Photoelectrocatalytic degradation of recalcitrant organic pollutants using TiO2 film electrodes: an overview

Photoelectrocatalytic (PEC) technology involved applying an electrical bias to a TiO₂ film electrode, has been widely applied to the degradation of refractory organic pollutants, owing to its high degradation efficiency. This paper reviews recent developments in the PEC degradation of recalcitrant organic contaminants using a TiO₂ film electrode. The preparation and application of various TiO₂ film electrodes have been investigated, as well as the parameters that influence PEC activity such as the crystal structure, the film thickness and substrate material, the applied electrical bias, the solution pH and conductivity. The improvement of PEC activity by doping the TiO₂ film electrode with metal and non-metal ions has been discussed. The mechanism and kinetics for the PEC degradation of organic pollutants have also been highlighted.     

Separation of dissolved iron from the aqueous system with excess ligand

A new technique for the separation and pre-concentration of dissolved Fe(III) from the ligand-rich aqueous system is proposed. A solid phase extraction (SPE) system with an immobilized macrocyclic material, commonly known as molecular recognition technology (MRT) gel and available commercially, was used. Synthetic Fe(III) solution in aqueous matrices spiked with a 100-fold concentration of EDTA was used. Dissolved iron that was ‘captured’ by the MRT gel was eluted using hydrochloric acid and subsequently determined by graphite furnace atomic absorption spectrometry. The effect of different variables, such as pH, reagent concentration, flow rate and interfering ions, on the recovery of analyte was investigated. Quantitative maximum separation (∼100%) of the dissolved Fe(III) from synthetic aqueous solutions at a natural pH range was observed at a flow rate of 0.2 mL min^-1. The extraction efficiency of the MRT gel is largely unaltered by the coexisting ions commonly found in natural water. When compared with different SPE materials, the separation performance of MRT gel is also much higher.     

Absorption of current use pesticides by snapping turtle (Chelydra serpentina) eggs in treated soil

Reptiles often breed within agricultural and urban environments that receive frequent pesticide use. Consequently, their eggs and thus developing embryos may be exposed to pesticides. Our objectives were to determine (i) if turtle eggs are capable of absorbing pesticides from treated soil, and (ii) if pesticide absorption rates can be predicted by their chemical and physical properties. Snapping turtle (Chelydra serpentina) eggs were incubated in soil that was treated with 10 pesticides (atrazine, simazine, metolachlor, azinphos-methyl, dimethoate, chlorpyrifos, carbaryl, endosulfan (I and II), captan, and chlorothalonil). There were two treatments, consisting of pesticides applied at application rate equivalents of 1.92 or 19.2 kg a.i/ha. Eggs were removed after one and eight days of exposure and analyzed for pesticides using gas chromatography coupled with a mass selective detector (GC-MSD) or high performance liquid chromatography (HPLC). Absorption of pesticides in eggs from soil increased with both magnitude and duration of exposure. Of the 10 pesticides, atrazine and metolachlor generally had the greatest absorption, while azinphos-methyl had the lowest. Chlorothalonil was below detection limits at both exposure rates. Our preliminary model suggests that pesticides having the highest absorption into eggs tended to have both low sorption to organic carbon or lipids, and high water solubility. For pesticides with high water solubility, high vapor pressure may also increase absorption. As our model is preliminary, confirmatory studies are needed to elucidate pesticide absorption in turtle eggs and the potential risk they may pose to embryonic development.     

Alkaline hydrothermal conversion of fly ash precipitates into zeolites 3: the removal of mercury and lead ions from wastewater

In this paper, the utilisation of zeolites synthesised from fly ash (FA) and related co-disposal filtrates as low-cost adsorbent material were investigated. When raw FA and co-disposal filtrates were subjected to alkaline hydrothermal zeolite synthesis, the zeolites faujasite, sodalite and zeolite A were formed. The synthesised zeolites were explored to establish its ability to remove lead and mercury ions from aqueous solution in batch experiments, to which various dosages of the synthesised zeolites were added. The test results indicated that when increasing synthesised zeolite dosages of 5-20 g/L were added to the acid mine drainage (AMD) wastewater, the concentrations of lead and mercury in the wastewater were reduced accordingly. The lead concentrations were reduced from 3.23 to 0.38 and 0.17 microg/kg, respectively, at an average pH of 4.5, after the addition of raw FA zeolite and co-disposal filtrate zeolite to the AMD wastewater. On the other hand, the mercury concentration was reduced from 0.47 to 0.17 microg/kg at pH=4.5 when increasing amounts of co-disposal filtrate zeolite were added to the wastewater. The experimental results had shown that the zeolites synthesised from the co-disposal filtrates were effective in reducing the lead and mercury concentrations in the AMD wastewater by 95% and 30%, respectively.     

