Bioaccumulation of As(III)/As(V) ions by living cells of Corynebacterium glutamicum MTCC 2745

Significant factors on simultaneous growth and bioaccumulation of arsenic ions by living cells of bacteria, Corynebacterium glutamicum MTCC 2745, were explored in growth media under experimental conditions like pH and concentrations of arsenic ions. Combined effects of the initial concentrations of peptone and arsenic (either As(III) or As(V)) ions on the specific growth rate and arsenic bioaccumulation competence of the bacteria were studied and optimized using the Response Surface Methodology. Optimum combination predicted via RSM demonstrated that the bacteria were capable of bioaccumulating As(III) and As(V) in the growth medium containing 1000 mg/L arsenic and 9 g/L peptone up to 78.4% and 77.6%, respectively.     

硅烷偶联剂改性硅藻土及其去除水中As(Ⅴ)的研究

以硅藻土为基体,γ-氨丙基三甲氧基硅烷(APES)作为改性剂,对硅藻土表面进行修饰,制备了针对As(V)吸附材料.采用单因素试验法,得到改性的最佳条件为:硅藻土为3 g,γ-氨丙基三甲氧基硅烷(APES)为4 mL,pH值为11,反应时间6 h,反应温度为30 ℃,该材料对As(V)的去除率可以达到87.11%.用扫描电镜(SEM)和傅里叶红外光谱仪(FT-IR)对材料进行表征,显示:改性前后的硅藻整体结构不发生变化;硅藻经改性后活性羟基峰消失,表面生成新的-NH2吸收峰.用Freundlich吸附模型能更好的描述吸附行为,吸附过程符合准二级动力学方程.     

氢化物发生-原子荧光光谱法测定土壤中水溶态As(Ⅲ)和As(Ⅴ)的方法研究

本文提出了氢化物发生—原子荧光光谱法测定微量砷的价态分析方法。研究比较了离子交换分离法和控制酸度差减法测定As(Ⅲ)利As(Ⅴ)的分析性能。将控制酸度差减法应用于测定土壤样品水溶态中As(Ⅲ)和总砷的含量，As(Ⅴ)的含量由两者之差求得。该法简单可靠，容易操作，分析速度快，精密度较高。本方法的检出限为0．10ng；样品各态的总砷测的相对标准偏差在11．4-18．9％之间。     

Vanadium(V) Removal by Adsorption onto Activated Carbon Derived from Starch Industry Waste Sludge

This study examines the adsorption potential of activated carbons for vanadium (V) removal from aqueous solution. Activated carbons were produced via chemical activation of waste treatment sludge from the starch industry. Specific surface area and pore sizes of waste sludge samples were determined through chemical activation and pyrolysis. Experimental data indicated that sludge samples had micropore structure and specific surface area of up to 1196 m²/g. First-order and second-order models were applied to determine adsorption kinetics. Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were used to analyze equilibrium data of adsorption. Equilibrium adsorption data showed the best fit to the Freundlich isotherm. Adsorption of vanadium (V) follows second-order kinetic models. Maximum adsorption was observed at pH 4.0. Langmuir adsorption capacity was found to be 37.17 mg/g. The results of the study indicated that activated carbon obtained from industrial sewage sludge was effective in removing vanadium from aqueous solutions, which creates a significant advantage for treatment of industrial wastewaters and management of solid wastes.     

焙烧态Ca-Mg-Al类水滑石的制备及其吸附As(V)的研究

实验合成了一种焙烧态Ca-Mg-Al类水滑石,通过吸附动力学、吸附热力学及pH值的影响实验研究其对As (V)的吸附性能;并通过X射线衍射(XRD)、比表面积及孔径(BET)、场发射扫面电子显微镜(FESEM)、傅里叶红外光谱(FTIR)和X射线光电子能谱(XPS)等测试对合成材料进行表征并分析其吸附机理.实验结果表明,焙烧态Ca-Mg-Al 类水滑石对As(V)具有较强的吸附能力,其最大吸附量为71.86 mg/g,其吸附行为较符合Freundlich吸附等温方程和准一级动力学方程,且在不同的pH值下均能保持较好的吸附能力.焙烧态Ca-Mg-Al 类水滑石吸附As(V)的吸附机理主要包括类水滑石晶体结构的重建以及其表面羟基官能团的络合作用.     

