Investigation on sorption equilibria of Mn(II), Cu(II) and Cd(II) on a carboxylic resin by the Gibbs-Donnan model

Sorption mechanism of bivalent metal ions on a weak cationic resin containing the carboxylic group is studied. The Gibbs-Donnan model is used to describe and then to predict the sorption through the determination of the intrinsic complexation constants. These quantities characterize the sorption being independent of experimental conditions. They are determined according to a well established procedure and using a recently proposed iterative method for calculation of counter ion concentration in the resin phase. Sorption mechanisms are also studied adding appropriate soluble ligands whose complexing properties are exactly known to the solution containing the resin and the metal ion. Competing with the resin for the complexation of the metal, they shift the sorption curve to higher pH and often this allows detecting other complexes between the metal and the resin. In this way for Mn(II), besides the 1:1 complex formed in the more acidic solution, with logbeta(110)=-4.55, the complex ML(2), characterized by logbeta(120)=-9.80, is found; for Cd(II), besides the ML complex, with logbeta(110)=-3.01, at pH higher than 7, the specie MLOH with logbeta(11-1)=-8.28. For Cu(II) the complex ML(2) is detected, confirming previous findings, with logbeta(120)=-7.24. In the presence of two different ligands, sulphosalicylic and malonic acid, a different complex, ML(2)OH, is identified, with the same intrinsic complexation constant for the two ligands, logbeta(12-1)=-13.35. As expected from the model, the intrinsic complexation constants, especially for the 1:1 complex, are in a good agreement with the complexation constants of acetic acid.     

Batchwise separation of gallium by an anion exchange resin loaded with a sulphonated azo dye

Gallium(III) is sorbed by a strong base anion exchange resin loaded with a sulphonated azo-dye, T-azo-R [1-(tetrazolylazo)-2-hydroxynaphthalene-3,6-disulphonic acid], which is able to complex it in aqueous solution. As sorption takes place at acidities at which the hydrolysis of gallium is not negligible, it must be considered as conconmitant equilibrium. The distribution equilibria depend on the amount of ligand sorbed, and on the volume, acidity and ionic composition of the aqueous solution, according to the Gibbs-Donnan model. The thermodynamic complexation constant in the resin phase can be calculated from the experimental distribution coefficients; the value of log K = -1.24(0.20) is in acceptable agreement with that in aqueous solution [log K = -0.75(0.33)] which was also determined in the present investigation. Two equations deriving from the Gibbs-Donnan model are used for predicting the conditions for sorption and elution of gallium by a batch procedure, and for separating it from aluminium.     

Sorption of protons and metal ions from aqueous solutions by a strong-base anion-exchange resin loaded with sulphonated azo-dyes

Two sulphonated azo-dyes, which bear a nitrogen donor atom in the diazo group and are known to complex many heavy metal ions in aqueous solution, have been found to be sorbed by a strong-base anion-exchange resin (Dowex 1-X8) simply by ion-exchange. The resin containing the dyes behaves like a chelating resin, able to sorb copper(II) and nickel(II) from aqueous solution, if the proper conditions are chosen. The acidity, ionic composition and volume of the aqueous solution, and the amount and nature of the sorbed ligand are the factors which determine the fraction of metal ion sorbed when the batch technique is used. The experimental results are interpreted by using a model of the resin based on the Donnan equilibrium concept, which allows prediction of the sorption conditions on the basis of some independently determined quantities, such as the protonation and complex formation constants in aqueous solution, and the activity of the counter-ion in the resin phase. The exchange of protons between the resin and the aqueous solution can also be explained with this model.     

STUDIES ON THE SORPTION OF MACROPOROUS PHOSPHONIC ACID RESIN FOR LANTHANUM

The influences of Medium pH,sorption temperature,sorption time,etc.on the sorption capacity of macroporous phosphonic acid resin for La^3+ were determined.The sorption rate constant was k298=7.64×10^-5 s^-1. The complex ratio of phosphonic groups of the resin to La^3+ was 3:1.The basic sorption parameters were determined. The sorption mechanism of macroporous phosphonic acid resin for La^3+ was examined by chemical analysis and IR-spectrometry.     

The influence of temperature on the ion exchange properties of phenolformaldehyde sorbents

The influence of temperature on cation exchange on phenol groups of macroporous materials based on phenolformaldehyde resins (PFRs) was studied for Amberlit XAD 761 with irregularly shaped grains obtained by breaking up polycondensation resin blocks and FFS-1.4/0.7 with spherical granules. An increase in temperature caused some decrease in the sorption capacity of PFRs in the alkaline region, but almost did not influence the selectivity of alkali metal ion exchange. The sorption capacity and selectivity of PFRs did not change after multiple (dozens of cycles) transfer of phenol groups from the hydrogen to salt form and back. Ion exchangers of this type can effectively be used for separating mixtures of alkali metal ions containing cesium and rubidium.     

