Thermochemical studies of the toxic action of heavy metal ions on<Emphasis Type="Italic">Escherichia coli</Emphasis> by microcalorimetry

By using an LKB2277, BioActivity Monitor (heat conduction microcalorimeter), stopped-flow method, the thermogenetic curves of Escherichia coli growth at 37°C inhibited by four kinds of heavy metal ions are determined, and parameters such as growth rate constants, inhibitory ratio, half-inhibitory concentration etc. were obtained. The experimental results show that heavy metal ions can inhibit Escherichia coli growth obviously, but low concentration of Cu²⁺ has a promoting action. The half inhibitory concentrations of Zn²⁺, Cd²⁺, Hg²⁺ and Cu²⁺ are 28.3, 10.9, 3.19 and 69.6 μg. mL⁻¹, respectively. Judged from the rate constant, the half-inhibitory concentration and the molecular mass, the inhibitory sequence is Hg²⁺>Cd²⁺>Zn²⁺>Cu²⁺. This microclorimetric bioassay for acute cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile; moreover, toxicological information can be obtained with cell from other species of interest. Li Xi: Born in 1968 Funded by the National Natural Science Foundation of China (29973030 and 30170010)     

Cu2+和Ni2+对水解-MBR工艺处理效能的影响特性

为降低电镀废水中重金属对生物处理系统的冲击,采用水解-膜生物反应器(MBR)组合工艺对电镀综合废水进行处理,以重金属离子Cu~(2+)、Ni~(2+)为代表,重点研究不同质量浓度的重金属冲击下对水解-MBR工艺处理电镀废水效能的影响,以及水中DOMs与微生物活性的变化情况.结果表明:在Cu~(2+)、Ni~(2+)质量浓度5~20 mg/L冲击下,水解-MBR组合工艺对COD和NH_4~+-N去除效率分别在75%和45%以上.硝化细菌抗重金属冲击能力较差,水解-MBR组合工艺对重金属Cu~(2+)、Ni~(2+)的耐受质量浓度可达20 mg/L,而单纯MBR工艺仅为10 mg/L.水解反应器可将污水中HPI大部分转化为HPO-A,改善难降解有机物可生化性,芳香族化合物的含量明显降低.随着重金属Cu~(2+)、Ni~(2+)质量浓度的升高,MBR反应器内活性污泥的SOUR值逐步下降,但水解-MBR工艺SOUR受重金属的抑制率均比单独MBR工艺低5%左右.由于水解使重金属毒性减弱,水解-MBR系统中微生物的活性较高,系统中EPS含量和出水质量浓度均显著低于单独MBR工艺,且可以有效减少膜表面胶体物质和溶解性有机物形成,降低污泥滤饼层的形成速度,有效减缓膜污染的速率.     

重金属污染土物理性质-强度定量关系试验研究

通过室内试验研究土体孔隙液中重金属离子影响土体物理-力学性状的机理,采用不同浓度的重金属Cu²⁺、Zn²⁺、Pb²⁺掺入高岭土、伊利石类黏土和钠基膨润土,研究土体界限含液率、不排水抗剪强度随重金属离子浓度的变化规律。试验结果表明：以高岭石、伊利石为主要黏土矿物的低活性土的液限、塑性指数随离子浓度的增加而增大,钠基膨润土则表现出相反的变化规律;低活性黏土的不排水抗剪强度随离子浓度增加而增大,高活性黏土强度则随之减小;基于已有的无污染土体物理-力学性状定量联系,分析重金属污染土的不排水抗剪强度与液性指数的定量关系,发现重金属离子引起的不排水抗剪强度的变化可以归结于重金属离子引起的液塑限变化,表明重金属Cu²⁺、Zn²⁺、Pb²⁺污染过程基本没有产生化学反应,其物理-力学定量关系与已有的无污染土经验关系式一致。     

Hydrothermal synthesis of zeolites-calcium silicate hydrate composite from coal fly ash with co-activation of Ca(OH)2-NaOH for aqueous heavy metals removal

