Photoelectro-Fenton mineralization of phenol through optimization of ferrous regeneration

The degradation of phenol in acidic solution at pH 3 has been investigated under various photo- and electrochemical conditions. A laboratory-scale reactor on which were mounted net electrodes (RuO₂/IrO₂-coated Ti anodes (DSA) and stainless steel cathodes) and 254 nm UV lamps was established to effectively reduce ferric reagents. The experimental results of the photoelectron-chemical reaction suggested that the current efficiency of reducing ferric ion was improved by increasing the number of electrodes used, and the UV lamps were important to inducing the reduction of ferric carboxylates, which were the major intermediates that were formed upon a particular degree of phenol oxidation. Accordingly, the addition of an initial concentration of 400 ppm ferrous salt and 10,200 ppm hydrogen peroxide (in a continuous mode) resulted in the removal of over 92 % of TOC (initial phenol?=?2,000 ppm, TOC?=?1,532 ppm) by 4 h of the photoelectro-Fenton and the sequential 2 h of the photo-Fenton processes. HPLC was utilized to monitor the formation of aromatic and carboxylate byproducts, and revealed that the aid of photo irradiation eliminated most of the oxalate residue from the final solution, which would have contributed to the 25 % of the TOC that was inactive in the electrolytic system.     

Radiolysis of aqueous phenol solutions with nanoparticles. 1. Phenol degradation and TOC removal in solutions containing TiO2 induced by UV,gamma-ray and electron beams

Aqueous phenol solutions containing TiO(2) nanoparticles were irradiated with ultraviolet (UV), gamma-ray and electron beams. Organic compounds were fully removed by each type of radiation in the presence of the particles. The absorbed energy of the ionizing radiation (gamma-ray and electron beams) needed for removal was much lower than that of UV photocatalysis. Phenol was decomposed by the ionizing radiation in the absence of the nanoparticles and the addition of TiO(2) had no significant effect on phenol decomposition rate. Instead, total organic carbon (TOC) removal using the ionizing radiation was accelerated drastically by TiO(2). It is suggested that TiO(2) particles affect the intermediate compounds produced through the decomposition of phenol. The amount of removed TOC per absorbed energy were compared in the absence and the presence of TiO(2) nanoparticles. Radiolysis with the nanoparticles showed consistently high rate and high efficiency of TOC removal.     

CuO / 过硫酸氢钾体系催化氧化苯酚简

本论文通过直接沉淀法制备了CuO催化剂,结合过硫酸氢钾,在常温常压下催化氧化处理苯酚模拟废水。采用电子显微镜（SEM）、X射线粉末衍射（XRD）对催化剂进行了表征,并研究了反应过程中各影响因素对降解效率的影响。实验结果表明,在催化剂用量为0.2 g/L,氧化剂浓度为0.25 g/L,pH值为7,反应时间为60 min的条件下,浓度为50 mg/L的苯酚降解率可达100%,TOC去除率达84%。进一步实验表明,催化剂具有良好的重复使用能力。最后,通过自由基捕捉实验,考察了体系中的自由基种类,并根据实验结果,讨论了CuO/过硫酸氢钾体系的催化降解机理。     

低温等离子体氧化氨气影响因素及动力学研究

采用电晕放电低温等离子体处理模拟氨气恶臭气体,考察了输入功率、初始浓度、气体湿度、停留时间等因素对降解效果和能量效率的影响,同时对反应过程进行了动力学研究。研究表明,输入功率以及停留时间对氨气降解的影响是积极的,但能量效率随着两者的增加先增大后减小。氨气的降解率随着初始浓度的增加而降低,而能量效率随着输入功率的增加而增加。氨气降解率和能量效率均随着气体湿度的增加而增加,当气体湿度为45%时达到最大值,然而随着气体湿度的进一步增加,其降解率和能量效率反而降低。反应尾气中臭氧浓度随着输入功率的增加而不断升高,而氨气的存在却使臭氧浓度有不同程度的降低。对电晕放电低温等离子体处理NH3的反应动力学进行了分析,得到NH3的反应速率常数为kNH3=0.0707 m3/(W·h)。     

微波辅助光催化降解水中酚的研究

利用改装的家用微波炉和自制的无电极灯(EDL)试验了5种酚在水溶液中的微波辅助光催化降解效果.结果表明,反应30 min,微波辅助光催化作用(MW/EDL/TiO2)能去除80%以上的苯酚、间硝基苯酚、对氯苯酚和对甲酚,相应溶液的总有机碳(TOC)均减少70%以上,2-萘酚的去除率为59%,溶液TOC减少54%;微波(MW或MW/TiO2)作用对酚的去除率有一定贡献;对上述5种酚的微波辅助光催化反应动力学进行了初步研究,发现均符合准一级动力学方程.     

