Inorganic Sorbents Research Articles

Comparison of biosorbents with inorganic sorbents for removing copper(II) from aqueous solutions

In comparison with several other reported inorganic sorbents, Camellia tree leaf and primary sludge obtained from a settling tank as a pretreatment to the activated sludge system in a Hong Kong sewage treatment plant were evaluated for removing Cu(II) from aqueous solutions. Experimental data were modeled by the Langmuir isotherm equation to estimate the maximum sorption capacity ( q max). Results show that, at pH 5.6, biosorbents, Camellia tree leaf and primary sludge in particular, exert higher sorption capacities ( q max > 40 mg g −1) than inorganic sorbents, Na-montmorillonite ( q max = 33.3 mg g −1), fly ash ( q max = 18.8 mg g −1), and goethite powder (10.3 mg g −1). Furthermore, a pseudo second-order kinetic model was found to properly describe the experimental data for both bio- and inorganic sorbents. Sorption of Cu(II) on the Camellia tree leaf and primary sludge were much faster than that on the inorganic sorbents. In addition, desorption tests revealed that the desorption capacities of the two biomaterials are higher than the other selected materials; and much more Cu(II) can be retrieved from the Cu(II)-loaded biosorbents. Finally, increasing solution pH was found to greatly increase q max and accelerate sorption processes.

Sorbents for treatment of water vapor-air flows to remove volatile organic compounds of radioactive iodine

Sorption of CH3 131I from water vapor-air medium on Fizkhimin and Siloksid inorganic sorbents and on SKT-3I activated carbon was studied. The sorption power of Fizkhimin, Siloksid, and SKT-3I sorbents toward CH3 131I was examined (1) after their 20-h contract with water, followed by removal of the liquid phase and drying at 110°C; (2) after 4-h treatment with steam (95–98°C), followed by drying at 25°C; (3) after keeping for 9 months in 100% humid air at ambient temperature of 10 to 45°C; and (4) after treatment with a water vapor-air flow (95–98°C, 60–80 vol % water vapor) for 2 h. In most cases, Fizkhimin sorbent and SKT-3I activated carbon preserve high sorption efficiency toward CH3 131I from water vapor-air flow.

An imprinted organic–inorganic hybrid sorbent for selective separation of copper ion from aqueous solution

A new organic–inorganic hybrid sorbent was prepared by a double-imprinting approach for the selective separation of Cu(II) from aqueous solution. In the prepared hierarchically imprinted sorbent, both Cu(II) and surfactant micelles (cetyltrimethylammonium bromide) were used as templates. The sorbent was prepared through self-hydrolysis, self-condensation, and co-condensation of the crosslinking agent (tetraethoxysilane) and the functional precursor (3-aminopropyltrimethoxysilane) in an alkaline media followed by gelation. The adsorption property and selective recognition ability of the sorbents were studied by equilibrium-adsorption method. Results showed that in the presence of Zn(II) the biggest selectivity coefficient of the imprinted sorbents for Cu(II) was over 500, which is much higher than those of non-imprinted sorbents. The largest relative selectivity coefficient (k′) of the ion-imprinted functionalized sorbent between Cu(II) and Zn(II) was over 500. The uptake capacities and the selectivity coefficients of the hierarchically imprinted sorbent were much higher than those of the sorbent prepared without CTAB template. Furthermore, the new imprinted sorbent possessed a fast kinetics for the removal of Cu(II) from aqueous solution with the saturation time less than 10 min, and could be used repeatedly. This sorbent has been successfully applied to the separation and determination of the trace Cu(II) in real water samples and those spiked with standards. This new sorbent can be used as an effective solid-phase extraction material for the highly selective preconcentration and separation of Cu(II) in environmental samples.

Sorption extraction of lanthanides from phosphoric acid solutions

The possibility of sorption extraction of lanthanides from nitric-phosphoric and phosphoric acid solutions with inorganic sorbents based on hydrated titanyl hydrophosphate was studied. New technological solutions were suggested for lanthanide sorption from the products which are formed in processing of the Khibiny apatite concentrate on mineral fertilizers (frozen nitric-phosphoric acid extract, a product of nitric acid decomposition of apatite, and the production phosphoric acid from the dihydrate process).

