Adsorption Behavior Of Metals Research Articles

Removal of Trace Level Metal Impurities from Ultrapure Water by Filter Cartridge Including Ion Exchange Grafted Membrane

Metal removal performance of filter cartridge with bi-layered structure was investigated. The filter was prepared using UHMWPE and ion exchange membrane made by grafting polymerization. In filtration experiment, feed ultrapure water was controlled spiking of 15 metals at ppt level, and removal performance of each metal was determined using ICP-MS measurement of filtrate. Metal adsorption behavior for most of the metals were following the classical fluid dynamic theory and the boundary layer controlled reaction. The results were compared to conventional UHMWPE membrane filter and discussed for each metal.

Adsorption behavior of mercury and precious metals on cross-linked chitosan and the removal of ultratrace amounts of mercury in concentrated hydrochloric acid by a column treatment with cross-linked chitosan.

Cross-linked chitosan was synthesized with chitosan and ethylene glycol diglycidyl ether. The adsorption behavior of trace amounts of metal ions on the cross-linked chitosan was systematically examined by packing it in a mini-column, passing a metal solution through it and measuring metal ions in the effluent by ICP-MS. The cross-linked chitosan adsorbed mercury and precious metals (Pd, Pt, and Au) at pH values from acidic to neutral. Especially, mercury in concentrated hydrochloric acids could be adsorbed on cross-linked chitosan quantitatively by an anion-exchange mechanism in the form of a stable chloride complex. This method was applied to the removal of mercury from commercially available hydrochloric acid; more than 97% of mercury was removed, and the residual mercury in the hydrochloric acid (Grade: for trace analysis) was found to be 0.15 ppb. Mercury adsorbed on the cross-linked chitosan could be easily desorbed with an eluent containing I M hydrochloric acid and 0.05 M thiourea. The thus-refreshed cross-linked chitosan could be repeatedly used for the removal of mercury in hydrochloric acid.

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Adsorption behavior of heavy metals on arabica and robusta roasted coffee beans treated in 5 roasting degrees was investigated. The coffee beans residue after extraction with hot water were suspended in aqueous solutions (pH = ca.6.6) containg Cu(II) or Cd(II) and the amount of heavy metal remaining in the solution was determined on an atomic absorption spectrophotometer. Adsorption ratios of Cu(II) were 60.5 and 79.6% for the light and French roasted coffee beans of Indonesia robusta employed as adsorbent, respectively. However, when the roasted coffee beans were washed with distilled water and then air-dried prior adsorption experiments, the adsorption ratios of Cu were 92.2 and 92.6%, respectively and that of Cd was 95.6 and 97.0%. Thus, the heavy metals were almost removed from aqueous solution by use of the roasted coffee beans with washing and drying treatments.

Metals in combined conventional and vegetated road runoff control systems

Combined conventional and vegetated runoff treatment systems were installed on the rural Newbury Bypass in Southern England, which was estimated to carry an average daily traffic of 30,000 vehicles. The system components were arranged in series to give progressive pollutant removal, comprising an oil separator, sediment trap, grassy slope and constructed wetland. In the absence of specific design criteria for road runoff control, the system design was based on available guidance notes. Since the road opened, an 18-month monitoring programme has examined the performance of these systems. Early indications are that the systems, and especially the wetlands, promote removal of suspended solids (>1.2 microm) and effectively trap fine (<63 microm) sediments. The waters were generally oxidising with neutral to basic pH which may have favoured metal partitioning to the solid phase. The distribution pattern for Zn and Cu in fine sediments contrasted in two of the systems studied, indicating the complex behaviour of metals in wetlands. Further work will increase the data set and examine the adsorption behaviour of metals. These results will contribute to the development of future design criteria for the application of wetlands to road runoff treatment.

Adsorption Behavior of Cadmium, Zinc, and Lead on Hydroxyaluminum– and Hydroxyaluminosilicate–Montmorillonite Complexes

