Sonophotocatalytic degradation of alazine and gesaprim commercial herbicides in TiO2 slurry

The photocatalytic degradation of alazine and gesaprim commercial herbicides was carried out in aqueous TiO(2) suspensions under UV light (15W, 352 nm). Degradation of these herbicides was also observed by the combined effects of photocatalysis with sonolysis (sonophotocatalysis) using an ultrasound source of 20kHz. Degradation profiles were recorded by measuring the concentration of the active compounds present in the alazine (alachlor and atrazine) and gesaprim (atrazine) by HPLC as a function of irradiation time (sound and/or light). Over 90% of the active component in the gesaprim was abated and those in alazine were completely degraded. The content of total organic carbon and chemical oxygen demand was also monitored. Mineralization of the commercial herbicides was achieved. Over 80% of chemical oxygen demand abatement was attained for both herbicides with sonophotocatalysis at 150 min of irradiation time. The photocatalytic degradation of the herbicides followed a pseudo-first order kinetics and their rate constant was increased by the combined effects of sonolysis.     

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。     

超声波降解水中的氯苯

考察了用超声波降解水中氯苯的可行性、动力学、产物和TOC变化。在 2 0kHz和 4 0W的超声波作用下 ,氯苯的一级降解常数为 0 0 5 /min。随着所加超声功率的增高 ,氯苯降解常数呈线性增加。 30min内超声脱氯效率达到 6 6 % ,TOC去除达到 4 3%。     

Kinetics of low frequency sonodegradation of linear alkylbenzene sulfonate solutions

The decomposition of sodium dodecylbenzene sulfonate (SDBS) in water by means of ultrasound irradiation at 20kHz was investigated. Experiments were conducted at surfactant concentrations of 175, 260 and 350 mg l(-1), liquid volumes of 120, 170 and 220 ml, temperatures of 20, 30 and 45 degrees C and applied power of 40, 80 and 125 W. The extent of degradation was followed monitoring substrate and organic carbon concentrations, while hydrogen peroxide concentration was also measured; the latter is a product of water sonolysis due to hydroxyl radical recombination. 80% SDBS conversion was achieved after 120 min of sonication at 125 W and 30 degrees C; nonetheless, SDBS and its degradation intermediates proved difficult to oxidise as only about 20-25% of the initial carbon content was transformed to carbon dioxide. At the initial stages of the reaction, degradation rate appears to be only weakly dependent on the substrate concentration with the rate increasing from 3.1 to 4 mg l(-1)min(-1) with increasing concentration from 175 to 350 mg l(-1). Degradation appears to occur at the bubble-liquid interface through hydroxyl radical-mediated reactions whose role was established by performing experiments in the presence of radical scavengers, namely potassium bromide and sodium benzoate. Degradation rates increased with increasing power and decreasing temperature and volume.     

Effect of various reaction parameters on THMs aqueous sonolysis

Ultrasonic irradiation was investigated for destruction of the following THMs: CHCl(3), CHBrCl(2), CHBr(2)Cl, CHBr(3), and CHI(3). The effect of pH, temperature, and the organics initial concentration on the THMs sonodegradation at acoustic frequency of 20 kHz was studied. An increase of the solution temperature resulted in a faster sonodegradation rates. Initial aqueous solution pH, in the range from 3 to 10, was found to have little effect on the degradation of the THMs. The THMs sonolysis efficiency was reduced when the initial organic compounds concentration was increased from 10 mg l(-1) to 300 mg l(-1).     

TiO2纳米管催化降解4，4’-二溴联苯的影响因素和动力学研究

利用TiO₂纳米管催化降解水中的4,4’-二溴联苯,对催化降解过程和影响因素进行研究。结果表明,TiO₂纳米管对其有较高的催化降解效率且降解过程符合Langmuir-Hinshelwood动力学模式。不同光源、4,4’-二溴联苯的初始浓度、纳米管添加量和pH值对催化降解过程都有较大影响,其中pH值的影响最为明显。反应液在中性状态下的降解率明显低于pH=1或11的情况。在pH=1时,4,4’-二溴联苯的降解率达86%。     

TiO2纳米管催化降解4，4’-二溴联苯的影响因素和动力学研究

利用TiO2纳米管催化降解水中的4,4’-二溴联苯,对催化降解过程和影响因素进行研究。结果表明,TiO2纳米管对其有较高的催化降解效率且降解过程符合Langmuir—Hinshelwood动力学模式。不同光源、4,4’-二溴联苯的初始浓度、纳米管添加量和pH值对催化降解过程都有较大影响,其中pH值的影响最为明显。反应液在中性状态下的降解率明显低于pH=1或11的情况。在pH=1时,4,4’一二溴联苯的降解率达86％。     

