Strontium(II) sorption by complexing polymeric sorbents with various structures

Optimal conditions for strontium(II) sorption by new complexing polymeric sorbents (CPSs) from aqueous solutions were studied, namely, optimal solution acidity (pH_opt), pH of 50% sorption (pH₅₀), and optimal time and temperature of quantitative sorption. The strontium(II) sorption capacities of the test sorbents (SCSs) were determined, and sorption isotherms were plotted. The strontium(II) sorption parameters determined were used to recognize the most efficient CPSs.     

Strontium(II) sorption by complexing o-hydroxy-azo-o’-hydroxy functionalized polystyrene polymer sorbents

Optimal parameters for strontium(II) complexing and sorption from aqueous solutions by sorbents based on styrene/divinylbenzene copolymers functionalized with a complexing o-hydroxy-azo-o-hydroxy functionality have been studied, namely, pH_opt, 50% sorption pH (pH₅₀), and the time and temperature of quantitative strontium(II) sorption. Strontium(II) sorption capacities have been determined for the sorbents under study; sorption isotherms have been constructed. For a complex formed with polystyrene-o-hydroxy-azo-o’-hydroxy-sulfobenzene, which is an efficient sorbent, the structure has been determined.     

Sorption of phosphorus(V) by polymeric sorbents based on aminopolystyrene and 4-amino-<Emphasis Type="Italic">N</Emphasis>-azobenzenesulfamide

Phosphorus(V) sorption on sorbents based on aminopolystyrene and 4-amino-N-azobenzenesfulamide from aqueous solutions is studied. The following sorption parameters are determined: the optimum acidity, pH_opt; 50% sorption pH, pH₅₀; optimal time τ, min; quantitative-sorption temperature; and phosphorus(V) sorption capacity of the sorbent (SCS). Sorption isotherms are plotted.     

Formation of mixed-ligand complexes in the complexing polymer sorbent-Pb<Superscript>2+</Superscript>-dinitrophenol systems

The complexation of lead(II) with a group of synthesized sorbents based on aminopolystyrene and substituted phenols having structurally different substituents of various electronic natures in the para position with respect to phenolic hydroxyl was studied. As third components, α-dinitrophenol and γ-dinitrophenol were examined. The following most important parameters of sorption were determined: the optimum pH value of quantitative sorption (pH_opt), the recovery (R, %), the sorption capacity of the sorbent (SCS_Pb, mg/g), the half-sorption pH value (pH₅₀), and the temperature and time (τ) of sorption in the presence of a third component. The structure of the mixed-ligand complex was determined.     

Chelating tendencies in the rows of polymeric sorbents and their copper(II) and lead(II) complexes

The physicochemical properties of chelating polymer sorbents (CPSs), derivatives of poly(styrene-2-hydroxy-〈1-azo-1′〉-2′-hydroxybenzene), are studied with respect to copper and lead ions. The following sorption parameters are determined: the optimum acidity, temperature, and duration; the sorption capacity of the sorbent (SCS); and stability constants of polychelates. Quantitative correlations are found between the dissociation constants (pK′ _a) of the analytical functional group (AFG) of the sorbent, and the pH₅₀ of chelation of the tested metals; between p K′ _a and the stability of the complexes (logβ); and between pK′_a and the charge of the oxygen atom of the complexing group (z); these correlations are intended for use in elucidating the effect of the structural features and acid-base properties of the AFG on the chemisorption parameters of copper(II) and lead(II). These correlations predict the physical-chemical properties of sorbents and the sorption parameters of trace elements for preconcentrating and separating them from biological, natural, and technical objects     

Regularities of complexation in the series of sorbents on the polystyrene matrix and their complexes with chromium(III) and manganese(II)

The physicochemical properties of polymeric complexing sorbents with the o,o′-dihydroxy-(1-azo-1′)-functional complexing group were studied. Optimal sorption parameters for chromium(III) and manganese(II) (medium acidity, temperature, time), the sorption capacity of the sorbents, and the stability constants (pK _a′)of the complexes were determined. Correlation relations were established between the dissociation constants (pK _a′) of the sorbent functional group and pH₅₀ of the complexation of the considered elements; between and the stability of the formed complexes (logβ); and between pK _a′ and the deprotonation energy (E _depr) of the sorbent hydroxy group located in the para-position to the introduced substituent. The established correlation relations are useful for targeted prediction of the physicochemical parameters of the sorbents, their complexes, and the sorption of manganese(II) and chromium(III) aimed at recovery and pre-concentration of these ions from objects with various chemical composition.     

