Capacity For Metal Ions Research Articles

Nanofibrous Membrane of Silk Fibroin/Cellulose Acetate Blend for Heavy Metal Ion Adsorption

Silk fibroin/cellulose acetate blend Nanofibrous membranes were prepared by electro- spinning and their performances were evaluated as a heavy metal ion adsorbent. The electrospun nanofibrous membranes were comprised of randomly oriented ultra-fine fibers of 100-600nm diameters. As a result of field emission electron microscope (FEEM), compared with pure nanofibrous membranes, the anti-felting shrinkage of SF/CA blend nanofibrous membranes with 20% CA content was markedly improved after treatment with 100% ethanol. Metal ion adsorption test was performed with Cu2+ as a model heavy metal ion in a stock solution. The pure SF nanofibrous membranes exhibited high metal ion capacities compared with that pure CA nanofibrous membrane. Especially, the SF/CA blend nanofibrous membranes had an exceptional performance for the adsorption of metal ions, and the maximum milligrams per gram of metal ions adsorbed reached 22.8mg/g for Cu2+. This indicated that SF and CA had synergetic effect.

Hypercrosslinked microporous polymer networks for effective removal of toxic metal ions from water

Sulfonic acid-modified microporous hypercrosslinked polymers (SAM-HCPs) synthesized by sulfonation of microporous hypercrosslinked polymers (HCPs, also known as “Davankov Resins”) have been investigated as a high-capacity adsorbent for toxic metal ions. The materials were characterized using proton magnetic resonance ( 1H NMR), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), thermogravimetric analysis (TGA), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and nitrogen adsorption method. The results show that the modified resins retained their original microporous structure and spherical morphology, and possess sulfonic acid groups as hydrophilic groups and active sites. Sulfonic acids-modified hypercrosslinked “Davankov Resins” (SAM-HCP-DR) have been found to attain very good adsorption capacity for metal ions (e.g., Cu 2+ 51.45 mg g −1 at 303 K, 54.82 mg g −1 at 313 K, and 57.68 mg g −1 at 323 K), which is due to the synergic effect of microporous structure and active sites. The kinetic data obtained from adsorption experiments supports a pseudo-second order model and adsorption isotherms obtained at different temperatures (303 K, 313 K and 323 K) are all fitted with the Langmuir isotherms. In addition, the thermodynamic parameters, i.e., Gibbs free energy change (Δ G 0), enthalpy change (Δ H 0), entropy change (Δ S 0) of the adsorption process were calculated, and the results confirmed the adsorption to be spontaneous and endothermic. Moreover, these modified resins can be recycled several times with minimal loss of adsorption capacity and thus may have potential industrial applications.

Preparation and Characterization of Poly(2,2-dimethyl-1,3-propylene oxalate) Polymer and the Study of its Metal Uptake Behavior Toward Pb(II), Cd(II), and Hg(II) Ions

Poly(2,2-dimethyl-1,3-propylene oxalate) was synthesized from oxalyl chloride and 2,2-dimethyl-1,3-propane diol. The polymer was characterized by inherent viscosity, FT-IR, XRD, SEM, 1H-NMR, 13C-NMR, DSC, and TGA. The polymer uptake behavior towards Pb(II), Cd(II), and Hg(II) ions was studied by the batch equilibrium technique as a function of pH and contact time. The adsorption isotherms of metal ions were also investigated. Column experiments were used to determine the loading capacity and study desorption of metal ions. The polymer showed high metal-ion uptake capacity towards Pb(II), but moderate capacity towards Cd(II) and Hg(II) ions. Interestingly, the polymer was found to be highly selective for Pb(II) ions at pH 5 and 25°C. The metal ion uptake properties of the polymer show fittings for both Langmuir's and Freundlich equations. The metal-bound polymer was regenerated by treatment with 1 M HNO3. Therefore, it may be employed for the removal of heavy metal pollutants in environmental and industrial applications.

Kinetic and thermodynamics of the removal of Zn2+ and Cu2+ from aqueous solution by sulphate and phosphate-modified Bentonite clay

The modification of pristine Bentonite clay with sulphate and phosphate anions was found to increase its cation-exchange capacity (CEC), adsorption capacity and overall pseudo-second order kinetic rate constant for the adsorption of Cu2+ and Zn2+. Modification with sulphate and phosphate anion decreased the specific surface area of pristine Bentonite clay. Phosphate-modified Bentonite clay was found to give the highest adsorption capacity for both metal ions. The adsorption process was observed to be endothermic and spontaneous in nature for both metal ions with Zn2+ being more adsorbed. Modification with phosphate anion increased the spontaneity of the adsorption process. The effective modification of pristine Bentonite clay with sulphate anion was confirmed from hypochromic shifts in the range of 13–18cm−1 which is typical of physisorption while modification with phosphate anion was confirmed by its hyperchromic shifts typical of chemisorption in the infrared red region using Fourier transformed infrared spectroscopy (FTIR). Using the model efficiency indicator, kinetic data were found to show very strong fit to the pseudo-second order kinetic model implying that the adsorption of Cu2+ and Zn2+ were basically by chemisorption.