Endocrine effects generated by photooxidation of coplanar biphenyls in water using titanium dioxide

The oxidative photodegradation behaviors of selected three coplanar polychlorinated biphenyls (PCBs), (CB77, CB81, and CB169) using titanium dioxide (TiO(2)) in water were investigated. The main purposes were to clarify the structural relation between the original PCBs and the intermediates derived by TiO(2) oxidation and to evaluate the estrogenic and thyroid hormonal activity in the treated three coplanar PCBs during the oxidative reactions. Approximately 90% of the three coplanar PCBs decomposed within 180 min. Intermediates from the decomposition of the three coplanar PCBs, such as some hydroxylated-PCBs (OH-PCBs), carboxylic intermediates, phenolic intermediates, and other intermediates produced by the cleavage of a benzene ring were identified and quantified. In the degradation pathways, the produced amounts of OH-PCBs increased within 60 min of irradiation time. The estrogenic activity and thyroid hormonal activity of the intermediates from the three coplanar PCBs in water at 0, 60, 120, 180 and 240 min of irradiation time were assessed by using a yeast two-hybrid assay system for human estrogen receptor alpha (hERalpha) and human thyroid hormone receptor alpha (hTRalpha). The maximal estrogenic activities were induced by the solutions of decomposed PCBs with irradiation time at 60-120 min similar and slightly lower than those after the irradiation time. We found that the solutions occuring during the irradiation times of 60-120 min contained several 4-OH-PCBs substituted with OH and Cl at para- and para'-positions having estrogenic activity. The thyroid hormonal activity was not detected in the decomposed three coplanar PCBs solutions.     

Photocatalytic oxidation of organic pollutants on titania-clay composites

TiO2/Ca-montmorillonite composites were prepared by wet grinding in an agate mill. Positively charged TiO2 nanoparticles are bound to the surface of the negatively charged montmorillonite layers via heterocoagulation; the clay mineral is used as adsorbent and support for the photooxidation process. Aquatic solution of 0.5mM phenol was degraded by irradiation with UV-VIS light (lambda=250-440 and 540-590 nm) in suspensions of TiO2-clay composites and significant photodegradation was observed at 40-60% TiO2/Ca-montmorillonite compositions. Synergistic effect was detected at solid/liquid interface for degradation of phenol and at solid/gas interface in the recycling flow reactors for photooxidation of ethanol and toluene vapors.     

固定化催化剂TiO2膜光催化降解三氯乙醛的研究

研究了负载于玻璃上的固定化催化剂TiO2膜光催化降解水中三氯乙醛的效果,探讨了TiO2膜光催化降解三氯乙醛的机理,考察了溶液pH值和三氯乙醛初始浓度埘TiO2膜光催化降解三氯乙醛的影响,并研究了固定化催化剂TiO2膜光催化降解三氯乙醛的动力学.结果表明,固定化催化剂TiO2膜光催化降解水中三氯乙醛的效果良好,当三氯乙醛初始浓度为2.25 mg/L时,在紫外光照时间3 h下,三氯乙醛的降解率高达100%.在相司紫外光照时间下,三氯乙醛的光催化降解率随着三氯乙醛初始浓度的增大而下降.在溶液pH=6.5时,三氯乙醛的降解效率最高.固定化催化剂TiO2膜光催化降解三氯乙醛的反应遵循一级反应动力学,反应速率常数随三氯乙醛初始浓度的增大而减小.     

负载型TiO2纳米管对水体中萘普生光催化作用

为了解决水体中光催化剂的分离和回收问题,对纳米TiO2的固载化及其应用进行了研究。首先以纳米TiO2为原料,采用水热合成法制备TiO2纳米管;再以聚氨酯膜片为载体制备负载型TiO2纳米管(PU/TiO2)。对负载材料进行FT-IR和SEM表征,表征结果表明:TiO2纳米管能很好地接枝在PU薄膜表面;然后在空气曝气、pH=5、T=26 ℃的条件下,进行光催化降解萘普生的实验。实验结果表明:制备的负载材料对水体中的萘普生有较强的吸附作用,在300 W紫外光的照射下,5 min内能使10.00 mg/L的萘普生降解完全;紫外光照与光催化剂对萘普生的降解具有协同效应;光催化反应近似符合一级模型。综合表明,负载型TiO2纳米管是一种具有潜在应用前景的光催化剂。     

Mechanism of decolorization and degradation of CI Direct Red 23 by ozonation combined with sonolysis

