Sorption of aqueous palladium onto synthetic hydroxyapatite

The sorption of Pd(II) on hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) has been studied at 25 °C as a function of pH, in 0.01 M NaClO₄, and 0.01 and 0.025 M Ca(ClO₄)₂ aqueous background electrolytes and Pd(II) concentration (9.3 to 47 ??M), trying to minimize some types of reactions, such as solid dissolution of and metal precipitation. The radiotracer palladium, ¹⁰⁹Pd, obtained by neutron irradiation, has been used to calculate the palladium??s distribution coefficients K _d between aqueous and solid phase. A mathematical treatment of results has been made by ion-exchange theory in order to interpret palladium sorption onto treated solid. For this, we take into account the existence of active sites at the hydroxyapatite surface, and the aqueous solution chemistry of palladium as well as the effect of phosphate anions from solid dissolution. The results can be explained as evidence of sorption of the species PdOH⁺, and of a mixed hydroxo complex of Pd²⁺ like (XCaO^?)?CPdOH⁺·nH₂O fixed onto {??Ca?COH} surface sites of the hydroxyapatite.     

Sorption of arsenic onto inorganic sorbents modified with iron compounds

Granulated inorganic sorbents based on silica gel of KSKG grade and aluminum oxide and modified with Fe(III) compounds were developed for water treatment to remove As(V). The influence of the particle size of the modifying additive on the ability of silica gel to take up As(V) was examined. The KSKG-based sorbents modified with nanoparticles of Fe(III) compounds exhibit the highest sorption capacity. The capacity of silica gel based sorbents modified with nanoparticles of iron compounds for As(V) is higher than that of analogous sorbents modified with iron oxides prepared by thermal decomposition of Fe(III) nitrate.     

Sorption of aqueous carbonic, acetic, and oxalic acids onto alpha-alumina

The presence of organic complexing agents can modify the behavior of a surface. This study aims to better understand the impact of carboxylic acids (acetic, oxalic, and carbonic acids) issued from cellulose degradation and equally naturally present in soils. First, evidence of two different kinds of sites for chloride adsorption onto alpha-alumina and another for sodium sorption was provided. Consequently, no competition between these cation and anion sorptions occurs on alpha-alumina. The associated exchange capacities and ionic exchange constants were measured. Second, the adsorption behavior of the carboxylic acids was studied as a function of aqueous -log[H(+)] and 0.01 to 0.1 M ionic strength (NaCl), and modeled by using mass action law for ideal biphasic systems. The carboxylic acids were found to be adsorbed on the same sites as chloride ions. The competition between organic ligands and chloride ions was satisfactorily accounted for by the model assuming the deprotonated form of the ligands was sorbed on alpha-alumina. The model also allowed us to interpret the adsorption of all species under various conditions without any extra fitting parameters.     

Sorption of anti-infective organic molecules from aqueous solutions onto zirconium phosphate

Amorphous zirconium phosphate (ZP), an inorganic ion exchange material of tetravalent metal acid (tma) salt, is synthesized by the sol-gel method and characterized by elemental analysis (ICP-AES), thermal analysis (TGA, DSC), FT-IR and X-ray diffraction studies. The resistivity of the material to acids, bases and organic solvents is assessed. The sorption behavior of the dyes acriflavin (AF) and brilliant green (BG) toward ZP was studied at 313, 323 and 333 K and the kinetic and thermodynamic parameters evaluated. Adsorption isotherms [Langmuir and Fruendlich], breakthrough capacity and elution behavior of these dyes are also studied. The sorption affinity of dyes towards ZP is BG > AF.     

Sorption of cadmium ions from aqueous solutions onto nanoporous modified carbon sorbents

Physicochemical properties of nanoporous modified carbon sorbents and sorption of cadmium ions (0.1–20 mg L^?1) onto them from nitrate solutions at pH 5–7 were studied. The acid-base nature of functional oxygen-containing groups on the carbon surface of the sorbents was determined. The ability to sorb cadmium ions depends on the kind of chemical modification of the sorbent surface.     

