适于工业应用的TiO2纳米管的阳极氧化法制备

通过阳极氧化法制备了适于工业应用的大尺寸二氧化钛纳米管阵列.考察了电极形状和面积、氧化电压、氧化时间、预处理等因素对阳极氧化法制备二氧化钛纳米管阵列形貌的影响.结果显示,电极形状对纳米管的制备没有影响;阳极氧化前打磨与否对纳米管也没有影响;氧化电压、氧化时间和电极面积对纳米管的影响较大,只有在合适的电压和时间下才能制成纳米管阵列.电极面积影响电流密度,从而影响纳米管的形貌,试验中电极最大面积为360cm2.通过试验得出工业化制备二氧化钛纳米管阵列的最佳条件是电压20V,电解时间30min,反应前不用进行打磨.实验结果显示制成的纳米管阵列对强酸强碱的耐受力强,完全可以适应工业化废水的pH变化.     

利用碳氮共掺杂二氧化钛纳米管阵列实现同时降解甲基橙和产氢

本研究结合阳极氧化和超声辅助沉积的方法合成碳氮共掺杂的二氧化钛纳米管阵列,并采用XRD、FESEM、UV-vis、XPS等技术对材料进行表征.光电化学(PEC)体系中,碳氮共掺杂二氧化钛纳米管阵列作为阳极,甲基橙溶液作为光电催化氧化的对象,对光催化剂的氧化性能进行了考察,与此同时,在阴极实现光解水产氢,最终在PEC体系中实现同时降解甲基橙和产氢.XRD、FESEM、UV-vis、XPS及TEM等表征结果表明,碳氮成功地掺入到了二氧化钛纳米管阵列中,并未破坏其多孔有序的结构,而且比二氧化钛纳米管阵列具有更高的光催化活性.光电催化降解甲基橙的实验当中,在酸性溶液条件下,二氧化钛纳米管阵列的催化氧化效率较高,降解效率达到了100%,其速率常数为2.3×10-3s-1(p H=4),同时也具有较高的产氢速率(0.95 mmol·h-1),因此,该实验体系在光电催化降解污水中的有机污染物同时产氢方面有应用前景.     

氧气热处理的TiO2纳米管阵列光电催化降解亚甲基蓝的研究

采用原位阳极氧化法在Ti基底上制备了高度有序的TiO2纳米管阵列薄膜,SEM图像表明TiO2纳米管定向排列整齐,分布均匀,其管径范围在70～100 nm.XRD结果证明,阳极氧化法制备的TiO2纳米管为无定型晶型,经退火后为具有良好光催化活性的锐钛矿型.以亚甲基蓝（methylene blue）为目标物研究了TiO2纳米管光电催化性能及影响因素,结果表明,以0.1 mol/L NaCl为电解质,在氧气热处理气氛下,外加偏压为0.5 V、pH=3.25、光照强度为1 000μW/cm2、纳米管薄膜表面积为2 cm×2 cm且MB初始浓度为10 mg/L的条件下,TiO2纳米管阵列薄膜光电催化降解MB的降解效率可达99.56%.电化学阻抗谱分析显示,光电催化降解过程的速控步骤均为表面反应步骤,外加偏压减小了界面电荷转移阻抗,提高了光生载流子的分离效率.     

石墨烯修饰的二氧化钛纳米管电极光电催化去除铜氰络合物研究

首先采用阳极氧化法制备了二氧化钛纳米管电极,进一步通过电化学循环伏安法制备了石墨烯(GO)修饰的二氧化钛纳米管电极.同时,采用SEM对电极的形貌进行了表征分析.光电化学测试分析结果表明,石墨烯修饰二氧化钛纳米管电极的电极光电响应性能得到了提高.最后,采用制备的电极为光阳极,通过光电催化氧化方法对铜氰络合物进行了去除研究.结果表明:在电压为2.0 V的条件下,采用二氧化钛纳米管电极,反应120 min后,剩余总氰的含量及铜的回收率分别为4.0%和96.3%;采用石墨烯修饰的二氧化钛纳米管,反应60 min后,剩余总氰的含量及Cu的回收率分别为0.3%和99%.可以看出,经石墨烯修饰的二氧化钛纳米管显示出了较好的光电催化去除铜氰络合物的效果.     