The decolorization and degradation of CI Direct Red 23, which is suspected to be carcinogenic, were investigated using ozonation combined with sonolysis. The results showed that the combination of ozonation and sonolysis was a highly effective way to remove color from waste water. The operational parameters, namely concentration of the dye, pH, ozone dose and ultrasonic density, were investigated during the process. The decolorization of the dye followed pseudo-first-order kinetics. Increasing the initial concentration of Direct Red 23 led to a decreasing rate constant. The optimum pH for the reaction was 8.0, and both lower and higher pH decreased the removal rate. The effect of the ozone dose on the dye decolorization was much greater than that of the sonolysis density. Intermediates such as naphthalene-2-sulfonic acid, 1-naphthol, urea and acetamide were detected by gas chromatography coupled with mass spectrometry in the absence of pH buffer, while nitrate and sulfate ions and formic, acetic and oxalic acids were detected by ion chromatography. A tentative degradation pathway was proposed without any further quantitative analyses. During the degradation, all nitrogen atoms and phenyl groups of Direct Red 23 were degraded into urea, nitrate ion, nitrogen and formic, acetic and oxalic acids, etc.     

Solar photocatalytic mineralization of commercial pesticides: acrinathrin

A comparative study of the degradation of commercial acrinathrin spiked in water using TiO2 photocatalysis and photolysis under sunlight was performed. Samples were analysed by liquid chromatography-diode array detector (HPLC-DAD) and gas chromatography-ion trap-mass spectrometric detector (GC-ITMS). Additional total organic carbon (TOC) analyses were carried out to evaluate the mineralisation rates. One photoproduct, 2-phenoxy benzaldehyde, was unequivocally identified and evaluated by GC-ITMS during the processes. Although acrinathrin is almost destroyed when exposed to irradiation for more than 400 h, photocatalysis with TiO2 noticeably reduced degradation to a few hours. In this case, with the additional presence of peroxydisulphate, in less than 2 h acrinathrin is completely destroyed. Mineralisation of acrinathrin, without catalyst, was only around 50% after 400 h of irradiation.     

TiO2膜降解水中污染物的稳定性考察与再生方法研究

针对实际水处理中对催化剂性能的要求,以光催化降解苯酚溶液作为探针反应,考察了玻璃纤维网上负载的TiO2膜催化剂长期使用条件下的稳定性,研究了催化剂在自来水中使用失活后的再生方法。结果表明,经过50次使用之后,膜催化剂120 min反应对苯酚的降解率从100%下降至83%,总体上看,所制催化剂还是具有相当好的稳定性;在反应器中用蒸馏水浸泡配合光催化反应对TiO2膜催化剂进行原位再生是一种可行的再生途径。     

镧负载改性TiO2太阳光催化降解微囊藻毒素的研究

考察了镧负载改性TiO2催化剂在太阳光下降解微囊藻毒素LR (MCLR)的效果及其影响因素。结果表明,镧负载改性的TiO2可显著增加MCLR在TiO2表面的吸附量,同时提高MCLR在太阳光下的降解率。随着镧负载量的增加,太阳光下MCLR降解率可从65%提高到95%,pH降低可促进MCLR的降解。改性TiO2对藻毒素的降解存在最佳投加量,实验结果表明,在pH=6,MCLR初始浓度为2 mg/L,0.001-La-TiO2的最佳投量为0.5 g/L,在3 600 μW/cm2太阳光下照射30 min,降解率可达97%。     

碘掺杂Ti02可见光光催化性能研究

在低于100℃温度条件下,采用溶胶一凝胶法以钛酸正丁酯为钛源,碘酸钾为碘源,制备了I掺杂纳米TiO2催化剂（I-TiO2）,运用x-射线衍射（XRD）、透射电镜（TEM）及x-射线光电子能谱（XPS）等对催化剂进行表征,结果表明,TiO2及I-TiO2催化剂均为锐钛矿,I吸附并包裹在TiO2表面或以间隙进入的形式存在,并未进入TiO2晶格。通过在可见光照射下（A〉420nm）以罗丹明B（RhodamineB,RhB）的光催化降解为探针反应研究了在不同条件下制备催化剂的催化性能,结果表明,掺杂比为n1：n^ti=0．05：l,焙烧温度为400℃,降解介质条件pH=7时,l-TiO2光催化活性明显优于未掺杂的TiO2。光催化降解过程通过红外光谱（IR）,总有机碳（TOC）跟踪测定,比较了TiO2掺杂前后降解RhB和对氯苯酚（4-CP）的光催化特性差异;同时采用苯甲酸荧光光度法跟踪测定体系中的氧化物种,表明在可见光下,I-TiO2光催化体系中产生·OH高活性氧化物种从而氧化降解目标化合物。     

Photocatalytic degradation of the herbicide erioglaucine in the presence of nanosized titanium dioxide: comparison and modeling of reaction kinetics