Sorption of thallous ion from acidic aqueous solutions onto ETS-10 titanosilicate

The sorption of the thallous ion from aqueous acidic solution (pH = 1.5) onto as-synthesized and modified ETS-10 titanosilicates was studied by using an isotope dilution method and a batch-mode technique. The present results show that the thallium(I) sorption was effective onto all three considered materials and is enhanced by the porosity and acidity modification of the ETS-10 titanosilicate. The best uptake performance was achieved by the meso-ETS-10. This behavior is explained based on the newly created additional mesoporous system and enriching the external surface with silanol groups. Also, the presence of phosphorus enhanced the inherent porosity allowing thus better internal diffusion properties of crystalline material. However, the chemically modified surface seems to have a negative contribution to the kinetic uptake of thallous ion as shown by the positive value of the activation energy E _a, in comparison with the processes more favorable energetically for ETS-10 and meso-ETS-10 materials.     

Simultaneous determination of arsenic, selenium and antimony species using HPLC/ICP-MS

A new method for the simultaneous separation and determination of four arsenic species [As(III), As(V), monomethylarsonic acid and dimethylarsinic acid], three selenium species [Se(IV), Se(VI) and selenomethionine] as well as Sb(III) and Sb(V) is presented. The speciation was achieved by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as the composition and pH of the mobile phase were optimised. Limits of detection are below 4.5 μg L^–1 (as element) for Sb(III) and the selenium species and below 0.5 μg L^–1 for the other species. Precisions of retention times were better than 2% RSD and of peak areas better than 8% RSD for all the species investigated. Received: 13 January 1999 / Accepted: 4 March 1999     

Simultaneous determination of arsenic, selenium and antimony species using HPLC/ICP-MS

A new method for the simultaneous separation and determination of four arsenic species [As(III), As(V), monomethylarsonic acid and dimethylarsinic acid], three selenium species [Se(IV), Se(VI) and selenomethionine] as well as Sb(III) and Sb(V) is presented. The speciation was achieved by on-line coupling of anion exchange high-performance liquid chromatography (HPLC) with inductively coupled plasma mass spectrometry (ICP-MS). Chromatographic parameters such as the composition and pH of the mobile phase were optimised. Limits of detection are below 4.5 μg L^–1 (as element) for Sb(III) and the selenium species and below 0.5 μg L^–1 for the other species. Precisions of retention times were better than 2% RSD and of peak areas better than 8% RSD for all the species investigated.     

Assessment of total arsenic and arsenic species stability in alga samples and their aqueous extracts

In order to achieve reliable information on speciation analysis, it is necessary to assess previously the species stability in the sample to analyse. Furthermore, in those cases where the sample treatment for species extraction is time-consuming, an assessment of the species integrity in the extracts is of paramount importance. Thus, the present paper reports total arsenic and arsenic species stability in alga samples (Sargassum fulvellum and Hizikia fusiformis), as well as in their aqueous extracts, which were stored in amber glass and polystyrene containers at different temperatures. Total arsenic determination was carried out by inductively coupled plasma atomic emission spectroscopy (ICP-AES), after sample acid digestion in a microwave oven, while arsenic speciation was conducted by anion exchange high performance liquid chromatography on-line coupled to ICP-AES, with and without sample introduction by hydride generation (HPLC-ICP-AES and HPLC-HG-ICP-AES), after aqueous microwave-assisted extraction. The results obtained for solid alga samples showed that total arsenic (for Hijiki alga) and arsenic species present (As(V) for Hijiki and NIES No. 9 Sargasso) are stable for at least 12 months when samples are stored in polystyrene containers at +20 degrees C. On the other hand, a different behaviour was observed in the stability of total arsenic and As(V) species in aqueous extracts for both samples, being the best storage conditions for Sargasso extracts a temperature of -18 degrees C and polystyrene containers, under which they are stable for at least 15 days, while Hijiki extracts must be stored in polystyrene containers at +4 degrees C in order to ensure the stability for 10 days.     