The effects of the treatment conditions on metal ions removal in the presence of complexing agents of a new generation

The sorption of Cu(II), Zn(II), Ni(II), Cd(II) and Pb(II) ions in the presence of chelating agents of a new generation was carried out to investigate the sorption characteristics of Dowex M 4195. Influence of type and stability of sorbed complexes, sorption time, initial concentration, pH, temperature and the presence of interfering ions was estimated. For the two new biodegradable complexing agents: GLDA (tetrasodium salt of N,N-bis(carboxylmethyl)- l-glutamic acid) and EDDS (ethylenediaminedisuccinic acid) the mechanism of the sorption process was also proposed. The investigations in the single component system were conducted in the initial concentration range from 7.5 × 10 − 4 to 2.5 × 10 − 2 mol/L. The pH varied from 2.0 to 12.0, whereas temperature changed from 303 to 333 K. The adsorption data were fitted to the Langmuir, Freundlich, Temkin and Dubinin–Raduschevich models. The experimental results show that Dowex M 4195 has higher sorption capacity for heavy metal ions in the presence of EDDS than GLDA. The results also indicate that the Langmuir adsorption model was able to adequately describe the sorption of Cu(II), Zn(II), Ni(II), Cd(II) and Pb(II) ions on Dowex M 4195. The sorption followed the pseudo second order sorption kinetics.

A new chitosan biopolymer derivative as metal-complexing agent: synthesis, characterization, and metal(II) ion adsorption studies

In this study, a new chitosan biopolymer derivative (CTSL) has been synthesized by anchoring a new vanillin-based complexing agent or ligand, namely 4-hydroxy-3-methoxy-5-[(4-methylpiperazin-1-yl)methyl] benzaldehyde, (L) with chitosan (CTS) by means of condensation. The new material was characterized by elemental (CHN), spectral (FTIR and solid state 13C NMR), thermal (TG-DTA and DSC), structural (powder XRD), and morphological (SEM) analyses. The CTSL was employed to study the equilibrium adsorption of various metal ions, namely, Mn(II), Fe(II), Co(II), Cu(II), Ni(II), Cd(II), and Pb(II), as functions of pH of the solutions. Its kinetics of adsorption was evaluated utilizing the pseudo first order and pseudo second order equation models and the equilibrium data were analyzed by Langmuir isotherm model. The CTSL shows good adsorption capacity for metal ions studied in the order Cu(II) > Ni(II) > Cd(II) ⩾ Co ⩾ Mn(II) > Fe(II) > Pb(II) in all studied pH ranges due to the presence of many coordinating moieties present in it.

Study of mango biomass (Mangifera indica L) as a cationic biosorbent

Unfertilizable fruiting buds of mango plant Mangifera Indica L, an agrowaste, is used as a biomass in this study. The efficacy of the biosorbent was tested for the removal of lead, copper, zinc and nickel metal ions using batch experiments in single and binary metal solution under controlled experimental conditions. It is found that metal sorption increases when the equilibrium metal concentration rises. At highest experimental solution concentration used (150 mg/L), the removal of metal ions were 82.76 % for lead, 76.60 % for copper, 63.35 % for zinc and 59.35 % for nickel while at lowest experimental solution concentration (25 mg/L), the removal of metal ions were 92.00% for lead, 86.84 % for copper, 83.96 % for zinc and 82.29 % for nickel. Biosorption equilibrium isotherms were plotted for metal uptake capacity (q) against residual metal concentrations (Cf) in solution. The q versus Cf sorption isotherm relationship was mathematically expressed by Langmuir and Freundlich models. The values of separation factor were between zero and one indicating favourable sorption for four tested metals on the biosorbent. The surface coverage values were approaching unity with increasing solution concentration indicating effectiveness of biosorbent under investigation. The non-living biomass of Mangifera indica L present comparable biosorption capacity for lead, copper, zinc and nickel metal ions with other types of biosorbent materials found in literature and is effective to remove metal ions from single metal solutions as well as in the presence of other co-ions with the main metal of solution.

