Polyelectrolyte enhanced ultrafiltration (PEUF) for the removal of Cd(II): effects of organic ligands and solution pH

This study focused on the effects of pH and organic ligands, namely ethylenediaminetetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and citric acids, on the removal and recovery of Cd(II) in polyelectrolyte enhanced ultrafiltration (PEUF). Polyethylenimine (PEI), which can bind with both positively charged metal ions by coordination bonding and negatively charged ligand-metal complexes by charge attraction, was employed as a chelating polymer. The removal and recovery of Cd species was greatly dependent on the chemistry of organic ligands according to solution pH, particularly being related to the distribution of Cd-ligand complexes at different pH levels. In the presence of EDTA, the dominant Cd species are negatively charged Cd(EDTA)(2-) and CdH(EDTA)(-) over the range of pH levels investigated, interacting with PEI via electrostatic attraction and being less pH dependent. On the other hand, the pH effects of both NTA and citric acid systems are similar to that for the system without organic ligands. This was associated with the fact that free Cd ions were predominant at the acidic pH range in both NTA and citric acid systems.     

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^-,SO4^2-,HPO4^2-/HPO4^2-,HCO3^-/CO3^2-和NO3^-）,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,HCO3^-/CO3^2-对TiO2薄膜光催化降解甲醛具有抑制作用,Cl^-和SO4^2-的影响不大,H2PO4^-/HPO4^2-和NO3-具有促进作用。造成上述结果的主要原因是HCO3^-/CO2^3-具有很强的.OH捕获作用;Cl^-,SO4^2-对.OH捕获作用以及竞争吸附都较弱;H2PO4^-/HPO4^2-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;NO3^-在紫外光的照射下可以产生.OH,此外NO3^-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。     

微电解法强化生物脱氮的实验及反应特征分析

通过铁炭微电解法强化SBR工艺脱氮效果的试验研究了解到,在进水中氨氮浓度分别为30、60和100 mg/L时,微电解-SBR工艺对氨氮的去除效果比独立的SBR工艺有明显的优势,去除率可以维持在95%左右.在进水中总氮浓度分别为30和60 mg/L时,微电解-SBR工艺对总氮的去除率比SBR工艺提高了20%～30%,利用DO-微小电极对铁污泥絮体及同样条件下的活性污泥内部物质变化进行测试,结果表明,微电解-SBR工艺所以能强化脱氮效果是微电解物化作用及后续铁污泥系统发生好氧同步硝化反硝化脱氮作用的共同结果.     

Effect of Earthworm（Pheretima sp.） Density on Revegetation of Lead/zinc Metal Mine Tailings Amended with Soil

The objective of this study was to investigate the effects of earthworm density on the availability of nutrients and heavy metals in metal contaminated soils. Pb/Zn mine tailings were mixed throughly with a red yellow podzolic soil at the ratio （w/w） of 75：25. Earthworms （Pheretima sp.） were introduced to the mixture at four different densities, zero, three, six and nine individuals per pot planted with ryegrass （Loliun multiflorum）. The results indicated that earthworm activity significantly enhanced ryegrass shoot biomass. However, as denser earthworm population was introduced, shoot biomass tended to decrease. Earthworm activity significantly increased soil pH and availability of N, P and K in the tailings and soil mixture. There was a general tendency that uptake of Zn by ryegrass increased after earthworm inoculation, although the increase in extractable Zn in tailings and soil mixture was not significant. On the contrary, there seemed to be a lower uptake of Pb by ryegrass under earthworm inoclation, despite the fact that higher extractable Pb concentrations were observed. The present project indicated that the improved growth of ryegrass was due to improved nutrient availability and other soil conditions, by inoculation of earthworms at an appropriate rate. Further studies are needed to illustrate the relationship between metal availability and earthworm activity in the field.     

废旧电路板制备的酚醛树脂的研究

废旧电路板中的树脂与碳酸钙共同加热,获得气体、固体和热解油3种热解产物.以电路板的热解油为原料、以热解过程中产生的氨气为催化剂,可以合成醇溶性热解油酚醛树脂,经分析测试表明,其组成、结构和固化特征与常规工业生产的氨催化酚醛树脂的性能相近,主要性能指标:粘度、游离酚浓度和胶合强度等均可达到醇溶性酚醛树脂产品的质量要求.     

再生水中内分泌干扰物质的存在及处理现状

随着污水回用大力开展,人们与再生水的接触机会增加,必须保障再生水的水质安全.资料调研发现,作为再生水水源的污水处理厂出水中含有多种内分泌干扰物质,活性炭吸附、超滤、高级氧化技术及膜技术可有效去除再生水中的内分泌干扰物质,但鉴于经济和管理上的困难,目前仍不能全面推广.中国常用的澄清(混凝沉淀)/过滤工艺不能有效去除污水处理厂二级出水中的内分泌十扰物质,这对接触人群的健康产生潜在威胁,对生物种群也有一定的影响.生物处理方法未来有可能成为去除内分泌干扰物质很有前途的方法.     

