Sorption of metal cations on natural sorbents: Current state,problems and prospects

Data obtained in recent years that characterize the sorption capacity of natural sorbents with respect to the cations of a number of metals from nonexchangeable solutions and working fluids are generalized. We develop a technique for estimating the slip of pollutants with solutions in which the concentration of toxic cations does not exceed regulatory requirements. A method for calculating the kinetic curves of sorption is considered, which makes it possible to estimate the concentration of the pollutant coming out of the adsorber and the specific dynamic capacity of the sorbent to any current point of time from the beginning of the process.     

Dealuminated zeolites in sorption treatment of industrial liquid wastes to remove alkylbenzenesulfonates

Comparative study of the fundamental aspects of the kinetics and statics (equilibrium) of sorption of alkylbenzenesulfonates from aqueous solutions and liquid wastes on industrial AV-17-OH and KAD-iodine sorbents and deeply dealuminated synthetic zeolites NaY and NaX was carried out. The kinetic curves and adsorption isotherms obtained were processed using the classical equations of the diffusion kinetics and the known Langmuir and Nikol’skii equations for equilibrium sorption processes.     

Comment on "Adsorption of naphthalene on zeolite from aqueous solution" by C.F. Chang, C.Y. Chang, K.H. Chen, W.T. Tsai, J.L. Shie, Y.H. Chen

A paper contributes not only by its originality and creativity, but also by its continuity and development toward subsequent research. Referencing and quotation accuracy are an important part of a scientific article. This study presents a literature review concerning the precision of 50 first authors' publications, which originally cited Ho's pseudo-second-order kinetic expression paper in kinetics model for solute sorption on various sorbents. This model applies to a range of solid-liquid systems such as metal ions, dyestuffs, herbicides, oil, and organic substances in aqueous systems onto various sorbents. In addition, citations of Lagergren and Elovich rate equations are also discussed. This comment offers information for citing the original idea of Ho's pseudo-second-order kinetic expression and Lagergren's pseudo-first-order kinetic equation. It is also suggested that the cited paper should be accurately quoted.     

Preconcentration of Naphthalene, Biphenyl, and Acenaphthene on Fluoroplastic Sorbents

New fluoroplastic sorbents were proposed for the preconcentration of naphthalene, biphenyl, and acenaphthene from aqueous solutions. The kinetic and thermodynamic parameters were determined for the sorption of naphthalene, biphenyl, and acenaphthene on the F-2M, F-40P, and F-4AN sorbents. The optimum conditions for the extraction of compounds were calculated, and the desorption conditions were found.     

Type “salt-in-a-porous-matrix” sorbents in hydrocarbon processing

The information on the preparation and physicochemical properties of composite water sorbents of the type “salt in a porous matrix” is summarized. Comparative analysis of the kinetic and dynamic features of drying gas and liquid media on such sorbents is performed. Separate attention is given to the possibility of the possible use of “salt-in-porous-matrix” sorbents in hydrocarbon processing. Original Russian Text E.A. Buluchevskii, A.V. Lavrenov, V.K. Duplyakin, 2007, published in Russkii Khimicheskii Zhurnal, 2007, Vol. 51, No. 4, pp. 85–91.     

Association of humic acid with metal (hydr)oxide-coated sands at solid-water interfaces

Mineral-bound humic acid (HA) can significantly modify the physicochemical properties of the mineral surfaces and vice versa, thereby influencing the fate and transport of organic pollutants in the subsurface. The effect of various mineral surfaces on the adsorption-desorption of dissolved bulk, terrestrial HA was evaluated using three model sorbents [uncoated, alpha-FeO(OH)-coated, and Al2O3-coated sands] at two equilibrium pH values. The results of SEM/EDS and XPS analyses revealed relatively uniform and stable metal (hydr)oxide coatings on quartz surface and the presence of the HA coating. Strong hysteresis effects were observed for both metal (hydr)oxide-coated sands whereas a weaker hysteresis effect was observed for uncoated sand, suggesting that the adsorption-desorption of HA to model sorbents is dependent on the affinity of chemical interactions between the HA and surface composition of model sorbents. Adsorption of HA molecules onto metal (hydr)oxide-coated sands can be attributed to ligand exchange for lower molecular weight (MW) HA fractions and hydrophobic interaction for higher MW HA fractions, illustrating that both kinetic and fractional adsorption-desorption of HA subcomponents are important considerations.     