Ceria Hollow Nanospheres Produced by a Template-Free Microwave-Assisted Hydrothermal Method for Heavy Metal Ion Removal and Catalysis

Ceria hollow nanospheres composed of CeO2 nanocrystals were synthesized via a template-free and microwave-assisted aqueous hydrothermal method. This is a low-cost and environmentally benign method. The chemicals used are all environmentally benign materials (cerium nitrate, urea, and water). An Ostwald ripening mechanism coupled with a self-templated, self-assembly process, in which amorphous solid spheres are converted to crystalline nanocrystals and the latter self-assemble into hollow structures, was proposed for the formation of the hollow structures. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, and N2 adsorption−desorption methods. These ceria hollow nanospheres show an excellent adsorption capacity for heavy metal ions, for example, 22.4 mg g−1 for As(V) and 15.4 mg g−1 for Cr(VI). These values are significantly higher than reported ...

Nanoporous Silica Polyamine Composites for Metal Ion Capture From Rice Hull Ash

Rice Hull Ash (RHA) was converted to amorphous silica gel using a modified version of published literature procedures. The gels were characterized by a comparison of their CPMAS [29] Si NMR and Scanning Electron Microscopy (SEM) images with commercial silica gels. The resulting gels were silanized with a 7.5:1 mixture of methyltrichlorosilane and chloropropyltrichlorosilane and then reacted with poly(allylamine) (PAA) to produce the silica polyamine composite (SPC) BP-1. The BP-1 was then further modified with pyridine-2-carboxaldehyde to form the copper selective SPC, CuSELECT. This procedure follows that used to produce the commercialized version of these composite materials from commercially available amorphous silica gels. The composites were characterized by solid state NMR techniques, elemental analysis, SEM, porosimetry, and metal ion capacity and selectivity. The overall goal of the project was to determine the feasibility of using RHA to make SPC. The observed strengths and weaknesses of this approach are discussed.

Surface display on gram positive bacteria.

Heterologous surface display on Gram-positive bacteria was first described almost a decade ago and has since then developed into an active research area. Gram-positive bacterial surface display has today found a range of applications, in immunology, microbiology and biotechnology. Live bacterial vaccine delivery vehicles are being developed through the surface display of selected foreign antigens on the bacterial surfaces. In this field, "second generation" vaccine delivery vehicles are at present being generated by the addition of mucosal targeting signals through co-display of adhesins, in order to achieve targeting of the live bacteria to immunoreactive sites to thereby increase immune responses. Engineered Gram-positive bacteria are further being evaluated as novel microbial biocatalysts with heterologous enzymes immobilized as surface exposed on the bacterial cell surface. A discussion has started whether bacteria can find use as new types of whole-cell diagnostic devices since single-chain antibodies and other variants of tailor-made binding proteins can be displayed on bacteria. Bacteria with increased binding capacity for certain metal ions can be created and potential environmental or biosensor applications for such recombinant bacteria as biosorbents are being discussed. This article explains the basis of Gram-positive bacterial surface display, and discusses current uses and possible future trends of this emerging technology.

A new electron exchange material Ti(IV) iodovanadate: Synthesis, characterization and analytical applications

Abstract A new inorganic cation exchange material Ti(IV) iodovanadate has been synthesized under a variety of conditions. The experimental parameters such as mixing volume ratio, order of mixing and pH established for the synthesis of the material. The most stable sample has been prepared by adding aqueous mixture of 0.1 M potassium iodate and 0.1 M sodium vanadate into 0.1 M solution (CCl 4 medium) of titanium chloride at pH 1. The material is characterized using various analytical techniques like XRD, FTIR, TGA–DTA and SEM. A tentative structural formula has been proposed on the basis of chemical composition, pH titration, FTIR and thermogravimetric analysis. The ion exchange capacity and distribution coefficients of various metal ions have been determined to understand the cation exchange behavior of the material. On the basis of distribution studies, the material was found to be selective for Pb 2+ ion. Its selectivity has been examined by achieving some important and analytically difficult binary separations, viz. Cr 3+ –Pb 2+ , Fe 3+ –Pb 2+ , Zn 2+ –Pb 2+ , Cd 2+ –Pb 2+ , etc. The material has bee also used as an electron exchange material. The oxidation of Fe(II) to Fe(III) has been achieved by batch-equilibrium technique successfully. The decomposition of hydrogen peroxide by the material has also been studied. The practical utility of Ti(IV) iodovanadate has been demonstrated by separating metal ions quantitatively from a synthetic mixture using the packed column of Ti(IV) iodovanadate.

