Fe(Ⅱ)-H_2O_2不同温度浸润改性活性炭吸附去除水中砷(Ⅴ)

Fe(Ⅱ)-H2O2不同温度浸润改性活性炭是采用FeSO4·7H2O添加H2O2在温度100℃下纯浸润24 h(Fe(Ⅱ)-24 h)和高温蒸发15 min(Fe(Ⅱ)-15 min)制备.对2类材料进行SEM表征并对其吸附1.1 mg/L砷(Ⅴ)的性能进行比较.SEM显示Fe(Ⅱ)(0.485%)-24 h(0.485%为Fe(Ⅱ)-24 h的铁含量,下同)表面覆盖厚的棒状纳米羟基铁,Fe(Ⅱ)(1.35%)-15 min表面覆盖薄而烧结扭曲羟基铁;高温蒸发15 min有利于铁负载;Fe(Ⅱ)-24 h(108~142 mg/gFe)对砷(Ⅴ)吸附的铁效率是Fe(Ⅱ)-15 min(57~63 mg/gFe)的2倍;Fe(Ⅱ)(0.485%)-24 h在2pH3.5或9pH12时对砷(Ⅴ)的吸附平衡容量高于Fe(Ⅱ)(1.35%)-15 min,同时Fe(Ⅱ)(0.485%)-24 h在不同pH值的条件下铁的溶出量低于Fe(Ⅱ)(1.35%)-15 min;SO42-、NO3-、ClO4-、PO43-抑制Fe(Ⅱ)(0.485%)-24 h对砷(Ⅴ)的去除,PO43-抑制效果更为明显,Cl-(100 mg/L)和BrO3-促进其对砷(Ⅴ)的去除.     

Effects of Surface-Bound Fe2+ on Nitrate Reduction and Transformation of Iron Oxide(s) in Zero-Valent Iron Systems at Near-Neutral pH

Nitrate reduction in an iron/nitrate/water system with or without an organic buffer was investigated using multiple batch reactors under strict anoxic conditions. Nitrate reduction was very limited (<10%) at near-neutral pH in the absence of the organic buffer. However, nitrate reduction was greatly enhanced if the system: (1) had a low initial pH ( ～ 2–3); (2) was primed with adequate aqueous Fe2+; or (3) was in the presence of the organic buffer. In Cases (1) and (3), nitrate reduction usually was involved in three stages. The first stage was quick, and H+ ions directly participated in the corrosion of iron grains. The second stage was very slow due to the formation of amorphous oxides on the surface of iron grains, while the third stage was characterized by a rapid nitrate reduction concurrent with the disappearance of aqueous Fe2+. Results indicate that reduction of nitrate by Fe0 will form magnetite; Fe2+ (aq.) can accelerate reduction of nitrate and will be substoichiometrically consumed. Once nitrate is exhausted in the system, no more Fe2+ will be consumed. In the presence of nitrate, Fe2+ (aq) will be adsorbed onto the surface of iron grains or iron oxides; the surface-complexed Fe(II) (extracted by acetate with pH = 4.1) might be oxidized and become structural Fe(III), resulting in a steadily increasing ratio of Fe(III)/Fe(II) in the oxides formed. The transformation of nonstoichiometric amorphous iron oxides into crystalline magnetite, a nonpassive oxide, triggers the rapid nitrate removal thereafter.     

Thermochemical Properties of Ternary Complexes of RE Perchlorate withGlycine and Imidazole

Ｒａｒｅｅａｒｔｈｉｏｎｓｐｏｓｅｓｓｏｍｅｓｐｅｃｉａｌｆｕｎｃｔｉｏｎｓｉｎｂｉｏｌｏｇｉｃａｌｂｏｄｙ．Ａｍｉｎｏａｃｉｄｓａｒｅｔｈｅｓｔｒｕｃｔｕｒｅｕｎｉｔｏｆｐｒｏｔｅｉｎｓ．Ｉｍｉｄａｚｏｌｅｉｓｈｅｔｅｒｏｃｌｙｃｌｉｃｃｏｍｐ...     

