Effect of Microbial Siderophore DFOB on Pb, Zn, and Cd Sorption Onto Zeolite

Recent studies suggest that siderophores form stable complexes with divalent metals and affect their mobility. In this work, effects of trihydroxamate microbial siderophores and desferrioxamine-B (DFOB) on Pb(II), Zn(II), and Cd(II) sorption by two kinds of synthesized zeolites (13X and Na?CY) as a function of pH were investigated. Results showed that 13X zeolite has a higher sorption affinity for studied metals than Na?CY. DFOB strongly affected metal sorption on both zeolites. Under slightly acidic to neutral condition, DFOB increased the metal sorption on zeolites due to the sorption of positively charged heavy metal?CDFOB complexes. Whereas by increasing pH (>7), the mobilizing effect of DFOB was observed for Pb, Zn, and Cd. DFOB drastically decreased (80?%) Zn sorption in alkaline condition. As a result, siderophores can weaken the treatment efficiency of zeolites and increase the bioavailability of metals in soils. Surface complexation modeling revealed that the effects of DFOB on metal sorption by 13X and Na?CY zeolites can be explained by the differences in their surface charge. In general, the result shows the influence of DFOB on metal sorption by zeolites over the pH range 4?C9 and decreasing in the sequence Zn?>?Pb?>?Cd.     

Modelling the sorption of Zn and Ni on Ca-montmorillonite

In some previous work titration and Ni/Zn sorption edge/isotherm measurements carried out under a wide variety of experimental conditions on purified Na-montmorillonite were modelled in terms of cation exchange and surface complexation mass action equations. A major objective of the experimental/modelling programme is to understand and predict sorption in commercial bentonite systems. Since montmorillonite is the dominant clay mineral in bentonite and is often present in a mixed Na/Ca form, a natural extension to the previous investigations was to study Ni/Zn sorption on a conditioned Ca-montmorillonite. An important open question was whether the same basic parameters such as site types, site capacities, and acidity constants could be used for both materials and to see to what extent the Ni and Zn surface complexation constants were influenced by the form of the montmorillonite. Sorption edges for Ni and Zn at different Ca(NO₃)₂ background electrolyte concentrations, together with sorption isotherms measured over a range of pH values, are presented and modelled using the MINSORB code. The parameters characterising the sorption of Ni and Zn on Na- and Ca-montmorillonite systems are compared. Finally, examples are given that illustrate how the modelling can provide insight into the sorption processes.     

含铬蒙脱石中铬离子占位位置研究

采用提纯后的蒙脱石在不同浓度硫酸铬溶液中进行交换吸附制备了含铬蒙脱石,并利用包括粉末X射线衍射术 （XRD）、电子自旋共振谱术（ESR） 和傅里叶变换红外吸收光谱术（FTIR） 等分析测试手段对铬在蒙脱石中的吸附位置进 行了探索研究。研究结果显示铬离子不仅置换了层间域中的Ca2+,K+和Na+等,而且置换了位于八面体位的Mn2+ 和少量 Al3+,并较大量的进入硅氧四面体的六边形孔洞、甚至有可能置换极少量的四面体位的Al3+和Fe3+等。此外,根据X射线衍 射分析可知,在0.2 mol/L硫酸铬溶液中充分交换吸附后的蒙脱石存在两层水型和单层水型两种含铬蒙脱石,其水合阳离子 分别为[Cr(H2O)6]3+和[Cr(H2O)3O3]3+,当吸附量增大至一定程度后水合铬离子借助TOT结构片的硅氧四面体的底氧形成配位多 面体。     

Effects of Pb^2＋, Cd^2＋ and Cu^2＋ on the Aqueous Zn^2＋ Sorption by Hydroxyapatite

