Photocatalytic oxidation of xenobiotics in water with immobilized TiO2 on agitator

A novel photocatalytic oxidation reactor, using Degussa P-25 TiO2 as a stationary phase with a thickness of 1.5-2.0 um on the blades of agitator, was developed to study the photocatalytic oxidation of xenobiotics. Particularly in this device, separation of photocatalyst from the purified water after oxidation reaction was not necessary, and no other aeration equipment was required to supply oxygen. To examine the efficiency of this device, photocatalytic degradation of xenobiotic organics such as carbofuran was studied as an example. Results indicated that carbofuran could be degraded completely with mineralization efficiency of 20% after 6 hours of oxidation under the imposed conditions. The mineralization rate of carbofuran was found to follow the pseudo-first order reaction kinetics. Moreover, the rate constant of mineralization was found to be proportional to TiO2 film area and the square root of UV light intensity. These results implied the mineralization efficiency of carbofuran could be improved through increasing TiO2 film area and UV light intensity. Accordingly, this novel device showed potential application for degrading xenobiotics in water.     

焦炭负载改性纳米TiO2阳光催化降解染料模拟废水的初步研究

以焦炭为载体,Na2SiO3为粘结剂,制备了负载型铁改性纳米TiO2光催化剂,并研究了该催化剂在太阳光照射下降解亚甲基兰染料废水的效果,通过正交和单因素优化试验,探讨了影响染料废水降解效果的主要因素,研究结果表明,影响降解因素的大小次序是:煅烧时间＞铁掺杂量＞Na2SiO3质量百分比＞煅烧温度.本光催化剂制备的最佳制备条件是:以20%的Na2SiO3溶液为粘结剂,掺杂2%的Fe,400℃煅烧温度下煅烧3 h.以太阳光为光源,亚甲基兰染料废水的降解率可达到87.1%.     

焦炭负载改性纳米TiO2阳光催化降解染料模拟废水的初步研究

以焦炭为载体，Na2SiO3为粘结剂，制备了负载型铁改性纳米TiO3光催化剂，并研究了该催化剂在太阳光照射下降解亚甲基兰染料废水的效果，通过正交和单因素优化试验，探讨了影响染料废水降解效果的主要因素，研究结果表明，影响降解因素的大小次序是：煅烧时间〉铁掺杂量〉Na2SiO3质量百分比〉煅烧温度。本光催化剂制备的最佳制备条件是：以20％的Na2SiO3溶液为粘结剂，掺杂2％的Fe，400℃煅烧温度下煅烧3h。以太阳光为光源，亚甲基兰染料废水的降解率可达到87．1％。     

Selective removal of diclofenac from contaminated water using molecularly imprinted polymer microspheres

A molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization using diclofenac (DFC) as a template. Binding characteristics of the MIP were evaluated using equilibrium binding experiments. Compared to the non-imprinted polymer (NIP), the MIP showed an outstanding affinity towards DFC in an aqueous solution with a binding site capacity (Q_max) of 324.8 mg/g and a dissociation constant (K_d) of 3.99 mg/L. The feasibility of removing DFC from natural water by the MIP was demonstrated by using river water spiked with DFC. Effects of pH and humic acid on the selectivity and adsorption capacity of MIP were evaluated in detail. MIP had better selectivity and higher adsorption efficiency for DFC as compared to that of powdered activated carbon (PAC). In addition, MIP reusability was demonstrated for at least 12 repeated cycles without significant loss in performance, which is a definite advantage over single-use activated carbon.     

A simple chemical free arsenic removal method for community water supply - A case study from West Bengal, India

This report describes a simple chemical free method that was successfully used by a team of European and Indian scientists (www.qub.ac.uk/tipot) to remove arsenic (As) from groundwater in a village in West Bengal, India. Six such plants are now in operation and are being used to supply water to the local population (www.insituarsenic.org). The study was conducted in Kasimpore, a village in North 24 Parganas District, approximately 25 km from Kolkata. In all cases, total As in treated water was less than the WHO guideline value of 10 μg L⁻¹. The plant produces no sludge and the operation cost is 1.0 US$ per day for producing 2000 L of potable water.     