Sorption of uranium(VI) from aqueous solution onto magnesium silicate hollow spheres

The sorption of uranium(VI) from aqueous solutions was investigated using synthesized magnesium silicate hollow spheres as a novel adsorbent. Batch experiments were conducted to study the effects of initial pH, amount of adsorbent, contact time and initial U(VI) concentrations on uranium sorption efficiency. The desorbing of U(VI) and the effect of coexisting ions were also investigated. Kinetic studies showed that the sorption followed a pseudo-second-order kinetic model. The Langmuir sorption isotherm model correlates well with the uranium sorption equilibrium data for the concentration range of 25–400 mg/L. The maximum uranium sorption capacity onto magnesium silicate hollow spheres was estimated to be about 107 mg/g under the experimental conditions. Desorption of uranium was achieved using inorganic acid as the desorbing agent. The practical utility of magnesium silicate hollow spheres for U(VI) uptake was investigated with high salt concentration of intercrystalline brine. This work suggests that magnesium silicate hollow spheres can be used as a highly efficient adsorbent for removal of uranium from aqueous solutions.     

Sorption behavior of Sn(II) onto Haro river sand from aqueous acidic solutions

The sorption behavior of Sn(II) onto Haro river sand has been examined with respect to nature of electrolyte, agitation time, dosage of sorbent and concentration of sorbate. Maximum sorption (95.5%) has been achieved from 0.034M hydrochloric acid solution after equilibrating sorbate (2·10⁻⁵M) and sorbent (50 mg) for 120 minutes at aV/W ratio of 90 cm³·g⁻¹. The kinetic data have been subjected to Morris-Weber and Lagergren equations. The kinetics of sorption proceeds a two stage process consisting of a relatively slow initial uptake followed by a much rapid increase in the sorption. The rate constant of intraparticle transport, K_d, comes out to be 8.75·10⁻⁸ mol·g⁻¹·min^−1/2 and the first order rate constant for sorption is 0.0416 min⁻¹. The sorption data of Sn(II) onto Haro river sand followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) type isotherms. The Langmuir constant,Q, related to sorption capacity and,b, related to sorption energy are computed to be 10.6±1.1 μmol·g⁻¹ and 1123±137 dm³·mol⁻¹, respectively. The D-R isotherm yields the values ofC _m=348±151 μmol·g⁻¹ and β=−0.01044±0.0008 mol²·kJ⁻² and ofE=6.9±0.3 kJ·mol⁻¹. In all three isotherms correlation factor (γ) is ≥0.99. The influence of common anions and cations on the sorption has been investigated. Zn(II), Mg(II), oxalate, Pb(II), Mn(II) and tartrate reduce the sorption significantly whereas Fe(II) causes substantial increase in the sorption. It is essential that all ions causing a decrease in the sorption of Sn(II) must be absent from the sorptive solution otherwise low sorption yields would result.     

Sorption of 60Co(II) from aqueous solutions onto biosynthesized zinc oxide nanocomposites

Journal of Radioanalytical and Nuclear Chemistry - Nano ZnO is biosynthesized using Lactobcillus sp. Poly Acrylic acid-co-Acrylonitrile/ZnO, PAACAN/ZnO, and poly Acrylic acid-co-Maleic acid/ZnO,...     

Sorption of uranium onto titanosilicate materials

The sorption properties of three titanosilicate materials, AM-4, ETS-4, and Na2Ti2O3SiO4 . 2H2O of different framework structure and cation exchange capacity were studied towards the uptake of uranium from aqueous systems. Selectivity factors were estimated by determining batch distribution coefficient (Kd) and uranium removal (mg) per gram of the exchanger as a function of contact time, uranium concentration and batch factor (solution volume to exchanger mass ratio). The difference in their ability to take up uranium was discussed by in terms of their framework structure and the determination of their cation exchange capacity. Comparisons to ETS-10 have been made.     

Sorption of iodine-containing vapor onto chitosan

The kinetics of sorption of vapor over aqueous and aqueous-alcoholic solutions of potassium iodide and potassium iodine–iodide and over crystalline iodine onto chitosan powder or film was studied. The vapor diffusion coefficients in the initial and final sorption steps were calculated from the data obtained. For all the chitosan–sorbate vapor systems studied, the mass transfer relationships are not described by Fick’s law and are characterized by anomalous sorption kinetics. The properties of chitosan powder after the uptake of the sorbate vapor were evaluated by electronic and IR spectroscopy, X-ray diffraction, and differential thermal and thermal gravimetric analysis. Sorption of iodine-containing vapor onto the polymer is accompanied by complexation of the components. The iodine–chitosan complexes are stable in storage and resistant to heat treatment. The results obtained served as a basis for developing a procedure for preparing kinetically and thermally stable powdered iodinated chitosan derivatives.     