Removal of Arsenic(III), Chromium(III) and Iron(III) Traces from Hydrofluoric Acid Solutions by Specialty Anion Exchangers

The removal of As(III), Fe(III), and Cr(III) at trace levels from HF solutions by means of specialty ion exchange resins has been investigated. These impurities are usually found in technical‐grade HF, and they need to be removed to prepare metal‐free HF for the semiconductor industry. It was assumed that Fe(III) and As(III) species in dilute HF were present in anionic form, while Cr(III) was probably in neutral form, CrF₃. First, a selection of specialty ion exchangers was performed. Then, fixed‐bed experiments were carried out to check the ability of selected resins to reach the impurity levels required in SEMI C29 for 5 wt.% HF (5 ppb of As, and 10 ppb of Cr and Fe). The effect of the flow rate and the HF concentration on the metal removal was studied with Purolite D‐3777 and Fuji PEI‐CS‐07 resins respectively. Fuji PEI‐CS‐07 showed the best performance for Fe(III) removal, even at high HF concentration (25 wt.%). A strong decrease in the Cr(III) and As(III) removal capacity with increasing concentration of HF was observed.     

Selective Competitive Biosorption of Au(III) and Cu(II) in Binary Systems by Magnetospirillum gryphiswaldense

The biosorption of Au(III) and Cu(II) ions in both single and binary systems by Magnetospirillum gryphiswaldense (MSR-1) was investigated. For comparison with the selective reinforced competitive biosorption process in a binary system, the experimental research first explored the biosorption of Au(III) and Cu(II) in a single system under various conditions. The biomass exhibited the highest single Au(III) and Cu(II) ion adsorption yields at room temperature (25°C), pH values of 2.5 and 5.0, respectively, and a biomass concentration of 10 g · L^?1 (3.83 g · L^?1, dry basis). The experimental data from the single component system for the two metallic ions fitted well to a Langmuir isotherm and a pseudo second-order kinetic models. In the Au(III)-Cu(II) binary system, the coexistence of Cu(II) cations promoted the adsorption of Au(III) within a certain range of ratios. A new sigmoidal Cu(II) biosorption isotherm was determined specifically to reveal the Cu(II) adsorption behavior in this case.     

Removal of As(V) by PVDF hollow fibers membrane contactors using Aliquat-336 as extractant

In this work, the removal of As(V) from an aqueous stream by non-dispersive solvent extraction in a hollow fibre membrane contactor was investigated. To this purpose, microporous hydrophobic poly(vinylidene fluoride) hollow fibres were prepared by the dry/wet spinning technique. Fibres were spun, changing the pore forming additives, to obtain micro-porous sponge-like structure membranes, with pore diameters of about 0.2 μm and porosity of 80%. The produced fibres were used to perform As(V) extraction experiments in a membrane contactor device, using Aliquat-336 as extractant. Different tests were carried out in order to study the effect of temperature, initial concentration, pH of the feed solution and membrane properties. The results showed that the extraction of As(V) by non-dispersive solvent extraction was influenced by the pH of the feed, with an optimum reached for neutral values, increased with the arsenic content in the feed and was not affected by temperature. The extraction was favoured by working with thinner membranes. The highest removal of arsenic achieved was around 70% after 6 h of operation. The produced fibres kept their performance for all the experimental activity, giving reproducible results with time.     

Optimizing adsorption of arsenic(III) by NH2-MCM-41 using response surface methodology

Response surface methodology (RSM) was used to optimize process parameters for arsenic (As(III)) removal from aqueous solution using amine-functionalized MCM-41 (NH₂-MCM-41). Four independent variables such as pH, initial metal concentration, temperature and adsorbent dosage were investigated. The optimal conditions to remove As(III) by NH₂-MCM-41 was found to be pH 5.62, initial As(III) concentration 5.00 mg/L, temperature 20 °C and NH₂-MCM-41 dosage 5.00 g/L. XRD, FTIR and SEM analyses testified to the obvious change of the surface morphology and the presence of metal on the sorbent after adsorption.     