A physicochemical study of the sorption of lead: Correlations in a series of chelating polymer sorbents

The sorption properties of chelating polymer sorbents (CPSs), the derivatives of poly(styrene-2-oxy-azo-2′-oxybenzene), with respect to the lead ion are studied. The parameters of the sorption processes—optimum conditions of sorption (acidity, temperature, and time), the sorption capacities of sorbents, the possibility of desorption, and the stability constants of the chelated polymers—are determined. Quantitative correlations between p K′_OH of the functional analytical group (FAG) of the sorbent and σ _{o + p(p)} for ortho-and para-substituents, between p K′_OH and pH₅₀ for the formation of chelate complexes of lead, between p K′_OH and the stability of lead complexes (logβ), and between σ _{o + p(p)} and pH₅₀ for the formation of chelate complexes of lead are established with the aim of studying regularities of the influence of the structure and acid-base properties of FAGs on parameters of chemisorption of Pb²⁺. It is shown that the established correlations provide a means for quantitatively predicting physicochemical parameters of sorbents and the process of sorption of lead with the aim of targeted synthesis of CPSs and their use in the chemistry of polymer compounds and in the process of concentrating.     

New correlation between metal-hydrolysis p<Emphasis Type="Italic">K</Emphasis> and sorbent-ionization p<Emphasis Type="Italic">K</Emphasis> for prediction of the pH of 50% metal-cation sorption on a chelating polymer sorbent

Metal sorption on chelating polymer sorbents (CPSs) is studied. A correlation is found between the 50%-sorption pH and the metal-hydrolysis pK, and pH₅₀ is predicted.     

Sorption of Copper(II) Ions with Nanosized Magnesium Phosphate

A new approach to the preparation of a nanosized sorbent based on magnesium phosphate has been developed. The patterns of copper(II) ions sorption with nanosized magnesium phosphate from aqueous solutions have been investigated. The sorption parameters have been determined, and the kinetics and mechanism of the processes have been elucidated. The high sorption ability of the nanoscale sorbent has been shown in comparison with existing sorbents based on magnesium phosphate.     

Electokinetic and adsorption properties of different titanium dioxides at the solid/solution interface

Six samples of titanium dioxide of different phase compositions and specific surface areas have been characterized by XRD, Raman-and FTIR spectroscopy, adsorption of nitrogen, electrophoresis. Adsorption of Zn(II) ions at the TiO₂/NaCl aqueous solution interface as well as the effect of adsorption on the structure of electrical double layer have been studied. The influence of ionic strength, pH and presence of ions on the adsorption of Zn(II) ions at the TiO₂/NaCl solution interface have also been investigated. The zeta potential, surface charge density, parameters of adsorption edge pH_50% and ΔpH_10–90% for different concentrations of basic electrolyte have been determined. Studied unpurified samples showed lower values of isoelectric point pH_iep compared with literature data due to the presence of anion impurities. The antibate dependence between pH_iep values and particle size has been established. Adsorption of Zn(II) ions using monophase samples is completed at a lower pH than for the biphase TiO₂. Appearance of the point CR3 is associated with the charge turnover from positive to negative at high values of pH and formation of Zn(OH)₂.      

Extraction and preconcentration of ultra trace amounts of beryllium from aqueous samples by nanometer mesoporous silica functionalized by 2,4-dihydroxybenzaldehyde prior to ICP OES determination

A new functionalized nanometer mesoporous silica (MCM-41) using 2,4-dihydroxybenzaldehyde (4-OHsal) was applied as an effective sorbent for solid phase extraction (SPE) of beryllium ions from aqueous solution followed by inductively coupled plasma optical emission spectrometric detection (ICP OES). The influences of some analytical parameters on the quantitative recoveries of the analyte ion were investigated in batch method. In order to perform the batch mode of SPE, known amount of sorbent was added to a test tube containing sample solution buffered at pH 7.2. After manual shaking and centrifugation the aqueous phase was decanted and beryllium was desorbed by adding 1.0 mL of 1.0 mol L^?1 HNO₃ to the sedimented sorbent. The sorbent was separated by centrifugation and the concentration of beryllium in the supernatant was determined by ICP OES. The maximum sorption capacity of the modified MCM-41 was found to be 34 mg g^?1. The sorbent exhibited good stability, reusability and fast rate of equilibrium for sorption/desorption of beryllium ions. The present method was used for preconcentration and determination of beryllium for water samples. Under optimal conditions, the limit of detection (LOD) obtained was 0.3 ng L^?1. The accuracy of the procedure was evaluated by analysis of the certified reference material (NIST 1640).     