Adsorption of lambda-cyhalothrin and cypermethrin on two typical Chinese soils as affected by copper

Background, aim, and scope  Pesticides and heavy metals pollution in soil environment has become a serious problem in many countries including China. Repeated applications of bordeaux mixture (a blend of copper sulfate and calcium hydroxide) and pyrethroid (Pys) insecticides have led to elevated copper (Cu) and Pys concentrations in vineyard surface soils. However, few studies focused on the interaction of Pys and heavy metals in the soil environment. Our previous studies had indicated the combined effect of cypermethrin (CPM) and Cu on soil catalase activity. Also, we had suggested that the addition of Cu could catalyze photo-degradation of CPM and lambda-cyhalothrin (λ-CHT) in aqueous solution and restrain their degradation in soil. To better understand the potential influence of Cu on the fate of Pys in the soil environment, the aim of the present work was to examine the effect of Cu on the adsorption of λ-CHT and CPM on two typical Chinese soils with different soil characteristics, which was one of the key processes controlling the fate of Pys, and to provide more information about the potential ecological risk of chemicals on the soil ecosystem. Fourier transform infrared and point charges analysis using the MOPAC program of the Gaussian system were also used to reveal the probable adsorption mechanism of λ-CHT and CPM on soils. Materials and methods  Two vineyard soils with different properties were chosen as experimental samples. They were sampled from 0 to 10 cm, dried, and sieved to 2 mm. Each soil was spiked with copper sulfate solution to obtain the following total soil Cu concentrations: 100, 200, 400, 800, and 1,600 mg·kg⁻¹. The treated soils were incubated for 2 weeks and then dried at 20°C. For each soil sample and at each soil Cu concentration, the adsorption of λ-CHT and CPM was measured using a batch equilibrium method. The concentration of λ-CHT was determined by HPLC, and the amount of λ-CHT and CPM adsorbed by the soil sample at equilibrium was determined by the difference between the initial and equilibrium concentrations in solution corrected by the blank adsorption measurement. Results  Without the addition of Cu, the adsorption of λ-CHT and CPM on Black soil is greater than that on Red soil, while the adsorption of λ-CHT on both soils is significantly stronger than that of CPM. As the soil Cu concentration increased from 19 (or 18; background) to 1,600 mg·kg⁻¹, the adsorption coefficient (K _d) of λ-CHT decreased from 12.2 to 5.9 L·kg⁻¹ for Red soil, and from 26.1 to 16.8 L·kg⁻¹ for Black soil, whereas the CPM adsorption coefficient in both soils decreased nearly by 100% (K _d decreased from 9.4 to 0.2 L·kg⁻¹ for Red soil and from 16.2 to 0.5 L·kg⁻¹ for Black soil). Discussion  Pys adsorption is a surface phenomenon which depends on the surface area and the organic matter content. Thus, the Black soil, having higher organic matter and greater surface area than that of the Red soil, show greater adsorption affinity to λ-CHT and CPM. In our study, the different adsorption affinity of the two Pys was obtained, which was probably attributed to differences with respect to their physical–chemical properties. Further comparison upon the two Pys was conducted. The point charges of halogen atoms in the λ-CHT and CPM were calculated, the differences of which probably lead to the fact that λ-CHT has a stronger binding capacity to soils than CPM. Also, FTIR spectra show that competitive adsorption occurs between CPM and Cu for the same adsorption sites, which is responsible for the obtained suppression of CPM adsorption affected by Cu. Conclusions  Lambda-cyhalothrin shows a significantly stronger adsorption than cypermethrin on both soils. This phenomenon may be due to several reasons: (1) λ-CHT has lower solubility and a higher octanol–water partition coefficient value than CPM; (2) λ-CHT consists of specific isomers, whereas CPM is mixtures of eight different isomers; (3) the chlorine and fluorine atoms in the λ-CHT have a negative point charge, whereas the chlorine atoms in the CPM have a positive point charge. As the soil Cu concentrations increased from 19 (or 18) mg·kg⁻¹ to 1,600 mg·kg⁻¹, the adsorption coefficient of λ-CHT and CPM decreased on both soils. This is mainly due to a competition between Cu and Pys for occupying the adsorption sites on soils. The information from this study have important implications for vineyard and orchard soils, which often contain elevated levels of Cu and Pys. These results are also useful in assessing the environmental fate and health effect of λ-CHT and CPM. Recommendations and perspectives  It is important for environmental scientists and engineers to get a better understanding of soil–metal–organic contaminant interactions. However, pesticide adsorption involves complex processes, and shortcomings in understanding them still restrict the ability to predict the fate and behavior of pesticide. Therefore, considerable research should be carried out to understand the mechanism of interaction between Pys and heavy metal on soils clearly.     

固定化对氯苯酚降解菌在生物流化床中的降解特性

为了获得固定化对氯苯酚降解菌在生物流化床中的降解特性,用海藻酸钠-壳聚糖-活性炭微胶囊对实验室保存的对氯苯酚降解菌株进行固定化,在生物流化床中用固定化菌株在不同单因素实验条件下降解对氯苯酚废水,用气相色谱仪测定废水中对氯苯酚的降解率.结果表明,固定化对氯苯酚降解菌株处理污水的适宜条件为:HRT为72 h,微胶囊接种体积...     

湿法烟气脱硫机理与工程对策

烟气脱硫关注的是对流扩散.脱硫工艺根据双膜理论的基本概念所确定的相际传质速度关系,为传质设备设计的主要依据.烟气脱硫技术中大量采用化学吸收法.合理提高吸收塔内烟气流速,有利于提高系统传质速率,减少传质阻力;通过对塔局部优化设计,可增强系统传质性能.对石灰石-石膏法而言,液气比决定了石灰石的消耗量.烟气中的飞灰既在液相膜表面结壳,阻碍石灰石的溶解,又影响脱硫系统含尘量排放指标,降低石膏品质.石灰石粒径确定原则为在保证一定脱硫率的前提下,获取最优的经济指标.浆液的pH值是影响脱硫效率的重要因素.通过对系统操作、运行和设计中几个重要参数的分析,提出相应工程对策.