Photocatalytic degradation of aromatic sulfonates present in industrial percolates

Photocatalytic treatment in the presence of aqueous TiO₂ suspensions was applied to an aqueous percolate containing various hydrophilic aromatic pollutants, in particular naphthalene sulfonates. A preliminary feasibility study was accomplished on standards of pure compounds, for which a degradation rate trend inversely proportional to the sulfonation degree was found, demonstrating the important role played by the substrate adsorption on semiconductor particles. The evolution of primary processes, the abatement of TOC and the release of sulfate were monitored. Further experiments performed on samples of percolates taken from an abandoned industrial site demonstrated the suitability of photocatalysis for the effective destruction and mineralization of the investigated contaminants in these complex matrices after a few hours irradiation.     

纳米二氧化钛光催化降解水中有机污染物的研究

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氮掺杂二氧化钛光催化降解超纯净水中有机化合物

UV氧化单元是生产超纯水过程中的一个重要组成部分。然而,常规UV氧化能耗大,寻求高效节能的UV氧化方式已成为当今超纯净水净化研究热点之一。文中采用溶胶凝胶法,以钛酸四丁酯为钛前驱体,乙醇为溶剂,成功制备了TiO2薄膜。TiO2薄膜在加温条件下氨化制得了含氮TiO2。实验通过光催化降解超纯净水中乙二醇、异丙醇及尿素,考查了合成催化剂的性能。实验表明:在相同紫外光源条件下,掺氮TiO2的催化效果明显优于TiO2的催化效果。将掺氮TiO2与254 nm UV灯结合使用能达到与仅使用185 nm UV灯的同样的氧化效果,将此技术应用于超纯净水处理将会大大降低清洁水净化能量消耗及生产成本。     

Photocatalytic degradation of thiocarbamate herbicide active ingredients in water

It has been shown that a wide range of organic compounds in aqueous solutions is photocatalytically oxidized to carbon dioxide in the presence of titanium dioxide with near-UV radiation. The photocatalytic mineralization of thiocarbamate derivative pesticides (EPTC, butylate, molinate, vernolate and cycloate) in water by illuminated TiO₂ has been studied. The determination of the effects of various kinetic factors on the photocatalytic degradation and the determination of the nature of the principal intermediates form part of the focus of this study. The degradation rate of these thiocarbamates in a continuous recirculation mode approximates first-order kinetics. It was demonstrated that photocatalyzed degradation of thiocarbamate active ingredients does not occur instantaneously to form carbon dioxide, but through the formation of long-lived intermediate species. Photocatalytic intermediates detected during the degradation of thiocarbamates were identified by GC/MS techniques. Intermediates detected in the photocatalytic oxidation of thiocarbamates in water solutions are in excellent agreement with products identified from the atmospherically important reactions of OH radical with thiocarbamates. Particular attention will be paid to the carbon dioxide formed from the illuminated suspension in order to demonstrate not only apparent destruction but also complete mineralization. The degradation of a two-component mixture was carried out and compared to results obtained with single-component studies.     

Continuous-mode photocatalytic degradation of chlorinated phenols and pesticides in water using a bench-scale TiO2 rotating disk reactor

Photocatalytic degradation of phenol, chlorinated phenols, and lindane was evaluated in a continuous flow TiO₂ rotating disk photocatalytic reactor (RDPR). The RDPR operated at a hydraulic residence time of 0.25 day and at a disk angular velocity of 12 rpm. At low molar feed concentrations (0.038 mmol/l), the removal efficiencies for phenol and chlorinated phenols were in the order of 86% or higher, whereas the removal efficiency for lindane at a feed concentration of 0.016 mmol/l was in the order of 63%.

For 2,4,6-trichlorophenol (TCP), an increase in the molar influent concentration resulted in a decrease in removal efficiency but in an increase in removal rate. The degradation rate of 2,4,6-TCP followed a saturation type dependancy with the effluent concentration, suggesting a Langmuir–Hinshelwood (L–H) reaction rate equation. A L–H equation was employed to determine the reaction rate constant and the adsorption coefficient for 2,4,6-TCP. The photonic efficiency increased from 0.68% at an influent concentration of 0.13 mmol/l to 2.06% at an influent concentration of 1.0 mmol/l.     