Study of <Superscript>63</Superscript>Ni(II) sorption on CMC-bound bentonite from aqueous solutions

Bentonite was investigated to remove Ni(II) from aqueous solutions because of its strong sorption ability. Herein, bentonite was modified with sodium carboxymethylcellulose (CMC) and used as an adsorbent to remove Ni(II) from aqueous solutions. The results indicated that CMC-bentonite had higher sorption capacity than bare bentonite in the sorption of Ni(II) from aqueous solutions. Sorption of Ni(II) on CMC-bentonite was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, but by inner-sphere surface complexation or surface precipitation at high pH values. The thermodynamic data calculated from temperature dependent sorption isotherms indicated that the sorption of Ni(II) to CMC-bentonite hybrids was an spontaneous process and enhanced with increasing temperature.     

弱碱性阴离子交换树脂的本征解离常数

根据Donnan膜平衡模型及外推法提出弱碱性阴离子交换树脂本征解离常数的测定方法。并测得大孔丙烯酸系弱碱性阴离子树脂D705的本征解离常数的负对数pK_b~(int)为3.72士0.04,结果表明,Marinsky在测弱酸性阳离子树脂的pK_a~(int)时,引入交换剂相中H~+及Na~+的活度系数相等的假定并非必要。     

Application of the new thermodynamic approach to the description of superequivalent sorption by ion exchangers

Using the example of sorption systems with the participation of amino acids, it is shown that the novel thermodynamic approach to describing superequivalent sorption as a combination of ion exchange and nonexchangeable absorption allows us to adequately describe such equilibria. Results from calculating the activity coefficients of components of a sorbent phase and the thermodynamic constants of ion exchange equilibrium and the superequivalent absorption of phenylalanine by AV-17-8 anion exchange resin are presented.     

Sorption of uranium(VI) on Na-attapulgite as a function of contact time,solid content,pH, ionic strength,temperature and humic acid

Sorption of U(VI) from aqueous solution to Na-attapulgite was investigated at different experimental chemistry conditions by using batch technique. The attapulgite sample was characterized by FTIR and XRD. Sorption of U(VI) on attapulgite was strongly dependent on pH and ionic strength. The sorption of U(VI) on attapulgite increased quickly with rising pH at pH < 6, and decreased with increasing pH at pH > 7. The presence of humic acid (HA) enhanced the sorption of U(VI) on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA with U(VI) on attapulgite surface. Sorption of U(VI) on attapulgite was mainly dominated by ion exchange and/or outer-sphere surface complexation at low pH values, whereas the sorption was attributed to the inner-sphere surface complexation or precipitation at high pH values. The sorption increased with increasing temperature and the thermodynamic parameters calculated from the temperature dependent sorption isotherms suggested that the sorption of U(VI) on attapulgite was a spontaneous and endothermic process. The results indicate that attapulgite is a very suitable material for the preconcentration of U(VI) ions from large volumes of aqueous solutions.     

Nickel(II) complexing with glycylglycine and acid-base equilibria of the ligand in aqueous ethanol solvents

The protonation and dissociation constants of glycylglycine and the stability constants of its complexes with nickel(II) in aqueous ethanol of a variable composition with the ethanol mole fraction ranging from 0.00 to 0.55 are determined potentiometrically at a 0.1 M (NaClO₄) ionic strength and temperature of 298 K. The stability of nickel(II) complexes of glycylglycine is found to grow with an increase in ethanol concentration in a solution. The solvation contributions of reagents into the displacement of complexing equilibria are analyzed. The change in the stability of nickel(II) glycylglycinate complexes is explained by the weakening of ligand solvation in aqueous ethanol.     

Thermodynamic parameters of complexation reactions between nickel(II) ion and L-serine in aqueous solutions

A thermochemical study of coordination equilibria in the nickel(II) ions-L-serine system was carried out. The heats of reaction between solutions of an amino acid and nickel(II) nitrate at 288.15, 298.15, and 308.15 K and ionic strength of 0.25, 0.50, and 0.75 (KNO₃) were measured. The heats of dilution of nickel nitrate solution in background electrolyte solutions were determined under identical conditions to make proper corrections. The results were processed with allowance for stepwise equilibria. The standard thermodynamic parameters of the complexation processes were calculated. The effect of temperature on heats of complexation reactions in the L-serine-nickel(II) ions was studied. The standard enthalpies of formation of NiSer⁺, NiSer₂, and NiSer ₃ ^? complexes in aqueous solutions were determined.     