Removal of Lignin from Pulp Waste Water's Black Liquor via By-Pass Cement Dust

The potential use of inexpensive and available by-pass cement dust as an inorganic sorbent for the removal of organic matter (lignin) from black liquor of pulp wastewater by adsorption methodology was investigated using the batch technique. The cement dust is found to remove lignin efficiently from black liquor (the untreated cement dust (70.47%), the thermally treated one at 1000 °C (78.63%), and chemically treated dust (80.62%). The factors affecting the uptake percentage such as time, dose, pH and temperature were investigated to assess the optimum conditions for lignin removal. X-ray patterns were studied to reveal the relationship between the main constituents of each cement dust phase (untreated, thermally and chemically treated) and lignin uptake. By applying Langmuir and Frendlich adsorption isotherms it was found that the adsorption process of lignin from black liquor on by-pass cement dust achieves Frendlich model, which suggests that adsorption is not restricted to one specific layer of sites but involves multi-layers. Also, stripping of lignin by using different strippers (organic, mineral acids, bases and salts) was investigated. The results obtained show that the organic strippers give high stripping percentage for cyclohexane (90.10%) because lignin is a non-polar compound that dissolves in non-polar solvents. In the case of acids, bases and salts the best results were obtained with much diluted solutions (0.001 mol/L). Stripping of lignin from by-pass cement dust is considered as a way of its recycling for different applications.

Preparation of 65Zn and 134Cs sealed sources based on commercial organic and synthesized inorganic sorbents for calibration purposes of γ-detectors

The sealed source of 65Zn was prepared by using permutit as a commercial organic resin in an anion form, while in case of the 134Cs, the sealed source was prepared by using the synthesized 12-molybdocerate(IV) gel as an inorganic exchanger in cation form. The batch technique was carried out for loading 65Zn from 0.2 M HCl-60% acetone medium and for loading 134Cs from 0.005 M HNO 3 onto the appropriate exchanger. The sealed source material of 65Zn-permutit or 134Cs-12-molybdocerate(IV), about 100 mg, was placed inside the cavity of a holder capsule (artelone) and its activity was measured to be 56.61±2.59 kBq (1.53±0.07 μCi) for 65Zn on 21 April 2008 and 1.48±0.089 kBq (0.04±0.0024 μCi) for 134Cs on 5 May 2008. The self absorption was calculated by using artelone and compared with the same thickness of stainless steel capsule as the holder material. The quality control was performed on the prepared sealed sources.

Chromium speciation, selective extraction and preconcentration by alumina-functionalised 2-pyridenecarboxyladehyde thiosemicarbazone

A method is proposed and explored for speciation of Cr(III) and Cr(VI), selective extraction and preconcentration in various water samples based on dynamic and static techniques. Three newly designed alumina phases-physically adsorbed-2-pyridenecarboxyladehyde-thiosemicarbazone [Al-2PC-TSC (I–III)] were synthesised and characterised. Stability tests and application of [Al-2PC-TSC (I–III)] as inorganic ion exchangers and chelating solid sorbents for various metal ions were studied and evaluated. The distribution coefficient and separation factors of chromium species versus other interfering metal ions were determined to examine the incorporated selectivity into these alumina phases. Quantitative recovery of Cr(VI) was accomplished by [Al-2PC-TSC (I–III)] at pH = 1.0 while Cr(III) was found to be quantitatively recovered on these sorbents at pH = 7.0 with minimal or no interference between these two species under the studied buffering conditions. Selective solid phase speciation and preconcentration of Cr(III) and Cr(VI) in various real water samples were successfully performed and accomplished via a micro-column, with 200 as a preconcentration factor. Selective speciation of Cr(VI) and Cr(III) via preconcentration from seawater and industrial water samples by alumina phases in pH = 1 was found to give percentage recovery values of Cr(VI) in the range 93.5–97.3 ± 3.0–5.0% and 94.0–97.5 ± 3.0–4.0%, for seawater and industrial water samples, respectively.

Development of a Method for Chromium Speciation by Selective Solid Phase Extraction and Preconcentration on Alumina-Functionalized Thiosemicarbazide

A speciation method is developed for Cr(III) and Cr(VI) at selected medium pH range via solid phase extraction on three designed and synthesized chelating inorganic solid sorbents based on adsorption of thiosemicarbazide, as the nitrogen and sulfur containing chelating compound, on alumina surface [Al-TSC (I–III)]. The influence of various parameters including medium pH, time of contact, and interference of matrix and coexistent elements on the speciation and selective extraction processes of chromium species are studied and evaluated on the basis of determination of the metal adsorption capacity, distribution coefficient, and separation factor. Quantitative recovery of Cr(VI) was accomplished by [Al-TSC (I–III)] at pH = 1.0, while Cr(III) was found to be recovered on these sorbents at pH = 7.0 with minimal or no interference between these two species under the studied buffering conditions. The proposed method has been successfully applied for speciation, selective extraction, and preconcentration of Cr(III) and Cr(VI) in water samples with a preconcentration factor of 200.