Characterization of aluminium-based water treatment residual for potential phosphorus removal in engineered wetlands

Aluminium-based water treatment residual (Al-WTR) is the most widely generated residual from water treatment facilities worldwide. It is regarded as a by-product of no reuse potential and landfilled. This study assessed Al-WTR as potential phosphate-removing substrate in engineered wetlands. Results indicate specific surface area ranged from 28.0 m² g⁻¹ to 41.4 m² g⁻¹. X-ray Diffraction, Fourier transform infrared and energy-dispersive X-ray spectroscopes all indicate Al-WTR is mainly composed of amorphous aluminium which influences its phosphorus (P) adsorption capacity. The pH and electrical conductivity ranged from 5.9 to 6.0 and 0.104 dS m⁻¹ to 0.140 dS m⁻¹ respectively, showing that it should support plant growth. Batch tests showed adsorption maxima of 31.9 mg P g⁻¹ and significant P removal was achieved in column tests. Overall, results showed that Al-WTR can be used for P removal in engineered wetlands and it carries the benefits of reuse of a by-product that promotes sustainability.     

Removal of mixed pesticides from drinking water system by photodegradation using suspended and immobilized TiO2

Lindane (1α, 2α, 3β, 4α, 5α, 6β-hexachloro cyclohexane), methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate) and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate) are removed from water individually and as a mixture by photo degradation using suspended and immobilized forms of TiO₂ (Degussa P-25). Studies were conducted to optimize the coating thickness of immobilized photo catalyst. The rate of degradation of pesticides was compared in both suspended and immobilized TiO₂ systems. Degradation studies of mixed pesticides were carried out with low concentrations (1.0 and 2.5 mg/L) of pesticides. Only three intermediate byproducts such as methyl paraoxon, O,O,O-trimethyl phosphonic thionate and p-nitrophenol were observed during the methyl parathion degradation in suspended, immobilized TiO₂ systems and mixed pesticides degradation studies. At the end of the reaction methyl parathion and its by-products were completely degraded. During lindane degradation hexachloro cyclohexane, pentachloro cyclohexane, hexachloro benzene, 1-hydroxy 2,3,4,5,6-chlorocyclohexane, 1-hydroxy 2,3,4,5,6-chlorobenzene, pentachloro cyclopentadiene, 1,2,3,4,5-hydroxy cyclopentene and 1,2,3-hydroxy cyclobutane were identified in suspended and immobilized TiO₂ systems, whereas only hexachloro cyclohexane, pentachloro cyclohexane, hexachloro benzene and pentachloro cyclopentadiene were observed during mixed pesticides degradation. No intermediate by-product was observed during the photo degradation of dichlorvos. Langmuir-Hinshelwood pseudo first order kinetic equation showed that there was not much change in the rates of degradation in both suspended and immobilized TiO₂ systems irrespective of the pesticide. During mixed pesticides degradation, the degradation pattern was not similar to that of single pesticide.     

Radiolysis of aqueous 4-nitrophenol solution with Al2O3 or TiO2 nanoparticles

Aqueous 4-nitrophenol solutions containing TiO₂ or Al₂O₃ nanoparticles were irradiated with electron beam. 4-nitrophenol was decomposed by the ionizing radiation process in the absence of the nanoparticles. The addition of TiO₂ or Al₂O₃ (2 g l⁻¹) before irradiation improved the removal of 4-nitrophenol, total organic carbon (TOC) but also nitrogen (TN). To identify the origin of the loss (catalysis or simply adsorption), TiO₂ or Al₂O₃ nanoparticles were added after irradiation. Experiments show that the effect of the presence of TiO₂ or Al₂O₃ during irradiation is just due to adsorption.     