In this paper, the behaviors of aqueous zinc sorption by hydroxyapatite in the co-existence of Pb^2＋, Cd^2＋ and Cu^2＋ are investigated, the effects of Pb^2＋, Cd^2＋ and Cu^2＋ on the sorption of Zn^2＋ are discussed, and the hydroxyapatite sorption capabilities for Pb^2＋, Cd^2＋, Cu^2＋ and Zn^2＋ are compared. The experimental results show that the Zn^2＋ removal efficiency decreases gradually with the increase of the Cd^2＋ concentration of the solution, and there is no sorption preference between Cd^2＋ and Zn^2＋. On the other hand, the Zn^2＋ removal efficiency rapidly decreases rapidly with the increase of the Cu^2＋ concentration of the solution, and there is a clear sorption preference between Cu^2＋ and Zn^2＋. It is noticed that the Zn^2＋ removal efficiency is hardly changed with the variance of Pb^2＋ concentration because the removal mechanisms for these two ions are totally different. It is concluded that the adsorption affinities of the heavy metals for the hydroxyapatite follows this sequence： pb^2＋〉 Cu^2＋〉 Cd^2＋〉 Zn^2＋.     

铝钛柱撑改性膨润土处理两种模拟废水的实验研究

以钠基膨润土为原料制备了铝钛无机柱撑、铝钛有机柱撑改性膨润土，确定了改性膨润土的最佳铝钛比和铝土比，并将其应用于模拟废水、化学实验室废水的处理。与原土进行比较，探讨了用量、pH值、搅拌时间等对COD去除率、色度去除率、浊度去除率的影响，通过正交实验对实验条件进行了优化。结果表明：有机柱撑改性膨润土、无机柱撑改性膨润土对废水的处理效果均明显好于原土，对废水色度、浊度的去除率均大于93％；对废水COD的去除效果，有机柱撑改性膨润土比无机柱撑改性膨润土有较大提高，去除率最高达66．31％，结果令人满意。     

蒙脱石中Cu2+的吸附态研究

对在ＰＨ≤４．５、痕量浓度条件下吸附了Ｃu＾２＋的蒙脱石的Ｘ射线衍射（ＸＲＤ）进 行了研究。该蒙脱石的ｄ（００１）由原始蒙脱石的１．４７９ｎｍ变为１．５２３ｎｍ,说明水合铜离子置换了蒙脱石的层间阳离子;在该蒙脱石的ＥＰＲ谱中记录到了ｇ＝２．０７、ｇ ＝２．１４精细结构线和ｇ为约２．７～２．２超精细结构线三组有关Ｃu＾２＋ 的信号,说明其中的Ｃu＾２＋有三种不同的结构状态。同时,该蒙脱石热处理产物的ＥＰ     

Removal of trace metals by coprecipitation with Fe,Al and Mn from natural waters contaminated with acid mine drainage in the Ducktown Mining District,Tennessee

This study examined the sorption of trace metals to precipitates formed by neutralization of 3 natural waters contaminated with acid mine drainage (AMD) in the former Ducktown Mining District, Tennessee. The 3 water samples were strongly acidic (pH 2.2 to 3.4) but had distinctively different chemical signatures based on the mole fractions of dissolved Fe, Al and Mn. One sample was Fe-rich (Fe=87.5%, Al=11.3%, and Mn=1.3%), another was Al-rich (Al=79.4%, Mn=18.0%, and Fe=2.5%), and the other was Mn-rich (Mn=51.4%, Al=25.7%, and Fe=22.9%). In addition, these waters had high concentrations of trace metals including Zn (37,700 to 17,400 μg/l), Cu (13,000 to 270 μg/l), Co (1,500 to 520 μg/l), Ni (360 to 75 μg/l), Pb (30 to 8 μg/l), and Cd (30 to 6 μg/l). Neutralization of the AMD-contaminated waters in the laboratory caused the formation of either schwertmannite at pH<4 or ferrihydrite at pH>4. Both phases were identified by XRD analyses of precipitates from the most Fe-rich water. At higher pH values (∼5) Al-rich precipitates were formed. Manganese compounds were precipitated at pH∼8. The removal of trace metals depended on the precipitation of these compounds, which acted as sorbents. Accordingly, the pH for 50% sorption (pH₅₀) ranged from 5.6 to 7.5 for Zn, 4.6 to 6.1 for Cu, 5.4 to 7.7 for Ni, 5.9 to 7.9 for Co, 3.1 to 4.3 for Pb, and 5.5 to 7.7 for Cd. The pH dependence of sorption arose not only because of changes in the sorption coefficients of the trace metals but also because the formation and composition of the sorbent was controlled by the pH, the chemical composition of the water, and the solubilities of the oxyhydroxide-sulfate complexes of Fe, Al, and Mn.     