Assessment of the sorption capacity and regeneration of carbon dioxide sorbents using thermogravimetric methods

Adsorption methods using solid sorbents are an alternative to the absorption technology in the processes of purification gases from carbon dioxide. There is a need to rapidly assess the suitability of sorbents for use it in PSA, TSA, or VPSA installations. Important parameters which determine the quality of the sorbent are the sorption capacity of sorbent, selectivity to CO₂ and the possibility of regeneration. This paper presents the results of sorption/desorption of CO₂ study on the impregnated porous materials using thermogravimetric methods. Thermogravimetry allows for rapid assessment of sorption capacity and regeneration of the sorbents. Specially selected temperature program allowed to determine the sorption capacity of sorbents depending on the concentration of CO₂ in the gas mixture and temperature. Degree of sorbent purification was determined in desorption process.     

Complexing properties of cation-exchangers grafted with carboxyl moieties

The complexing properties of CM-52, Olvagel-COOH, MacroPrep 50 CM, and hypercrosslinked polystyrene MN (carboxyl-grafted sorbents) toward Cu²⁺, Co²⁺, Ni²⁺, Cd²⁺, Zn²⁺, Mn²⁺, and Pb²⁺ have been studied. The optimal parameters for the sorption of these metal ions from solution have been determined. The pH effect on the ion uptake has been studied. The uptake is maximal at pHs higher than 5–6. When pH is lower than 2, the indicated ions are quantitatively desorbed. Olvagel-COOH is most selective toward these ions.     

Standard pH values for phosphate buffer reference solutions in acetonitrile-water mixtures up to 50% (m/m)

Reference pH_ps values for 0.025 mol/kg potassium dihydrogen phosphate + 0.025 mol/kg disodium hydrogen phosphate primary standard buffer solutions in 10, 30, 40 and 50% (m/m) acetonitrile-water mixtures at 298.15 K have been determined from reversible e.m.f. measurements of the cell Pt/Ag/AgCl/primary standard buffer + KCl in acetonitrile-water/glass electrode. The consistency of the results is confirmed by multilinear regression analysis of the pH_ps values obtained for each solution composition. Considering the high number of possible acetonitrile-water mixtures, the methodology of linear solvation energy relationships (LSER) was applied and pH_ps data have been correlated with the Kamlet-Taft solvatochromic parameters of the acetonitrile-water mixtures over the whole of the experimental range.     

Application of a carbonized apricot stone for the treatment of some radioactive nuclei

Apricot stone shells were carbonized under certain chemical and thermal conditions to produce sorbents having a quantitative affinity to retain some radioactive nuclei. The sorbent shows a thermal stability upto 500 °C. The diffraction patterns clarify that the sorbent is mainly amorphous in structure. Carbon in these shells was elementally analyzed and the data reveal a predominant content of acidic surface centers with hydrophilic properties. The isoelectric point (pH_PZC) was determined and found to be 4.2 implying the acidic nature of the sorbent surface. The sorption of Cs⁺, Co²⁺ and Eu³⁺ on the prepared sorbent was studied from aqueous solution under different variables and the sorption capacity had values from 0.23-1.15 meq/g.     