负载型纳米TiO2光催化降解水中微量溶解性间二甲苯

以高压汞灯为光源 ,采用浸涂 -烧结法制备的负载型纳米TiO2 作为光催化剂 ,通过对水中微量溶解性间二甲苯的光催化氧化过程的研究表明 ,初始浓度在 6 .6 8— 17.36mg/L的范围内 ,间二甲苯的光催化反应遵循表观一级反应动力学规律 ,反应的表观速率常数随溶液初始浓度的增大而减小 ,半衰期则随初始浓度的增大而增加 ,经 1.5h反应后 ,溶液中间二甲苯的去除率从 17.36mg/L的 5 4 .4 4 %增加到 6 .6 8mg/L的 75 .90 %。     

纳米TiO2光催化氧化去除水中痕量双氯芬酸的研究

以TiCl4为前驱体,采用水解法经不同温度煅烧制备了具有不同理化性能的纳米TiO2光催化剂。利用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、物理吸附仪、紫外—可见光漫反射吸收光谱(UV-Vis DRS)等手段对纳米TiO2的晶相结构、粒径、孔径分布以及禁带宽度等进行了表征。以蒸馏水配制的双氯芬酸溶液为目标物,进行了纳米TiO2光催化氧化去除双氯芬酸的活性测试,研究了纳米TiO2的理化性能与光催化氧化活性之间的关系。结果表明,经400℃煅烧制得的纳米TiO2样品具有最高的光催化氧化活性,其在紫外光照射60min下对双氯芬酸的去除率为98%左右,比单独紫外光照射高出85百分点。纳米TiO2光催化氧化去除双氯芬酸的反应近似一级反应动力学模型,其中经400℃煅烧制得的纳米TiO2光催化氧化去除双氯芬酸的表观反应速率常数为0.054 54min-1,是普通商用TiO2的2倍左右,与德国Degussa P-25TiO2的光催化氧化活性最相近。     

Eco-restoration: Simultaneous nutrient removal from soil and water in a complex residential-cropland area

An eco-restoration system to remove excess nutrients and restore the agricultural ecosystem balance was proposed and applied from August 2006 to August 2008 in a residential-cropland complex area (1.4 × 10⁵ m²) in Kunming, western China, where the self-purifying capacity of the agricultural ecosystem had been lost. The proposed eco-restoration system examined includes three main foci: farming management, bioremediation, and wastewater treatment. The results showed that the removal efficiencies of total phosphorus (TP) and total nitrogen (TN) from the complex wastewater were 83% and 88%, respectively. The Simpson’s diversity indices of macrophytes and zoobenthos indicated that the system had increased macrophyte and zoobenthic diversity as well as improved growth conditions of the plankton habitats. The results demonstrated that the proposed eco-restoration system is a promising approach for decreasing the output of nutrients from soil, improving agricultural ecosystem health, and minimizing the downstream eutrophication risk for surface waters.     

Comparative studies of the Fe3+/2+-UV, H2O2-UV, TiO2-UV/vis systems for the decolorization of a textile dye X-3B in water

The degradation of a common textile dye, Reactive-brilliant red X-3B, by several advanced oxidation technologies was studied in an air-saturated aqueous solution. The dye was resistant to the UV illumination (wavelength λ  320 nm), but was decolorized when one of Fe³⁺, H₂O₂ and TiO₂ components was present. The decolorization rate was observed to be quite different for each system, and the relative order evaluated under comparable conditions followed the order of Fe²⁺–H₂O₂–UV  Fe²⁺–H₂O₂ > Fe³⁺–H₂O₂–UV > Fe³⁺–H₂O₂ > Fe³⁺–TiO₂–UV > TiO₂–UV > Fe³⁺–UV > TiO₂–visible light (λ  450 nm) > H₂O₂–UV > Fe²⁺–UV. The mechanism for each process is discussed, and linked together for understanding the observed differences in reactivity.     