Application of thermogravimetric analysis to the evaluation of aminated solid sorbents for CO<Subscript>2</Subscript> capture

In this work a series of solid sorbents were synthesized by immobilizing liquid amines on the surface of a mesoporous alumina. The samples were chemically characterized and BET surface areas calculated from the N₂ adsorption isotherms at 77 K. The CO₂ capture performance of the sorbents and their thermal stability was studied by thermogravimetric methods. The effect of amine loading on the CO₂ capture performance of the prepared sorbents was also evaluated. Analysis of TG-DTG curves showed that thermal stabilization of the amines is significantly improved by immobilizing them on an inorganic support. Temperature-programmed CO₂ adsorption tests from 298 K up to 373 K at atmospheric pressure, proved to be a useful technique for assessing the capacity of sorbents for CO₂ capture. Alumina impregnated with diethylenetriamine presented the highest CO₂ adsorption capacities throughout the tested temperature range.     

Study on the fluoride adsorption of various apatite materials in aqueous solution

The aim of this study was to evaluate the defluoridation efficiencies of various sorbents in aqueous solution. These sorbents include synthetic nano-hydroxyapatite (n-HAp), biogenic apatite (bone meal), treated biogenic apatite (bone meal prepared by H₂O₂ oxidation) and geogenic apatite (rock phosphate), which were characterized by XRD, FTIR, TEM and SEM. It has been observed that the defluoridation capacities follow the order: n-HAp > BH₂O₂ > B > rock phosphate. The controlling factors, sorbent dose, initial fluoride concentration, pH, contact time and temperature were investigated. The defluoridation capacities increased with the increase in the initial fluoride concentration and contact time, decreased with the increase in the sorbent dose. The optimum pH range for removal of fluoride on various apatite sorbents was considered to be 5.0-6.0. The fluoride adsorption can be explained by Langmuir, Freundlich isotherms, and the adsorption kinetic data follow the pseudo-second-order model. Thermodynamic parameters such as ΔH⁰, ΔS⁰ and ΔG⁰ indicated that the adsorption on various apatite sorbents was spontaneous and endothermic. These results showed that bone meal is a promising material for fluoride adsorption.     

Purification of the specific immunoglobulin G1 by immobilized metal ion affinity chromatography using nickel complexes of chelating porous and nonporous polymeric sorbents based on poly(methacrylic esters). Effect of polymer structure

Ni2+ complexes of the chelating nonporous and porous bead sorbents based on methacrylic esters crosslinked with ethylene dimethacrylate were used in isolation of the horseradish peroxidase-specific immunoglobulin IgG1 from the crude mouse ascitic fluid by immobilized metal ion affinity chromatography (IMAC). Iminodiacetic and aspartic acids were attached to porous poly(glycidyl methacrylate) beads differing in size, morphology and chemical composition. Ethylenediaminetriacetic acid and quinolin-8-ol chelating groups were attached mainly to the surface hydroxyl groups in nonporous poly(diethylene glycol methacrylate) beads through spacers. The latter sorbents exhibited better kinetic characteristics than the former but a very low IgG1 sorption capacity. In a single-step IMAC procedure, the best efficiency in the specific IgG1 purification was obtained with porous sorbents (recovery 92%, purity 73%). Differences in IMAC separations are discussed from the point of view of morphology of polymer beads as well as of the type and concentration of chelating ligands.     

Sorption of cesium on copper hexacyanoferrate/polymer/silica composites in batch and dynamic conditions

The sorption of cesium ions from aqueous solutions on composite sorbents was investigated in static (by the batch method) and dynamic (on column) conditions. The composite sorbents consisted of copper hexacyanoferrate retained by an anion-exchange polymeric layer bound to porous silica beads. The influence of cesium concentration and solution flow rates on cesium sorption were studied. The cesium sorption isotherm obtained is of the Langmuir type. The shape of the breakthrough curves and the sorption capacity for cesium depend on the preparation procedure of the composites.     

