity does not cause decline in light utilization efficiency. The experiment related to initial substrate concentration shows decolorization rate of different substrate concentration (20–1000 mg L^?1) are closed to each other. Besides, optimal H₂O₂ concentration, comparative study with low photon flux light, decolorization of other types of dyes and TOC removal were also studied.  相似文献   

Production of Laccase from Coriolus versicolor and Its Application in Dye Decolorization in Combination with UV/H2O2 Technique     

A. J. Damle  S. R. Shukla 《洁净——土壤、空气、水》2010,38(7):663-669

The relative ability of Coriolus versicolor to grow on coir fiber as a ligninocellulosic material was examined. Addition of yeast extract to the culture increased laccase activity, which was further enhanced to the level of 1976 U/L by addition of 1 mM copper sulfate. Laccase thus produced was used without further purification for the decolorization of various dye solutions. Decolorization efficiency was compared with the conventional environment friendly oxidation technique using hydrogen peroxide in the presence of UV radiations. Laccase showed good decolorization in most of the cases. Excellent results were achieved when the dye solution was treated successively with laccase and UV/H₂O₂ wherein more than 80% decolorization was achieved. This value is remarkably higher than that attained either by the enzyme or UV/H₂O₂ photolysis alone.  相似文献   

Degradation of an Azo Dye with Homogeneous and Heterogeneous Catalysts by Sonophotolysis     

Zeynep Eren 《洁净——土壤、空气、水》2012,40(11):1284-1289

This study illustrates the degradation of an azo dye, Reactive Yellow 81 (RY81), by the combined irradiation of UV‐C and ultrasound in the presence of homogeneous (Fe²⁺) and heterogeneous (TiO₂, ZnO) catalysts. The efficiency of homogeneous and heterogeneous oxidation systems was evaluated in regard of the decolorization and mineralization of RY81. Decolorization followed pseudo‐first‐order kinetics with homogeneous and heterogeneous catalysts. Complete color removal was accomplished by homogeneous sonocatalytic and sonophotocatalytic oxidation processes with apparent rate constants of 0.96 × 10^?3 and 46.77 × 10^?3 s^?1, respectively, in the presence of Fe²⁺. However, partial color removal was obtained by heterogeneous sonocatalytic, photocatalytic, and sonophotocatalytic oxidation processes with apparent rate constants of 2.32 × 10^?3, 3.60 × 10^?3, and 3.67 × 10^?3 s^?1, respectively, in the presence of ZnO. TiO₂ had the worst catalytic effect of all of the oxidation processes. The addition of hydrogen peroxide increased the rate constants of the heterogeneous oxidation processes and decreased the rate constants of the homogeneous oxidation processes. RY81 mineralization was 62.8% for the US/UV/Fe²⁺ homogeneous oxidation process, which was the best oxidation process, whereas it was 43.5% for the US/UV/ZnO/H₂O₂ heterogeneous oxidation process within 2 h reaction time.  相似文献   

Performance of A Combination Process of UV/H2O2/Micro‐Aeration for Oxidation of Dichloroacetic Acid in Drinking Water     

WenHai Chu  N. Y. Gao  Y. Deng 《洁净——土壤、空气、水》2009,37(3):233-238

The decomposition of dichloroacetic acid (DCAA) in water using a UV/H₂O₂/micro‐aeration process was investigated in this paper. DCAA cannot be removed by UV radiation, H₂O₂ oxidation or micro‐aeration alone, while UV/H₂O₂/micro‐aeration combination processes have proved effective and can degrade this compound completely. With initial concentrations of about 110 μg/L, more than 95.1% of DCAA can be removed in 180 min under UV intensity of 1048.7 μW/cm², H₂O₂ dosage of 30 mg/L and micro‐aeration flow rate of 2 L/min. However, more than 30 μg/L of DCAA was left after 180 min by UV/H₂O₂ combination process without micro‐aeration with the same UV intensity and H₂O₂ dosage. The effects of applied UV radiation intensity, H₂O₂ dose, initial DCAA concentration and pH on the degradation of DCAA have been examined in this study. Degradation mechanisms of DCAA with hydroxyl radical oxidation have been discussed. The removal rate of DCAA was sensitive to operational parameters. There was a linear relationship between rate constant k and UV intensity and initial H₂O₂ concentration, which indicated that a higher removal capacity can be achieved by improvement of both factors. A newly found nitrogenous disinfection by‐product (N‐DBP)‐DCAcAm, which has the potential to form DCAA, was easier to remove than DCAA by UV/H₂O₂ and UV/H₂O₂/micro‐aeration processes. Finally, a preliminary cost comparison revealed that the UV/H₂O₂/micro‐aeration process was more cost‐effective than the UV/H₂O₂ process in the removal of DCAA from drinking water.  相似文献   