近中性溶液条件下富镉铅锌矿矿石的风化淋滤实验研究

在近中性溶液条件下对富镉锌矿石进行了风化淋滤实验研究,发现淋滤液中产生大量以石膏为主要成分的沉淀物。淋滤液呈碱性,淋滤出来的Zn、Cd以水溶态和沉淀态形式存在,而以后者为主。淋滤50天后,黄铁矿闪锌矿石中Zn、Cd的淋滤率为0．03％和0．01％,而半氧化闪锌矿石Zn、Cd的淋滤率则高得多,分别0．10％和0．60％。     

Sorption of metals on humic acid

The sorption on humic acid (HA) of metals from an aqueous solution containing Hg(II). Fe(III), Pb, Cu, Al, Ni, Cr(III), Cd, Zn, Co and Mn, was investigated with special emphasis on effects of pH, metal concentration and HA concentration. The sorption efficiency tended to increase with rise in pH, decrease in metal concentration and increase in HA concentration of the equilibrating solution. At pH 2.4. the order of sorption was: Hg? Fe? Pb? CuAl ? Ni ? CrZnCdCoMn. At pH 3.7. the order was: Hg and Fe were always most readily removed, while Co and Mn were sorbed least readily. There were indications of competition for active sites (CO₂H and phenolic OH groups) on the HA between the different metals. We were unable to find correlations between the affinities of the eleven metals to sorb on HA and their atomic weights, atomic numbers, valencies, and crystal and hydrated ionic radii. The sorption of the eleven metals on the HA could be described by the equation $\text{Y =}\text{100}\text{[1 + exp ? (A + BX)]}$, where Y = % metal removed by HA; X = mgHA; and A and B are empirical constants.     

Coordination of Cd ions in the internal pore system of zeolite-X: A combined EXAFS and isotopic exchange study

The effect of prolonged contact time (up to 130 days) on the immobilization of Cd by sorption to calcium exchanged zeolite-X (CaX), under environmentally relevant conditions, was studied using both isotopic exchange and extended X-ray absorption fine structure spectroscopy (EXAFS). Sorption and isotopic exchange measurements revealed time-dependent Cd sorption and indicated the movement of Cd²⁺ ions into less accessible sites due to ageing. EXAFS suggested progressive fixation of Cd in the double six-ring (D6R) unit of the CaX structure. Proportional allocation of the apparent Cd-Si bond distance to two ‘end-members’, across all contact times, indicated that the bond distance for labile Cd was 3.41 Å and for non-labile (or fixed) Cd was 3.47 Å.     

Chemistry of metal–humic complexes contained in Megalopolis lignite and potential application in modern organomineral fertilization

Lignite samples from two deposits located in the Megalopolis Basin, Southern Greece, were evaluated for their potential applicability as raw materials for the production of organomineral fertilizers. Fundamental chemical analyses were carried out to demonstrate high humic substances and metal contents. To determine their relative distribution in the Megalopolis lignite extract, eight elements, namely Na, K, Cd, Mn, Mg, Pb, Zn, and Cu, were studied both in H₂O and in Na₄P₂O₇/NaOH solutions. The behavior of these metals showed significant variations; Zn, Pb, Cd, and Cu associate mostly to the humic substances and proved scarce in the water extract. Contrarily, K and Mg gave a significantly low total yield in the Na₄P₂O₇/NaOH solution, while Mn was classified among the least extracted elements. Further enrichment of Megalopolis humic substances in these metals was achieved; Pb and Mg proved the most and least retained metal, respectively. Decomplexation titration curves of humic matter saturated with these metal ions demonstrated that novel organomineral fertilizing materials may develop based on optimized metal ion and humate contents, which can retain metals in a soluble form within a wide pH range. Formation of complexes between humic substances and Zn, Cd, and Mg was clearly indicated.     