Coal fly ash is a typical secondary aluminum/silicon resource. The preparation of zeolite-type absorbent is a potential way for its value-added utilization, while the purity and adsorption property of zeolite are limited due to the occurrence of side reactions in the synthesis process. In this study, a designated composite consisted of crystalline zeolites and amorphous calcium silicate hydrate was selected, which was direct synthesized from fly ash under conditions of a Ca/Si molar ratio of 0.8, an initial NaOH concentration of 0.5 mol/L, a hydrothermal temperature of 170 ℃ and a liquid–solid ratio of 15 mL/g. The results indicated that this composite had superior adsorption property for a variety of heavy metals, which was based on the exchange of calcium and sodium ions in zeolites and calcium silicate hydrate. Its adsorption capacities for Pb²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Cu²⁺ and Cr³⁺ attained 409.4, 222.4, 147.5, 93.2, 101.1 and 157.0 mg/g, respectively, in single solution with a pH of 4.5. After regulating the synthesis conditions, the transformation of amorphous calcium silicate hydrate into crystallized tobermorite weakened the adsorption capacity of the composite. Besides, due to the competitive adsorption in a multiple ions solution, the adsorption capacities for these heavy metals had a reduction.     

用于Pb2+、Hg2+离子选择性固相萃取的微流控芯片

为实现微流控芯片对重金属Pb~(2+)、Hg~(2+)离子的选择性固相萃取,首先采用3-氯丙基三甲氧基硅烷和5-甲基苯并三氮唑对纳米二氧化硅进行硅烷偶联改性,随后以改性纳米二氧化硅为基础,设计并制备了可更换吸附剂的一体化填充式固相萃取芯片.测试结果表明:改性后不仅吸附剂的团聚现象得到明显改善,且当pH=5时,对Pb~(2+)的吸附率可达99.1%,对Hg~(2+)的吸附率可达98.9%,而对Cr~(3+)的吸附率为20.4%,对Mn~(2+)的吸附率仅为13.2%.即使样品中混有干扰离子(K~+、Na~+或Mn~(2+))时,对Pb~(2+)、Hg~(2+)离子的吸附率仍均可达97%以上.当进样流速≤1.5 mL/min时,微流控芯片对Pb~(2+)或Hg~(2+)的吸附率可达98%以上;以0.5 mol/L的盐酸和2%的硫代尿素为洗脱液,控制流速在0.20.3 mL/min范围内时,芯片对Pb~(2+)或Hg~(2+)的洗脱率均达到92%以上.用于Pb~(2+)、Hg~(2+)离子的选择性固相萃取芯片的成功制备,有助于微流控技术在重金属污染监测领域的应用和推广.     

铁铜微电解处理Cu2+-EDTA溶液及其机理研究

电镀废水中常含有EDTA等络合剂,部分重金属呈现络合态,这给重金属的去除带来了极大的挑战.微电解法处理络合废水破络效果好,成本低廉.为此,采用铁铜微电解法处理EDTA络合铜溶液,通过微电解过程的金属离子变化及沉淀物红外光谱分析可知,在微电解过程中主要变化为铁屑溶解、Fe2+和Fe3+质量浓度升高、Cu~(2+)质量浓度降低,并伴随EDTA质量浓度略微下降和Fe(OH)3沉淀生成;采用MINTEQ软件模拟Cu~(2+)、Fe2+和Fe3+与EDTA的络合形态分布,发现加入Fe3+能使EDTA与Cu~(2+)解络,Fe3+与Cu~(2+)摩尔比越大,p H越低,解络效果越好;在碱性条件下加入Fe2+能使EDTA与铜解络.Fe2+与Cu~(2+)摩尔比越大,p H越高,解络效果越好.结合实验和模拟结果可以明确Fe3+在酸性条件下的解络作用和铁屑对游离态Cu~(2+)的还原作用是微电解去除Cu~(2+)-EDTA的主要原因.     

Retention of clay-solidified grouting curtain to Cd^2＋ , Pb^2＋ and Hg^2＋ in landfill of municipal solid waste

The effects of components and their ratio of groups on anti-seepage capability of clay-solidified grouting curtain and its permeability of heavy metal cations were investigated by permeating experiments, using reactive solute transport model to study the permeation of heavy metals (Cd²⁺, Pb²⁺ and Hg²⁺). The study of permeating for different mixture ratios of cement and clay indicates that hydraulic conductivity of clay-solidified groupting curtain with different ratios of solid to liquid or with the same ratio of solid to liquid but with different ratios of cement to clay is changed. The laboratory simulation test results also show that precipitates produced in heavy metal cation migration process in curtain block up water flowing passage which makes the hydraulic conductivity of the solution-permeated curtain decrease with the leakage time. The permeation velocities for different heavy metal cations vary with ionic concentration, exchange capacity and ion radius etc. The test results indicate that the permeation rapidity order of heavy metals cations in clay-solidified grouting curtain is Hg²⁺ > Pb²⁺ in the same experimental circumstance. In addition, permeability for different mixture ratios and antisepsis capabilities of clay-solidified grouting curtain were studied in tests. Foundation item: Project (2000-65) supported by the Fund for University Key Teacher by the Ministry of Education of China     