Color Removal from Synthetic Textile Wastewater by Sono‐Fenton Process     

Celalettin Özdemir  Muhammed Kamil Öden  Serkan Şahinkaya  Erkan Kalipçi 《洁净——土壤、空气、水》2011,39(1):60-67

In this study, the oxidative decolorization of C.I. reactive yellow 145 (RY 145) from synthetic textile wastewater including RY 145 and polyvinyl alcohol by Fenton and sono‐Fenton processes which are the combination of Fenton process with ultrasound has been carried out. The effects of some operating parameters which are the initial pH of the solution, the initial concentration of Fe²⁺, H₂O₂, and the dye, temperature, and agitation speed on the color and chemical oxygen demand (COD) removals have been investigated. The optimum conditions have been found as [Fe²⁺] = 20 mg/L, [H₂O₂] = 20 mg/L, pH 3 for Fenton process and [Fe²⁺] = 20 mg/L, [H₂O₂] = 15 mg/L, pH 3 for sono‐Fenton process by indirectly sonication at 35 kHz ultrasonic frequency and 80 W ultrasonic power. The color and COD removal efficiencies have been obtained as 91 and 47% by Fenton process, and 95 and 51% by sono‐Fenton processes, respectively. Kinetic studies have been performed for the decolorization of RY 145 under optimum conditions at room temperature. It has been determined that the decolorization has occurred rapidly by sono‐Fenton process, compared to Fenton process.  相似文献   

Central Composite Design Optimization of Biological Dye Removal in the Presence of Macroalgae Chara sp.     

Ali R. Khataee  Gholamreza Dehghan  Elahe Ebadi  Minoo Pourhassan 《洁净——土壤、空气、水》2010,38(8):750-757

Response surface methodology (RSM) was employed to investigate the effects of different operational parameters on the biological decolorization of a dye solution containing malachite green (MG) in the presence of macroalgae Chara sp. The investigated variables were the initial pH, initial dye concentration, algae amount, and reaction time. Central composite design (CCD) was used for the optimization of biological decolorization process. Predicted values were found to be in good agreement with experimental values (R² = 0.982 and Adj‐R² = 0.966), which indicated suitability of the employed model and the success of RSM. The results of optimization predicted by the model showed that maximum decolorization efficiency was achieved at the optimum condition of the initial pH 6.8, initial dye concentration 9.7 mg/L, algae amount 3.9 g, and reaction time 75 min. UV–VIS spectra and FT‐IR analysis showed degradation of MG.  相似文献   

Kinetics of Methyldiethanolamine Mineralization by Using UV/H2O2 Process     

Sabtanti Harimurti  Anisa Ur Rahmah  Abdul Aziz Omar  Murugesan Thanapalan 《洁净——土壤、空气、水》2013,41(12):1165-1174

The UV/H₂O₂ is one of the popular techniques in the advanced oxidation processes (AOPs) and has been applied in the wastewater treatment during recent two decades. UV exposure on the H₂O₂ generate highly reactive hydroxyl radicals (OH^?), which are used to degrade organic contaminants through oxidation processes in wastewater. This present study involves the estimation of hydroxyl radical rate constants of methyldiethanolamine (MDEA) mineralization at different temperatures by using UV/H₂O₂ in aqueous solution. Laboratory experiments have been conducted and the profile of MDEA mineralization has been established. The hydroxyl radical rate constants and the activation energy of mineralization process have been calculated. The estimated hydroxyl rate constants and the activation energy are in good agreement with those reported in the literature.  相似文献   