Fungal biomass with grafted poly(acrylic acid) for enhancement of Cu(II) and Cd(II) biosorption

The biomass of Penicillium chrysogenum was modified by graft polymerization of acrylic acid (AAc) on the surface of ozone-pretreated biomass. The sorption capacity for copper and cadmium increased significantly as a large number of carboxyl groups were present on the biomass surface, especially when the carboxylic acid group was converted to carboxylate ions using NaOH. When modeled using the Langmuir isotherm, the sorption capacities were 1.70 and 1.87 mmol g(-1) for copper and cadmium, respectively. The loaded biosorbent was regenerated using HCl solution and used repeatedly over five cycles with little loss of uptake capacity beyond the second cycle. The sorption of the two metals was time-dependent, and the kinetics fitted the pseudo-second-order equation well. The Freundlich, Langmuir, Temkin, and Dubinin-Redushkevich isotherms were used to model the metal sorption isotherms, and the thermodynamic parameters calculated show that the sorption was spontaneous and endothermic under the condition applied and that the biomass has similar sorption affinities for the two metals. Fourier transform infrared and X-ray photoelectron spectroscopy reveal that carboxyl, amide, and hydroxyl groups on the biomass surface were involved in the sorption of copper and cadmium and ion exchange and complexation dominated the sorption process.     

Adsorption of Cu(II), Zn(II), Ni(II), Pb(II), and Cd(II) from aqueous solution on Amberlite IR-120 synthetic resin

The adsorption of copper(II), zinc(II), nickel(II), lead(II), and cadmium(II) on Amberlite IR-120 synthetic sulfonated resin has been studied at different pH and temperatures by batch process. The effects of parameters such as amount of resin, resin contact time, pH, and temperature on the ion exchange separation have been investigated. For the determination of the adsorption behavior of the resin, the adsorption isotherms of metal ions have also been studied. The concentrations of metal ions have been measured by batch techniques and with AAS analysis. Adsorption analysis results obtained at various concentrations showed that the adsorption pattern on the resin followed Freundlich isotherms. Here we report the method that is applied for the sorption/separation of some toxic metals from their solutions.     

Removal of Co(II) from aqueous solution by using hydroxyapatite

Herein, hydroxyapatite (HAP) was prepared by aqueous precipitation technique and was characterized by using FT-IR and XRD to determine its chemical functional groups and micro-structure. The removal of cobalt from aqueous solution to HAP was studied by batch technique as a function of various environmental parameters such as contact time, pH, ionic strength, foreign ions, fulvic acid (FA), and temperature under ambient conditions. The results indicated that the sorption of Co(II) on HAP was strongly dependent on pH and ionic strength. The presence of FA enhanced the sorption of Co(II) on HAP at low pH, whereas reduced Co(II) sorption on HAP at high pH. The Langmuir, Freundlich and D-R models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent sorption isotherms indicated that the sorption process of Co(II) on HAP was spontaneous and endothermic. The sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The results suggest that the HAP is a suitable material in the preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Preconcentration of U(VI) ions on few-layered graphene oxide nanosheets from aqueous solutions

Graphene oxide nanosheets have attracted multidisciplinary attention due to their unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using a modified Hummers method and were characterized by TEM, AFM, Raman spectroscopy, XPS, FTIR spectroscopy, TG-DTA and acid-base titrations. The prepared few-layered graphene oxide nanosheets were used as adsorbents for the preconcentration of U(VI) ions from large volumes of aqueous solutions as a function of pH, ionic strength and temperature. The sorption of U(VI) ions on the graphene oxide nanosheets was strongly dependent on pH and independent of the ionic strength, indicating that the sorption was mainly dominated by inner-sphere surface complexation rather than by outer-sphere surface complexation or ion exchange. The abundant oxygen-containing functional groups on the surfaces of the graphene oxide nanosheets played an important role in U(VI) sorption. The sorption of U(VI) on graphene oxide nanosheets increased with an increase in temperature and the thermodynamic parameters calculated from the temperature-dependent sorption isotherms suggested that the sorption of U(vi) on graphene oxide nanosheets was an endothermic and spontaneous process. The maximum sorption capacities (Q(max)) of U(VI) at pH 5.0 ± 0.1 and T = 20 °C was 97.5 mg g(-1), which was much higher than any of the currently reported nanomaterials. The graphene oxide nanosheets may be suitable materials for the removal and preconcentration of U(VI) ions from large volumes of aqueous solutions, for example, U(VI) polluted wastewater, if they can be synthesized in a cost-effective manner on a large scale in the future.     