The current imperfect understanding about the adsorption behavior of heavy metals on hydroxyaluminum (HyA)‐ and hydroxyaluminosilicate (HAS)‐interlayered phyllosilicates led us to conduct this study. We examined the adsorption behavior of Cd, Zn, and Pb on synthetically prepared HyA– and HAS–montmorillonite (Mt) complexes in comparison with that on untreated Mt. A very dilute initial metal concentration of 10−6 M in 0.01 M NaClO4 background was used in all the adsorption systems. The presence of HyA and HAS polymers on Mt greatly promoted the adsorption of all three metals. Such promoting effects of HyA and HAS polymers on the metal adsorption were, however, not very different from each other. The observed adsorption selectivity sequences of Pb &gt; Zn &gt; Cd on Mt as well as Pb ≫ Zn ≥ Cd on the complexes resemble the reported metal selectivity sequences on amorphous Fe and Al hydroxides. At different pHs, partitioning the adsorbed metals into strongly and weakly held fractions indicated that specific adsorption rather than nonspecific adsorption might have largely controlled the metal selectivity, particularly on the complexes. This led us to assume a predominant involvement of interlayered HyA or HAS polymers in metal adsorption from such dilute solutions. On Mt, the metals were predominantly adsorbed on the permanent charge sites in an easily replaceable state. However, a substantial involvement of the edge OH− groups of Mt in specific adsorption of the metals was also evident, especially at higher pH. Obviously, on Mt and on the complexes, the relative abundance of each type of site and their affinity to heavy metals were substantially different.

Adsorção de íons Cu2+ em latossolo vermelho-amarelo húmico

In environmental studies it is necessary to know the adsorption behavior of metals by soils, since the unfavorable effects of heavy metals and even the micronutrients at high concentrations in the environment are related to these adsorbents' ability to immobilize them. A sample of a humic yellow red oxisol from Araponga region in the State of Minas Gerais, Brazil, was used to verify the adsorption behavior of Cu2+ ions in this substrate. The mathematical model described by Langmuir's adsorption equation in its linearized form was applied and the values of the maximum capacity b and those of the constant related to the bonding energy a were obtained. Aliquots of copper nitrate solutions containing several concentrations of this metal were added to soil samples, the pH being predetermined for developing the adsorption experiments. The chemical and physical characterization of soil sample were performed by determining the organic carbon, nitrogen and phosphorus concentrations, cation exchange capacity (CEC), pH, concentration of metals (Al, Fe, K, Mg, Ca, Zn, Cu, Ni, Cr, Co, Pb, and Cd), granulometric analysis and X-ray diffraction. Langmuir isotherms presented two distinct adsorption regions at both pH 4 and pH 5, showing that the adsorptive phenomenon occurs in two distinct stages. The adsorption sites for the lower part presented greater bonding energy and low adsorption capacity compared with the adsorption sites of the part of the curve corresponding to higher Cu concentrations in the equilibrating solution.

Dynamic Adsorption of Heavy Metals under Various Incineration Temperatures

Previous studies have indicated that an effective control technology, for heavy metal emissions from incinerators, is to use solid sorbents to capture metals by physical deposition and chemical adsorption. The controlling efficiency is affected by the kind and size of sorbents, the operating temperature, and the specific compositions of the waste. However, the dynamic adsorption behavior of heavy metals on sorbents during incineration is rarely discussed, because it is difficult to analyze and identify trace metals at high temperatures. The main objective of this study is to investigate the dynamic adsorption behavior of Cr, Cu, Pb, and Cd on sorbents (silica sand with limestone) at different operating temperatures (600, 700, and 800°C) and to find the adsorption saturation point of the sorbents during fluidized bed incineration. This will help us to determine when the sorbents should be renewed and investigate the adsorption mechanism. The results show that the adsorption saturation points of three of th...

Modeling of Copper(II), Cadmium(II), and Lead(II) Adsorption on Red Mud

The adsorption of toxic heavy metal cations, i.e., Cu(II), Cd(II), and Pb(II), on red muds has been modeled with the aid of a modified Langmuir approach assuming single-site adsorption and of a double-site binding model incorporating the effect of pH. For equilibrium concentrations of metal solutions between 0.03 and 5.8 mmol.dm−3and equilibrium pH between 4.4 and 5.6, adsorption equilibrium constants corresponding to single- and double-site binding were found by linear and nonlinear least-squares approximation, respectively, and the double-site model was shown to conform better to experimental data. The contributions of the monomeric and dimeric hydroxo-complexes of Cu(II) to total copper adsorption at a fixed pH were also investigated. The Langmuir parameters of adsorption were found with the aid of the linearized Langmuir isotherm. This work aims to clarify heavy metal adsorption behavior on composite sorbents consisting of hydrated oxides.