Factors Affecting UV/H2O2 Oxidation of 17α‐Ethynyestradiol in Water     

Qingsong Li  Naiyun Gao  Yang Deng  Xiaoyan Ma  Wenhai Chu 《洁净——土壤、空气、水》2013,41(2):143-147

In this study, bench‐scale experiments were conducted to examine the UV/H₂O₂ oxidation of 17α‐ethynyestradiol (EE2) in water in a batch operation mode. The EE2 degradation exhibited pseudo‐first‐order kinetics, and the removal was ascribed to the production of hydroxyl radicals (^?OH) by the UV/H₂O₂ system. Typically, the EE2 oxidation rate increased with increasing UV intensity and H₂O₂ dose, and with deceasing initial EE2 levels and solution pH. At EE2₀ = 650 µg/L, UV intensity = 154 µW/cm², H₂O₂ = 5 mg/L, and neutral pH, the UV/H₂O₂ treatment was able to remove 90% of the EE2 content within 30 min. Four anions commonly present in water were found to inhibit EE2 degradation to varying degrees: > > Cl^? > . Our results demonstrate that the described UV/H₂O₂ process is an effective method to control EE2 pollution in water.  相似文献   

Treatment of Refractory Organics Contained in Actual Agro‐Industrial Wastewaters by UV/H2O2     

Ahmed Bedoui  Kaiis Sindi  Nasr Bensalah 《洁净——土壤、空气、水》2008,36(4):373-379

In this work, the treatment of actual agro‐industrial wastewaters (IWW) by a UV/H₂O₂ process has been investigated. The aqueous wastes were received from industrial olive oil mills and then treated by laboratory scale physicochemical methods, i. e., coagulation using ferrous and aluminum sulfate, decantation, filtration and adsorption on activated carbon. These wastes are brown colored effluents and have a residual chemical oxygen demand (COD) in the range of 1800 to 3500 mgO₂ L^–1, which cannot be further eliminated with physicochemical processes. The UV/H₂O₂ treatments were carried out under monochromatic irradiation at 254 nm using a thermostated reactor equipped with a mercury vapor lamp located in an axial position. The effects of initial H₂O₂ concentration, initial COD, pH and temperature have been studied in order to determine the optimum conditions for maximum color and COD removals. The experimental results reveal the suitability of the UV/H₂O₂ process for both removal of high levels of COD and effectively decolorizing the solution. In particular, 95% of color removal and 90% of COD removal were obtained under conditions of pH = 5 and 32°C using 2.75 g H₂O₂ g^–1 COD L^–1 during 6 h of UV‐irradiation. The treatment is unaffected by pH over the range 2 to 9. In addition, the COD removal is improved by increasing the temperature, whereas the color removal has not been affected by this parameter. The results show that the hydroxyl radicals generated from the catalytic decomposition of H₂O₂ by UV‐irradiation of the solution could be successfully used to mineralize the organics contained in IWW. The mineralization of the organics seems to occur in three main sequential steps: the first is the rapid decomposition of tannins leading to aromatic compounds, which are confirmed by the decolorization of the IWW; the second step corresponds to the oxidation of aromatics leading to aliphatic intermediates, which occurs by the cleavage of an aromatic ring, and is established by the removal of aromatics, and the final step is the slow oxidation of the aliphatic intermediates, which is measured by the COD removal.  相似文献   

Degradation of Bezafibrate with UV/H2O2 in Surface Water and Wastewater Treatment Plant Effluent     