Photocatalytic oxidation of xenobiotics in water with immobilized TIO2 on agitator

Abstract

A novel photocatalytic oxidation reactor, using Degussa P‐25 T_iO₂ as a stationary phase with a thickness of 1.5–2.0 um on the blades of agitator, was developed to study the photocatalytic oxidation of xenobiotics. Particularly in this device, separation of photocatalyst from the purified water after oxidation reaction was not necessary, and no other aeration equipment was required to supply oxygen. To examine the efficiency of this device, photocatalytic degradation of xenobiotic organics such as carbofuran was studied as an example. Results indicated that carbofuran could be degraded completely with mineralization efficiency of 20 % after 6 hours of oxidation under the imposed conditions. The mineralization rate of carbofuran was found to follow the pseudo‐first order reaction kinetics. Moreover, the rate constant of mineralization was found to be proportional to T_iO₂ film area and the square root of UV light intensity. These results implied the mineralization efficiency of carbofuran could be improved through increasing T_iO₂ film area and UV light intensity. Accordingly, this novel device showed potential application for degrading xenobiotics in water.     

紫外波长对UV/Cl2高级氧化去除水中有机物的影响

为明确紫外波长对UV/Cl2高级氧化体系的影响,使用中心波长分别为267、275和286 nm的发光二极管LED作为光源,探究Cl2光解动力学、UV/Cl2体系自由基生成、对模式化合物溶液以及天然水、再生水TOC的去除。结果表明：在中性或酸性体系中,267 nm最接近HClO最大吸收波长237 nm,吸光度和量子产率均较大,羟基自由基产生水平较高,有机物去除效果较好;在碱性体系中,286 nm最接近ClO-最大吸收波长292 nm,尽管量子产率较小,但吸光度很大,有机物去除效果较好;由于水杨酸在292 nm附近有较强的竞争吸收,使用UV286去除水杨酸效果被削弱。应用UV/Cl2技术选择波长时需要考虑吸光度、量子产率、竞争吸收等因素;对于弱碱性天然水或再生水,采用波长为292 nm的紫外光一般可获得较优处理效果。     

粉煤灰沸石负载铈掺杂TiO2对水体中蒽的去除

采用溶胶-凝胶法在80℃条件下制备了锐钛矿型稀土铈掺杂Ti02负载粉煤灰沸石光催化剂(以下简称光催化剂).利用X射线衍射(XRD)、扫描电镜(SEM)对光催化剂进行了表征,同时考察了稀土铈掺杂量、光催化剂投加量、溶液pH以及蒽初始浓度对其光降解过程的影响,并研究了蒽的光降解动力学特性.结果表明,稀土铈掺杂量为0.50％(质量分数)、pH偏碱性时蒽的光降解效果最佳.光催化反应符合Langmuir-Hinshelwood动力学模型,蒽的光降解过程符合一级反应动力学模型,反应速率常数为0.0173min-i.     

高气泡表面积通量浮选柱气浮除藻的研究

湖泊、水库等水源的富营养化,使藻类去除成为饮用水生产的重要任务.本研究采用高气泡表面积通量浮选柱气浮除藻,考察了混凝剂、气泡表面积通量和浮选柱高度等因素的影响.试验表明,高气泡表面积通量浮选柱气浮可高效地去除绿藻、硅藻和蓝藻,叶绿素a和藻类去除率达95%以上,比传统浮选柱气浮和沉降作业有较大幅度提高.与普通气浮柱比较,高气泡表面积通量浮选柱增加了气泡与藻的碰撞几率,防止因大表观充气速率造成的紊流和扰动,使气泡/藻结合体有相对静态的浮升环境,避免了气泡/藻结合体在浮升过程中的脱落,实现对藻类的迅速捕集和转移.     