Decomposition and mineralization of cefaclor by ionizing radiation: kinetics and effects of the radical scavengers

There has been recent growing interest in the presence of antibiotics in different environmental sectors. One considerable concern is the potential development of antibiotic-resistant bacteria in the environment, even at low concentrations. Cefaclor, one of the beta-lactam antibiotics, is widely used as an antibiotic. Kinetic studies were conducted to evaluate the decomposition and mineralization of cefaclor using gamma radiation. Cefaclor, 30 mg/l, was completely degraded with 1,000 Gy of gamma radiation. At a concentration of 30 mg/l, the removal efficiency, represented by the G-value, decreased with increasing accumulated radiation dose. Batch kinetic experiments with initial aqueous concentrations of 8.9, 13.3, 20.0 and 30.0mg/l showed the decomposition of cefaclor using gamma radiation followed a pseudo first-order reaction, and the dose constant increased with lower initial concentrations. At a given radiation dose, the G-values increased with higher initial cefaclor concentrations. The experimental results using methanol and thiourea as radical scavengers indicated that ()OH radicals were more closely associated with the radiolytic decomposition of cefaclor than other radicals, such as e(aq)(-) or ()H. The radical scavenger effects were tested under O(2) and N(2)O saturations for the enhancement of the TOC percentage removal efficiencies in the radiolytic decomposition of cefaclor. Under O(2) saturation, 90% TOC removal was observed with 100,000 Gy. Oxygen is well known to play a considerable role in the degradation of organic substances with effective chain reaction pathways. According to the effective radical reactions, the enhanced TOC percentage removal efficiencies might be based on the fast conversion reactions of e(aq)(-) and ()H with O(2) into oxidizing radicals, such as O(2)(-) and HO(2)(), respectively. 100% TOC removal was obtained with N(2)O gas at 20,000 Gy, as reducing radicals, such as e(aq)(-) and ()H, are scavenged by N(2)O and converted into ()OH radicals, which have strong oxidative properties. The results of this study showed that gamma irradiation was very effective for the removal of cefaclor in aqueous solution. The use of O(2) or N(2)O, with radiation, shows promise as effective radical scavengers for enhancing the TOC or COD removal efficiencies in pharmaceutical wastewaters containing antibiotics. However, the biological toxicity and interactions between various chemicals during the radiolytic treatment, as well as treatments under conditions more representative of real wastewater will require further studies.     

Photodecomposition of humic acid and natural organic matter in swamp water using a TiO2-coated ceramic foam filter: Potential for the formation of disinfection byproducts

This paper reports on the photodecomposition of aqueous humic acid (HA) by a TiO₂-coated ceramic foam filter (TCF) reactor and on the potential for the formation of disinfection byproducts (DBPs) upon chlorination of the photocatalytically treated solutions. This photocatalytic reactor can also be applied to the removal of natural organic matter (NOM) in swamp waters. The proposed photocatalytic reaction system was operated as per standardized methodologies. First, the ability of the TCF to decompose HA (a representative compound of NOM) was evaluated from the changes in the total organic carbon (TOC) and UV₂₅₄ with the reaction time. Remarkably, TOC removal and UV₂₅₄ values ranging from 44% to 61% and from 60% to 83%, respectively, were achieved. The potential for the formation of DBPs (total trihalomethane and total haloacetic acid) by chlorination of the phototreated solution was strongly dependent on the TOC removal and UV₂₅₄ values in the solution. The degree of photodecomposition of NOMs in the swamp water samples and the DBP formation potential showed similar trends as in the case of the standard solutions containing HA. The method used in this study could be effectively used to evaluate the efficiency of TCF for reducing HA and NOM, while suppressing the formation of DBP products.     