Hui Yuan  YaLei Zhang  XueFei Zhou 《洁净——土壤、空气、水》2012,40(3):239-245

Bezafibrate (BZF), a widely used lipid regulator, is a potential threat to ecosystems and human health in water, and the recent research showed that advanced oxidation processes (AOPs) are much more effective for BZF degradation. In this study, we investigated the photochemical decomposition of BZF in surface water and effluent from waste water treatment plants (WWTP) by UV/H₂O₂ process. The results showed that the UV/H₂O₂ process was a promising method to remove BZF at low concentration, generally at µg L^?1 level. When initial concentrations reach 100 µg L^?1 in the deionized water, >99.8% of BZF could be removed in 16 min under UV intensity of 61.4 µm cm^?2, at the H₂O₂ concentration of 0.1 mg L^?1, and neutral pH condition. Moreover, BZF degradation was inhibited in this process when humic acid (HA) and inorganic solution anions were added to the deionized water solutions, including chloride, nitrate, bicarbonate, and sulfate, significantly. In the surface water and effluent of WWTP, however, the removal efficiency of BZF was lower than that in the deionized water because of the interference of complex constituents in the surface water and effluent. Some main intermediates at the m/z range of 100–400 were observed by high performance LC‐MS (HPLC/MS) and a simple pathway of BZF degradation by UV/H₂O₂ was proposed.  相似文献   

Degradation of Monoazo Pigments Red 53:1 and Red 48:2 by Fenton,Photo‐Fenton and UV/Peroxide Reactions     

Clóvis E. G. Ilha  Antônio J. M. G. dos Santos  Jurandir R. SouzaDe 《洁净——土壤、空气、水》2009,37(10):799-805

The degradation reactions of two monoazo pigments, namely, Red 53:1 and Red 48:2, by Fenton, photo‐Fenton and UV/H₂O₂ systems have been studied. The efficiencies of the Fenton reactions increased with temperature, but the formation of solid agglomerates was observed when the reactions were carried out above 50°C indicating a coagulant action of Fe⁺² or Fe⁺³. Photo‐Fenton reactions irradiated by sunlight presented the best rate constants for cleavage of the azo bond and the naphthalene rings. The UV/H₂O₂ system exhibited the highest efficiency with respect to the consumption of H₂O₂. The presence of a carbonyl group in the ortho position of the naphthol ring hampered the oxidation of pigment Red 48:2 by hydroxyl radicals. This finding may be explained in terms of the acceptor character of the COOH group, and suggests the formation of a complex containing two six‐membered rings between Fe⁺³ and the pigment molecule.  相似文献   

Degradation of Textile Dyeing Wastewater by a Modified Solar Photo‐Fenton Process Using Steel Scrap/H2O2     

Ganesan Ramachandran  Thanasekaran Kumarasamy 《洁净——土壤、空气、水》2013,41(3):267-274

This experimental research deals with using steel scrap as a heterogeneous catalyst. This catalyzes the oxidation reaction of real textile dye wastewater based on a modified solar photo‐Fenton oxidation process. Morphologic analysis and mapping of the elementary composition of the steel scrap have been carried out by scanning electron microscopy. The effects of concentration of H₂O₂, the pH of the solution and the catalyst loading on the degradation of textile dye wastewater are elucidated. Kinetic studies have been performed for the decolorization of wastewater under optimum conditions. It could be concluded that the steel scrap is a potential substitute for ferrous salts as a catalyst for the solar photo‐Fenton reaction.  相似文献   

Efficiency of Pleurotus florida Laccase on Decolorization and Detoxification of the Reactive Dye Remazol Brilliant Blue R (RBBR) under Optimized Conditions     

Palanivel Sathishkumar  Kannan Balan  Thayumanavan Palvannan  Seralathan Kamala‐Kannan  Byung‐Taek Oh  Susana Rodríguez‐Couto 《洁净——土壤、空气、水》2013,41(7):665-672

Laccase from the white‐rot fungus Pleurotus florida, produced under solid‐state fermentation conditions, was used for the decolorization of reactive dye Remazol Brilliant Blue R (RBBR). RBBR was decolorized up to 46% by P. florida laccase alone in 10 min. In the presence of N‐hydroxybenzotriazole (HBT), the rate of decolorization was enhanced 1.56‐fold. Central composite design of response surface methodology with four variables namely, dye, enzyme, redox mediator concentrations, and time at five levels was applied to optimize the RBBR decolorization. The predicted optimum level of variables for maximum RBBR decolorization (87%) was found to be 52.90 mg L^?1 (RBBR), 1.87 U mL^?1 (laccase), 0.85 mM (HBT), and 7.17 min (time), respectively. The validation results showed that the experimental value of RBBR decolorization (82%) was close to the predicted one. The disappearance of C–N and C–X groups, and a small shift in N–H groups in Fourier‐transform infra red (FTIR) spectroscopy confirms the degradation of RBBR chromophore by laccase enzyme. The phytotoxicity of RBBR was considerably reduced after the treatment with laccase. RBBR decolorization kinetics; K_m and V_max were calculated to be 145.82 mg L^?1 and 24.86 mg L^?1 min, respectively.  相似文献   