Sorption of Na+, Ca2+ ions from aqueous solution onto unbleached kraft fibers-kinetics and equilibrium studies

The sorption of Na+ and Ca2+ from aqueous solutions onto unbleached kraft fiber was investigated. The sorption kinetics was found to be highly dependent on pH, initial concentration, and temperature. The sorption rate increased as the initial concentration and pH were increased. Thermodynamic and kinetic results indicated that the sorption of Na+ and Ca2+ onto kraft fiber was exothermic, reversible, and spontaneous with activation energies of 11.0 and 23.3 kJ/mol, respectively. The sorption kinetics followed a pseudo-second-order model and the equilibrium data followed the Langmuir isotherms. The fiber sorption capacities calculated from the Langmuir isotherms were similar to the fiber charges determined by potentiometric titration at pH > 7.     

Sorption of arsenic,antimony and bismuth on glycolmethacrylate gels with bound thiol groups for direct sampling in electrothermal atomic absorption spectrometry

Batch sorption of arsenic, antimony and bismuth from solutions in 1 M sulphuric acid has distribution coefficients of 10⁴–10⁵. Quantitative sorption on the hydrophilic methacrylate gel containing thiol groups (Spheron Thiol) is possible within 60 min for bismuth or arsenic and 120 min for antimony. Conditions for the electrothermal atomization of arsenic sorbed on Spheron Thiol and injected into the graphite tube as a suspension are optimized. The sensitivities possible are 3.2 ng As ml^-1, 13 ng Sb ml^-1 and 2.8 ng Bi ml^-1; the coefficient of variation for 10 ng of As is 4%. Complete recovery of 40 ng As ml^-1 added to solutions of 5% KCI or 5% MgCl₂ and to river water was obtained.     

Studies on Batch Sorption Methodologies: Eu Sorption onto Kivetty Granite

Six different methodological features of the batch sorption experiment were investigated using ¹⁵²Eu, Kivetty granite, saline water with initial pH of 8.5, 9 and 10, [Eu]tot=5·10^-7M, S:L = 1:20, pre-washing of granite, occasional shaking, centrifugation, wall sorption correction with separate tubes. This gave final Rd= 8.3±2.1, 7.3±2.6 and 8.6±3.7m³/kg at 6 months for each pH, respectively. Then [Eu]tot and S:L were varied, filtration was compared with centrifugation, separate tubes for wall sorption was compared with wall desorption, pre-washing of granite was compared with no washing and two shaking methods were compared. Two of the investigated methodological features gave too large apparent Rd due to: 1) filter sorption, and 2) low radiotracer concentration, leading to detection problems.     

Selective determination of trace arsenic and antimony species in natural waters by gas chromatography with a photoionization detector

Traces amounts of arsenic and antimony in water samples were determined by gas chromatography with a photoionization detector after liquidnitrogen cold trapping of their hydrides. The sample solution was treated with sodium hydroborate (NaBH₄) under weak-acid conditions for arsenic(III) and antimony(III) determination, and under strong-acid conditions for arsenic(III+V) and antimony(III+V) determination. Large amounts of carbon dioxide (CO₂) and water vapor obscured determination of arsine and stibine. Better separation from interference could be achieved by removing CO₂ and water vapor in two tubes containing sodium hydroxide pellets and calcium chloride, respectively. The detection limits of this method were 1.8 ng dm^?3 for arsenic and 9.4 ng dm^?3 for antimony in the case of 100-cm³ sample volumes. Therefore, it is suitable for determination of trace arsenic and antimony in natural waters.     

