TiO2光催化降解水中土霉素的动力学研究

环境中抗生素的出现及其引起的危害正受到越来越多的关注。以高压汞灯为光源,选用较为广泛的抗生素土霉素（OTC）为处理对象。考察了初始质量浓度、反应过程中光照、催化剂投加量、溶液起始pH、溶液中DOM和NO^-₃对光催化降解的影响,研究了其光降解动力学。结果表明,TiO₂光催化氧化法能够有效去除水中半微量的OTC,OTC的光降解过程符合一级反应动力学模型;UV/TiO₂联用工艺对TOC也有很好的去除效果,反应90 min,TOC去除率可达74%;OTC的初始浓度从30 mg/L增大到90 mg/L,反应速率从0.0619 min^-1降低到0.0130 min^-1;随着光催化剂投加量的增大,光降解速率常数先增大后减小;增加溶液的pH值,速率常数逐渐减小;溶液中的DOM和NO^-₃也可以影响光降解效率。     

水体中常见无机阴离子对TiO2薄膜光催化降解甲醛的影响

选择了5种水体中常见的阴离子(Cl^-,SO^2-₄,HPO^2-₄/HPO^2-₄,HCO^-₃/CO^2-₃和NO^-₃),分别考查了其对TiO₂薄膜光催化降解模拟甲醛废水的反应速率的影响;从上述离子的光吸收,对·OH的捕获及其生成的相应的无机自由基的氧化作用以及与甲醛的竞争吸附3个方面讨论了上述离子影响TiO₂薄膜光催化降解模拟甲醛废水的反应速率的原因。结果表明,HCO^-₃/CO^2-₃对TiO₂薄膜光催化降解甲醛具有抑制作用,Cl^-和SO^2-₄的影响不大,H₂PO^-₄/HPO^2-₄和NO^-₃具有促进作用。造成上述结果的主要原因是HCO^-₃/CO^2-₃具有很强的·OH捕获作用;Cl^-,SO^2-₄对·OH捕获作用以及竞争吸附都较弱;H₂PO^-₄/HPO^2-₄在TiO₂表面具有较强的吸附能力,释放出的H⁺起到了酸催化剂的作用;NO^-₃在紫外光的照射下可以产生·OH,此外NO^-₃作为电子受体而降低了TiO₂表面光生电子和空穴的复合几率。     

仿生矿化法制备壳聚糖/纳米CdS复合粒子对猩红B光催化降解研究

用仿生矿化法制备了壳聚糖/纳米CdS复合粒子,并用于可见光光催化降解猩红B染料模拟废水,系统地研究了染料初始浓度、pH值、催化剂投加量、光照情况和催化剂重复使用等因素对猩红B的光解脱色效率的影响。结果表明,当pH=3.0,催化剂投加量为0.7 g/L的条件下,对初始溶液为20 mg/L的猩红B模拟废水,60 min之内脱色率超过96%。酸性媒介比碱性媒介更有利于猩红B染料光解脱色。实验范围内Br^-、NO^-₃和Cl^-等无机阴离子,均对降解脱色有促进作用,其中NO₃^-对脱色作用促进最显著。处理前后的UV-Vis谱图分析表明猩红B在壳聚糖/纳米CdS复合粒子可见光光解处理过程中脱色是因为染料发生氧化光降作用。催化剂重复利用5次后,处理60 min对猩红B的脱色率仍可达到80.7%。     

Fe0/厌氧微生物体系降解2,4,6-三氯酚特性研究

通过摇床间歇实验,研究了厌氧微生物与零价铁（Fe⁰）联合体系降解2,4,6-三氯酚（TCP）的特性,结果表明,在pH 7.5,35℃,150 r/min,Fe⁰ 10 g/L条件下,TCP初始浓度为30 mg/L时,TCP降解的拟一级反应速率常数为0.0207 h^-1,添加少量碳源可达到0.0390 h^-1,其降解速率是前者的1.88倍;添加碳源的体系在220 h内连续多次投加TCP降解率都达到80%以上,而不加碳源的体系在第2次投加TCP后降解率就只有30%左右;添加不同碳源,降解速率不同;添加2-溴乙烷磺酸钠（BESA）以及SO^2-₄、NO^-₃和S^2-对TCP降解有不同的抑制作用。     