Pretreatment of Olive Oil Mill Wastewater by Two Different Applications of Fenton Oxidation Processes     

Celalettin Özdemir  Hayrunnisa Tezcan  Serkan Sahinkaya  Erkan Kalipci 《洁净——土壤、空气、水》2010,38(12):1152-1158

The removal of chemical oxygen demand (COD) and phenol from olive oil mill wastewaters (OOMW) was investigated experimentally by using conventional Fenton (CFP) and Fenton type processes (FTP) with zero valent iron (ZVI). Different operational parameters such as initial pH, Fe²⁺, Fe⁰, and H₂O₂ concentrations were examined. Kinetic studies in terms of COD and phenol removals for both CFP and FTP were performed. The original pH value (4.6) of OOMW for CFP was found as the optimum pH. The determined optimum conditions are [Fe²⁺] = 1500 mg L^?1, [H₂O₂] = 1750 mg L^?1, and pH = 4.6 for CFP; [Fe⁰] = 2000 mg L^?1, [H₂O₂] = 2000 mg L^?1, and pH = 3 for FTP. 82.4% COD and 62% phenol removals were performed under the optimum conditions by CFP, while 82% COD and 63.4% phenol were removed by FTP. According to the results of kinetic studies, it was observed that COD and phenol were removed by FTP more rapidly, compared to CFP. Consequently, it was determined that both CFP and FTP were effective processes for the pretreatment of OOMW.  相似文献   

Degradation of Aqueous Atrazine and Metazachlor Solutions by UV and UV/H2O2 — Influence of pH and Herbicide Concentration Abbau von Atrazin und Metazachlor in wäßriger Lösung durch UV und UV/H2O2 — Einfluß von pH und Herbizid-Konzentration     

D. P. Hessler  V. Gorenflo  F. H. Frimmel 《洁净——土壤、空气、水》1993,21(4):209-214

The degradation of two pesticides: atrazine and metazachlor was investigated in aqueous solution under UV-irradiation with and without H₂O₂. Rate constants of the photochemical degradation were determined applying a first order kinetics and quantum yields of the processes were calculated. This approach leads to an apparent decrease of the quantum yield with increasing initial pesticide concentration. At low H₂O₂ initial concentrations, the pesticide degradation was shown to be much more efficient than the degradation under UV-irradiation only. However, at high H₂O₂ concentrations (>2 mmol L^?1), the efficiency of the UV/H₂O₂ system dropped down and the quantum yields of degradation were lower than for the direct photolysis. In the absence of H₂O₂, no influence of the pH value on the photodegradation of the pesticides could be noticed in a range between pH 3 and pH 11. At low H₂O₂ initial concentrations, the photochemical degradation of the pesticides was much faster at pH 3 and pH 7 compared with the degradation at pH 11. The results emphasize the potential of optimized reaction conditions in advanced oxidation.  相似文献   

Optimization of a Photo‐assisted Fenton Oxidation Process: A Statistical Model for MDF Effluent Treatment     

Maedeh Galehdar  Habibollah Younesi  Mojtaba Hadavifar  Ali Akbar Zinatizadeh 《洁净——土壤、空气、水》2009,37(8):629-637

In the present study, the effects of initial COD (chemical oxygen demand), initial pH, Fe²⁺/H₂O₂ molar ratio and UV contact time on COD removal from medium density fiberboard (MDF) wastewater using photo‐assisted Fenton oxidation treatment were investigated. In order to optimize the removal efficiency, batch operations were carried out. The influence of the aforementioned parameters on COD removal efficiency was studied using response surface methodology (RSM). The optimal conditions for maximum COD removal efficiency from MDF wastewater under experimental conditions were obtained at initial COD of 4000 mg/L, Fe²⁺/H₂O₂ molar ratio of 0.11, initial solution pH of 6.5 and UV contact time of 70 min. The obtained results for maximum COD removal efficiency of 96% revealed that photo‐assisted Fenton oxidation is very effective for treating MDF wastewater.  相似文献   