The present work mainly deals with photocatalytic degradation of a herbicide, erioglaucine, in water in the presence of TiO2 nanoparticles (Degussa P-25) under ultraviolet (UV) light illumination (30 W). The degradation rate of erioglaucine was not so high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. We have studied the influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time and initial concentration of erioglaucine on the photodegradation efficiency of erioglaucine. A kinetic model is applied for the photocatalytic oxidation by the UV/TiO2 system. Experimental results indicated that the photocatalytic degradation process could be explained in terms of the Langmuir-Hinshelwood kinetic model. The values of the adsorption equilibrium constant, K, and the second order kinetic rate constant, k, were 0.116 ppm-1 and 0.984 ppm min-1, respectively. In this work, we also compared the reactivity between the commercial TiO2 Degussa P-25 and a rutile TiO2. The photocatalytic activities of both photocatalysts were tested using the herbicide solution. We have noticed that photodegradation efficiency was different between both of them. The higher photoactivity of Degussa P-25 compared to that of rutile TiO2 for the photodegradation of erioglaucine may be due to higher hydroxyl content, higher surface area, nano-size and crystallinity of the Degussa P-25. Our results also showed that the UV/TiO2 process with Degussa P-25 as photocatalyst was appropriate as the effective treatment method for removal of erioglaucine from a real wastewater. The electrical energy consumption per order of magnitude for photocatalytic degradation of erioglaucine was lower with Degussa P-25 than in the presence of rutile TiO2.     

Photocatalytic degradation of an organophosphorus pesticide phosalone in aqueous suspensions of titanium dioxide

The present work deals with photocatalytic degradation of an organophosphorus pesticide, phosalone, in water in the presence of TiO2 particles under UV light illumination (1000 W). The influence of the basic photocatalytic parameters such as pH of the solution, amount of TiO2, irradiation time, stirring rate, and distance from UV source, on the photodegradation efficiency of phosalone was investigated. The degradation rate of phosalone was not high when the photolysis was carried out in the absence of TiO2 and it was negligible in the absence of UV light. The half-life (DT50) of a 20 ppm aqueous solution of phosalone was 15 min in optimized conditions. The plot of lnC (phosalone) vs. time was linear, suggesting first order reaction (K=0.0532 min(-1)). The half-life time of photomineralization in the concentration range of 7.5-20 ppm was 13.02 min. The efficiency of the method was also determined by measuring the reduction of Chemical Oxygen Demand (COD). During the mineralization under optimized conditions, COD decreased by more than 45% at irradiation time of 15 min. The photodegradation of phosalone was enhanced by addition of proper amount of hydrogen peroxide (150 ppm).     

Kinetics and mechanism of TNT degradation in TiO2 photocatalysis

The photocatalytic degradation of TNT in a circular photocatalytic reactor, using a UV lamp as a light source and TiO(2) as a photocatalyst, was investigated. The effects of various parameters such as the initial TNT concentration, and the initial pH on the TNT degradation rate of TiO(2) photocatalysis were examined. In the presence of both UV light illumination and TiO(2) catalyst, TNT was more effectively degraded than with either UV or TiO(2) alone. The reaction rate was found to obey pseudo first-order kinetics represented by the Langmuir-Hinshelwood model. In the mineralization study, TNT (30 mg/l) photocatalytic degradation resulted in an approximately 80% TOC decrease after 150 min, and 10% of acetate and 57% of formate were produced as the organic intermediates, and were further degraded. NO(-)(3) NO(-)(2), and NH(+)(4) were detected as the nitrogen byproducts from photocatalysis and photolysis, and more than 50% of the total nitrogen was converted mainly to NO(-)(3)in the photocatalysis. However, NO(-)(3) did not adsorbed on the TiO(2) surface. TNT showed higher photocatalytic degradation efficiency at neutral and basic pH.     

Photocatalytic degradation of imazethapyr herbicide at TiO2/H2O interface

The photocatalytic degradation of imazethapyr, a herbicide of the imidazolinone family, was investigated in an aqueous suspension of titanium dioxide used as a catalyst. A pseudo-first order kinetic model was employed to discuss the results. The effect of catalyst loading, initial concentration of imazethapyr, hydrogen peroxide, pH value, and temperature were investigated. Imazethapyr disappearance as a function of irradiation time was analyzed by HPLC. The ammonium ion formation was determined spectrophotometrically at 694 nm. The degradation was observed to proceed more favorably at natural pH (ca. 4.4) when the pH was varied in the range from 2 to 11. The addition of hydrogen peroxide to the TiO2 suspension enhanced the degradation rate constant up to 5.0x10(-3) mol l-1, but decreased it at higher concentrations. The degradation rate constants decreased by 19% with a temperature increase from 20 to 40 degrees C in the TiO2 suspension, whereas a 16% increase in imazethapyr direct photolysis was observed for the same temperature range. This behavior indicates the occurrence of physisorption between TiO2 and imazethapyr molecules.