Bi-TiO2纳米管阵列电极对水中硝酸盐的去除

为研究电化学技术对硝酸盐氮的去除作用,本实验以TiO₂纳米管（TiO₂-NT）为基体,利用电沉积法制备了Bi-TiO₂纳米管阵列电极（Bi-TNA）.同时,采用X-射线衍射仪（XRD）、扫描电子显微镜（SEM）对电极涂层表面形貌和晶体结构进行表征,并分析了电流密度、pH、初始浓度对硝态氮去除、亚硝态氮和氨氮转换、总氮去除及氮气选择性的影响.最后分析了Bi-TNA电极对硝态氮去除的动力学模型.结果表明,在单因素水平下,最佳操作条件为：硝态氮浓度为50 mg·L^-1,电流密度为30 mA·cm^-2,pH值为8.5.Bi-TNA电极对硝态氮的还原过程都遵循一级反应动力学.     

TiO_2纳米管修饰电极处理反渗透浓水研究

研制了新型的TiO2纳米管修饰电极,应用于反渗透膜浓水的电化学氧化处理;利用扫描电镜和线性极化曲线对电极进行了表征;考察了电解时间、电流密度和pH值因素对电化学氧化处理反渗透膜浓水的影响;并分析了电极对反渗透浓水中各有机物组分的去除效果。实验结果表明TiO2纳米管修饰电极对反渗透浓水具有较高的电催化性能。     

SiO-TiO2纳米管的制备及其光催化性能的研究

文章采用水热法制备SiO2-TiO2纳米管,通过扫描电镜(SEM)和透射电镜(TEM)考察了该纳米管的结构形态,并用X-射线衍射考察其晶体结构.实验结果表明所制得的纳米管是锐钛晶型,其两端开口,具有多层管壁;管径为8 nm左右,管壁厚1～2 nm.光催化降解酸性橙Ⅱ实验表明:SiO2-TiO2纳米管光催化速率比TiO2纳米管高出10%.这可能是因为Si元素的存在增大了钛纳米管的比表面积,同时SiO2的存在能降低光生电子和空穴的复合率.     

SiO_2-TiO_2纳米管的制备及其光催化性能的研究

文章采用水热法制备SiO2-TiO2纳米管,通过扫描电镜(SEM)和透射电镜(TEM)考察了该纳米管的结构形态,并用X-射线衍射考察其晶体结构。实验结果表明所制得的纳米管是锐钛晶型,其两端开口,具有多层管壁;管径为8nm左右,管壁厚1～2nm。光催化降解酸性橙Ⅱ实验表明:SiO2-TiO2纳米管光催化速率比TiO2纳米管高出10%。这可能是因为Si元素的存在增大了钛纳米管的比表面积,同时SiO2的存在能降低光生电子和空穴的复合率。     

臭氧/TiO_2纳米管工艺处理水中2,4-二氯酚的效能研究

采用水热合成法制备TiO2纳米材料,用BET、XRD、TEM技术对样品进行表征,结果表明,制备出来的样品均为纳米管,随着煅烧温度的增加,晶型从锐钛矿变成金红石相。实验考察了体系参数对臭氧/TiO2纳米管工艺降解2,4-二氯酚废水影响,结果表明:随着臭氧投加量的增加,废水COD的去除效率随之增加,初始浓度的增加会抑制降解效率,中性或弱碱性水环境有利于反应的进行。另外,通过研究叔丁醇对反应体系的影响,表明实验反应遵循羟基自由基的反应机理。     

基于传感器阵列的可燃混合气体RBF网络分析

为克服传感器阵列在混合气体检测中的交叉敏感现象,采用具有最佳逼近和全局最优性能的RBF神经网络对传感器阵列的输出信号进行分析。建立了多种可燃气体分析的数学模型,并对CO,H2和CH4的混合气体样本进行了实验。结果表明,传感器阵列和RBF神经网络处理单元构成的气体分析系统可以较好地实现对可燃混合气体的分析,误差不大于2%。     

Degradation of metabolites accumulated of benzo[a]pyrene by coupling Penicillium Chrysogenum with KMnO4

Several main metabolites of benzo[a]pyrene （BaP） formed by Penicillium chrysogenum, Benzo[a]pyrene-1,6-quinone （BP 1,6- quinone）, trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene （BP 7,8-diol）, 3-hydroxybenzo[a]pyrene （3-OHBP）, were identified by high-performance liquid chromatography （HPLC）. The three metabolites were liable to be accumulated and were hardly further metabolized because of their toxicity to microorganisms. However, their further degradation was essential for the complete degradation of BaP. To enhance their degradation, two methods, degradation by coupling Penicillium chrysogenum with KMnO4 and degradation only by Penicillium chrysogenum, were compared; Meanwhile, the parameters of degradation in the superior method were optimized. The results showed that （1） the method of coupling Penicillium chrysogenum with KMnO4 was better and was the first method to be used in the degradation of BaP and its metabolites; （2） the metabolite, BP 1,6-quinone was the most liable to be accumulated in pure cultures; （3） the effect of degradation was the best when the concentration of KMnO4 in the cultures was 0.01% （w/v）, concentration of the three compounds was 5 mg/L and pH was 6.2. Based on the experimental results, a novel concept with regard to the bioremediation of BaP-contaminated environment was discussed, considering the influence on environmental toxicity of the accumulated metabolites.     

