Chelating Sorbent Research Articles

Insights into neodymium interaction with carboxylate-graphene-like support in presence of nitrate: A comparative DFT investigation

Recently, we demonstrated that carboxylate mesoporous carbon improved the adsorption of rare earth elements as neodymium (Nd). Here, calculations based on Density Functional Theory were carried out to give insight on binding of the Nd with carboxylates. Different phenyl carboxylate-Nd complexes were first identified, considering nitrate and water molecules as ligands, in order to obtain reliable carboxylate-graphene models. The optimized structures are used to compute the binding and complexation energies then the competition for metal between carboxylate group and solvent was analysed. The results, in agreement with the experimental evidence, indicated that the Nd favors the anchored carboxylate groups compared to the bulk water. Findings showed that, the graphene support did not significantly alter the carboxylate-Nd binding energies. The partial charges revealed the coupling electron-withdrawing effect of the nitrate and water oxygens. The binding and complexation energies provided here can be regarded as references for designing of REE chelating sorbents.

Selective recovery of boron, cobalt, gallium and germanium from seawater solar saltworks brines using N-methylglucamine sorbents: Column operation performance

The European Union (EU) identified a list of Critical Raw Materials (CRMs) crucial for its economy, aiming to find alternative sources. Seawater is a promising option as it contains almost all elements, although most at low concentrations. However, to the present, the CRMs' recovery from seawater is technically and economically unfeasible. Other alternatives to implement sea mining might be preferred, such as reverse osmosis brines or saltworks bitterns (after sodium chloride crystallisation). The CRMs' extraction in a selective way can be achieved using highly selective recovery processes, such as chelating sorbents. This study focuses on extracting Trace Elements (TEs) from solar saltworks brines, including boron, cobalt, gallium and germanium, using commercial N-methylglucamine sorbents (S108, CRB03, CRB05). The application of these sorbents has shown potential for boron recovery, but their selectivity for cobalt, gallium, and germanium requires further investigation. This research aims to assess these sorbents' kinetics and column mode performance for TEs recovery from synthetic bitterns. Boron and germanium were rapidly sorbed, reaching equilibrium (>90 %) within 1 h, except for S108, which took 2 h. In column mode, 20–25 pore volumes of bittern were treated to remove boron and germanium, but competition from other elements reduced treatment capacity. An acidic elution (1 M hydrochloric acid) allowed to elute them (>90 %), reaching concentration factors for germanium and boron of 35 and 11, respectively, while cobalt and gallium had less affinity for the sorbents. In addition, the experiments performed were fitted by a mass transfer model to determine the equilibrium constants and selectivities. Therefore, bittern mining has been proven as a secondary/alternative source to obtain CRMs, which can lead the EU to a position in which its dependence on other countries to obtain these raw materials would be decreased.

Modification of pre-oxidized polyacrylonitrile fibers as chelating sorbents for removal of Copper(II) ions

Pre-oxidized polyacrylonitrile (PAN) fibers were chemically modified by sulfuric acid. In the process, conjugated imine sequences were retained and amide groups were transformed from unreacted nitrile groups. The adsorption experiments of Cu(II) ions by modified PAN fibers indicated that the adsorption capacities were significantly improved by increasing initial concentrations of metal ions, reaction time and temperature. The adsorption equilibriums followed Langmuir isotherm with correlation coefficients greater than 0.99. Kinetics analysis demonstrated that the adsorption of copper ions on the modified fiber was fitted well with pseudo-second-order kinetics equation. Indicated by energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) results, channels for metal ions diffusing from the surface to the inner of the fiber were generated by the strong etching of sulfuric acid. The active sites of conjugated imine sequences and amides in the whole modified fiber can thus be easily accessed by the metal ions.

Selective Removal of Transient Metal Ions from Acid Mine Drainage and the Possibility of Metallic Copper Recovery with Electrolysis

ABSTRACT The low pH and high salinity of acid mine drainage (AMD) fundamentally complicates the sorption processes. We explored the selective removal of Cu, Ni and Co ions present in AMD from the excess of ferrous ions of using a chelating resins Lewatit® MonoPlus TP 220 and Lewatit® TP 208. Also, the recovery of metal copper from desorption solution using electrolysis was investigated. The results showed that the most effective sorption of metal ions was achieved with chelating sorbent Lewatit® TP 220. The dynamic capacity of the sorbent under the given conditions (pH= 2.5 ± 0.03, presence of Fe(II/III), Zn(II), Mn(II)) decreased in the following order: Cu(II) (43.3 ± 1.4 g/L) > Ni(II) (22.1 ± 2.1 g/L) > Co(II) (3.6 ± 0.4 g/L). Chelating resin Lewatit® TP 208 under the same conditions showed lower efficiency: Cu(II) (30.6 ± 1.3 g/L) > Ni(II) (9.1 ± 0.17 g/L) > Co(II) (1.3 ± 0.08 g/L). The weak base anion exchanger Purolite® A 832 was successfully used to take up Cu(II) from ammonia solution and easily regenerated with sulfuric acid. The sorption capacity for Cu(II) was calculated to be 19.2 ± 0.5 g/L. Electrolysis experiments were performed with a fluidized bed electrolysis reactor where metallic copper was regenerated from desorption solutions and purified sulfuric acid solutions were obtained.