Dual Modification of Banana Starch: Partial Characterization

AbstractBanana starch was double modified by cross‐linking and substitution, using two different cross‐linking agents, i.e. phosphorus oxychloride (POCl3) and a mixture of sodium trimetaphosphate/sodium tripolyphosphate. The morphological and physicochemical properties and the absorption capacity for heavy metals of the modified starches were assessed. Double modified starch granules (cross‐linked carboxymethyl starches CCSA and CCSB) presented changes in the surfaces. These starches had a bigger average particle size than unmodified starch due to the swelling of the granules during the chemical modification, also aggregates were formed. The double modified banana starches presented an A‐type X‐ray diffraction pattern with slightly decreased crystallinity compared with the unmodified counterparts. The double modification of banana starch decreases the temperature and enthalpy of gelatinization and the decomposition temperature. These results are related to partial disorganization during the chemical treatment. The double modified banana starch possess sorption capacity for heavy metal ions in the order Cd2+ >Pb2+>Cu2+>Hg2+. Due to their physicochemical characteristics and absorption capacity, the double modified banana starches can be used in diverse applications.

Synthesis and characterization of electrically conducting poly- o-methoxyaniline Zr(1V) molybdate Cd(II) selective composite cation-exchanger

In this study a composite cation-exchanger poly- o-methoxyaniline Zr(1V) molybdate was prepared and the ion-exchange properties like ion-exchange capacity for different metal ions, elution behavior, pH titration and a temperature dependent study of ion-exchange capacity were explored. The physical properties of the material were also determined using TGA–DTA, FTIR, X-ray and SEM studies. The results of physical properties were found progressive in terms of their specific properties. Electrical conductivity of this composite determined by four-in-line probe method was found to be in semi-conducting range i.e. 10 − 4 –10 − 2 S cm − 1 . The adsorption efficiency towards heavy metal ions was determined by distribution studies and material was found highly selective for cadmium a heavy toxic metal ion indicating the utility for the removal from waste stream.

Metal coordination and selectivity with oxine ligands bound to silica polyamine composites

AbstractA series of oxine ligands, 5‐X, 8OHC9H6N (X = H, Cl, SO3H) have been covalently bound to a silica gel polyamine composite made from a silanized amorphous silica xerogel and poly(allylamine) (BP‐1) by the Mannich reaction. The resulting modified composites WP‐4(X = H), CB‐1(X = Cl), and SB‐1(X = SO3H) were characterized by elemental analysis, FTIR, and solid state CPMAS‐13C‐NMR. Using the analytical data before and after the ligand modification, the ligand loading could be estimated and in combination with metal ion capacities a metal to ligand ratio could be obtained. The composites WP‐4 and CB‐1 both showed ratios of approximately 1 : 1 while the sulfonate modified composite, SB‐1, showed a metal to ligand ratio of 1 : 2. This is tentatively interpreted in terms of a zwitterionic oxine as the dominant species at pH = 2 where the sulfonic acid group is ionized, the quinoline nitrogen is protonated and where two sulfonate groups on adjacent oxines bind a trivalent or divalent ion. All the modified composites show a clear selectivity for trivalent over divalent ions and a good selectivity for gallium over aluminum. The substituent groups on the oxine ligand have only a minor influence on these selectivity trends but SB‐1 shows slightly better capture kinetics. The selectivity for gallium over aluminum is applied to the separation of gallium from aluminum, ferrous, and zinc in an acid ore leach of solid tailings obtained from a zinc mine using WP‐4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis and Characterization of Zirconium Titanium Hydroxy Ethylidene Diphosphonate and Its Application in Separation of Metal Ions

A novel hybrid ion exchanger, zirconium titanium hydroxy ethylidene diphosphonate (ZTHEDP), of the class of tetravalent bimetallic acid (TBMA) salt has been synthesized by the sol gel route. ZTHEDP has been characterized for ICP-AES, TGA, FTIR, and XRD. Chemical resistivity of ZTHEDP in various media—acids, bases, and organic solvents have been assessed. Ion exchange capacity (IEC) and the effect of calcination (100°C to 500°C) on IEC has also been studied. The distribution behavior of metal ions Co2+, Ni2+, Cu2+, Zn2+ (d-block), Cd2+, Hg2+, Pb2+, Bi3+ (heavy) and La3+, Ce3+, Th4+, (f-block) towards ZTHEDP has been studied and the distribution coefficient (K d ) evaluated in aqueous as well as various electrolyte media/concentrations. Based on differential selectivity, the breakthrough capacity (BTC) and elution behavior of various metal ions towards ZTHEDP, a few binary and ternary metal ion separations have been carried out.