Competitive adsorption of heavy metal ions on peat

The uptake capacities, and the adsorption kinetics, of copper, Cu(Ⅱ), nickel, Ni(Ⅱ), and cadmium, Cd(Ⅱ), on peat have been studied under static conditions. The results show that the adsorption rates are rapid: equilibrium is reached in twenty minutes. The adsorption of copper, nickel and cadmium is pH dependent over the pH range from 2 to 6. The adsorption kinetics can be excellently described by the Elovich kinetic equation. The adsorption isotherm fits a Langmuir model very well. The adsorption capacifies follow the order Cu2 ＞Ni2 ＞Cd2 in single-component systems and the competitive adsorption capacities fall in the decreasing order Cu2 ＞ Ni2 ＞Cd2 in multi-component systems. The adsorption capacities of these three heavy metal ions on peat are consistent with their observed competitive adsorption capacities.     

Characterization and application of tourmaline and beryl from Brazilian pegmatite in adsorption process with divalent metals

In this study, the original tourmaline and beryl mineral samples have been collected from a Brazilian pegmatite. The objective of this study was to examine the adsorption behavior of Brazilian ciclosilicate samples, towards divalent metals (Pb²⁺, Mn²⁺, and Zn²⁺) in ethanol solution has been studies by a batch technique. The ciclosilicate samples were characterized by elemental analysis, Fourier transform infrared spectroscopy, helium picnometry, mercury porosity, and nitrogen adsorption–desorption. The Langmuir expression for adsorption isotherm was applied in order to determine the adsorption capacity to form a monolayer and the constant related to the adsorption intensity. In aqueous solution there was a significant adsorption increase with the temperature and pronounced synergistic effects were observed. The maximum number of moles adsorbed was determined to be 12.48 and 11.49 mmol/g for systems Pb²⁺/beryl and Pb²⁺/tourmaline, respectively. The energetic effects caused by metal cations adsorption were determined through calorimetric titrations. Thermodynamics indicated the existence of favorable conditions for such Pb²⁺-, Mn²⁺-, and Zn²⁺–OH interactions.     

Preparation and antimicrobial ability of natural proous antibacterial materials

The liquid ion exchange method, solid salt melt method and dry-wet circulation method were used to prepare natural porous antimicrobial materials with natural minerals, such as zeolite, spilite, palygorskite and montmorillonite, respectively. Atomic absorption spectrum and X-ray diffraction analysis were carried out to investigate the effects of Ag⁺, Cu²⁺ and Zn²⁺ on antimicrobial abilities of natural porous minerals, and the effect of preparation method on ion exchange capacity of antimicrobial material, respectively. The results show that for the ion exchange capacity, clay mineral is higher than fibrous mineral, i. e. both zeolite and montmorillonite are higher; the antimicrobial ability of material with Ag⁺ is the best; the exchange capacities of materials with Cu²⁺ or Zn²⁺ are all higher, but the antimicrobial ability of Cu²⁺ is better than that of Zn²⁺. Foundation item: Project (40072020) supported by the National Natural Science Foundation of China; project (2001AA322070) supported by the National High Technology Research and Development Program of China     

Effects of different conditions on Pb2+ adsorption from soil by irrigation of sewage in South China

Pb²⁺ adsorption onto a soil by irrigation of sewage in the Pearl River Delta of South China was examined as a function of the reaction time, solution pH, initial lead concentration, organic matter (humic acid) and competitive ions (Cu²⁺). The adsorption of Pb²⁺ onto the soil was investigated on batch equilibrium adsorption experiments. Results show that the Pb²⁺ adsorption on the soil is relatively rapid in the first 30 min and reaches equilibrium at 2 h, and the kinetics of the adsorption process on the soil is well characterized by the pseudo-second order reaction rate. Langmuir, Freundlich and Temkin isothermal models are fit for the adsorption of Pb²⁺ onto the soil, and the maximum amount of Pb²⁺ adsorption (Q _m) is 7.47 mg/g. The amount of Pb²⁺ adsorption increases with increasing the pH at the range of 1.2–4.5 and reaches a plateau at the range of 4.5–12. The presence of humic acid in soil decreases the adsorption of Pb²⁺ onto the soil at solution pH of 8 since the negatively charged humic acid with Pb²⁺ is difficult to be adsorbed on the negatively charged soil surface. The adsorption of Pb²⁺ onto the soil also decreases in the presence of Cu²⁺ due to the competition adsorption between Pb²⁺ and Cu²⁺.     