Evaluation of contaminant ion adsorption/desorption on goethite using pressure jump relaxation kinetics

The adsorption/desorption of contaminant ions on soil constituents such as metal oxides occurs within milliseconds. The rapid kinetics of Cu e+ and arsenate adsorption/ desorption on goethite (α-FeOOH) were investigated using the pressure-jump (p-jump) relaxation technique, which provides rate constants and mechanistic information for fast reactions. Results of p-jump experiments at 25°C revealed that both Cu 2+ and arsenate were specifically adsorbed on goethite. The divalent copper ion formed an inner-sphere monodentate surface complex, while arsenate formed an inner-sphere bidentate surface complex with goethite. In both cases, the rate constants for the adsorption reactions exceeded those for desorption, indicating that the desorption of Cu 2+ and arsenate from the goethite surface was the rate-limiting process. Pressure jump relaxation techniques can be used to predict the adsorption behavior of heavy metals in soil environments.

Ligand effect on the adsorption of heavy metals: The sulfate ? Cadmium ? Goethite case

Complexing ligands may alter the adsorption behaviour of heavy metals compared to a ligand free system, either by changes in solution speciation, or by interactions at the adsorbing mineral surface. In this paper the effect of sulfate on the adsorption of cadmium onto goethite has been studied. Adsorption experiments under defined conditions revealed the following effects: Cadmium adsorption from sulfate containing solutions by goethite was higher than from pure NaNO3-solutions. Simultaneously sulfate adsorption increased, indicating synergic effects. Increasing the ionic strength of the metal-sulfate solutions caused a decrease both in heavy metal and in sulfate adsorption. Model calculations on simultaneous adsorption of cadmium and sulfate lead to the following conclusions: 1.) Sulfate adsorption reduces the surface potential so that the surface becomes more attractive to heavy metals. 2.) In addition, new, so called ternary surface complexes (SOCd+-SO4 2−) between reactive surface sites, heavy metals and sulfate-anions must be assumed in order to get agreement between observed and calculated effects.

The Removal of Cadmium (II) from Dilute Aqueous Solutions by Fungal Adsorbent

The metal adsorption behavior of 12 species of fungi was investigated using batch reactors. Specific surface area and surface charge characteristics of the fungal biomass were determined. The metal adsorption capacity was assessed at various pH values. A modified Langmuir adsorption isotherm including competitive H+ ions was used to describe the adsorption characteristics. Physical-chemical treatment of fungal biomass does not affect metal adsorption behavior exemplified by Cd(II). The adsorption capacity of fungal biomass is also compared with other adsorbents such as activated carbon, oxide, soils and hydroxyapatite. Cd(II)-laden fungal biomass was regenerated.

Computer simulation of interactions of model Pt particles and films with the silica surface

The molecular dynamics method was used to simulate adsorption and particle growth behavior of model Pt metal on the vitreous silica surface. Analysis of depositions from single atoms through the development of a continuous film of metal were simulated, and were then compared to similar systems analyzed in the laboratory. Consistent with experimental findings, the single atom depositions showed both adsorption onto the surface of the substrate as well as penetration into the interior (subsurface) sections. Multiple Pt atom interactions resulted in more complex absorption behavior. This finding yielded better quantitative agreement with the ‘‘real’’ systems analyzed previously. Applications of this type of study are discussed.

REMOVAL OF CADMIUM (II) FROM DILUTE AQUEOUS SOLUTIONS BY FUNGAL BIOMASS

ABSTRACT The metal adsorption behavior of nine different species of fungi was investigated. Both batch and kinetic reactors were used to determine the heavy metal, exemplified by cadmium(II), adsorption capacity and the rate of the adsorption reaction. The metal adsorption capacity was assessed at various pH value. Fresh and freeze-dried fungal biomass exhibit similar adsorption behavior. The adsorption capacity of fungal biomass is also compared with other adsorbents such as activated carbon, oxide, soil and hydroxyapatite. The results clearly show that fungal biomass can be as effective as other metal adsorbents.

Activated carbon adsorption of heavy metal chelates from single and multicomponent systems

AbstractAn extensive experimental investigation was conducted with activated carbon to establish the adsorption (equilibrium and kinetics) behavior of several metals from single and two metals systems in the presence of complexing agents. Triethylenetetramine (TRIEN) and EDTA were used as complexing agents. The extent of adsorption was found to be a function of metal and ligand types, ligand to metal ratio, pH, and metal chelate species distribution. Selective separation of valuable metals can also be achieved by the addition of complexing ligands to a mixture of strongly complexable metal (such as Cd2+ and Ni2+) and weakly complexable metal (such as Ba2+ and Ca2+).