Terminal Electron Acceptor Mass Balance: Light Nonaqueous Phase Liquids and Natural Attenuation

Light nonaqueous phase liquids (LNAPLs) in subsurface systems may contain a relatively large amount of biodegradable organic material. During the biochemical oxidation of the organic compounds in the LNAPL, electrons are transferred to terminal electron acceptors (TEA) [i.e., O2, NO3?, Mn(IV), Fe(III), SO4?2, CO2] via coupled redox reactions. A mass balance between the TEA required for mineralization of benzene, toluene, ethyl benzene, and xylene (BTEX) compounds contained in the subsurface (ground water, soil, LNAPL) and the total TEA available from the ground water and aquifer sediments is proposed and evaluated. The total TEA available is predominantly attributed to the solid phase material; the aqueous phase TEA constitutes a minor amount; and the TEA required for BTEX mineralization is predominantly from the LNAPL. Consequently, a TEA deficit exists in the LNAPL source area. Under these conditions, it may be invalid to assume an infinite supply of TEA and sustained bioattenuation rates. LNAPL removal is one remedial option to reduce the TEA deficit in the source area.     

Relating Batch and Column Diffusion Coefficients for Leachable Contaminants in Particulate Waste Materials

For constructed facilities in which waste materials are used as partial substitutes for traditional aggregates, it is usually necessary to perform contaminant leachability tests to assess the long-term emission of contaminants from the facilities during service. Such tests can be performed under batch and column flow-through conditions. It is usually desirable to establish the relationship between leached contaminant concentrations obtained through both tests. Using Al and Cu diffusion coefficients as the target parameter, an analytical model is developed and presented herein with experimental data from acidic solution (pH of 4.5) leach testing of asphalt concrete that was amended with municipal solid waste incinerator bottom ash in weight percentages ranging from 0 to 20 to assess the equivalence of both sets of leaching conditions. The results for Al show that at higher column flowrates indexed by Peclet numbers in excess of 5.5, there is no defined relationship between Al diffusion coefficients obtained through both methods. Fluid flow at lower Peclet numbers approach batch conditions and afford an opportunity for the use of the analytical model presented in this paper provided comparisons are made at equivalent liquid/solid ratios. The values of the batch diffusion coefficients obtained for Al are of the order of 10?10–10?6?cm2/s. For column leaching of Al, the range is 10?8–10?7?cm2/s. No measurable quantity of Cu was obtained under both batch and column leaching conditions.     

Enhancement of Nitrate Reduction in Fe0-Packed Columns by Selected Cations

Tests were conducted in Fe0-packed columns to investigate the effects of adding selected cations on nitrate removal by Fe0. Due to a rapid passivation of Fe0, only negligible nitrate was reduced in the columns without adding the selected cation. However, adding certain selected cations (Fe2+, Fe3+, or Al3+) in feed solution can significantly enhance nitrate reduction. Extending hydraulic retention time (HRT) increased nitrate removal by the columns, but the increase was not linearly proportional to HRT. Decreases in columns’ hydraulic conductivity (K) were monitored in an 8?month operating period. A modest decrease in K was recorded in the upper and the middle section of the media bed, whereas a significant decrease in K occurred in the inlet section. X-ray diffraction analyses indicate that magnetite (Fe3O4) was the dominant species of the iron corrosion products in the entire height of the column media under anoxic and other test conditions. In the inlet section, however, lepidocrocite and goethite were also identified. Cementation was found to occur only in the inlet section, suggesting that lepidocrocite and goethite, rather than magnetite, might be responsible for the cementation and thereby cause the hydraulic clogging. The magnetite coating would not necessarily cause clogging of the media.     

Nitrogen Removal in Recirculating Sand Filter Systems with Upflow Anaerobic Components

Septic systems can present a risk to human health by releasing highly soluble nitrate–nitrogen into the groundwater. A research and demonstration study undertaken in Black River Falls, Wisconsin, evaluated several promising biofilter technologies for on-site nitrogen removal. Duplicate recirculating sand filter-upflow anaerobic systems with a design hydraulic loading rate of 954?L/day (250?gal/day) were used to treat septic tank effluent from a correctional institution and produced a treated wastewater with a total nitrogen concentration of 15.2?mg/L for System 1 and 18.2?mg/L for System 2, or 72.0 and 63.0% nitrogen removal, respectively. The differences between the two systems appear to have been the result of process configuration changes made over the duration of the study. This paper evaluates the nitrogen removal performance of the recirculating sand filter-upflow anaerobic systems and the effect of operational and environmental factors, including the recirculation ratio, BOD5/NO3?, and temperature. Nitrogen removal was limited by the recirculation ratio with the maximum total nitrogen removal of 70.1% when the recirculation ratio = 3. Improved performance was also noted for temperatures ≥ 20°C and BOD5/NO3? ≥ 8. Low temperatures adversely affected nitrification and low BOD5/NO3? adversely affected denitrification. The relationships among nitrogen removal, recirculation ratio, BOD5/NO3?, and temperature are also discussed.     