水中痕量有机物光催化降解初始速率排序和预测

TiO2光催化技术消除饮用水中痕量有毒有机物的实际应用不像实验室基础研究一样有令人满意的进展，理论研究体系的相对简单与实际应用体系复杂多变的矛盾是现阶段存在的主要问题之一。通过有机物聚类分析将现有的有机物降解实验数据进行归类和排序;同时，从有机物初始浓度与初始降解速率的关系出发，通过Freundlich动力学方程，用研究成熟、检测方便的常量和微量浓度区域的实验数据来预测痕量和超痕量浓度范围内的降解速率，而这个浓度范围正是饮用水深度净化过程所必须涉及的。两方面的结合为理论研究体系与实际应用体系的衔接探索了一条新的思路。     

纳米TiO2光催化降解有机污染物的研究与应用

以光催化剂TiO2为例,讨论了光催化降解有机污染物的机理,总结了TiO2光催化剂在降解有机污染物(氯代物与芳香族化合物、含氮化合物、表面活性剂、染料、农药等)方面的应用,并对TiO2光催化氧化法的发展与应用前景进行了展望。     

Photocatalytic degradation of organic pollutants using green oil palm frond-derived carbon quantum dots/titanium dioxide as multifunctional photocatalysts under visible light radiation

The present work suggested the use of waste oil palm frond as an alternative precursor for nitrogen-doped carbon quantum dots (NCQDs) and proposed a straightforward in-situ hydrothermal method for the preparation of NCQDs/TiO₂ nanocomposites. The elemental composition, morphological, structural and optical characteristics of NCQDs/TiO₂ nanocomposites have been comprehensively investigated. The successful grafting of NCQDs on TiO₂ matrix was confirmed by the formation of TiOC bond and the electronic coupling between the π-states of NCQDs and the conduction band of TiO₂. For the first time, the oil palm frond-derived NCQDs/TiO₂ was adopted in the photodegradation of methylene blue (MB) under visible-light irradiation. As a result, the photocatalytic efficiency of NCQDs/TiO₂ nanocomposites (86.16%) was 2.85 times higher than its counterpart TiO₂ (30.18%). The enhanced performance of nanocomposites was attributed to the pivotal roles of NCQDs serving as electron mediator and visible-light harvester. Besides, the optimal NCQDs loading was determined at 4 ml while the removal efficiency of NCQDs/TiO₂-4 was the highest at a catalyst dosage of 1 g·L^-1 under alkaline condition. This research work is important as it proposed a new insight to the preparation of biomass-based NCQDs/TiO₂ using a facile synthetic method, which offers a green and sustainable water remediation technology.     

高纯二氧化氯工业循环水处理系统的应用

二氧化氯作为水处理剂已得到广泛的应用,但其纯度和使用成本越来越成为制约其应用的瓶颈.在DTJHP法高效、高纯稳定二氧化氯溶液生产技术的基础上,作者研制了新型高纯二氧化氯工业循环水处理系统.该项技术运行成本低、性能稳定、无泄漏、安全可靠.该装置运行的综合费用仅为电解法二氧化氯发生器的30%左右、纯二氧化氯发生器(以亚氯酸钠为原料)的5%～10%左右.     

微波辅助光催化降解4-氯酚的研究

采用了一种新的水处理技术微波辅助光催化(MW／UV／P25)降解4-氯酚(4CP)模拟废水。初始质量浓度为30mg/L的4CP在微波光催化下发生了降解,反应120min,4CP的降解率达到82．85％,Cl^-质量浓度增加值为7．95mg/L。4CP的降解率与溶液的pH、通气条件、紫外灯光照度等因素有关,外加H2O2氧化剂能够加速4CP的降解。微波辅助光催化降解4CP服从一级反应动力学方程。     

Photocatalytic degradation of dyes and microorganism inactivation using solution blow spun silver-modified titania fibers

This work investigated the photocatalytic effect of silver-modified titania fibers on the degradation of rhodamine B (RB) and methylene blue (MB) and the inactivation of Escherichia coli and Staphylococcus aureus strains. Fibrous cotton-wool-like structures resulted from a combination of the sol-gel route to solution blow spinning followed by calcination of hybrids fibers at 700 °C. Analysis of X-ray diffraction and transmission electron microscopy confirmed the presence of anatase and rutile polymorphs and metallic silver on fibers. Silver-modified titania fibers inhibited bacterial growth in all experimental conditions regardless of the ion content or UV-irradiation. The effectiveness of microorganism inactivation of titania fibers increases upon UV-irradiation. pH did not influence the photodegradation of RB, and solutions with basic pH enhanced the removal of MB. In a fixed pH, MB presents a faster photodegradation rate as compared to RB, but they match when applying silver-modified titania fibers and UV-irradiation.     