Interactions between Cd,Cu, Pb,and Zn and four different mine soils

The chemical associations of Cd, Cu, Pb, and Zn in four mine soil samples from the Amizour-Bejaia Pb/Zn mine (Algeria) have been investigated by a five-step sequential extraction procedure. Although Cd preferentially binds to carbonates, Cu, Pb, and Zn are mainly associated with the organic and reducible fractions. Batch adsorption experiments with either mono- or multi-metallic solutions are described with the Freundlich isotherm model. Whatever the nature of the soil sample, the sorption behavior for each given metal except Pb is very similar, indicating that the binding sites at the soil surface are progressively occupied by the metal from the solution. On each soil sample, the decreasing order of sorption can be established as Pb >> Cu > Cd > Zn. When the four metals are simultaneously applied to each soil sample, their specific behavior is strongly affected by their interactions and/or competition for the available surface sites: we generally observed isotherm curves with a slight maximum before the plateau at higher solution concentration. Although Cu is only slightly affected by the other metals, in the case of Pb, Cd, and Zn, the sorbed amounts strongly decreased.     

Competitive sorption of intermixed heavy metals in water repellent soil in Southern Australia

In water repellent soil, Cr, Pb and Cu showed higher adsorption intensities than Zn, Cd and Ni did. Soil water repellency is much more widespread than formerly thought. In order to promote fertility and productivity, the irrigation of recycled water onto water repellent soil may be an applied technology to be used in some areas of Southern Australia. Therefore, heavy metals in recycled water potentially enter into the soil. The competitive sorption and retention capacity of heavy metals in soil are important to be determined, especially considering the special geochemical origin of water repellent soil that was caused by waxes on or between the soil particles. Batch equilibrium sorption experiments on Cd, Cr, Cu, Ni, Pb and Zn in their typical proportion in recycled water were conducted in water repellent soil. The sorption intensity, sorption isotherm in the experiments together showed that Cr, Pb and Cu have higher sorption intensity than those of Zn, Ni and Cd in the competitive system. The risk assessment for the application of recycled water onto water repellent soil is definitely necessary, especially for the metal cations with relatively weak sorption.     

富含Na~ 、Ca~(2 )、Al~(3 )、Cr~(3 )蒙脱石对垃圾渗滤液中有机物的吸附

由于层间含有高价态金属阳离子的蒙脱石对特定有机物的吸附能力可大大增强 ,故分别用层间含有Na 、Ca2 、Al3 和Cr3 的蒙脱石对垃圾渗滤液中的有机物进行吸附实验 ,研究它们吸附苯酚、二甲苯和COD的能力及离子形态对吸附效果的影响。结果表明 ,含高价金属阳离子的蒙脱石对苯酚和COD的吸附能力较高 ,吸附能力由小到大的顺序为 :Na 相似文献   

Sequestration of arsenate from aqueous solution using 2-line ferrihydrite: equilibria,kinetics, and X-ray absorption spectroscopic analysis

Arsenic(V), as the arsenate (AsO₄ ^3?) ion and its conjugate acids, has a strong affinity on Fe, Mn, and Al (oxyhydr)oxides and clay minerals. Removal of arsenate from aqueous solution by poorly crystalline ferrihydrite (hydrous ferric oxide) via a combination of macroscopic (equilibria and kinetics of sorption) and X-ray absorption spectroscopic studies was investigated. The removal of arsenate significantly decreased with increasing pH and sorption maxima of approximately 1.994 mmol/g (0.192 mol_As/mol_Fe) were achieved at pH 2.0. The Langmuir isotherm is most appropriate for arsenate sorption over the wide range of pH, indicating that arsenate sorption preferentially takes place at relatively homogenous and monolayer sites rather than heterogeneous and multilayer surfaces. The kinetic study demonstrated that arsenate sorption onto 2-line ferrihydrite is considerably fast, and sorption equilibrium was achieved within the reaction time of 2 h. X-ray absorption near-edge structure spectroscopy indicates no change in oxidation state of arsenate following interaction with the ferrihydrite surfaces. Extended X-ray absorption fine structure spectroscopy supports the efficient removal of arsenate by the 2-line ferrihydrite through the formation of highly stable inner-sphere surface complexes, such as bidentate binuclear corner-sharing (²C) and bidentate mononuclear edge-sharing (²E) complexes.     