Separation of La(III), Eu(III), and Ho(III) with Sorbents Impregnated by Mixtures of Acidic Phosphoryl Podands and Amines in Nitric Acid Solutions

ABSTRACT

The possibility of separation of La(III), Eu(III), and Ho(III) as respective individual representatives of light, medium, and heavy rare earth elements was studied using sorbents impregnated by mixtures of acidic phosphoryl podands derived from diethylene glycol and octyl, dioctyl, and trioctyl amines from nitric acid solutions of various concentrations. The influence of the phosphoryl podands structure, their percentage content, and proportion in a sorbent and the nature of an acid on the efficiency of separation of La(III), Eu(III), Ho(III) was studied. It is shown that the greater is the concentration of HNO₃, the smaller are the separation factors of REEs, and remarkably so. The most efficient separation is achieved with the concentration of HNO₃ not over 0.04 mol/L. The optimal conditions of separation of La(III), Eu(III), and Ho(III) with the developed sorbent were found. Repeated use of the sorbent for the separation of La(III), Eu(III), and Ho(III) after its regeneration with 0.04 mol/L HNO₃ was estimated. It was found that the efficiency of separation of REEs with the sorbents impregnated by a mixture of 1,5-bis(2-oxyethoxyphosphoryl-4-ethylphenoxy)-3-oxapentane and trioctylamine (TOA) exceeds markedly that made of a mixture of di-(2-ethylhexyl)phosphoric acid (DEHPA) and TOA.     

Multivariate Optimization and Adsorption Characterization of As(III) by Using Fraxinus Tree Leaves

This study introduces Fraxinus tree leaves as a new, efficient biosorbent of As(III). A suitable response surface was achieved by running a central composite design. Simultaneous optimization of both responses (R% and q) was carried out and 67% of the goal of desirability function was attained. The results obtained for simultaneous optimization are R = 70% and q = 80.6 mg g^?1 with 67% desirability in m = 600 mg L^?1 where s = 0.10 g and pH = 3.9. Langmuir and Freundlich isotherms model were applied in explaining the sorbent–sorbate equilibrium study, and maximum capacity uptake equals 99.97 mg g^?1 and K_L = 0.05 L mg^?1 has been obtained. Fourier Transfer Infra-Red (FT-IR) and kinetic results were considered to examine the functional groups involved and the adsorption mechanism.     

活性炭负载Fe(III)吸附剂去除饮用水中的As(V)

利用活性炭负载水合铁氧化物制备了复合吸附剂,并用于饮用水中As(V)的去除. 研究了活性炭种类、粒度、溶液pH值、Fe(III)盐浓度和干扰离子等对As(V)去除的影响. 结果表明,煤质活性炭作为基质负载水合铁氧化物比椰壳炭和果壳炭具有更好的除砷效果. 随着炭粒度降低,除砷效率显著增加. 在pH 3~9范围内,活性炭负载水合铁氧化物可有效吸附As(V). F-, Cl-, SO42-的加入对As(V)的去除效率基本无影响,而SiO32-和PO43-则明显抑制As(V)的去除. Langmuir模型比Freundlich模型能更好地描述复合吸附剂对As(V)的吸附平衡. 动力学研究表明,As(V)吸附反应可用二级速率方程描述.     

Development of Green Energy Waste Activated Carbon for Removal of Trivalent Chromium: Equilibrium and Kinetic Modeling

The present work reports on the potential of using a modified activated carbon as an eco-friendly adsorbent (second stage waste), obtained from a bio-diesel waste production plant, for the removal of Cr(III) ions from aqueous solutions. Chemical activation of the green energy waste (GEW), using sulfuric acid as a dehydrating agent, was adapted in this study The effects of pH, contact time, dosage, and initial concentration were evaluated and optimized in a batch processing mode. The modified activated carbon was fully characterized to observe morphological changes using SEM, XRD, and FT-IR techniques. SEM images however, showed significant changes in the carbon morphology before and after the adsorption of Cr(III) ions. The adsorption results indicated that the equilibrium data were in accordance with the Langmuir isotherm, yielding a maximum monolayer adsorption capacity of 171.0 mg g ? 1 at 29° C. Moreover, the kinetic studies indicated that the adsorption process followed a pseudo-second-order model. Assessment of our results revealed that GEW-AC was considered as a prospective adsorbent which could be used as a cost-effective substitute for marketable activated carbons for the removal of Cr(III) ions from wastewater systems.     