Sorption of Cobalt on Modified Silica Gel Materials

Various silica gel materials were chemically modified with imidazole, diaza-18-crown-6 (DA18C6) and dibenzod-18-crown-6 (DB18C6). The degree of functionalization of the covalently attached molecule was calculated from C, H, N analysis and ranged between 0.270 and 0.552 mmol/g (for sorbents with imidazole) and between 0.043 and 0.062 mmol/g (for sorbents with DA18C6 and DB18C6). The degree of functionalization depends on the reflux time and silica gel matrix used. Experimental sorption capacity ranged between 0.038 and 0.228 mmol/g (for sorbents with imidazole) and between 0.019 and 0.050 mmol/g (for sorbents with DA18C6 and DB18C6). Synthesized hexagonal mesoporous silica matrix MCM-41 with uniform pore diameter <40 Å was used too. Change of pore diameters of silica gel support to larger pores should have a positive influence on access of cobalt ion to sorption centers to increase of sorption capacity of sorbents. The sorption kinetics of cobalt and the influence of cobalt concentration, pH of various kinds of silica gel matrix with immobilized imidazole group in static conditions on sorption were measured. The sorption of cobalt in various conditions (pH, contact time of phases) with constant liquid-solid ratio (V/m = 50 ml/g) was studied. The distribution coefficients ranged between 200 and 50 000 ml/g (for imidazole), 85 and 120 ml/g (for DB18C6) and between 230 and 500 ml/g (for DA18C6) according to silica gel matrix used and according to the method of sorbent preparation. pH plays important role in the sorption of cobalt on prepared sorbents with immobilized crown ethers due to protonization of crown ethers. Protons significantly competes to sorption of cobalt in acidic solutions. The influence of presence of other heavy or toxic metals (Hg(II), Cd(II), Mn(II), Zn(II), Cu(II), Fe(III), Cr(III), Al(III) and the influence of sodium and potassium on sorption Co(II) from aqueous solutions was investigated. Sorption of cobalt decreases in order Hg > Cu > Cd > Zn, Fe > Mn > Al, Cr. The presence of sodium and potassium ions at concentration 0.05 mol/l significantly influences on the sorption of cobalt with sorbent with immobilized DB18C6 functional group.     

Regularities of the sorption behavior of actinide ions on mineral colloid particles

It is shown that an alternative to K _d in describing sorption at low degrees of surface saturation of colloid particles is pH₅₀ which takes into account both the properties of the sorbent and sorbate. The correlations of pH₅₀ with cation charge density for the An(III)-An(IV)-An(V)-An(VI) series and with hydrolysis constants are presented. The redox reactions with plutonium that accompany its sorption onto Fe(III) oxides are discussed.     

Performance of Pleurotus ostreatus Mushrooms and Spent Substrate for the Biosorption of Cd(II) From Aqueous Solution

The capacities of Pleurotus ostreatus mushroom and spent substrate were evaluated for the biosorption of cadmium (II) from aqueous solution in order to select the most efficient material for bioremediation. The optimum sorption conditions were optimized, including the pH of the aqueous solution, contact time, biomass dosage, initial metal concentration, and temperature. The sorption of cadmium on both biosorbents was also evaluated by several kinetic, equilibrium, and thermodynamic models. The possible heavy metal biosorption mechanisms were evaluated through point of zero charge (pH_pzc), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Based on the results of column studies, the effectiveness of the P. ostreatus spent substrate was confirmed as a biosorbent for Cd(II) removal from aqueous solutions.     

Immobilization of novel the semicarbazone derivatives of calix[4]arene onto magnetite nanoparticles for removal of Cr(VI) ion

A series of novel the semicarbazone derivatives of calix[4]arene have been synthesized and then immobilized onto amino functionalized magnetic nanoparticles. Magnetic Fe₃O₄ nanoparticles were prepared by the chemical co-precipitation of Fe(III) and Fe(II) ions and the nanoparticles were modified directly by 3-aminopropyltriethoxy silane (APTES) to introduce reactive amine groups onto the particles’ surface. The characterization of the prepared compounds was made by FT-IR, elemental analysis, TGA/DTG and NMR techniques. The sorption properties of the new calix[4]arene based magnetic sorbents toward Cr(VI) ion were also studied. The results showed that the prepared magnetic nanoparticles were effective sorbents for the removal of Cr(VI) ion. Also, Langmuir and Freundlich isotherm models were applied for Cr(VI) ion sorption by using MN-C2 and it was found that the experimental data confirmed to Langmiur isotherm model.     

Americium(III) sorption from multicomponent solutions by macrocyclic polyester-based sorbents

Americium sorption by crown-ether-impregnated polymeric sorbents from nitric acid solutions and multicomponent nitrate solutions that model process solutions was studied. Sorption of ballast elements by the unimpregnated Porolas-T support was studied. The sorption coefficients K _d of these elements on Porolas-T do not exceed 0.01. Sorption of the same elements by crown-ether-impregnated sorbents was also studied. Dicyclohexano-18-crown-6 (DCH18C6) and its alkyl derivatives were used. Sorption coefficients were determined for all ballast elements. At the final stage of the study, ²⁴¹Am sorption coefficients of from multi-component solutions were determined. The data obtained signify the utility of crown-ether-impregnated sorbents for recovering ²⁴¹Am from multicomponent technological solutions.