Competitive adsorption of trace elements in calcareous soils as affected by sewage sludge,poultry manure,and municipal waste compost

The competitive adsorption of trace elements is a key issue in assessing the mobility of trace elements in calcareous soils and can be affected by disposal of sewage sludge, municipal waste, and poultry manure. The effect of municipal sewage sludge, poultry manure, and municipal waste compost on the sorption of cadmium (Cd), copper (Cu), zinc (Zn), and nickel (Ni) in surface samples of three calcareous soils was studied. As the applied concentrations increased, Cu and Cd adsorption increased, while Zn and Ni adsorption decreased in all treatments. Based on the distribution coefficient (K _d) values and proportion of increase or decrease in metal adsorption, the selectivity sequence in control and amended soils found was Cu ≫ Cd ≫ Ni > Zn and Cu ≫ Cd ≫ Zn > Ni, respectively. In general, among control and amended soils, control soils showed the highest K _d for Cd, Cu, and Ni, while sludge, poultry manure, and composted waste-amended soils had lowest K _d for Cd, Cu, and Ni, respectively. In the case of Zn, composted waste-amended and control soils had highest and lowest K _d, respectively. The present experimental results indicated that the addition of organic amendments to these calcareous soils reduced the sorption of Cd, Cu, and Ni. Thus, the effects of preferential adsorption and organic matter should be considered in assessing the risk associated with applying sewage sludge, poultry manure, and composted material to calcareous soils.     

Metal contamination of soils at Scott Base,Antarctica

Soil samples taken from excavated pits on traverses across New Zealand’s Scott Base, Antarctica, were leached with water and 0.01 M HNO₃ and the leachates analysed for Ag, Al, As, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn. The soils had high conductivity and pH values generally increasing with depth and in the range 8.3–10.1. The water leachate generally contained most of the extractable metals except Mn and Cd, and As. Linear relationships were observed between some metals leached into alkaline solution and the Fe in those solutions. The ratios to Fe were comparable to those of the host basanite, and this observation is interpreted as showing that these metals are incorporated in fine mineral particulates derived directly from the rock mass. Outliers in leachable metal concentrations in the soils indicated appreciable contamination of the soil from anthropogenic sources with Ag, Cd, Cu, Pb and Zn as well as As. In some locations high concentrations of Ag and Cd correspond to specific sources and drainage channels. High concentrations of Pb were widely spread and in the top soil layers whereas the elevated concentrations of Zn were distributed throughout the soil profiles indicating atmospheric sources and different mobilities within the soils. Transport within the soils is evident for some metals, as is lateral movement over and through the soils.     

Crystal chemistry, structure analyses and phase transition experiment on an omphacite from eclogitic metagabbro from Syros island, Greece

Summary Pyroxene samples, from the Greek island of Syros, taken from a blueschist-eclogite facies Mg-rich metagabbro, were investigated by chemical and XRD analyses and M?ssbauer spectroscopy. Single-crystal XRD and microprobe analysis showed that the natural sample is a typical omphacite of intermediate composition in the Ca–Na pyroxene solid solutions. The space group P2/n was confirmed and the cations Mg, Al and Ca, Na were found to be ordered in the M1 and M2 positions, respectively. M?ssbauer spectroscopy showed that there is both ferrous and ferric iron in the structure, with the ratio 1.38:1. The M2 sites are fully occupied by Ca and Na, thus the iron (Fe²⁺ and Fe³⁺) can substitute only for Mg and Al in the M1 sites. Partial disorder was attained by annealing the sample at 850 °C, 20 kbar for 7 days, as confirmed by decrease of intensity of reflections affected by the C-type extinction.     