几种阴阳离子对磷钨酸光催化降解甲基橙的影响

以磷钨酸为光催化剂,在紫外灯照射下,对甲基橙溶液进行光催化降解,考察了几种阴阳离子对磷钨酸光催化降解甲基橙溶液的影响。结果表明：Mg²⁺、Ca²⁺、NO^-₃、SO^2-₄和CO^2-₃均对催化活性有促进作用,其中Mg²⁺和Ca²⁺仅有微弱的促进作用;NO^-₃和SO^2-₄随着浓度的增加促进作用也有所增加;CO^2-₃则随着浓度的增加促进作用呈下降趋势;Mn²⁺、Al³⁺和Cl^-对光解反应存在较强的抑制作用,且Al³⁺和Cl^-随着其浓度的增加,抑制作用增强。     

水位波动带氮素迁移转化规律

为考察水位波动对非饱和-饱和土层中氮素迁移转化的影响,设计土柱实验装置Ⅰ和Ⅱ分别模拟水位稳定与波动两种情景,测定一个水位波动周期内地下水中NO₃^--N、NO₂^--N和NH₄⁺-N浓度变化情况。结果表明,柱Ⅱ水位第1次下降柱内1^#,2^#,3^#,4^#采样点NO₃^--N浓度均增大,增幅分别为6.5%、14.9%、15.33%和19.8%。水位上升时结果相反,分别降低17.3%、26.15%、50.29%和44.61%。第2次水位下降至初始位置4个采样点NO₃^--N浓度再次增大,幅度分别为7.1%、10.6%、13.89%和7.76%。铵态氮呈相反趋势不同程度的变化。水位波动柱Ⅱ连通水槽内总氮量增加显著高于柱I水槽,即水位波动有利于波动带地下水中氮素垂向迁移,加重波动带以下地下水硝酸盐污染。因此,水位波动对氮素迁移转化的影响不容忽视。     

催化臭氧化降解技术中的两个问题

探讨了有机物特性及中间产物H₂O₂在催化臭氧化中的作用。结果表明,有机物在自由基链反应过程中的特性直接影响催化臭氧化的降解效率。当目标有机物是对链反应具有促进作用的甲酸时,自由基引发反应可以明显提高甲酸的臭氧化效率。当目标有机物是对自由基链反应具有抑制剂作用的乙酸时,O₃和Fe²⁺/O₃对乙酸有着相似的降解效率。以上结果表明,自由基引发反应并不是臭氧化降解效率提高的充分条件。另外,当臭氧化过程有H₂O₂产生时,必须考虑类Fenton反应对臭氧化效率的影响。     

Fe/活性炭多相类Fenton法湿式氧化罗丹明B废水的研究

采用自制的Fe/活性炭（Fe/AC）为催化剂,H₂O₂为氧化剂,组成多相类Fenton试剂催化降解罗丹明B染料废水。实验结果表明,在催化剂加入量为0.8 g/L,H₂O₂体积分数为0.3%,废水pH值为13,反应时间为30 min的条件下,质量浓度为200 mg/L的罗丹明B染料废水的脱色率达100%。反应动力学研究表明,罗丹明B脱色反应近似为一级反应,30℃时反应速率常数为0.02675 min^-1,表观活化能为69.47 kJ/mol。     

电催化氧化处理除草剂异草酮废水的效能简

为有效处理含异草酮除草剂废水,以Sb掺杂Ti/SnO₂电极为阳极,不锈钢板为阴极,采用电催化氧化技术对异草酮废水进行降解,研究了不同影响因素对异草酮去除率的影响,并分析了异草酮的降解效果。结果表明,当异草酮初始浓度为100 mg/L、电流密度为20 mA/cm²、电解质投加量为0.10 mol/L,反应120 min后,异草酮去除率达到94%,此时TOC去除率为57.9%,能耗为25 kWh/m³,且废水的可生化性能显著提高。     