高气泡表面积通量浮选柱气浮除藻的研究

湖泊、水库等水源的富营养化，使藻类去除成为饮用水生产的重要任务。本研究采用高气泡表面积通量浮选柱气浮除藻，考察了混凝剂、气泡表面积通量和浮选柱高度等因素的影响。试验表明，高气泡表面积通量浮选柱气浮可高效地去除绿藻、硅藻和蓝藻，叶绿素a和藻类去除率达95％以上，比传统浮选柱气浮和沉降作业有较大幅度提高。与普通气浮柱比较，高气泡表面积通量浮选柱增加了气泡与藻的碰撞几率，防止因大表观充气速率造成的紊流和扰动，使气泡／藻结合体有相对静态的浮升环境，避免了气泡／藻结合体在浮升过程中的脱落，实现对藻类的迅速捕集和转移。     

A novel application of H2O2-Fe(II) process for arsenate removal from synthetic acid mine drainage (AMD) water

Batch experiments were carried out to investigate the influences of H₂O₂/Fe(II) molar ratio, pH, sequence of pH adjustment, initial As(V) concentration, and interfering ions on As(V) removal in H₂O₂-Fe(II) process from synthetic acid mine drainage (AMD). The optimum H₂O₂/Fe(II) molar ratio was one for arsenate removal over the pH range of 4-7. Arsenate removal at pH 3 was poor even at high Fe(II) dosage due to the high solubility of Fe(III) formed in situ. With the increase of Fe(II) dosage, arsenate removal increased progressively before a plateau was reached at pH 5 as arsenate concentration varied from 0.05 to 2.0 mg L⁻¹. However, arsenate removal was negligible at Fe/As molar ratio <3 and then experienced a striking increase before a plateau was reached at pH 7 and arsenate concentration ≥1.0 mg L⁻¹. The co-occurring ions exerted no significant effect on arsenate removal at pH 5. The experimental results with synthetic AMD revealed that this method is highly selective for arsenate removal and the co-occurring ions either improved arsenate removal or slightly depressed arsenate removal at pH 5-7. The extended X-ray absorption fine structure (EXAFS) derived As-Fe length, 3.27-3.30 Å, indicated that arsenate was removed by forming bidentate-binuclear complexes with FeO(OH) octahydra. The economic analysis revealed that the cost of the H₂O₂-Fe(II) process was only 17-32% of that of conventional Fe(III) coagulation process to achieve arsenate concentration below 10 μg L⁻¹ in treated solution. The results suggested that the H₂O₂-Fe(II) process is an efficient, economical, selective and practical method for arsenate removal from AMD.     

Removal of emerging pollutant dibutylhydroxytoluene from water with CNT/TiO2 catalysts in a visible LED photoreactor

Environmental Science and Pollution Research - For the photocatalytic degradation of antioxidant 2,6-di-tert-butyl-hydroxytoluene (BHT), several TiO2-based composites have been prepared in MWCNT...     

Zero-valent iron nanoparticles in treatment of acid mine water from in situ uranium leaching

Acid mine water from in situ chemical leaching of uranium (Straz pod Ralskem, Czech Republic) was treated in laboratory scale experiments by zero-valent iron nanoparticles (nZVI). For the first time, nZVI were applied for the treatment of the real acid water system containing the miscellaneous mixture of pollutants, where the various removal mechanisms occur simultaneously. Toxicity of the treated saline acid water is caused by major contaminants represented by aluminum and sulphates in a high concentration, as well as by microcontaminants like As, Be, Cd, Cr, Cu, Ni, U, V, and Zn. Laboratory batch experiments proved a significant decrease in concentrations of all the monitored pollutants due to an increase in pH and a decrease in oxidation-reduction potential related to an application of nZVI. The assumed mechanisms of contaminants removal include precipitation of cations in a lower oxidation state, precipitation caused by a simple pH increase and co-precipitation with the formed iron oxyhydroxides. The possibility to control the reaction kinetics through the nature of the surface stabilizing shell (polymer vs. FeO nanolayer) is discussed as an important practical aspect.