Adsorption of aqueous Pb(II), Cu(II), Zn(II) ions by amorphous tin(VI) hydrogen phosphate: an excellent inorganic adsorbent

Amorphous tin(VI) hydrogen phosphate (ATHP) was synthesized using the liquid phase precipitation method and served as an adsorbent to remove Pb(II), Cu(II), and Zn(II) from aqueous solutions. The ATHP was characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption–desorption techniques. Adsorption properties were evaluated as a function of pH, reaction time, concentration of reactants, and salinity. Their equilibrium adsorption data were modeled using Freundlich, Langmuir, and Dubinin–Kaganer–Radushkevich isotherms, respectively. The results revealed that adsorption equilibrium reached within 180 min. ATHP indicated good adsorption even below the pH_ZPC, and best adsorption at pH 5 for Pb(II) and Cu(II) and at pH 5.5 for Zn(II) was observed. Equilibrium data fitted better to the Langmuir model for Pb(II) and Cu(II) and fitted better to the Freundlich model for Zn(II). The saturated adsorption capacities deduced from the Langmuir model were 2.425, 1.801, and 0.600 mmol/g for Cu(II), Pb(II), and Zn(II), respectively, indicating an adsorption affinity order of Cu > Pb > Zn. There is a negative correlation between the concentration of NaCl and adsorption capacity of ATHP, yet ATHP still exhibited excellent adsorption having an adsorption capacity of 19.35, 15.16, 6.425 mg/g when the concentration of NaCl was 0.6 mol/L. The free energy (E) was 12.33, 10.70, and 14.74 kJ/mol for Pb(II), Cu(II), and Zn(II), respectively. An adsorption mechanism based on ion exchange between heavy metal ions and H⁺ in the ATHP is proposed. Furthermore, the used ATHP was regenerated by HCl solution and the adsorbent was used repeatedly.     

Behavior of metals (Cu,Zn and Cd) in the initial stage of water system contamination: Effect of pH and suspended particles

The fate of potentially harmful metals (PHM) after their entry into an unpolluted fresh water body depends on the physicochemical and biological parameters of the aquatic ecosystem. This paper considers the effect of pH and suspended particles (SP) on the behavior of Cu, Zn and Cd when they enter a fresh water reservoir. In a field experiment, four mesocosms were constructed in the Novosibirskoye Reservoir to allow systematic variation of SP concentration (15 or 250 mg/L) and pH (8.5 or 6.5). The initial concentrations of Cu, Zn and Cd in the mesocosms were 1000, 1000 and 200 μg/L, respectively. Natural bottom sediments were used to provide additional mineral SP, and water hyacinth was used as a floating plant species. Over 11 days, measurements were made of several indicators: residual metal concentration in solution ([PHM]_w); metal concentration in SP ([PHM]_s); primary productivity of the phytoplankton community; mass of settled SP; PHM concentration in settled SP; and PHM bioaccumulation by water hyacinth. The ratio [PHM]_w/[PHM]_s in the water varied in the order Cu < Zn < Cd and was higher at pH 6.5 than at pH 8.5. This observation reflects different PHM sorption (Cu > Zn > Cd) onto mineral SP and PHM biosorption by planktonic organisms. Phytoplankton acts as a renewable source of organic SP and plays an important role in metal removal from the water in the mesocosms. After 11 days the residual concentrations of Cu, Zn and Cd in the mesocosm without SP addition (initial SP concentration was 15 mg/L) were 272, 355 and 84 μg/L, respectively. The residual concentrations of Cu, Zn and Cd in mesocosms with SP addition were 57, 100 and 14 μg/L at pH 8.5 and 80, 172 and 20 μg/L at pH 6.5, respectively. Therefore, addition of SP resulted in faster and more complete removal of metals into the bottom sediments. Floating plants (water hyacinth) accumulated PHM (Cu > Zn > Cd) more effectively at pH 8.5 than at pH 6.5, and PHM concentrations in the roots were higher than in settling SP. The general trends of PHM removal from contaminated water via sedimentation and bioaccumulation are compared with changes of metal speciation in solution.