双频超声辐射协同H2O2降解偶氮染料废水的研究

采用双频超声协同H₂O₂降解酸性绿20染料废水,考察超声功率密度、染料初始浓度和pH、饱和气体及H₂O₂投加量等因素对酸性绿20降解效果的影响,结果表明,在给定实验条件下,双频降解效果优于单频超声波,且降解率随超声功率密度的增大而增大。酸性条件有利于酸性绿20的降解,当染料废水初始pH=4可取得最佳的降解效果;酸性绿20的降解效率随染料初始浓度的增大而降低,其优化初始浓度为40 mg/L。在反应体系中通入空气并投加H₂O₂,可取得最佳的降解效果。在优化实验条件下, 采用双频超声协同H₂O₂降解5 h,酸性绿20的色度和TOC去除率分别为94.6%和36.3%;分析降解前后的紫外可见光谱图可知,酸性绿20并非完全被降解为CO₂和H₂O,而是生成一些小分子有机中间体。     

Ozonation of an azo dye C.I. Remazol Black 5 and toxicological assessment of its oxidation products

The effect of ozonation (20.5 mgl(-1)) on the degradation processes of an azo dye, Remazol Black 5 (RB5; CI) was studied. Conventional parameters such as chemical oxygen demand (COD), total organic carbon (TOC), pH, conductivity, colour removal, biodegradability (BOD(5/28)), and toxic potential of the dye and its degradation products were monitored during the process. The results obtained indicated that ozonation is a highly effective way to remove the colour of a corresponding dye solution. However, a considerable organic load still remained as indicated by high COD and TOC residues. The COD, TOC reductions were about 40% and 25% for 6 h ozonation of 2 gl(-1) RB5 aqueous solution. During the ozonation process the rapid decrease of pH and the sharp increase of conductivity indicated the formation of acidic by-products and small fragments and ions which were identified by high performance ion chromatography. The BOD28 data revealed that first by-products after partial ozonation (10-150 min) of RB5 were more biodegradable than the parent compound and ozonation can enhance the biodegradability of azo dyes. During the first 150 min of total 360 min of oxidation, the formation of first by-products with high toxic potential took place as it could be confirmed by two acute toxicity-screening tests, the bioluminescence test (Vibrio fischerii) and the neutral red cytotoxicity assay (rat hepatoma cells). The significant enhancement of microbial biodegradability after long-term ozonation could also be seen as a decrease of toxic intermediates in correlation with the ozonation time as indicated in BOD28 biological degradation test results.     

Ozonation of hydrolyzed azo dye reactive yellow 84 (CI).

The combination of chemical and biological water treatment processes is a promising technique to reduce recalcitrant wastewater loads. The key to the efficiency of such a system is a better understanding of the mechanisms involved during the degradation processes. Ozonation has been applied to many fields in water and wastewater treatment. Especially for textile mill effluents ozonation can achieve high color removal, enhance biodegradability, destroy phenols and reduce the chemical oxygen demand (COD). However, little is known about the reaction intermediates and products formed during ozonation. This work deals with the degradation of hydrolyzed Reactive Yellow 84 (Color Index), a widely used azo dye in textile finishing processes with two monochlorotriazine anchor groups. Ozonation of the hydrolyzed dye in ultra pure water was performed in a laboratory scale cylindric batch reactor. Decolorization, determined by measuring the light absorbance at the maximum wavelength in the visible range (400 nm), was almost complete after 60 and 90 min with an ozone concentration of 18.5 and 9.1 mg/l, respectively. The TOC/TOC0 ratio after ozonation was about 30%, the COD was diminished to 50% of the initial value. The BOD5/COD ratio increased from 0.01 to about 0.8. Oxidation and cleavage of the azo group yield nitrate. Cleavage of the sulfonic acid groups of aromatic rings caused increases in the amount of sulfate. Formic acid and oxalic acid were identified as main oxidation products by high performance ion chromatography (HPIC). The concentrations of these major products were monitored at defined time intervals during ozonation.     