Photocatalytic degradation of benzene,toluene, ethylbenzene,and xylene (BTEX) using transition metal-doped titanium dioxide immobilized on fiberglass cloth

Transition metal (Fe, V and W)-doped TiO₂ was synthesized via the solvothermal technique and immobilized onto fiberglass cloth (FGC) for uses in photocatalytic decomposition of gaseous volatile organic compounds—benzene, toluene, ethylbenzene and xylene (BTEX)—under visible light. Results were compared to that of the standard commercial pure TiO₂ (P25) coated FGC. All doped samples exhibit higher visible light catalytic activity than the pure TiO₂. The V-doped sample shows the highest photocatalytic activity followed by the W- and Fe-doped samples. The UV-Vis diffuse reflectance spectra reveal that the V-doped sample has the highest visible light absorption followed by the W- and Fe-doped samples. The X-ray diffraction (XRD) patterns indicate that all doped samples contain both anatase and rutile phases with the majority (>80%) being anatase. No new peaks associated with dopant oxides can be observed, suggesting that the transition metal (TM) dopants are well mixed into the TiO₂ lattice, or are below the detection limit of the XRD. The X-ray absorption near-edge structure spectra of the Ti K-edge transition indicate that most Ti ions are in a tetravalent state with octahedral coordination, but with increased lattice distortion from Fe- to V- and W-doped samples. Our results show that the TM-doped TiO₂ were successfully synthesized and immobilized onto flexible fiberglass cloth suitable for treatment of gaseous organic pollutants under visible light.     

Photocatalytic degradation of malic acid using a thin coated TiO2‐film: Insights on the mechanism of photocatalysis

Decontamination of opaque fluids using photocatalysts and near Ultraviolet (UV) irradiation involves major technical challenges. This study considers a thin TiO₂ layer placed in a new Chemical Reactor Engineering Centre (CREC)‐photoreactor cell. This new photoreactor cell is used for the photocatalytic degradation of malic and malonic acids, typical apple juice components. Conversion of organic species can only proceed through the “dark side” of the TiO₂ layer, which is in direct contact with the fluid. Under the selected operating conditions both external mass‐transfer limitations and photolysis are found to be negligible. Macroscopic radiation balance shows that 92% of near UV radiation is absorbed by the ‘back side” of the TiO₂‐film. Photocatalytic degradation experiments with 10, 20, 30, and 40 ppm malic acid initial concentrations, show that malonic acid is a main intermediate. Complete malic acid conversion occurs after 5–8 h of irradiation. Kinetic modeling of malic and malonic acid photodegradation with kinetic parameter estimation is performed using both an “in series” and an “in series‐parallel” reaction networks. The “in series‐parallel” reaction network displays better ability for predicting CO₂ formation, showing maximum quantum yields of 14.2%. Given that in the CREC‐photoreactor cell with a thin TiO₂‐film, photocatalysis can only proceed via the transfer of mobile “h⁺” sites from the irradiated side to the “dark side', this study demonstrates the significance of this step on the overall photocatalysis mechanism. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3286–3299, 2014     

纳米TiO2光电催化降解工业废水技术研究进展

纳米TiO2光电催化技术,能有效减少太阳能光催化降解工业废水反应中光生电子与光生空穴的复合,提高量子利用率,从而大幅度提高光催化效率。简要介绍了纳米TiO2光电催化技术机理和应用该技术处理工业废水的技术特点;综述了二维纳米TiO2光电催化体系、三维纳米TiO2光电催化体系、分隔式纳米TiO2光电催化体系,以及矿物担载纳米TiO2光电催化体系等在国内外的研究进展;展望了纳米TiO2光电催化技术降解工业废水的应用前景。     

纳米二氧化钛在水处理中的研究进展

介绍了纳米TiO2制备方法及光催化氧化还原机理,概述了纳米TiO2光催化技术在降解农药废水、含油废水、染料废水、造纸废水及自来水处理中的应用,提出了纳米TiO2在水处理应用中存在的问题及解决措施,并对TiO2光催化材料在水处理中的发展趋势进行了展望。     