Microspheres based on poly(3-hydroxy)butyrate for prolonged drug release

The kinetics of the controlled release of the antiproliferative drug dipyridamole from microspheres based on the biocompatible and biodegradable polymer poly(3-hydroxy)butyrate is studied. As carriers for dipyridamole, microspheres prepared from a solution of poly(3-hydroxy)butyrate by single emulsion method are used. Under in vitro conditions, the kinetic curves describing the release of dipyridamole from microspheres with diameters of 19, 63, and 92 μm show two characteristic regions: the region of fast drug release within a short time period and a well-pronounced continuous linear region. For microspheres with a diameter of 4 μm, the linear region is missing. Analysis of the kinetic curves illustrating controlled drug release together with the measurements on polymer degradation shows that their kinetic profiles depend on the diffusion-controlled process and hydrolytic degradation of poly(3-hydroxy)butyrate. The diffusion kinetic equation describing both linear and nonlinear regions of dipyridamole released from the microspheres involves the sum of two terms: desorption from the sphere via the diffusion-controlled mechanism and drug release via the zero-order reaction. The linear region of the drug release curve is explained by the zero-order hydrolysis of poly(3-hydroxy)butyrate. The diffusion coefficients and kinetic constants are calculated. For bigger microspheres, the existence of the continuous linear region in the corresponding kinetic curves makes it possible to use microsystems based on poly(3-hydroxy)butyrate and dipyridamole as novel systems for local prolonged drug delivery.     

Optimization of working conditions for polyelectrolyte sorbents

Matters affecting the working stability of polyelectrolyte sorbents are considered. The decrease in retention time during exploitation is found not to relate to desorption of the modifying polymer. It is found that dissociation of surface silanol groups influences significantly the extra retention of ionene on the surface of silica-based sorbents. Sorption of heavy metals and microbial contamination of the sorbent are identified as causes of decreased efficiency of polyectrolyte sorbents. The influence of organic additives on the chromatography behavior of a number of inorganic anions is studied. Finally, exploitational conditions for chromatography polyelectrolyte-containing columns are elaborated, allowing the initial parameters of separation to be maintained for a period of 1.5 months or longer.     

Kinetic determination of substrates and enzymes by integration of response curves which show maxima,minima or inflections

This paper describes quantitative kinetic procedures based on the integration of response vs. time curves. In these procedures, concentrations or activities are evaluated from the difference between integrals of signal vs. time before the reaction has been initiated and during a significant fraction of the reaction. The procedure have the advantage that they are applicable to response curves with maxima, minima, or inflections. Results are presented for computed response curves and for experimental measurements on selected enzyme-catalyzed reactions used for quantifying glucose, ethanol and creatine kinase. For situations in which calibration plots pass through maxima or minima, supplementary information such as the times at which maxima or minima occur in response curves are used to differentiate between low and high values of concentration that could yield the same differences between integrals. Relative standard deviations of triplicate runs are generally quite good, ranging from 0.5% to 1%.     

Sorption Preconcentration of Platinum-Group Metals with Filled Fibrous POLYORGS Sorbents

The sorption of platinum, palladium, and rhodium with fibrous filled POLYORGS sorbents was studied depending on the concentration of hydrochloric acid and the time of contact of the solution with the sorbent in the batch mode. The equilibrium and kinetic characteristics of the sorption of platinum with the POLYORGS 17-n sorbent were determined, on the basis of these data the conditions for the dynamic preconcentration of platinum from a 1 M HCl solution were calculated. Conditions were selected for the group preconcentration of palladium, platinum, and gold in the dynamic mode and for their subsequent determination in the sorbent. It was demonstrated that rhodium can be preconcentrated with the POLYORGS 17-n sorbent in the dynamic mode in the presence of tin chloride.     

Sorption and kinetic properties of radiocesium-selective organomineral sorbents

Comparative analysis of the sorption and kinetic properties was carried out for organomineral sorbents synthesized by two routes: (1) from an organomineral suspension and (2) from aqueous-organic solutions.     