The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol

The efficiency of different Fenton-related oxidative processes such as Fenton, solar-Fenton and UV-Fenton were examined using phenol as a model compound in simulated and industrial wastewater. A batch study was conducted to optimize parameters like pH, hydrogen peroxide concentration and ferrous ion concentration governing the Fenton process. At optimum conditions, different Fenton-related processes were compared for the degradation of phenol. Increased degradation and mineralisation efficiency were observed in photo-Fenton processes as compared to conventional Fenton process. The maximum mineralising efficiency for phenol with Fenton, solar and UV-Fenton processes were 41%, 96% and 97% respectively. In Fenton process, carboxylic acids like acetic acid and oxalic acid were formed as end products during the degradation of phenol while in photo-Fenton processes, both these ions were identified during the early stages of phenol degradation and were oxidized almost completely at 120 min of the reaction time. In photo-Fenton processes (solar and UV light) complete degradation were observed with 0.4 mM of Fe2+ catalyst as compared to 0.8 mM of Fe2+ in conventional Fenton process. In Fenton and solar-Fenton processes, an iron reusability study was performed to minimize the amount of iron used in treatment process. The efficacy of Fenton and solar-Fenton processes was applied to effluent from phenol resin-manufacturing unit for the removal and mineralisation of phenol.     

高铁酸盐氧化降解水中苯酚的动力学及机理研究

以自制高铁酸钾(K₂FeO₄)为原料,探讨了影响高铁酸盐氧化降解苯酚的主要因素,并研究了苯酚降解的动力学特征和反应机理。结果表明,高铁酸盐加入量、pH值、持续搅拌、反应温度、反应时间都影响苯酚去除效果。其中高铁酸盐加入量是影响苯酚去除效果的关键因素,高铁酸盐氧化降解苯酚的最佳pH值范围为9～10,持续搅拌和提高反应温度只影响苯酚降解速率而不影响苯酚降解率。苯酚的降解过程遵循一级反应动力学模型。苯酚被高铁酸盐氧化生成CO₂、H₂O以及一部分难矿化的有机物。     

铈离子光催化降解茜素绿的性能和机理

主要研究了简单铈离子（Ce3＋）在紫外光（uv）的作用下对蒽醌染料茜素绿（AG）的光催化降解效果和反应机理。结果表明,UV／Ce3＋体系能够有效降解AG,初始反应速率随AG浓度的倒数值和Ce3＋浓度的增加而线性增加,随初始溶液pH的增加先降低后增加,在酸性条件下有很高的TOC去除率。荧光探针实验表明,反应过程中可以产生·OH自由基。UV／Ce3＋体系对其他类型染料和对硝基苯酚都有较好的降解效果。     

微波辅助光催化降解高浓度活性黑

利用改装的家用微波炉、微波无极灯和TiO2催化剂研究了水中高浓度活性黑的光催化降解.系统考察了TiO2投加量、pH、微波无极灯数量对微波辅助光催化处理效果的影响,得出微波辅助光催化的最佳操作条件,并在最佳条件下对活性黑的脱色及矿化效果进行研究.结果表明,TiO2投加量存在最佳值2 g/L,降低pH和增加微波无极灯数量均可提高活性黑的降解率.在TiO2的投加量为2 g/L,pH =3,微波无极灯数量为3的最佳光催化条件下,400 mg/L的活性黑溶液反应180 min时可实现完全脱色,反应300 min时,TOC去除率高达89.1％.     

铈离子光催化降解茜素绿的性能和机理简

主要研究了简单铈离子（Ce³⁺）在紫外光（UV）的作用下对蒽醌染料茜素绿（AG）的光催化降解效果和反应机理。结果表明,UV/Ce³⁺体系能够有效降解AG,初始反应速率随AG浓度的倒数值和Ce³⁺浓度的增加而线性增加,随初始溶液pH的增加先降低后增加,在酸性条件下有很高的TOC去除率。荧光探针实验表明,反应过程中可以产生·OH自由基。UV/Ce³⁺体系对其他类型染料和对硝基苯酚都有较好的降解效果。     

Phenol removal from high salinity effluents using Fenton's reagent and photo-Fenton reactions

The removal of pollutants in saline medium by the Fenton's reagent needs a more detailed investigation, since the presence of chloride may inhibit or retard degradation. Phenol was used as a model pollutant and the influence of some important process variables for the removal of total organic carbon and phenol were investigated, such as FeSO4 and H2O2 concentrations, pH and salinity. The reactivity of iron cations and alternative procedures of applying UV radiation (photo-Fenton) were evaluated. Phenol was fast and completely removed by the Fenton's process even in a high saline medium (50,000mg NaCll(-1)). However, TOC was only moderately or poorly removed in saline media, depending on the salt concentration. When the photo-Fenton process was used, mineralization was improved and high TOC removals were observed in moderately saline media (NaCl concentration < or =10,000mgl(-1)). For the highest NaCl concentration tested (50,000mgl(-1)) only a moderate TOC removal was observed (50%).     