Novel Diglycolamic Acid Functionalized Iron Oxide Particles for the Mutual Separation of Eu(III) and Am(III)

Iron oxide (Fe₃O₄) particles functionalized with diglycolamic acid (Fe-DGAH) were synthesized and characterized by TG-DTA, X-Ray diffraction,¹H NMR, and scanning electron microscopy (SEM). The extraction behavior of Am(III) and Eu(III) in Fe-DGAH was studied from dilute nitric acid medium to examine the feasibility for the mutual separation of trivalent actinides and lanthanides using Fe-DGAH. For this purpose, the effect of various parameters such as the duration of equilibration and concentrations of europium, nitric acid, and diethylenetriaminepentaacetic acid (DTPA) in the aqueous phase on the distribution ratio (K_d) of Am(III) and Eu(III) was studied. The conditions needed for the efficient separation of Am(III) from Eu(III) were optimized using DTPA. The distribution ratio of ?10⁴ mL/g was obtained for both Am(III) and Eu(III) at pH 3, and it decreased with an increase in the concentration of nitric acid. However, a separation factor of Eu(III) over Am(III) of ?150 was achieved in the presence of DTPA. Rapid sorption of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 2 h. The sorption data were fitted to the Langmuir adsorption model, and the apparent europium sorption capacity was determined to be ?50 mg/g. The study indicated the feasibility of using Fe-DGAH particles for magnetic separation of Eu(III) from Am(III) with high separation factors.     

钢渣对水溶液中砷的吸附动力学和热力学特性试验

以炼钢厂固体废弃物钢渣为材料,通过批量平衡吸附法,并结合宏观热力学和动力模型应用,分析和研究了钢渣对水溶As(III)的吸附特征。结果表明钢渣在吸附As(III)过程中,初始阶段吸附量迅速增加,随着浓度的增加,吸附逐渐趋于饱和,最后达到平衡,具有"快速吸附、缓慢平衡"的特点。钢渣吸附材料具有极高的最大吸附容量,高达3.58×104mg/kg。钢渣对As(III)的吸附均符合Langmuir和Freundlich吸附等温线,其中钢渣对As(III)的吸附特征与Freundlich等温吸附方程吻合性最好,相关系数(R2)达到0.99以上。钢渣对As(III)的吸附动力学数据均符合一级动力学方程、Elovich方程和双常数方程,拟合优度用相关系数(R2)为0.92~0.98,相比较而言,钢渣对As(III)的吸附以Elovich方程为最佳模型。     

Removal of As(V) species from extremely contaminated mining water

The effective removal of arsenic compounds from strongly contaminated mining water with a high content of As (about 50 mg/l) and other metals, especially iron (about 5000 mg/l) has been studied. The process ran in two steps. At first, the raw acid mining water containing predominantly Fe²⁺ ions was partially precipitated with a small amount of an alkaline agent. On a small portion of the precipitated iron (about 30–40%), more then 90% of the arsenic was adsorbed forming a toxic precipitate, which was then stirred under an inert agent (Ar) and further in air for 1 h. Secondly, the precipitation of the first step liquid residue (using the same or a different alkaline agent) enabled the final treatment of the mining water at pH 8.5. While arsenic was substantially removed by the first precipitation, the other components including residual iron, manganese, zinc and sulfates were precipitated quantitatively during the second step. The mass of the second precipitate depended strongly on the alkaline agent used in the second step.The mechanism and kinetics of arsenic sorption onto iron species, and phase changes of the sorbent during the sorption process were investigated. The composition of the precipitates was verified by XRD and XRF analyses, as well as by infrared and Raman spectroscopy. The precipitation of a raw mining water resulted in formation of a complex inorganic system where amorphous phases dominated. Various crystalline phases, predominantly concerning Fe(II)–Fe(III), As, Zn and sulfates also appeared, depending on the actual oxidizing state of the whole system and on redistribution of its components.The two-step precipitation of arsenic contaminated mining water results in a significant ecological and economical improvement due to the decrease in the amount of waste toxic mass.     

Synthesis of the cotton cellulose based Fe(III)-loaded adsorbent for arsenic(V) removal from drinking water

A novel macroporous bead adsorbent, Fe(III)-loaded ligand exchange cotton cellulose adsorbent [Fe(III)LECCA], is synthesized for selective adsorption of arsenate anions [As(V)] from drinking water in batch and column systems. As(V) adsorption on Fe(III)LECCA was independent of pH, especially in drinking water pH range. Film diffusive control mechanism will benefit As(V) exchange with Fe(III)LECCA whether in batch or in column experiments. When treating the tap water at 26.0 BV/h, the column still preserves 83% of the original saturation adsorption capacity of the As(V) aqueous solution. These results have indicated that Fe(III)LECCA has the potential to act as an adsorbent for the removal of As(V) from drinking water considering its availability, nontoxicity and cost-effectiveness.