Solar Photocatalytic Decolorization and Detoxification of Industrial Batik Dye Wastewater Using P(3HB)‐TiO2 Nanocomposite Films     

Nanthini Sridewi  Liu‐Tzea Tan  Kumar Sudesh 《洁净——土壤、空气、水》2011,39(3):265-273

Solar photocatalytic decolorization and detoxification of batik dye wastewater using titanium dioxide (TiO₂) immobilized on poly‐3‐hydroxybutyrate (P(3HB)) film was studied. The effects of initial dye concentration, catalyst concentration, P(3HB) film thickness, and fabrication methods of the nanocomposite films were evaluated against methylene blue, a standard organic dye. It was observed that 0.4 g of P(3HB)‐40 wt% TiO₂ removed 96% of the color under solar irradiation. P(3HB) and TiO₂, mixed concurrently in chloroform followed by stirring for 24 h showed a more even distribution of the photocatalyst on the polymer surface and yielded almost 100% color removal. The photocatalytic films were able to completely decolorize real industrial batik dye wastewater in 3 h and induced a chemical oxygen demand (COD) reduction of 80%. Reusability of the 0.4 g P(3HB)‐40 wt% TiO₂ film in decolorizing the batik dye wastewater was also possible as it gave a high consistent value of decolorization percentage (>80%) even after the sixth repeated usage. Recovery step of the photocatalysts was also not required in this simple treatment system. The decolorized batik dye wastewater had less/no toxic effects on mosquito larvae, Aedes aegypti, and microalgae, Scenedesmus quadricauda indicating simultaneous detoxification process along with the decolorization process.  相似文献   

Photochemistry of Ions at D-region Altitudes of the Ionosphere: A Review   总被引：2，自引：2，他引：0  

A. V. Pavlov 《Surveys in Geophysics》2014,35(2):259-334

The current state of knowledge of the D-region ion photochemistry is reviewed. Equations determining production rates of electrons and positive ions by photoionization of atmospheric neutral species are presented and briefly discussed. Considerable attention is given to the progress in the chemistry of O⁺(⁴S), O⁺(²D), O⁺(²P), N⁺, N₂ ⁺, O₂ ⁺, NO⁺, N₄ ⁺, O₄ ⁺, NO⁺(N₂), NO⁺(CO₂), NO⁺(CO₂)₂, NO⁺(H₂O) _n for n = 1–3, NO⁺(H₂O)(N₂), NO⁺(H₂O)₂(N₂), NO⁺(H₂O)(CO₂), NO⁺(H₂O)₂(CO₂), O₂ ⁺(H₂O), H₃O⁺(OH), H⁺(H₂O) _n for n = 1–8, O^?, O₂ ^?, O₃ ^?, O₄ ^?, OH^?, CO₃ ^?, CO₄ ^?, NO₂ ^?, NO₃ ^?, ONOO^?, Cl^?, Cl^?(H₂O), Cl^?(CO₂), HCO₃ ^?, CO₃ ^?(H₂O), CO₃ ^?(H₂O)₂, NO₃ ^?(H₂O), NO₃ ^?(H₂O)₂, OH^?(H₂O), and OH^?(H₂O)₂ ions. The analysis of the D-region rocket ion mass spectrometer measurements shows that, among these ions, O₂ ⁺, NO⁺, NO⁺(H₂O), and H⁺(H₂O) _n for n = 1–7 can make the main contribution to the total positive ion number density, and O^?, O₂ ^?, Cl^?, OH^?(H₂O), CO₃ ^?, HCO₃ ^?, NO₃ ^?, ONOO^?, CO₄ ^?, NO₃ ^?(H₂O), NO₃ ^?(H₂O)₂, and ³⁵Cl^?(CO₂) ions can be responsible for the main contribution to the total negative ion number density. Photodetachment of electrons from O^?, Cl^?, O₂ ^?, O₃ ^?, OH^?, NO₂ ^?, and NO₃ ^?, dissociative electron photodetachment of O₄ ^? and OH^?(H₂O), and photodissociation of O₃ ^?, O₄ ^?, CO₃ ^?, CO₄ ^?, ONOO^?, HCO₃ ^?, CO₃ ^?(H₂O), NO₃ ^?(H₂O), O₂ ⁺(H₂O), O₄ ⁺, N₄ ⁺, NO⁺(H₂O), NO⁺(H₂O)₂, H⁺(H₂O) _n for n = 2–4, NO⁺(N₂), and NO⁺(CO₂) are studied, and the photodetachment and photodissociation rate coefficients are calculated using the current state of knowledge on the cross sections of these processes and fluxes of solar radiation.  相似文献   