Study of fractal characteristics and rheological properties of Karbodon combined sorbent and its constituents

The structure-sorption properties of the bottom sediments and their compositions with the KAU carbon modified with K⁺, Mg²⁺, and Zn²⁺ cations, which were synthesized for the first time, were studied. The adsorption data were used to calculate the surface fractal dimension for composites under study and their constituents. The rheological curves of the composites synthesized in a wide range of the shear rates were obtained. The effect of their composition on the structure-mechanical properties (viscosity) of the sorbents was determined.     

Time-dependent CO2 sorption hysteresis in a one-dimensional microporous octahedral molecular sieve

The development of sorbents for next-generation CO(2) mitigation technologies will require better understanding of CO(2)/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO(2) sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO(2) sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a "gate-keeping" role of the cation in the tunnel, only allowing CO(2) molecules to enter fully into the tunnel via a highly unstable transient state when CO(2) loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO(2) is responsible for the observed hysteretic behavior.     

Kinetic analysis of the mechanism of plasminogen activation by streptokinase

A kinetic study is made of plasminogen activation to plasmin catalyzed by streptokinase. The goal of the present paper is the resolution of the mechanism corresponding to the activation process by a global way, considering the mechanism as a whole and under less restrictive assumptions that those used by other authors. The kinetic equations describing the evolution with time of species involved in the system have been obtained. These equations are valid for both the transient phase and the steady state of the reaction. A kinetic data analysis procedure to evaluate the kinetic parameters, based on the derived kinetic equations has been suggested, for the first time, in the present paper. The validity of the results obtained has been checked by using simulated progress curves of the species involved. Finally, we have demonstrated that the time course equations obtained can be applied directly to different mechanisms of zymogen activation that could be considered to be particular cases of the general studied mechanism.     

Thermal decomposition study of sewage sludge and of organicwaste used in the sorption of metals

The conventional treatments of effluents containing heavy metals produce significant quantities of byproducts with recalcitrant characteristics, making necessary looking after alternative techniques in order to avoid the production of new contaminated residues. Sorption process of chromium and zinc in vertical columns loaded with sewage sludge and organic solid waste has been studied in this work. The data from the TG curves of the two sorbents presented significant differences when they were submitted to the metal uptake, being noticed the displacement of the thermal events towards lower temperatures for both types of sorbents studied. As it was expected, for both sorbents, an increase in the mass of samples has been observed at the completion of the thermal tests upon metal uptake. Therefore, these facts demonstrate that during the biosorption process a physico-chemical interaction took place between sorbents and metals, as it was evidenced by the more than 100 K increase in the decomposition temperatures as well as the variation of the ΔH values of the samples.     

Characteristics of immunosorbents used as a new approach to selective solid-phase extraction in environmental analysis

Summary The trace-level determination of organic pollutants in complex matrices is difficult and often not reliable because theccurrent extraction procedures are non-selective. New extraction sorbents involving antigen-antibody interactions, called immunosorbents (ISs), have been synthesised in order to trap a group of structurally related pollutants. The IS capacity is always high for the analyte-antigen used to make the antibodies, but can be low for some related compounds. In this work, we show the relationship that exists between capacity, break-through volume and recovery of analytes because of the competition between the structurally related compounds for antibody sites. Breakthrough due to the overloading of the column should be avoided because calibration curves are no longer linear. The capacity of two ISs, one made for trapping the triazine pesticide group and the second for the phenylurea, group, have been optimised by selecting silica with 50 nm pore size. Calibration curves are linear for all the compounds in a mixture of ten phenylureas up to a concentration of 5 to 10 μg L⁻¹ for each compound when handling 50 mL water samples through a precolumn packed with 0.22 g of IS. Under these conditions, reliable quantitative results are obtained because calibration curves are similar when compounds are alone or in a mixture. Application to the clean-up of soil extracts illustrates the high selectivity and the high potential of these new sorbents in environmental analysis. Presented at the 21^st ISC held in Stuttgart, Germany, 15^th–20^th September, 1996