Photo-dissociation of dimethylamine by KrBr excilamp

A study of dimethylamine photo-dissociation in the gas phase has been conducted using UV radiation delivered from a KrBr^* excilamp, driven by a sinusoidal electronic control gear with maximum emission at wavelength of 207 nm. The electrical input power and radiant power of the lamp were measured to determine their effects on the degradation. The influence of flow velocity and initial concentration of dimethylamine were also examined. In order to evaluate the photo-dissociation process comprehensively, several parameters were investigated, including removal efficiency, energy yield, carbon balance and CO₂ selectivity. It is shown that the removal efficiency increases with enhanced input power and decreased gas flow rate. A high removal efficiency of 68% is achieved for lamp power 102 W and flow velocity 15 m³ h⁻¹. The optimum dimethylamine initial concentration is around 3520 mg m⁻³, for which the energy yield reaches up to 442 g kW h⁻¹ when the input power is 65 W. In addition, two chain compounds (1,3-bis-dimethylamino-2-propanol; 3-penten-2-one, 4-amino) and three ring organic matters (1-azetidinecarboxaldehyde, 2,2,4,4-tetramethyl; N-m-tolyl-succinamic acid; p-acetoacetanisidide), were identified by GC–MS as secondary products, in order to demonstrate the pathways of the dimethylamine degradation.     

Decomposing phenol by the hidden talent of ferromagnetic nanoparticles

Researches on modified Fenton reactions applied in phenol degradation have been focused on reducing secondary pollution and enhancing catalytic efficiency. Newly developed methods utilizing carriers, such as Resin and Nafion, to immobilize Fe(2+) could avoid iron ion leakage. However, the requirement of high temperature and the limited reaction efficiency still restrained them from broad application. Based on a recently discovered "hidden talent" of ferromagnetic nanoparticles (MNPs), we established a MNP-catalyzed phenol removal assay, which could overcome these limitations. Our results showed that the MNPs removed over 85% phenol from aqueous solution within 3h even at 16 °C. The catalytic condition was extensively optimized among a range of pH, temperature as well as initial concentration of phenol and H(2)O(2). TOC and GC/MS analysis revealed that about 30% phenol was mineralized while the rest became small molecular organic acids. Moreover the MNPs were thermo-stable and could be regenerated for at least five rounds. Thus, our findings open up a wide spectrum of environmental friendly applications of MNPs showing several attractive features, such as easy preparation, low cost, thermo-stability and reusability.     

Enhanced degradation of azo dye alizarin yellow R in a combined process of iron–carbon microelectrolysis and aerobic bio-contact oxidation

Purpose

With the aim of enhanced degradation of azo dye alizarin yellow R (AY) and further removal of the low-strength recalcitrant matter (LsRM) of the secondary effluent as much as possible, our research focused on the combination of aerobic bio-contact oxidation (ABO) with iron/carbon microelectrolysis (ICME) process.

Materials and methods

The combined ABO (with effective volume of 2.4?l) and ICME (with effectively volume of 0.4?l) process were studied with relatively short hydraulic retention time (HRT) of 4 or 6?h.

Results

At the HRT of 6?h with the reflux ratio of 1 and 2, the AY degradation efficiency in the final effluent was >96.5%, and the total organic carbon (TOC) removal efficiency were 69.86% and 79.44%, respectively. At the HRT of 4?h and the reflux ratio of 2, TOC removal efficiency and AY degradation efficiency were 73.94% and 94.89%, respectively. The ICME process obviously enhanced the total AY removal and the generated micromolecule acids and aldehydes then that wastewater backflow to the ABO where they were further biodegraded.

Conclusion

The present research might provide the potential options for the advanced treatment azo dyes wastewater with short HRT and acceptable running costs.     