氯化钠—丙醇体系溶剂浮选铋Ⅲ

研究了氯化钠—丙醇体系溶剂浮选铋的行为及丙醇水溶液的分相条件。实验表明 ,当溶液pH =5～ 7时 ,Bi 水解生成碱式盐〔Bi(OH) 2 Cl〕沉淀可以溶剂浮选于丙醇与水两相界面之间。此时 ,Bi 可与Cd ,Mn ,Mo ,Fe ,Ni ,Zn 等得到满意的分离     

Citric Acid Enhanced Remediation of Soils Contaminated with Uranium by Soil Flushing and Soil Washing

Laboratory bench-scale soil washing (batch) and flushing (column flow) experiments were conducted to determine the efficiency of citric acid as an agent to extract uranium from a synthetically contaminated sandy soil. The results of soil washing and flushing experiments indicate that citric acid is highly effective in removing uranium, and that the extraction efficiency increases with increasing citric acid concentration, especially under slightly acidic to alkaline conditions in systems containing sand coated with secondary minerals (e.g., Fe). The enhanced U(VI) desorption in the presence of citrate may be explained through several processes, including the complexation of U(VI) with citrate and extraction of secondary coatings (e.g., Fe), which results in the liberation of Fe-citrate complexes into solution. In batch washing systems, the presence of 10?3?M citric acid enhances the extraction of uranium 2.8 times greater than water alone for the conditions of the experiment. A comparison of soil washing and flushing shows that the extraction efficiency is higher in bench-scale washing experiments. A removal efficiency of up to 98% was achieved with 10 mL of 10?3?M citric acid in batch systems, whereas it required 4 pore volumes (150 mL) of 0.1 M citric acid to accomplish similar extraction efficiencies in column soil flushing systems.     

Porous Reactive Walls for the Prevention of Acid Mine Drainage: A Review

Abstract

Laboratory tests and field-scale demonstrations indicate that permeable reactive walls, designed to induce bacterially mediated sulfate reduction within aquifers, have the potential to prevent the discharge of acidic, metal-rich waters. Laboratory batch studies were conducted to determine optimal mixtures of organic materials. Column studies were conducted to evaluate the potential for sulfate reduction and metal sulfide precipitation under dynamic flow conditions at groundwater velocities similar to those observed in the field. These laboratory studies established that sulfate reduction and metal sulfide precipitation mechanisms result in decreases in the concentrations of sulfate and iron and other metals. In the column experiments, sulfate and Fe were removed from synthetic mine drainage water at rates of 500-800 mmol/day/m³. In a pilot-scale field study, test cells installed into an aquifer containing a plume of mine waste-impacted groundwater, induced sulfate reduction and metal-sulfide precipitation. Within a flow path of less than one metre sulfate reduction and metal sulfide precipitation reactions resulted in the removal of iron, and production of alkalinity to the extent that the acid generating potential of the plume water was removed. A full-scale porous reactive wall was installed at the same site in August 1995. Comparing water entering the wall to treated water exiting the wall; sulfate concentrations decrease from 2,400-4,500 mg/L to 200-3,600 mg/L and Fe concentrations decrease from 250- 1,300 mg/L to 1.0 - 40 mg/L. After passing through the reactive wall, groundwater is transformed from acid producing to acid consuming.     

Electrochemical Removal of AlCl3 from LiCl-KCl Melts

In order to remove impurity AlCl₃ from LiCl-KCl melts before Li electrolysis, the Al³⁺ reduction potential on a tungsten electrode and the relation between Al³⁺ reduction peak current and AlCl₃ concentration in LiCl-KCl-AlCl₃ melts were determined by cyclic voltammetry (CV). Constant potential electrolysis at –1.6 V vs Cl₂/Cl^– on both solid Fe and liquid Zn cathodes was performed to remove AlCl₃ impurity from the LiCl-KCl-AlCl₃ melts. The removal rate of Al³⁺ from the melts was analyzed by both electrochemical methods and inductively coupled plasma–atomic emission spectrometry (ICP-AES) analysis. The results showed that 96.11 wt pct of Al were removed on a Fe cathode and 99.90 wt pct on a Zn cathode through 10 hours electrolysis, respectively. While stirring the melts by argon gas, 99.21 wt pct of Al³⁺ was separated from the melts by 4 hours of electrolysis at 723 K (450 °C), which effectively expedited the Al³⁺ electrochemical reduction rate and shortened the electrolysis time.     