Photocatalytic Decolorization Kinetics and Mineralization of Reactive Black 5 Aqueous Solution by UV/TiO2 Nanoparticles     

Sandeep Kumar Sharma  Haripada Bhunia  Pramod Kumar Bajpai 《洁净——土壤、空气、水》2012,40(11):1290-1296

The photocatalytic decolorization and mineralization of Reactive Black 5 (RB5) dye in presence of TiO₂ Degussa P25 has been studied using artificial light radiation in a shallow pond slurry reactor. The equilibrium adsorption of dye, influence of pH (3–11), catalyst load (0.5–3.0 g/L), and dye concentration (20–100 mg/L) on decolorization kinetics were studied. The effect of area to volume ratio of photoreactor on decolorization kinetics has been also studied. Mineralization studies were performed at optimized conditions of pH (3) and catalyst load (1.5 g/L). The maximum adsorption (26.5 mg/g) of dye was found to occur at pH 3. The apparent pseudo first order decolorization rate constant (k_app) value followed the order pH 3 > pH 11 > pH 9 > pH 7. As compared to available literature reduction in total organic carbon (TOC) was minimal by the time there was complete decolorization. Initial reduction in TOC was followed by subsequent increasing trend till complete decolorization. Final decreasing trend in TOC was observed only after complete decolorization. Twelve hours of treatment under experimental conditions reduced TOC content by 70% only. Discussion of results suggest that photocatalytic treatment of colored effluent under low UV intensity, and low A/V ratio may result in completely decolorized effluent but still having high COD.  相似文献   

Influence of Atmospheric Solar Radiation Absorption on Photodestruction of Ions at D-Region Altitudes of the Ionosphere     

A. V. Pavlov 《Surveys in Geophysics》2016,37(4):811-844

The influence of atmospheric solar radiation absorption on the photodetachment, dissociative photodetachment, and photodissociation rate coefficients (photodestruction rate coefficients) of O^?, Cl^?, O₂ ^?, O₃ ^?, OH^?, NO₂ ^?, NO₃ ^?, O₄ ^?, OH^?(H₂O), CO₃ ^?, CO₄ ^?, ONOO^?, HCO₃ ^?, CO₃ ^?(H₂O), NO₃ ^?(H₂O), O₂ ⁺(H₂O), O₄ ⁺, N₄ ⁺, NO⁺(H₂O), NO⁺(H₂O)₂, H⁺(H₂O) _n for n = 2–4, NO⁺(N₂), and NO⁺(CO₂) at D-region altitudes of the ionosphere is studied. A numerical one-dimensional time-dependent neutral atmospheric composition model has been developed to estimate this influence. The model simulations are carried out for the geomagnetically quiet time period of 15 October 1998 at moderate solar activity over the Boulder ozonesonde. If the solar zenith angle is not more than 90° then the strongest influence of atmospheric solar radiation absorption on photodestruction of ions is found for photodissociation of CO₄ ^? ions when CO₃ ^? ions are formed. It follows from the calculations that decreases in the photodestruction rate coefficients of ions under consideration caused by this influence are less than 2 % at 70 km altitude and above this altitude if the solar zenith angle does not exceed 90°.  相似文献