Fe (III) supported on resin as effective catalyst for the heterogeneous oxidation of phenol in aqueous solution

FeIII supported on resin as an effective catalyst for oxidation was prepared and applied for the degradation of aqueous phenol. Phenol was selected as a model pollutant and the catalytic oxidation was carried out in a batch reactor using hydrogen peroxide as the oxidant. The influent factors on oxidation, such as catalyst dosage, H2O2 concentration, pH, and phenol concentration were examined by considering both phenol conversion and chemical oxygen demand (COD) removal. The FeIII-resin catalyst possesses a high oxidation activity for phenol degradation in aqueous solution. The experimental results of this study show that almost 100% phenol conversion and over 80% COD removal can be achieved with the FeIII-resin catalyst catalytic oxidation system. A series of prepared resin were investigated for improving the oxidation efficiency. It was found that the reaction temperature and initial pH in solution significantly affected both of phenol conversion and COD removal efficiency. The activity of the catalyst significantly decreased at high pH, which was similar to the Fenton-like reaction mechanism. Results in this study indicate that the FeIII-resin catalytic oxidation process is an efficient method for the treatment of phenolic wastewater.     

Radiation degradation of Congo Red in aqueous solution

Radiation-induced degradation of Congo Red (an azo dye) in aqueous solution was studied both with steady-state radiolysis and time-resolve techniques of pulse radiolysis and laser flash photolysis. Decomposition and mineralization of Congo Red by gamma-rays was investigated with the changes of absorption spectra, degradation efficiency, TOC removal and pH changes of the solutions in different irradiation systems. The main radiolytic products resulting from steady-state radiolysis of Congo Red were examined by HPLC and LC-MS. Complete degradation of Congo Red was observed at different absorbed doses under diverse irradiation condition. The TOC removal of the solutions saturated with O2 or N2O reached 76% and 86% at the absorbed dose of 11.9 kGy, respectively. Pulse radiolysis and laser flash photolysis experiments were carried out to study the reaction of Congo Red with e(aq)- and ()OH. The reaction rate constants were determined.     

Degradation of Carbofuran in Water by Solar Photocatalysis in Presence of Photosensitizers

The effect of the presence of photosensitizers, methylene blue (MB) and rose Bengal (RB), on the degradation of carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate) in water in a solar photocatalytic system was investigated. It was found that as compared to MB, RB generally showed a stronger effect on the decomposition of carbofuran under comparable conditions. Among the conditions studied, adding 2 × 10^?6 M of RB, that corresponding to 2% of the initial concentration of carbofuran solution in the system, rendered the most effective degradation of carbofuran. As a result, a carbofuran removal percentage of 69.9%, a mineralization efficiency of 28.0%, and a microtoxicity reduction of 65.0% could be achieved. The degradation and mineralization of carbofuran was found to follow the pseudo-first order reaction kinetics. The decomposition mechanism of carbofuran was further investigated through identification of the intermediates to elaborate the influence of dye photosensitizer on the solar photocatalysis of carbofuran in water. On the basis of the intermediates identified, including carbofuran phenol, 3-hydroxy carbofuran phenol, and substituted alcohols (3-phenoxy 1-propanol, 2-ethyl 1-hexanol, 2-butoxyl ethanol), it appears that hydrolysis and hydroxylation were the two key mechanisms for decomposing carbofuran during the process of solar photocatalysis with the aid of dye photosensitizer.     

Enhanced electrokinetic remediation of lead-contaminated soil by complexing agents and approaching anodes

Optimizing process parameters that affect the remediation time and power consumption can improve the treatment efficiency of the electrokinetic remediation as well as determine the cost of a remediation action. Lab-scale electrokinetic remediation of Pb-contaminated soils was investigated for the effect of complexant ethylenediaminetetraacetic acid (EDTA) and acetic acid and approaching anode on the removal efficiency of Pb. When EDTA was added to the catholyte, EDTA dissolved insoluble Pb in soils to form soluble Pb–EDTA complexes, increasing Pb mobility and accordingly removal efficiency. The removal efficiency was enhanced from 47.8 to 61.5 % when the EDTA concentration was increased from 0.1 to 0.2 M, showing that EDTA played an important role in remediation. And the migration rate of Pb was increased to 72.3 % when both EDTA and acetic acid were used in the catholyte. The “approaching anode electrokinetic remediation” process in the presence of both EDTA and acetic acid had a higher Pb-removal efficiency with an average efficiency of 83.8 %. The efficiency of electrokinetic remediation was closely related to Pb speciation. Exchangeable and carbonate-bounded Pb were likely the forms which could be removed. All results indicate that the approaching anode method in the presence of EDTA and acetic acid is an advisable choice for electrokinetic remediation of Pb-contaminated soil.