Preparation and characterization of novel composites based on chitosan and clinoptilolite with enhanced adsorption properties for Cu 2+

Novel ionic composites based on chitosan (CS) and clinoptilolite (CPL), a widespread natural zeolite, were prepared in this work as microspheres by a “tandem” ionic/covalent cross-linking. The mass ratio between CPL and CS was varied in the range 1:10–1:2. The ionic gelation of CS was performed with sodium tripolyphosphate and epichlorohydrin was used as covalent cross-linker. An abrupt increase of the adsorption capacity for Cu 2+ with the increase of the CPL content loaded in the composite compared with cross-linked CS was observed, up to 20 wt.% of CPL. The external stimuli which control the adsorption of Cu 2+ were solution pH and temperature. The optimum adsorption pH was 5.0 and the adsorption process was well described by the pseudo-second-order kinetics. The maximum adsorption capacity of metal ions was observed after the 2nd cycle of adsorption, for all composites.

Surface-modified nanoscale carbon black used as sorbents for Cu(II) and Cd(II)

Commercial carbon blacks often have low adsorption capacity for metal ions. Surface modification of them by appropriate physical and chemical treatments could improve their absorption capacities, and hence extend their environmental application. A surface-modified nanoscale carbon black was prepared by oxidizing the carbon black with 65% HNO 3. Batch experiments showed that the adsorption quantities of Cu(II) or Cd(II) on this modified carbon black (MCB) were significantly increased compared with those on the parent one, and the maximum adsorption quantities of Cu(II) and Cd(II) on the MCB were 438 and 282 mmol kg −1, respectively. The desorption percentages of Cu(II) or Cd(II) from the MCB increased with the increasing quantities initially adsorbed. In the binary system of Cu(II) and Cd(II), these two metal ions exhibited competition on the MCB, preferential for Cu(II). It could be concluded that the MCB had very good adsorption properties for the metal ions, and could be applied in the purification of wastewater containing such metal ions.

Surface modification and adsorption of eucalyptus wood-based activated carbons: Effects of oxidation treatment, carbon porous structure and activation method

The incorporation of oxygen functional groups onto the surface of eucalyptus activated carbon and its sur- face chemistry were investigated as a function of oxidation conditions, carbon porous properties and carbon preparation method. Under all treatment conditions of increasing time, temperature and oxidant concentration, liquid oxidation with HNO3, H2O2 and (NH4)2S2O8 and air oxidation led to the increase of acidic group concentration, with carboxylic acid showing the largest percentage increase and air oxidation at the maximum allowable temperature of 350 o C pro- duced the maximum content of both carboxylic acid and total acidic group. Nitric acid oxidation of chemically activated carbon produced higher total acidic content but a lower amount of carboxylic acid compared to the oxidized carbon from physical activation. The increased contents of acidic groups on oxidized carbons greatly enhanced the adsorption capacity of water vapor and heavy metal ions.

Synthesis, characterization, and ion-exchange properties of colloidal zeolite nanocrystals

Here, we present physical–chemical properties of Linde type A (LTA) zeolite crystals synthesized via conventional hydrothermal and microwave heating methods. Both heating methods produced LTA crystals that were sub-micron in size, highly negatively charged, super-hydrophilic, and stable when dispersed in water. However, microwave heating produced relatively narrow crystal size distributions, required much shorter heating times, and did not significantly change composition, crystallinity, or surface chemistry. Moreover, microwave heating allowed systematic variation of crystal size by varying heating temperature and time during the crystallization reaction, thus producing a continuous gradient of crystal sizes ranging from about 90 to 300 nm. In ion-exchange studies, colloidal zeolites exhibited excellent sorption kinetics and capacity for divalent metal ions, suggesting their potential for use in water softening, scale inhibition, and scavenging of toxic metal ions from water.

Synthesis and characterization of zirconium titanium phosphate and its application in separation of metal ions

An advanced inorganic ion exchanger, zirconium titanium phosphate (ZTP) of the class of tetravalent bimetallic acid (TBMA) salt has been synthesized by sol–gel route. ZTP has been characterized for ICP-AES, TGA, FTIR and XRD. Chemical stability of the material in various media-acids, bases and organic solvents has been assessed. Cation exchange capacity (CEC) and effect of calcination (100–500 °C) on CEC has also been studied. Distribution behaviour of metal ions Co 2+, Ni 2+, Cu 2+, Zn 2+ (d-block), Cd 2+, Hg 2+, Pb 2+, Bi 3+ (heavy) and La 3+, Ce 3+, Th 4+, UO 2 2+ (f-block) towards ZTP has been studied and distribution coefficient ( K d ) determined in aqueous as well as various electrolyte media/concentrations. Based on the differential selectivity, breakthrough capacity (BTC) and elution behaviour of various metal ions towards ZTP, a few binary and ternary metal ion separations have been carried out.