高炉灰与转炉灰微波协同处理提取锌、铁有价组分

为了最大程度地发挥高炉灰与转炉灰的经济价值, 提高冶金固废资源利用率, 以高炉灰和转炉灰为原料, 采用微波法还原高炉灰与转炉灰中Zn、Fe等有价值元素并对其回收。此法利用微波热扩散均匀、升温速率快的特性, 大大降低反应时间, 同时还充分利用粉尘中的C进行自还原反应, 无需外配。通过正交实验探究不同因素对脱锌率的影响, 寻找还原Zn、Fe的较优条件; Zn提取完成后, 采用磁选法提取还原渣中的Fe。结果表明: 高炉灰和转炉灰配比为7:3, 还原温度区间为950~1 100℃时, 混合灰中的C可将Zn、Fe完全还原; 正交实验得到Zn脱除率因素由大到小顺序为还原温度、保温时间、料层高度、水分; 脱Zn较优工艺条件是: 还原温度1 100℃, 保温时间40 min, 料层高度0.5 cm, 水分含量为10%, 此时Zn脱除率为99.37%;还原渣经磁选后Fe回收率可达92.04%, 可作为铁精矿返回炼铁工序使用。      

A Numerical Model Describing Multiphase Binary Diffusion in Liquid Metal/Solid Metal Couples

A numerical model for multiphase binary diffusion in liquid metal/solid metal infinite couples is developed by introducing a bisection method which determines a location of the Matano interface. The model makes use of phase diagram sources and kinetic data without any adjustable parameters. The model gives displacements of the interphase interfaces including the liquid/solid interface relative to the x = 0 plane, a change in the mass of a solid metal and a distance-composition profile at diffusion time given. The calculated rates of phase layer growth agreed reasonably well with the measured rates by other researchers in liquid Sn saturated with Cu/solid Cu couples and liquid Zn/solid Fe couples in the diffusion-controlled stage.     

微量Fe元素对氧化钨粉还原过程的影响

采用液–固掺杂结合两步氢还原法分别制备未添加和添加质量分数0.1％和1.0％Fe的金属W粉,研究了微量Fe元素对WO3还原过程及产物结构特征的影响.结果表明:WO3前驱体粉体经掺杂和煅烧处理后,在其颗粒表层晶格中形成了含Fe固溶体;在氢气还原过程中,Fe的固溶能够降低WO2.9→WO2和WO2→W的还原温度,促进WO3...     

碱金属对铁氧化物气-固还原行为的影响

 利用热重分析的方法研究了Fe2O3在竖式电阻炉内被CO/CO2混合气体还原,Na2O对其还原行为的影响,共设计了4个成分,分别为纯Fe2O3、Fe2O3-1％Na2O、Fe2O3-3％Na2O和Fe2O3-5％Na2O。在还原过程中由于还原失氧引起的试验小饼失重量被实时记录下来,根据这些数据可以计算出还原反应速率以及化学反应的速率常数,以此来判断Na2O对Fe2O3还原性的影响。同时利用扫描电镜观察了还原后试样的微观形貌变化。研究发现：Na2O的存在将阻碍Fe2O3的还原。通过对还原后小饼的显微形貌观察,结合FeO-Na2O二元相图,发现这种负面影响主要是由于在还原过程中产生液相引起的。另外,还检测了还原前后试验小饼的孔隙率和体积变化。检测结果确认：还原后含Na2O的试验小饼的孔隙率和体积都有所下降。分析认为这种现象同样归因于还原过程中液相的产生。     

固相萃取-原子荧光光谱法测定不锈钢中痕量砷

通过氢化物发生原子荧光光谱法测定不锈钢样品中痕量砷,采用On-Guard H柱去除消解液中重金属,避免了共存金属元素和大量基体元素铁对砷测定的干扰,且On-Guard H柱对测定无明显干扰。结果表明:砷检出限为0.02μg/L,采用该方法测定不锈钢标准样品,测定结果与理论值相符合。该方法操作简单,且大大提高了不锈钢中痕量砷测定的灵敏度和准确度。     

Application of Natural Clayey Soil as Adsorbent for the Removal of Copper from Wastewater

Use of clayey soil has been explored in the laboratory scale experiment as a low cost adsorbent for the removal of copper from wastewater. The influence of metal ion concentration, weight of adsorbent, stirring rates, influence of temperature, pH are also evaluated and the results are fitted using adsorption isotherm models. From the experimental results it is observed that almost 90–99% copper can be removed from the solution using clay at optimized pH 5.5. Langmuir adsorption isotherm, Freundlich isotherm and Tempkin isotherm model have been used to describe the distribution of copper between the liquid and solid phases in batch studies and it has been observed that Langmuir isotherm better represents the phenomenon. From the experimental results rate constant, activation energy, Gibbs free energy, enthalpy, and entropy of the reaction are calculated to determine the mechanism of the sorption process. Thomas, Adams-Bohart, and Yoon-Nelson models are applied to the experimental data to determine the characteristic parameters of the column for process design.     