Decomposition of 2-mercaptothiazoline in aqueous solution by ozonation

This study investigates the ozonation of 2-mercaptothiazoline (2-MT). The 2-MT is one of the important organic additives for the electroplating solution of the printed wiring board industry and has been widely used as a corrosion inhibitor in many industrial processes. It is of concern for the aquatic pollution control especially in the wastewaters. Semibatch ozonation experiments in the completely stirred tank reactor are performed under various concentrations of input ozone. The concentrations of 2-MT, sulfate, and ammonium are analyzed at specified time intervals to elucidate the decomposition of 2-MT during the ozonation. In addition, the time variation of the dissolved ozone concentration (C(ALb)) is continuously monitored in the course of experiments. Total organic carbon (TOC) is chosen and measured as a mineralization index of the ozonation of 2-MT. The results indicate that the decomposition of 2-MT is efficient, while the mineralization of TOC is limited via the ozonation only. Simultaneously, the yield of sulfate with the maximum value of about 47% is characterized by the increases of TOC removal and ozone consumption. These results can provide some useful information for assessing the feasibility of the treatment of 2-MT in the aqueous solution by the ozonation.     

Ozonation of Cationic Red X-GRL in aqueous solution: degradation and mechanism

Ozonation of the azo dye Cationic Red X-GRL was investigated in a bubble column reactor at varying operating parameters such as oxygen flow rate, temperature, initial Cationic Red X-GRL concentration, and pH. The conversion of dye increased with the increasing of pH and oxygen flow rate. As the reaction rate constant and the volumetric mass transfer coefficient increase while the ozone equilibrium concentration decreases with the temperature, there is a minimum conversion of dye at 25 degrees C. The increasing of initial dye concentration leads to a decreasing conversion of dye while the ozonation rate increases. The formation of intermediates and the variation of pH, TOC, and nitrate ion during ozonation were investigated by the use of some analytical instruments such as GC/MS, GC, and IC. The intermediates of weak organic acids lower the pH value of the solution. The probable degradation mechanism of the Cationic Red X-GRL in aqueous solution was deliberated with the aid of Molecular Orbital calculations. The N(12)-C(13) site in Cationic Red X-GRL, instead of the N(6)-N(7) site, is found to be the principal site for ozone cycloaddition in the degradation processes. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one is converted into an amine compound, and the remaining four are transformed into two molecules of nitrogen.     

Synergistic effects of combination of photolysis and ozonation on destruction of chlorophenols in water.

Synergistic effects including TOC elimination, ozone consumption and microtoxicity reduction for combination of photolysis and ozonation compared to those of direct photolysis and ozonation alone on destruction of chlorophenols including 2-chlorophenol, 4-chlorophenol and 2,4-dichlorophenol were studied. It was found that the synergistic effects of combination of photolysis and ozonation increased obviously with increasing initial pH of solution to basic pH levels. Results showed that the synergistic effects of photolytic ozonation under the conditions imposed was notable with mineralization rate enlarging more than 100%, oxidation index (OI) decreasing 50%, and microtoxicity being reduced by 30%, indicating that the potentialities of photolytic ozonation compared to direct photolysis and ozonation alone was remarkable for treatment of industrial wastewater containing chlorophenols.     

Mineralization of C.I. Reactive Yellow 84 in aqueous solution by sonolytic ozonation

The operational parameters and mechanism of mineralization of C.I. Reactive Yellow 84 (RY84), one of the azo dyes, in aqueous solution were investigated using sonolytic ozonation (US/O(3) oxidation). Of the pseudo-first-order degradation rate constants of TOC reduction, 9.0 x 10(-4), 7.3 x 10(-3) and 1.8 x 10(-2)min(-1) were observed with US, O3, and a combination of US and O3, respectively. These results illustrate that ozonation combined with sonolysis for removal of TOC is more efficient than ozonation alone or ultrasonic irradiation alone without considering the operating costs. With the initial pH value at 10.0, the ozone dose at 4.5 g h(-1), the energy density of ultrasound at 176 W l(-1), and the initial concentration of RY84 at 100 mg l(-1), the extent of mineralization measured as TOC loss was maximized. The variation of the concentrations of related ions (oxalate, formate, acetate, NO3(-), NO2(-), NH4(+), Cl(-), and SO4(2-)) during the reaction process was monitored. Other organic intermediates detected by GC/MS were N-methyleneaniline, phthalic acid, 4-hydroxyphthalic acid, isocyanatobenzene, aniline, 4-iminocyclohexa-2,5-dien-1-one, butene diacid and urea. Based on these findings, a tentative degradation pathway was proposed.     