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.     

Toxicity assessing for chlorpyrifos-contaminated soil with three different earthworm test methods

Earthworm toxicity tests are useful tools for terrestrial risk assessment but require a hierarchy of test designs that differ in effect levels (behavior, sublethal, lethal). In this study, the toxicity of chlorpyrifos contaminated soil on earthworms was assessed. In addition to the acute and chronic tests, an avoidance response test was applied. Earthworms were exposed to sublethal and lethal concentration of chlorpyrifos, and evaluated for acute toxicity, growth, fecundity and avoidance response after a certain exposure period. The test methods covered all important ecological relevant endpoints (acute, chronic, behavioral). Concentration of 78.91 mg/kg, chlorpyrifos caused significant toxic effects in all test methods, but at lower test concentrations, only significant chronic toxic effects could be observed. In the present study, chlorpyrifos had adverse effect on growth and fecundity in earthworm exposed to 5 mg/kg chlorpyrifos after eight weeks. The avoidance response test, however, showed significant repellent effects concentration of 40 mg/kg chlorpyrifos. For chlorpyrifos, concentration affecting avoidance response was far greater than growth and fecundity, it seemed likely that earthworms were not able to escape from pesticide-contaminated soil into the clean soil in field and hence were exposed continuously to elevated concentrations of pesticides.     

Leaching of styrene and other aromatic compounds in drinking water from PS bottles

Bottled water may not be safer, or healthier, than tap water. The present studies have proved that styrene and some other aromatic compounds leach continuously from polystyrene （PS） bottles used locally for packaging. Water sapmles in contact with PS were extracted by a preconcentration technique called as ＂purge and trap＂ and analysed by gas chromatograph-mass spectrometer （GC/MS）. Eleven aromatic compounds were identified in these studies. Maximum concentration of styrene in PS bottles was 29.5 μg/L. Apart from styrene, ethyl benzene, toluene and benzene were also quantified but their concentrations were much less than WHO guide line values. All other compounds were in traces. Quality of plastic and storage time were the major factor in leaching of styrene. Concentration of styrene was increased to 69.53 μg/L after one-year storage. In Styrofoam and PS cups studies, hot water was found to be contaminated with styrene and other aromatic compounds. It was observed that temperature played a major role in the leaching of styrene monomer from Styrofoam cups. Paper cups were found to be safe for hot drinks.     

Sludge concentration dynamic distribution and its impact on the performance of UNITANK

UNITANK is a biological wastewater treatment process that combines the advantages of traditional activated sludge process and sequencing batch reactor, which is divided into Tank A, B and C. In this study, the sludge distribution and its impact on performance of UNITANK were carried out in Liede Wastewater Plant （WWTP） of Guangzhou, China. Results showed that there was a strong affiliation between Tank A and B of the system in sludge concentration distribution. The initial sludge concentration in Tank A could present the sludge distribution of the whole system. The sludge distribution was mainly influenced by hydraulic condition. Unsteady sludge distribution had an impact on variations of substrates in reactors, especially in decisive reactor, and this could lead to failure of system. Settler could partially remove substrates such as COD and NO3-N, but there was adventure of sludge deterioration. The rational initial sludge concentration in Tank A should be 4000-6000 mg/L MLSS.     

Treated wastewater irrigation effect on soil, crop and environment： Wastewater recycling in the loess area of China

A study was carried out at the Loess Plateau in Dongzhi,China,to test the feasibility of using secondary treatment sewage effluent and to determine whether the water quality would then meet the recommended irrigation norm.Seven crops,including celery,wheat, maize,millet,apples,rapeseed and yellow beans,were tested in the study.Physical and chemical properties of the soil,crop yield and quality and leachate at different soil depths were measured.In most cases,the quality of the crops that made use of treated sewage was not distinctively different from those that did not use treated sewage.However,yields for the former were much higher than they were for the latter.Leachates at different soil depths were analyzed and the results did not show alarming levels of constituents.For a period of approximately 14 months,the treated sewage irrigation had no significant effect on the loess soil and no cases of illness resulting from contact with the treated sewage were reported.With treated sewage irrigation,a slight increase in the organic content of the soil was observed.     