Aerobic Methane Oxidation Coupled to Denitrification: Kinetics and Effect of Oxygen Supply

Aerobic methane oxidation coupled to denitrification (AME-D) is a process in which aerobic methanotrophs oxidize methane and release organic compounds that are used by coexisting denitrifiers as electron donors for denitrification. This process is potentially promising for denitrification of wastewater or landfill leachate poor in organic carbon using methane produced onsite as external electron donor. We studied the kinetics of an aerobic methane-oxidizing denitrifying culture and investigated the effect of dissolved oxygen (DO) concentration and air supply rate on AME-D using a batch reactor and a semicontinuous reactor setup. At methane concentrations of 18–33% in air and air flow rates of 15–35?mL?air?L?1?liquid?min?1, the DO concentration was less than 0.01?mg?L?1 and the nitrate removal reached a maximum value of 56.7?mg?NO3–N?g?1?VSS?d?1 with 79% being attributed to denitrification. When the air supply rate was increased to 70?mL?air?L?1?liquid?min?1 resulting in a drop in methane content to 10%, the DO concentration in the bioreactor rose to about 0.8–1.0?mg?L?1 and the total nitrate removal dropped to about 10?mg?NO3–N?g?1?VSS?d?1 with none of it being attributed to denitrification.     

高效液膜法分离富集与测定钢、钼中的痕量锌

用HDEHDTP、PX - 10 0和n -Hexane高效液膜体系研究Zn2 的迁移行为。在适宜条件下10min内Zn2 的迁移率达 99.5 %以上。液膜体系 :膜相为 7%HDEHDTP、2 %PX - 10 0和 91%n -Hexane;内相为 0 .2mol/LH2 SO4溶液 ;外相为pH 3～ 4。实验表明 ,Fe3 、Al3 、Cu2 、Cd2 、Mo6 、Co2 、Ni2 、Hg2 等 ,碱金属、碱土金属 ;Cl-、NO-3 、ClO-4、F-、SiO2 -3 、SO2 -4等离子都不影响 ,只有Zn2 能从这些离子中得到满意的分离富集。此法已用于富集、测定钢铁和钼中痕量锌 ,结果相当满意。     

Leaching of a limonitic laterite in ammoniacal solutions with metallic iron

The leaching of a limonitic laterite (containing approximately 1% Ni, 0.1% Co and 50% Fe) was studied in ammoniacal solution. The laterite was leached in the presence of metallic iron which acted as a reductant. The kinetic parameters studied included the effect of temperature, metallic iron concentration, total ammonia concentration and ammonium sulphate to ammonium hydroxide ratios. Tests were performed in a batch cell with temperature ranging from 50 to 80 °C at atmospheric pressure. The kinetic behavior for nickel and cobalt extraction was observed to be different. Cobalt extraction was initially faster than nickel and it showed good extractions at lower temperatures, however, after reaching a maximum value of approximately 80%, extraction decayed by as much as 50%. This was likely due to cobalt co-precipitation and/or adsorption into iron and/or manganese oxides and hydroxides which could form during the process. Cobalt losses tended to increase with temperature, total ammonia concentration, ammonium hydroxide to ammonium sulphate ratio and metallic iron concentration. Nickel extraction was increased by higher temperature, total ammonia concentration and metallic iron concentration up to a maximum of roughly 70% after 48 h at 80 °C.Through feed and solid residue analysis, by X-ray diffraction and SEM, it was possible to characterize and understand how the feed mineral reduction occurred. The main phases present in the feed and residue were goethite and magnetite, respectively. Results suggest that the reduction occurs through two main reactions. First, the reaction between goethite and metallic iron produced Fe(II) ammines. The Fe(II) ammines are capable of reducing goethite and producing magnetite. The Fe(II) ammines play an important role because they accelerate the reduction and favor the extraction kinetics of nickel. The main advantage of using metallic iron as a reducing agent is the possibility of generating an autocatalytic system.