可光助再生二氧化钛/层状双氢氧化物去除水体中有机染料

利用吸附-光催化技术去除水体中有机染料,是高效节能的方法之一。然而,碳基吸附剂在光催化降解污染物过程中,由于活性氧的攻击会发生自身的逐渐氧化。本研究中,采用尿素水解水热法制备二氧化钛/层状双氢氧化物(TiO₂/LDH)非碳基复合材料,不仅对水体中有机染料具有较高的吸附容量,也在光辐射后具有可重复的再生能力。对甲基橙的吸附量为527.5 mg/g,在4轮循环再生后仍具有88.6%的再生率;对亚甲基蓝的吸附量为208.3 mg/g,在4轮循环再生后仍具有94.7%的再生率。在吸附-光再生过程中,LDH基底自身具有强抗氧化能力和高吸附能力,同时提高了负载剂TiO₂的光吸收效率,为水中有机污染物去除和吸附-光催化复合材料设计优化提供了可行的策略。     

Photocatalytic degradation of methyl tert‐butyl ether (MTBE) in contaminated water by ZnO nanoparticles

BACKGROUND: Over the past several decades methyl tert‐butyl ether (MTBE) as additive to gasoline, intended to either boost ratings of fuel or to reduce air pollution, has been accepted worldwide. Since MTBE has high water solubility, the occurrence of fuel spills or leaks from underground storage tanks or transferring pipeline has led to the contamination of natural waters. In this study the degradation of aqueous MTBE at relatively high concentrations was investigated by a UV‐visible/ZnO/H₂O₂ photocatalytic process. The effects of important operational parameters such as pH, amount of H₂O₂, catalyst loading and irradiation time were also investigated. Concentration of MTBE and intermediates such as tert‐butyl formate and tert‐butyl alcohol were measured. RESULTS: Time required for complete degradation increased from 20 to 150 min when the initial concentration was increased from 10 to 500 mg L^?1. The first‐order rate constants for degradation of MTBE were estimated to be 0.183–0.022 min^?1 as the concentration increased from 10 to 500 mg L^?1. Study of the overall mineralization monitored by total organic carbon analysis showed that at an initial concentration of 100 mg L^?1 MTBE complete mineralization was obtained after 100 min under UV‐visible/ZnO/H₂O₂ photocatalysis. CONCLUSION: The data presented in this paper clearly indicated that UV‐visible/ZnO/O₂ as an advanced oxidation process provides an efficient treatment alternative for the remediation of MTBE‐contaminated waters. Copyright © 2008 Society of Chemical Industry     

纳米二氧化钛光催化处理废水中亚硝酸根的研究

综述了纳米二氧化钛光催化的机理 ,提出了测定废水中亚硝酸根的方法 ,探讨了纳米二氧化钛的用量 ,反应物起始浓度 ,空穴清空剂甲酸等因素对反应的影响 ,拟合出了反应动力学方程 ,并对空穴清空剂甲酸的作用机理提出看法。     

Chemical degradation of aldicarb in water using ozone

The use of ozone to degrade aldicarb in water was investigated under different conditions. The oxidation develops through the direct attack of ozone since the presence of hydroxyl radical inhibitors, such as tert-butanol, does not affect the degradation rate of aldicarb. The combination of ozone with hydrogen peroxide does not improve the oxidation rate which also confirms the absence of radical reactions to eliminate aldicarb. However, TOC removal increases 51% in the presence of hydrogen peroxide after 65 min of oxidation. The oxidation rate is strongly affected by the type of device for feeding ozone, which indicates that a fast gas-liquid reaction is taking place. Therefore, mass transfer and chemical reaction steps are important factors in the establishment of the global rate of oxidation. Application of kinetic equations derived from gas absorption theories allows the determination of the rate constant of the direct ozone–aldicarb reaction, which was found to be: k = 3·18 × 10¹¹ exp(–6000/T) m³ mol^?1s^?1.     

Photocatalytic degradation of gaseous trichloroethene using immobilized ZnO/SnO2 coupled oxide in a flow‐through photocatalytic reactor

The photocatalytic degradation of gaseous trichloroethene (TCE) was investigated on immobilized ZnO/SnO₂ coupled oxide in a flow‐through photocatalytic reactor. It was found that gaseous photocatalysis is an efficient method for volatile organic compounds' abatement and air purification. Degradation of ～100% was found for TCE at the concentrations examined, up to 400 ppmv, in a flow‐through dry synthetic gas stream. In our tested conditions, the flow rate had little influence on the photocatalytic degradation efficiencies of TCE, while the relative humidity had a significant influence on the photocatalytic degradation of TCE. The photocatalytic degradation efficiencies of TCE increased slowly below 20% relative humidity and then decreased as the relative humidity increased further. The deactivation of used immobilized photocatalyst was not observed within the 200 h testing period in the present experiment, although the surface of the photocatalyst changed greatly during the use of the photocatalyst. Copyright © 2004 Society of Chemical Industry