Degradation and toxicity reduction of textile effluent by combined photocatalytic and ozonation processes

To minimize the environmental impact of textile effluents, mainly related to their high coloration and the presence of toxic or carcinogenic reactive dyes, the efficiency of photochemical and ozonation processes, applied in the form of isolated and combined procedures, were evaluated. The investigation was focused on the reduction of total organic carbon content (TOC), color and acute toxicity (monitoring by inhibition of Escherichia coli respiration). For a reaction time of 60 min, the anatase TiO2-assisted photocatalytic process produces color and TOC reduction of about 90% and 50%, respectively. Meanwhile, the ozonation process gives a decolorization of about 60% but negligible TOC reduction. When the processes were applied in a simultaneous form, the decolorization was almost complete and the TOC reduction was higher than 60%. The three treatments studied yield an acute toxicity reduction of around 50%.     

Catalytic activity of Ru/Al2O3 for ozonation of dimethyl phthalate in aqueous solution

With dimethyl phthalate as the model pollutant and Ru/Al(2)O(3) as catalyst, this paper systemically investigates the removal of total organic carbon (TOC) of system. Our results have confirmed that Ru/Al(2)O(3) can significantly increase the effect of ozonation. TOC removal in 120 min can reach 72% while only 24% with ozone alone. The optimal catalyst preparing condition was 0.1 wt% Ru content, 600 degrees C calcination temperature, 0.5-1.0mm particle diameter, which is characterized by a high surface area and a large population of surface active sites. The contrasting experiments of ozone alone, catalyst adsorption after ozonation, and catalytic ozonation confirmed that catalytic reaction was the most important process to TOC removal in system with Ru/Al(2)O(3) as catalyst.     

Decomposition pathways and reaction intermediate formation of the purified, hydrolyzed azo reactive dye C.I. Reactive Red 120 during ozonation

In this study, an aqueous solution of purified, hydrolyzed C.I. Reactive Red 120 (RR 120, Color Index), was selected as a model to investigate the degradation pathways and to obtain additional information on the reaction intermediate formation. The dye was purified to avoid the influence of the impurities on the ozonation process and on the formation of oxidation by-products. To simulate the dye-bath effluents from dyeing processes with azo reactive dyes, a hydrolyzed form of the dye was chosen as a representative compound. High performance liquid chromatography/mass spectrometry and its tandem mass spectrometry was chosen to identify the decomposition pathways and reaction intermediate formation during the ozonation process. In addition total organic carbon and high performance ion chromatography analysis were employed to obtain further information on the reaction processes during ozonation. Purified, hydrolyzed RR 120 was decomposed under the direct nucleophilic attack by ozone resulting in oxidation and cleavage of azo group and aromatic ring, while the triazine group still remained in the solution even after prolonged oxidation time (120 min) due to its high resistance to ozonation. Phenol, 1,2-dihydroxysulfobezene, 1-hydroxysulfonbezene were detected as the degradation intermediates, which were further oxidized by O(3) and *OH to other open-ring products and then eventually led to simple oxalic and formic acid identified by HPIC.     

Ozonation of aniline promoted by activated carbon

The removal of aniline from aqueous solutions by simultaneous use of ozone and activated carbon was investigated at different solution pH. For comparative purposes, single ozonation and adsorption on activated carbon were carried out in the same experimental set-up. In order to evaluate the role of the activated carbon surface chemistry during ozonation, a commercial activated carbon, Norit GAC 1240 PLUS, was submitted to oxidation in the liquid phase with HNO(3). The texture and surface chemistry of the activated carbon samples were characterized. During ozonation, complete conversion of aniline was achieved after approximately 20 min, regardless of the presence of activated carbon. In all cases, several by-products were formed during ozonation. Nitrobenzene, o- and p-aminophenol were the primary aromatic oxidation by-products identified. In terms of TOC removal, best results were achieved by the simultaneous use of ozone and activated carbon. Though there is a strong contribution of adsorption, a considerable synergetic effect between ozone and activated carbon is observed. In general, activated carbon promotes the reaction of ozonation enhancing the efficiency of this treatment process. The basic activated carbon presented greater activity in this process leading to higher mineralization rates.