Spatial variability of organochlorine pesticides （DDTs and HCHs） in surface soils from the alluvial region of Beijing, China

The spatial variability in the concentrations of 1,2,3,4,5,6-hexachlorocyclohexane (HCH) and 1,1,1-trichloro-2,2-bis-(p-chlorophenyl) ethane (DDT) in surface soils was studied on the basis of the analysis of 131 soil samples collected from the surface layer (0-20 cm depth) of the alluvial region of Beijing, China. The concentrations of total HCHs (including α-, β-, γ-, and δ-isomers) and total DDTs (i ncluding p,p'-DDT, p,p'-DDD, p,p'-DDE, and o,p'-DDT) in the surface soils tested were in the range from nondetectable to 31.72 μg/kg dry soil, with a mean value of 0.91, and from nondetectable to 5910.83 μg/kg dry soil, with a mean value of 32.13,respectively. It was observed that concentrations of HCHs in all soil samples and concentrations of DDTs in 112 soil samples were much lower than the first grade (50 μg/kg) permitted in "Environment quality standard for soils in China (GB15618-1995)". This suggests that the pollution due to organochlorine pesticides was generally not significant in the farmland soils in the Beijing alluvial region. In this study, the spatial distribution and trend of HCHs and DDTs were analyzed using Geostatistical Analyst and GS (513).Spatial distribution indicated how these pesticides had been applied in the past. Trend analysis showed that the concentrations of HCHs,DDTs, and their related metabolites followed an obvious distribution trend in the surface soils from the alluvial region of Beijing.     

Heavy metal availability and impact on activity of soil microorganisms along a Cu/Zn contamination gradient

All the regulations that define a maximum concentration of metals in the receiving soil are based on total soil metal concentration. However, the potential toxicity of a heavy metal in the soil depends on its speciation and availability. We studied the effects of heavy metal speciation and availability on soil microorganism activities along a Cu/Zn contamination gradient. Microbial biomass and enzyme activity of soil contaminated with both Cu and Zn were investigated. The results showed that microbial biomass was negatively affected by the elevated metal levels. The microbial biomass-C （Cmic）/organic C （Corg） ratio was closely correlated to heavy metal stress. There were negative correlations between soil microbial biomass, phosphatase activity and NH4NO3 extractable heavy metals. The soil microorganism activity could be predicted using empirical models with the availability of Cu and Zn. We observed that 72% of the variation in phosphatase activity could be explained by the NH4NO3-extractable and total heavy metal concentration. By considering different monitoring approaches and different viewpoints, this set of methods applied in this study seemed sensitive to site differences and contributed to a better understanding of the effects of heavy metals on the size and activity of microorganisms in soils. The data presented demonstrate the relationship between heavy metals availability and heavy metal toxicity to soil microorganism along a contamination gradient.     

Bioaccumulation of heavy metals in fishes from Taihu Lake, China

The Cr,Zn,Cu,Cd,Pb contents were determined in Cyprinus carpio Linnaeus,Carassius auratus Linnaeus,Hypophthalmichthys molitrix and Aristichthys nobilis,which were caught from Meiliang Bay,Taihu Lake,a large,shallow and eutrophic lake of China.The results showed that:(1)the Cr,Cu,Pb,Cd contents in the edible parts of the four fish species were much lower than Chinese Food Health Criterion(1994),but the Zn contents were higher than the Criterion;(2)Cd contents were the highest in the liver of fish,Pb contents were almost the same in all organs of fish,Cr contents mainly enriched in the skin and gonads,Zn contents were the highest in the gonad(♀),and Cu contents were the highest in the liver;(3)the total metal accumulation was the greatest in the liver and the lowest in the muscle.The total metal accumulation was the highest in C.auratus L.This investigation indicated that fish products in Taihu Lake were still safe for human consumption,but the amount consumed should be controlled under the Chinese Food Health Criterion to avoid excessive intake of Zn.     

Biological control experiment of excess propagation of Cyclops for drinking water security

Cyclops of zooplankton propagated excessively in eutrophic water body and could not be effectively inactivated by the conventional disinfections process like chlorination due to its stronger resistance to oxidation. In this study, an ecological project was put forward for the excess propagation control of Cyclops by stocking the filter-feeding fishes such as silver carp and bighead carp under the condition of no extraneous nutrient feeding. The results of experiments with different stocking biomass showed that the propagation of Cyclops could be controlled effectively, and the water quality was improved simultaneously by impacting on nutriment level and plankton community structure at proper stocking density of 30 g/m^3 of water. The growth of Cyclops may not be effectually controlled with lower biomass of fish （10 g）, and the natural food chain relation may be destroyed for Cyclops dying out in water while the intense stocking of 120 g per cubic meter of water. In addition, the high predator pressure may accelerate supplemental rate of nutrients from bottom sediments to water body to add the content of total nitrogen and phosphorus in water.