Chromatographic behaviour of trace metal ions on a strong base anion exchange resin functionalized by azo ligands

A model which allows the evaluation of the elution volume V(E) and the central point V(C) of the breakthrough curve of a metal ion at trace level on a chromatographic column containing a chelating resin is presented. V(E) and V(C) mainly depend on the complexation properties of the active groups, and on the acidity and composition of the aqueous solution, according to the Gibbs-Donnan model for the resin. The model has been tested in the case of strong base anion exchange resins in chloride form functionalized with two different sulphonated azo ligands (T-azo-C, T-azo-R). The chromatographic behaviour of copper(II) and thorium(IV) is as expected from the formation of a complex with the azo dye in the resin, while that of zinc(II) and cadmium(II) is fully described by also taking into account the formation of anionic chloro complexes inside the resin.     

胺基修饰的高度交联聚苯乙烯树脂对间苯二酚吸附行为研究

研究了AH系列胺基修饰的超高交联树脂对水溶液中间苯二酚的静态吸附行为特征,结果表明,它们对间苯二酚的吸附容量明显高于母体交联树脂NDA-100和大孔弱碱性阴离子交换树脂D301.AH系列树脂与吸附质分子之间不仅有范德华作用力,还存在着氢键等作用力.该类树脂对间苯二酚的吸附为自发的放热过程,属于以物理作用为主兼有弱化学作用的吸附过程.吸附速率符合准一级动力学方程,表观吸附速率常数随树脂胺基含量的升高而降低.     

Sorption behavior of hydroxyapatite for 109Cd(II) as a function of environmental conditions

In this work, hydroxyapatite (HAP) was prepared by aqueous precipitation technique and was characterized by using FT-IR to determine its chemical functional groups. A series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, foreign ions, fulvic acid (FA) and temperature on the sorption behavior of HAP towards radionuclide ¹⁰⁹Cd(II). The results indicated that the sorption of ¹⁰⁹Cd(II) on HAP was strongly dependent on pH and ionic strength. A positive effect of FA on ¹⁰⁹Cd(II) sorption was found at pH <7.0, whereas a negative effect was observed at pH >7.0. The Langmuir, Freundlich and D-R models were used to simulate the sorption isotherms at three different temperatures of 298.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH⁰, ΔS⁰ and ΔG⁰) calculated from the temperature dependent sorption isotherms indicated that the sorption process of ¹⁰⁹Cd(II) on HAP was spontaneous and endothermic. At low pH, the sorption of ¹⁰⁹Cd(II) was dominated by outer-sphere surface complexation and ion exchange on HAP surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that HAP has good potentialities for cost-effective treatments of ¹⁰⁹Cd(II)-contaminated wastewaters.     

Sorption Studies of Nickel ions Onto Sawdust of Dalbergia Sissoo

Sawdust of Dalbergia sissoo, a byproduct of sawmills, was found to be a promising adsorbent for the removal of nickel ions from aqueous solution. Sorption of nickel ions onto sawdust of Dalbergia sissoo was studied using the batch technique. Kinetics studies show that nickel ions sorption process obeys a first order rate law. The applicability of the Langmuir and Freundlich models for the data was tested. Both the models adequately describe the experimental data of the biosorption of nickel ions. The sorption capacities and energies were calculated. Langmuir parameters X_m and K₁ were found to increase with rise in temperature; Freundlich constants 1/n and K_f have been evaluated for 293K, 303K, 313K and 323K. Thermodynamic parameter ΔH° = 4.80 kJ mol^?;1 shows that sorption of nickel ions onto sawdust is an endothermic process.     

乙酰丙酮基聚苯乙烯在萃取金属离子上的应用

大孔的苯乙烯-二乙烯苯共聚物经氯甲基化后,分别与乙酰丙酮镍、乙酰丙酮钠和四正丁基乙酰丙酮铵三种不同的乙酰丙酮盐反应,可制得聚3-(p-乙烯苄基)戊二酮-[2,4]。其中以由乙酰丙酮镍制得的聚合物最好,除二乙烯苯外,78%左右的苯环乙酰丙酮化了。该聚合物螯合Fe~(3 )和Ni~(2 )的能力与β-二酮基高聚物相仿或稍优。还比较了此类高聚物的物理机械性能。