Sorption of radiostrontium from liquid rubidium metal

Sorption of radiostrontium (in particular, 82Sr) from liquid rubidium metal on various inorganic sorbents (metals and oxides) was studied. The temperature dependence and dynamics of the adsorption were studied, and the observed relationships were accounted for. The procedure developed allows efficient isolation of 82Sr from Rb targets after their irradiation with accelerated protons. Various versions of the procedure are considered, and prospects for the development of a new high-performance process for preparing 82Sr, in particular, using circulating Rb targets, were discussed.

Immobilization of Liquid Radioactive Waste in Mineral-Like Matrices Derived From Inorganic Cenosphere-Based Sorbents as Precursors

AbstractThe progress in study of immobilization of liquid radioactive waste in mineral-like aluminosilicate matrices (feldspar and feldspathoids) derived from cenosphere-based microspherical zeolite sorbents is reported. Based on the analysis of ‘composition – morphology –C characteristics’ correlation obtained for more than 70 cenosphere products with a high content of one morphological type of imperforated cenospheres, optimal ranges of cenospheres composition were identified for the synthesis of zeolites with the predetermined structural type. Given that the cenosphere-based zeolite sorbents are precursors of the final waste form, further activity proceeds toward developing a highly efficient zeolite sorbent of NaP1 type, which would ensure the effective trapping of Cs+ and/or Sr2+ ions and the phase transformation under relatively mild conditions (T≤1000°C). The paper details the main criteria for realization of the ‘precursor’ approach for fixation of Cs-Sr fraction using cenosphere-based systems; also shown are experimental results indicating practical realization of the proposed approach.

Sorption-Desorption Processes of Metals and Metalloids in Soil Environments

Trace elements may be present in solution with positive or negative charges and in different redox state. They occur predominantly in cationic form (Pb, Cu, Zn, Ni, Cd, Hg, Cr(III), Co) but some trace elements are present in anionic form (As, Se, Cr(VI), Mo and B). In soil environments, sorption/desorption reactions on/from inorganic and organic sorbents control the concentration of metals and metalloids in solution and affect their bioavailability, leaching and toxicity. Sorption-desorption processes of elements in cationic form differ greatly from those in anionic form. These reactions are affected by many factors, such as pH, nature of the sorbents, presence and concentration of organic and inorganic ligands, including humic and fulvic acids, root exudates and nutrients. Furthermore, redox reactions, both biotic and abiotic, are of great importance in controlling the oxidation state and thus, the mobility, the phytoavailability and the toxicity of many elements, such as Cr, Se, Co, Pb, As, Ni and Cu (Kabata-Pendias, 2001; Huang and Germida, 2002; Violante et al., 2002; Sparks, 2003; Huang and Gobran, 2005; Violante et al., 2007). The aim of this presentation is to provide information on the factors which affect the mobility of trace elements. Special attention is devoted to the influence of inorganic and organic ligands, including nutrients and root exudates, on the sorption/desorption processes of trace elements in cationic and anionic forms on/from soil components, soils and selected synthetic minerals (double layered hydroxides, the so called “anionic clays”). The soil components responsible for trace element sorption include, soil humic substances, phyllosilicates, carbonates and variable charge minerals (constituents such as Fe, Al, Mn and Ti oxides, short-range ordered aluminosilicates as well as phyllosilicates coated by OH-Al or OH-Fe species whose charge varies with the pH of the soil solution). Recently, evidence on the sorption of heavy metals on microorganisms have been reported (Jackson, 1998). Soil components differ greatly in their sorption capacities, their cation and anion exchange capacities, and the binding energies of their sorption sites. Trace element sorption kinetics depend on the type of surface and trace element, but generally are rapid. Half times for bivalent cations, such as Pb, Zn, Cu and Cd, sorption on peat range from 5 to 15 seconds. Except for some noncrystalline minerals that have very high specific surface charge density with highly reactive sites, humic substances appear to have the greatest capacity for sorption of trace elements in cationic form. A body of evidence has demonstrated that humic matter and metal oxides are much more effective scavengers of trace elements in cationic form, than even the most efficient sorbent among phyllosilicates, indicating that specific sorption and other complexation processes are the dominant binding mechanisms (Jackson, 1998; Huang and Germida, 2002; Spark, 2003). Complexation reactions have the following effects: i) metal ions are prevented from being precipitated; ii) complexing agents can act as carriers for trace elements in soil solution; iii) their toxicity is often reduced by complexation.