Treatment of Landfill Leachate Wastewater by Nanofiltration Membrane

Abstract

Nanofiltration (NF) membrane is an alternative lower energy membrane type compared to reverse osmosis membrane. NF is suitable for rejection of ions and molecules with molecular weight greater than 200 Da. In this study leachate wastewater from a sanitary landfill site in Malaysia was filtered through a NF membrane in order to determine the rejection capability of the membrane towards pollutants such as chemical oxygen demand (COD), conductivity, nitrate, ammonia-nitrogen, and heavy metals such as Pb, Cd, Cu, Zn, Fe. The NF membrane used was HL membrane, which under the atomic force microscope (AFM) imaging, showed visible discrete pores. The overall rejections of the pollutants were more than 85% except for nitrate and ammonia nitrogen. NF can be considered an alternative for advanced filtration especially within a hybrid treatment system combining biological–physical treatment and membrane filtration.     

原子荧光光谱法测定空气中硒化氢的不确定度评定

依据JJF1059.1-2012,确立测量结果和不确定度评价的数学模型,从采集气样体积和采气后滤膜消解液待测物浓度和定容体积三个部分,A类不确定度和B类不确定度二个方面评定测量过程的不确定度,量化各不确定度分量。本次测量相对合成标准不确定度为0.024,较大的不确定度是样品浓度测量过程中的A类不确定度,主要由标准曲线测量和样品测量随机偏差引入,分量值分别为0.013和0.011。本次测量结果为0.169±0.008mg/m3(包含区间在0.161～0.177mg/m3),k=2。即在包含概率约为95%的条件下,可以判定该工作场所空气中硒化氢的含量已经超过了PC-TWA标准限值。     

石墨炉原子吸收法测定水中微量镍的研究

研究了石墨炉原子吸收光谱法测定生活饮用水中微量镍的方法,对基体改进剂和最佳加热程序进行了探讨。结果表明,本方法不需添加基体改进剂,灰化温度为1 200℃、原子化温度2 300℃,加标回收率为93.7%~1 03.0%,RSD<5.2%,该方法的检测下限为5.0μg/L。方法简便、准确,适用于生活饮用水中镍的测定。     

绍兴部分河道水中重金属的检测及污染评估

为探索绍兴部分河道水中重金属元素的含量,采用电感耦合等离子体发射光谱(ICP-AES)方法测定绍兴河道水中铬、锰、铁、汞、铅、镍、锡、镉、砷、铜、锌和钴12种重金属元素含量。参照国家有关标准,对重金属检测结果进行与国标标准限值进行比较而达到对重金属的污染评价。结果表明:绍兴部分河流不存在重金属污染情况,但个别元素接近标准限值。     

气相与气质联用测定地表水中VOC的方法比较

在水环境保护形势趋紧、水质监测要求逐步提高的背景下,地表水中挥发性有机物测定的精确性、高效性要求也需不断提高。文章分别用国标规定的气相色谱法与美国EPA的气-质联用法对地表水环境质量标准要求监测的109项中的23种挥发性有机物进行了测定比对。结果发现:国标规定的气相色谱法测定各挥发性有机物虽能达到规定的检出限、准确度、精密度,但相对于气-质联用,国标规定的气相色谱法存在步骤繁琐、仪器设备需求量大、实验人员多、实验效率低、浪费更多实验资源等缺点。     

氢化物发生—原子荧光光谱法测定地表水中的痕量锡

利用AFS-9330双道原子荧光光度计测定水中的锡,以1.0%的盐酸作为载流液、1.0%的硼氢化钾为还原剂,荧光强度与其质量浓度在0⁴0μg/L范围内,线性良好,相关系数为0.9992,方法检出限为0.06μg/L,相对标准偏差在1.79%40μg/L范围内,线性良好,相关系数为0.9992,方法检出限为0.06μg/L,相对标准偏差在1.79%².83%之间,加标回收率为91.0%2.83%之间,加标回收率为91.0%¹03%。