膨润土对废水中Cu2+的吸附性能研究

研究了钙基膨润土和钠基膨润土对废水中铜离子的吸附特性.结果表明,钠基膨润土和钙基膨润土的吸附行为都依赖于溶液的pH值,初始离子浓度和吸附剂用量.在低pH值时主要是H+与Cu2+竞争吸附位.pH值在3到7时基本的吸附机制是离子交换的过程.在高pH值(＞8.3)时,在膨润土颗粒表面形成氢氧化铜的吸附或沉淀.随初始金属离子浓...     

蛭石对重金属离子吸附作用的研究

以蛭石为吸附剂,研究了蛭石对Cu^2 ,Pb^2 ,Cd^2 的吸附作用,实验结果表明蛭石具有较强的吸附性能,吸附速度快,PH值是影响吸附的因素,探讨了蛭石的吸附作用机理,得出蛭石对C ^2 ,C^2 ,P^2 吸附符合Langmuir和Freundlich吸附等温式,离子交换是主要的吸附形式,通过蛭石对实际废水的处理结果表明蛭石可以用于实验废水的处理。     

Effect of Zn2+ content on the microstructure and magnetic properties of nanocrystalline Ni1−x Zn x Fe2O4 ferrite by a spraying-coprecipitation method

Nanocrystalline Ni1-xZnxFe2O4 ferrites with 0≤x≤1 were successfully prepared by a spraying-coprecipitation method.The microstructure was investigated by using XRD and TEM.Magnetic properties were measured with vibrating sample magnetometer(VSM) at room temperature.The results show that the grain size of nanocrystalline Ni1-xZnxFe2O4 ferrite calcined at 600 ℃ for 1.5 h is about 30 nm.Lattice parameter and specific saturation magnetization Ms of nanocrystalline Ni1-xZnxFe2O4 ferrite increase with the Zn2+ ions content at room temperature,and maximum Ms is 66.8 A·m2·kg-1 as the Zn2+ ions content is around 0.5,and coercivity Hc of the nanocrystalline Ni1-xZnxFe2O4 ferrite decreases with Zn2+ ions content.     

Microscopic evidence of destroying the order of magnetic sequence in CuO2 chain by Zn, Ni, Co Doping in Sr14Cu24O41 compound

The Zn2＋, Ni2＋ and Co3＋ doped Sr14Cu24041 compounds were synthesized by standard solid state method. X-ray diffraction results show that the changes in lattice parameters are very small. Selected area electron diffraction patterns （EDPs） show that the diffraction spots corresponding to the CuO2 chain substructure are extended to streaks along a＊ and b＊ directions for all the samples, while the diffraction spots produced merely by the Cu203 ladder substructure are still very sharp. This means that the periodicities of chains in a＊ and b＊ directions are partially destroyed upon doping ofZn, Ni and Co due to that the initial phase of each chain becomes a random variable. The temperature dependence of magnetic properties was measured for every sample. And the number of dimers in CuO2 chain per formula unit （f.u.） and dimer coupling constant are obtained by fitting the temperature dependence of the magnetic susceptibility. It is found that the degree of initial phase disorder is related to the order degree of magnetic sequence in CuO2 chain. For the un-doped sample, the decoupling of dimers is weak, the magnetic sequence is slightly destroyed, and the streaks in EDP are also very weak, which implies the degree of initial phase disorder in CuO2 chain is very low. When Zn2~ and Ni2＋ ions are doped, the number of dimers per f.u. decreases, and the intensity of diffraction streaks increases in comparison with the corresponding spots. Furthermore, when the high spin magnetic ions Co3＋ are doped, the number of holes in Sr14Cu24041 decreases, the magnetic sequence is destroyed very seriously, and the spots in EDP are extended to streaks almost completely. The phenomenon that the diffraction spots ofCuO2 chain extend to streaks in EDP appears as evidence that the magnetic sequence in the CuO2 chain is destroyed by doping of Zn, Ni, Co.     