Cadmium(II) sorption from water samples by powdered marble wastes

A series of batch adsorption experiments were carried out, with the aim of removing cadmium ions from aqueous solutions and water samples using powdered marble wastes (PMW) as an effective inorganic sorbent. PMW is inexpensive, widespread, and may be considered as environmental problem. The main parameters (i.e. solution pH, sorbent and cadmium concentrations, stirring time, and temperature) influencing the sorption process were investigated. The results obtained for sorption of cadmium ions onto PMW are well described by the Freundlich and Langmuir models. The Dubinin-Radushkevick (D–R) isotherm model was applied to describe the nature of the adsorption of the metal ion; it was found that the adsorption process was chemical in nature. The thermodynamic parameters were also calculated from the Gibbs free energy change (ΔG°), enthalpy (AH°) and entropy (ΔS°). These parameters indicated that the adsorption process of cadmium(II) ions on PMW was spontaneous and endothermic in nature. Under the optimum experimental conditions employed the removal of ca ~100% of Cd2+ ions was attained. The procedure was successfully applied to removal of the cadmium ions from aqueous and various natural water samples. The adsorption mechanism is discussed.

Synthesis and characterization of inorganic sorbents and their application to sorption of radionuclides

Synthesis and characterization of inorganic sorbents and their application to sorption of radionuclides

Preparation of 137Cs and 60Co sealed sources based on inorganic sorbents for radiometric calibration purposes

Abstract Sealed sources of 183.15 ± 5% kBq (4.95 ± 5% μCi) 137 Cs and 38.48 ± 5% kBq (1.04 ± 5% μCi) 60 Co based on inorganic sorbents were easily prepared, standardized, and successfully passed quality control tests. 137 Cs ( t 1/2 = 30.07 y) radionuclides were sorbed by equilibration of 137 CsNO 3 solution with 6-tungstocerate(IV) inorganic ion-exchanger at pH 3 for 48 h at 25 ± 1 °C, whereas 60 Co ( t 1/2 = 5.27 y) radionuclides were retained by coprecipitation from 60 Co(NO 3 ) 2 solution with Al(OH) 3 at pH 9.5. Then, the matrices retaining 137 Cs and 60 Co were washed and dried to be ready for use as cores of the sealed sources of the corresponding radionuclides. A calibrated amount of each matrix was separately packed in a stainless steel capsule in the form of round disc. After radiometric standardization and encapsulation, the sealed sources were submitted to quality control tests and finally checked radiometrically before release to the local market for calibration purposes of radiation measurement and identification instruments.

Governing factors for motor oil removal from water with different sorption materials

This paper has been focused on the sorbent efficiency for motor oil removal from water. Two types of sorbents were investigated: organic and inorganic. Natural wool fibers (NWFs) and recycled-wool-based nonwoven material (RWNM)) were tested as organic type of sorbents. Sepiolite, bentonite and zeolite have been chosen as representative inorganic sorbents. Sorption was carried out in batch sorption system. Efficiency of oil removal was determined by measuring the oil concentration before and after the sorption process. Extractive-gravimetric method and refractive index determination have been applied as analytical methods for determination of oil concentration in water. Governing factors for sorbent efficiency were proposed, analysed and compared. It was concluded that sorption process is mostly affected by mass of sorbent, sorption time, temperature and pH value of water. NWFs, which were the most efficient sorbent showed maximal efficiency and maximal sorption capacity: 0.1 g of NWFs after 10 min at 20 °C and pH 8.00 sorbed 3.3 g of motor oil from 300 mL of water polluted with 4.5 g of motor oil. Maximal efficiency for all sorbents investigated was reached after 30 min of sorption processes, it was 95.0% for NWF, 43.0% for NRWM, 20.7% for sepiolite, 19.6% for bentonite and 21.2% for zeolite. Physical adsorption onto all sorbents is a favorable process (sorption efficiency decrease with increasing temperature) while sorption onto bentonite and zeolite is a result of both physical adsorption and chemisorption (sorption efficiency increase with increasing temperature, up to 80 °C).