Factors Affecting the Adsorption of Complexed Heavy Metals on Hydrous Al2O3

Factors influencing the adsorption behavior of heavy metals, viz Cu(II), Zn(II), Cd(II), Pb(II) and Ni(II), onto Al2O3 from aqueous solutions containing complexing ligands were investigated using batch adsoption experiments. For the Cu(II)/NTA/ γ-Al2O3, system, increasing the system ionic strength reduced Cu adsorption through activity coefficient and surface electrical double layer effects. The presence of alkaline earth cations (Ca(II) and Mg(II)) also reduced Cu removal from solution by lowering the ability of NTA to prevent Cu(OH)2 precipitation and through specific adsorption to the alumina surface. The adsorption of the heavy metals on Al2O3 from solutions containing NTA followed the sequence: Cu &amp;gt;Zn &amp;gt; Cd &amp;gt; Pb ≈ Ni. Increase in system temperature tended to decrease metal adsorption.

Heavy-metal adsorption by ferromanganese coatings on stream alluvium: Natural controls and implications for exploration

The adsorption of Cu and Zn by natural ferromanganese coatings on stream pebbles, collected from varied geologic environments, was studied utilizing aqueous solutions of Cu and Zn. Special emphasis was given to determining the effect on adsorption of several natural variables including metal concentration, pH and ionic strength. Conditions covered the range known to occur in streams. The potential of stream turbulence, coating age and periodic drying of coatings to alter adsorption characteristics was also investigated. Composition of the coatings studied varied considerably, but their adsorption characteristics were remarkably similar. Adsorption increased with metal concentration but was not significantly affected by solution aeration (simulating increased stream turbulence), increased ionic strength, air-drying for one year, or coating age. These results suggest that coatings represent a uniform sampling medium perhaps subject to less variation in metal adsorption behavior than fine-grained stream alluvium.

The effect of complex formation on the adsorption characteristics of heavy metals

In most aqueous environmental systems, inorganic and organic metal complexes represent a significant contribution to the total soluble metal. Metal adsorption is often a highly pH-dependent phenomena. Such behavior can generally be attributed to changes in metal speciation with solution acidity as well as variation in the extent of surface protonation. Thus, because adsorbability may vary drastically between different metal species, (e.g. Cu 2+ (aq) compared to CuOH +) a knowledge of metal species distribution is essential to understanding and interpreting metal adsorption behavior. Organic complexation has been reported to enhance, suppress and have no perceptible effect on trace metal adsorption. Such differences arise because adsorption depends on factors such as the ligand/metal ratio, adsorbability of the free ligand, and various solution parameters (e.g. pH). Most important in determining the effect of complexation on adsorption is the adsorbability of the resulting complexes. Thus, it is difficult to make generalizations about the influence of organic complexation on metal adsorption. Adsorption of metal complexes is frequently reported to be predominantly coulombic in nature; that is, binding of an anionic or cationic complex to an oppositely charged colloidal particle. However, electrostatic forces can often represent an insignificant contribution to the total free energy of adsorption and can be overshadowed by chemical reactions with the surface, hydrogen bonding, and hydrophobic effects.

Adsorption behavior of metals on TEAE-cellulose from hydrochloric acid and hydrochloric acid-thiocyanate media

Adsorption behavior of metals on TEAE-cellulose from hydrochloric acid and hydrochloric acid-thiocyanate media

The chromatography of metals on DEAE-cellulose layers in phosphoric acid media

The adsorption behaviour of forty-eight metals on DEAE-cellulose thin layers has been examined in aqueous phosphoric acid media. R F values are given as a function of phosphoric acid concentration over the range 0.01–1.0 M and are compared with those obtained in a similar manner with a crystalline cellulose, Avicel SF. Particularly strong retention on DEAE-cellulose occurred for Mo(VI), W(VI), Re(VII), the platinum group metals, Au(III) and Bi(III). Weak to moderate retention was also observed for several metals, such as V(V), Fe(III), Se(IV), In(III), the rare earths and U(VI), at lower concentrations of phosphoric acid (<0.1 M).

Adsorption behavior of various metals on a weakly basic anion-exchange resin in sulfuric acid media

A systematic study is presented on the adsorption behavior of some 20 metals on a weakly basic condensed phenol resin, Amberlite CG-4B, in sulfuric acid media. The distribution coefficients were determined over a sulfuric acid concentration range of 0.005 M to 2 M. The metals adsorbed are similar to those which exhibit strong adsorption on a strongly basic resin, but the magnitudes of the distribution coefficients and the adsorption sequences differ considerably between the two types of the resin. Several two- and three-component separations of analytical interest are possible. A new method for the separation of titanium(IV) is described; this is based on its high adsorption on CG-4B from sulfuric acid media containing hydrogen peroxide.