Laser welding of Zr41Ti14Cu12Ni10Be23 bulk metallic glass and zirconium metal

The laser bonding technology between the Zr41 Ti14 Cu12 Ni10 Be23 bulk metallic glass and zirconium metal was investigated under welding parameters of 1.3 kW and 7 m/min. The welded bead, microstructure, and micro-hardness of the welded joint were examined by Keyence, transmission electron microscopy, scanning electron microscopy, and Vickers hardness, respectively. The experimental results showed that the Zr41 Ti14 Cu12 Ni10 Be2 bulk metallic glass and zirconium metal were successfully bonded together. The Zr41 Ti14 Cu12 Ni10 Be2 in the base material zone maintained amorphous structure, and the welding fusion zone kept the hardness as high as as-received BMG. Therefore, the laser welding technology can be used to achieve successful bonding of bulk metallic glasses and crystallization metal.     

Removal of Pb^2＋ and Cd^2＋ by adsorption on clay-solidified grouting curtain for waste landfills

Pb^2＋ and Cd^2＋ in leachate were adsorbed on clay-solidified grouting curtain for waste landfills with equilibrium experiment. The cation exchange capacity was determined with ammonium acetate. And the concentration of heavy metal cations in leachate was determined with atomic absorption spectrophotometer. Their equilibrium isotherms were measured, and the experimental isotherm data were analyzed by using Freundlich and Langmuir models. The results show that the adsorption capacities of the heavy metal cations are closely related to the compositions of clay-solidified grouting curtain, and the maximum adsorption appears at the ratio of cement to clay of 2 ： 4 in the experimental conditions. At their maximum adsorption and pH 5.0, the adsorption capacities of Pb^2＋ and Cd^2＋ are 16.19 mg/g and 1.21 mg/g. The competitive adsorption coefficients indicate that the adsorption of clay-solidified grouting curtain for Pb^2＋ is stronger than that for Cd^2＋. The adsorption process conforms to Freundlich＇s model with related coefficient higher than 0. 996.     

赤泥在脱除废水中重金属离子的应用研究

为去除废水中的重金属对环境的危害,采用具有高的比表面积和孔隙率、较好的吸附性能廉价赤泥作为废水中重金属离子的吸附剂。实验结果表明,赤泥对Pb^2＋,Cd^2＋,Cr^3＋,Zn^2＋,Ni^2＋的对数吸附等温线都近似直线,基本符合Freundlich公式,且在室温条件下进行就能很快达到吸附平衡,不需要进行温度和pH的调节。当赤泥的添加量为2,0g／L时,Pb^2＋,Cr^3＋和Cd^2＋的吸附率分别达到90％,94％,85％以上。赤泥对重金属离子的吸附率随废水中其初始浓度的增大而减小。     

Determination of the entropy change for electrode reaction and dilute enthalpy of some ions by thermo-eletrochemical technology

Based on thermo-electrochemical equation for an electrode reaction, the entropy change of it can be obtained by the thermo - electrochemical technology (TECT). The entropy changes of Fe (CN) ₆ ⁻³ /Fe (CN) ₆ ⁻⁴ , H⁺/H₂(P⁰), Cu⁺²/Cu and Zn⁺²/Zn electrode reaction systems and the dilute enthalpies of the H⁺, Cu²⁺ and Zn²⁺ ions under the ion concentrations studied have been determined by a specially designed thermo-electrochemical equipment. The enthalpy change and entropy change for the five systems at unlimitedly diluted concentrations agree well with the literature. Project supporterd by the National Natural Science Foundation of China Synopsis of the first author Fang Zheng, Ph. D. and professor, born in April 1944, majoring the metallurgical thermodynamics and thermoelectrochemistry, supervised and participated in three projects supported by the National Natural Science Fundation of China and some other projects. More than 70 academic papers have been published.     

化学沉淀-铁氧体法处理重金属废水试验研究

重金属离子排放到环境中只能改变形态或被转移、稀释、积累,对生物危害很大。为了处理含多种重金属离子的废水,本试验采用化学沉淀-铁氧体法处理主要含铅、锌、镉离子的废水。以云南弛宏锌锗股份有限公司废水为原水,在对影响处理效果的各种要素如温度、pH值、搅拌时间进行了条件试验后,得出了去除重金属离子废水静态试验的最佳条件。