Selectivity modification by ion memory of magneso-silicate and magnesium alumino-silicate as inorganic sorbents

Synthetic magneso-silicate and magnesium alumino-silicate as inorganic ion exchange materials with the formula MgSi 5.59O 12.18·5.93H 2O and MgAl 2.32Si 5.2O 14.88·18.23H 2O, respectively, have been found to be suitable for the removal of Cs +, Co 2+ and Eu 3+ ions with the selectivity sequence Eu 3+ > Co 2+ > Cs +. Samples of Cs-, Co- and Eu-loaded were prepared and thermally treated at 850 °C in a furnace for the creation of specific cavity. Surface area, IR and X-ray diffraction patterns of the products were conducted. Surface area values of OMS, OMAS, TMS, TMAS, ETMS and ETMAS were measured and indicated an increasing in the surface area values for the TMS and TMAS samples and decreasing in the ETMS and ETMAS samples. Desorption studies in nitric acid medium were carried out and reloading of the eluted solids with the studied cations were conduced and the data show an ion memory behaviour for the eluted solids. Finally, the rate of Cs + ion sorption on OMS, OMAS, ETMS and ETMAS was studied. The diffusion coefficients calculated indicated that the diffusion of Cs + ion is high for the ETMS and ETMAS samples compared to the OMS and OMAS samples.

Gas-chromatographic identification of fluorine-containing organic compounds

The gas-chromatographic retention of a series of fluoroalkylarenes on the standard nonpolar polydimethylsiloxane stationary phase OV-101 was characterized, and the retention indices of these compounds were determined. It was found that large negative values of the homological increments of these constants can serve as a sign of fluorine derivatives that contain no less than three fluorine atoms per molecule. The retention indices on polar inorganic sorbents, the silica gels Silipor 75 and Silipor 600, were chosen as the second chromatographic parameter. On these sorbents (unlike partition separation), the nonadditivity effect of the retention indices of polyfunctional organic compounds with respect to their simpler structural analogs was found for the first time. It was found that a mutual correlation between indices for this combination of a phase and a sorbent was lower than that for the combinations of phases with different polarities; this fact is responsible for the higher information content of this combination for the identification of compounds from this class.

Inorganic sorbents based on modified microspheres for treatment of liquid radioactive waste

Sorbents based on hollow microspheres of entrained ash, with the surface modified by various chemical compounds (ferrocyanides, phosphates, oxides, etc.), were synthesized. Their physical and ion-exchange characteristics were examined. These sorbents show promise for treatment of low-and intermediate-level liquid waste of various origins in the dynamic and static sorption modes. The use of microspheres as matrices is not only technically but also environmentally efficient, because waste from thermal power engineering is utilized for disposal of nuclear waste.

Uptake of dissolved arsenic during the retrieval of silica from spent geothermal brine

A study has been made on the uptake of dissolved arsenic in a recirculation system designed to extract silicates for secondary use from spent (i.e. cooled) geothermal brine. Excess dissolved calcium, due to addition of lime (CaO), favours the precipitation of As-bearing phases in the retrieved materials. Controlling dissolved calcium in a continuous recirculation system is not easy to achieve; arsenic removal prior to precipitation of silicates is expected to be more practical. Predicted and measured arsenic speciation in the spent geothermal brine is dominated by arsenite species that were previously shown to lack affinity with most inorganic sorbents. However, synthetic schwertmannite was able to selectively remove dissolved arsenic without any significant accompanying decrease in silica concentrations. Its use prior to the introduction of spent geothermal brine into the recirculation system will likely make silica retrieval more feasible.

Sorption of 131I2 and CH3 131I from gas-water vapor medium with porous inorganic sorbents containing d elements

Sorption of 131I2 and CH3 131I from gas-water vapor medium on porous inorganic sorbents based on silica gel of the MSKG type, containing d elements, was studied. Sorbents containing Zn, Ni, Cu, and Co ammoniates show a low degree of recovery of 131I2 and CH3 131I from the gas-water vapor flow (less than 30%); their calcination at a temperature above 250°C does not noticeably affect the sorption power of the sorbent. The sorbents containing Zn, Ni, and Cu nitrates, both unmodified and modified, show a low degree of recovery of CH3 131I from the gas-water vapor medium (less than 1%). At the same time, whereas for unmodified sorbents the degree of recovery of 131I2 from the gas-water vapor phase does not exceed 70%, their modified analogs have higher degree of absorption of 131I2 (more than 99%), comparable with the similar data for Ag-containing sorbents based on silica gel of the MSKG type.