Unusual neutral ligand coordination to arsenic and antimony trifluoride

The preparations and spectroscopic characterisation of the hydrolytically unstable As(III) complexes, [AsF(3)(OPR(3))(2)] (R = Me or Ph) and [AsF(3){Me(2)P(O)CH(2)P(O)Me(2)}] are described and represent the first examples of complexes of AsF(3) with neutral ligands. The crystal structure of [AsF(3){Me(2)P(O)CH(2)P(O)Me(2)}] contains dimers with bridging diphosphine dioxide, but there are also long contacts between the dimers to neighbouring phosphine oxide groups, completing a very distorted six-coordination at arsenic and producing a weakly associated polymer structure. The reaction of AsF(3) with OAsPh(3) affords Ph(3)AsF(2), and no arsine oxide complex was formed. Reaction of SbF(3) with OER(3) (R = Me or Ph, E = P or As), Me(2)P(O)CH(2)P(O)Me(2) and Ph(2)P(O)(CH(2))(n)P(O)Ph(2) (n = 1 or 2) in MeOH produces [SbF(3)(OER(3))(2)], [SbF(3){Me(2)P(O)CH(2)P(O)Me(2)}] and [SbF(3){Ph(2)P(O)(CH(2))(n)P(O)Ph(2)}] respectively. The X-ray structures reveal that the complexes contain square pyramidal SbF(3)O(2) cores with apical F and cis disposed pnictogen oxides. However, whilst [SbF(3)(OER(3))(2)] (R = Ph: E = P or As; R = Me: E = As) and [SbF(3){Ph(2)P(O)CH(2)P(O)Ph(2)}] are monomeric, [SbF(3){Me(2)P(O)CH(2)P(O)Me(2)}] is a dimer with bridging diphosphine dioxides producing a twelve-membered ring, and [SbF(3){Ph(2)P(O)(CH(2))(2)P(O)Ph(2)}] is a chain polymer with diphosphine dioxide bridges. In the OAsR(3) reactions with SbF(3), R(3)AsF(2) are also formed. Notably the Sb-O(P) bonds are shorter than As-O(P), despite the covalent radii (As < Sb), consistent with very weak coordination of the AsF(3). IR and multinuclear ((1)H, (19)F and (31)P) NMR data are reported and discussed. BiF(3) does not react with pnictogen oxide ligands under similar conditions and halide exchange of bismuth chloro complexes with Me(3)SnF gave BiF(3).     

Sorption profile and chromatographic separation of uranium (VI) ions from aqueous solutions onto date pits solid sorbent

The retention profile of uranium (VI) as uranyl ions (UO(2)(2+)) from the aqueous media onto the solid sorbent date pits has been investigated. The sorption of UO(2)(2+) ions onto the date pits was achieved quantitatively (98+/-3.4%, n=5) after 15 min of shaking at pH 6-7. The sorption of UO(2)(2+) onto the used sorbent was found fast, followed by a first order rate equation with an overall rate constant, k of 4.8+/-0.05 s(-1). The sorption data were explained in a manner consistent with a "solvent extraction" mechanism. The sorption data were also subjected to Freundlich isotherm model over a wide range of equilibrium concentration (1-20 microgmL(-1)) of UO(2)(2+). The results revealed that, a "dual-mode" of sorption mechanism involving absorption related to "solvent extraction" and an added component for "surface adsorption" is most likely operated simultaneously for uranyl ions uptaking the solid sorbent. The thermodynamic parameters (-DeltaH, DeltaS and DeltaG) of the uranyl ions uptake onto the date pits indicated that, the process is endothermic and proceeds spontaneously. The interference of some diverse ions on the sorption UO(2)(2+) from the aqueous media onto the date pits packed column was critically investigated and the data revealed quantitative collection of UO(2)(2+) at 5 mLmin(-1) flow rate. The retained UO(2)(2+) was recovered quantitatively with HCl (3.0 molL(-1)) from the column at 5 mLmin(-1) flow rate. The mode of binding of the date pits with UO(2)(2+) was determined from the IR spectral date bits before and after extraction of uranium (VI). The height equivalent (HETP) and the number (N) of theoretical plates of the date pits packed column were determined from the chromatograms. Complete retention and recovery of UO(2)(2+) spiked to wastewater samples by the date pits packed column was successfully achieved. The capacity of the used sorbent towards retention of uranium (VI) from aqueous solutions was much better than the most common sorbents.