New magnetic chelating sorbent for chromium speciation by magnetic solid phase extraction on-line with inductively coupled plasma optical emission spectrometry

A novel sorbent material employing magnetic nanoparticles (MNPs) coupled to graphene oxide (GO) functionalized with 4-aminobenzenesulfonic acid (M@GO-ABS) has been synthesized and applied to develop an inexpensive and automatic method for Cr(III) and Cr(VI) speciation in environmental samples; the developed method combines inductively coupled plasma optical emission spectrometry (ICP-OES) with on-line magnetic solid phase extraction (MSPE). Two magnetic-knotted reactors containing M@GO-ABS were installed in the eight-port injection valve of a flow injection (FI) manifold. Two different eluents were used, one for Cr(VI) (the most toxic chromium species) and one for total Cr concentration. Cr(III) concentration was calculated by the difference between Cr(VI) concentration and total Cr concentration. The optimized method presented detection limits (LOD, peak height) of 0.1 μg L−1 for chromium (VI) and 0.08 μg L−1 for total chromium, and enrichment factors of 15 and 23, respectively. Certified reference materials (TMDA 54.5 fortified lake water and SPS-SW2 surface water) and spiked aqueous samples were used to validate the developed method. The developed method was fruitfully applied to chromium speciation in environmental water samples such as seawater, well water and tap water collected in Málaga (Spain). The obtained values were in good agreement with the certified values, and the recoveries were found in the range of 91–108% for the spiked samples.

The use of chelating sorbents for the effective extraction of heavy metals from alcoholic beverages in order to ensure their quality and safety

The article describes a combined method for the determination of lead, copper and cadmium in alcoholic beverages, based on the preliminary extraction of these elements using the chelating sorbent POLYRGSA-VII-M and their subsequent determination by the absorption method with flameless atomization. Optimal sorption conditions have been developed. Concentration levels of lead, copper and cadmium in alcoholic beverages were determined. It is established that the content of these elements in the studied beverages does not exceed their maximum permissible concentrations.

Sorption-photometric definition of thorium (IV) in clays

A simple and selective method for sorption-photometric determination of thorium (IV) micro amounts in clay using a new chelating sorbent, a copolymer of maleic anhydride with styrene modified with N1,N1,N2-triphenylguanidine, is proposed. The sorbent is white substance, insoluble in water, acids, weak alkalis and organic solvents. Sorbents were first ground in an agate mortar and sieved through a sieve (0.14 mm). The effect of pH of the medium, the ionic strength of the solution, contact time of the phases, concentration of thorium (IV) in the solution and on the sorption was studied under static conditions. Thorium concentration was determined by the photometric method using 2,2’,3,4-tetrahydroxy-3’-sulfo-5’-chloro-benzene. The concentration of thorium (IV) was calculated using a calibration curve, the results were processed statistically. The full static sorption capacity of the resulting sorbent on K+ ion was 13 mmol/g. An emphasis was also made on the study of the effect of the kinetic properties of sorbents on the sorption process. The maximum degree of thorium extraction by the sorbent was achieved from the solutions with pH 4. The time dependence of sorption was also studied. The results of the study showed that the sorption equilibrium is achieved after 2.5 h of contact of the sorbent with the metal. The sorption of thorium increases with an increase in the thorium concentration in the solution and attains maximum at a concentration of 8 × 10–3 M (pH 4, = 8 × 10–3 M, Vgen = 20 ml, mabsorbed = 0.05 g, sorption capacity = 348 mg/g). The degree of thorium (IV) extraction in optimal conditions exceeds 95%. It is shown that the main micro- and macro-components of clay do not affect the results of the determination of thorium. The developed technique was applied to determine thorium in a clay sample from the Shemakhi region of Azerbaijan. The correctness of the obtained results was confirmed by the spike test.

Flax fiber grafted with Cd(II)-imprinted 2-pyridylthiourea for selective ion removal

The surface ion-imprinting technique was employed in the development of Cd(II) ion-selective chelating sorbent based on cellulosic flax fibers. The flax fibers (F) were first amino-functionalized via grafting of polyacrylamide followed by Hofmann degradation and then the 2-pyridylthiourea (PTU) chelating units were inserted by reaction with 2-pyridylisothiocyanate. The chelating fibers were then loaded with Cd(II) ions and treated with glutaraldehyde before eliminating the metal ions to get the Cd(II) ion-imprinted PTU functionalized F fibers (Cd-PTU-F). The chemical changes along with the Cd(II) ions chelation by the inserted PTU units were investigated by spectral methods including FTIR, and XPS. In addition, the conditions for the Cd(II) ion adsorption were optimized and the maximum adsorption capacity of the obtained Cd-PTU-F sorbent was reached up to 310 mg/g calculated using the Langmuir model, which presents the best correlation with the resulted isotherms. Also, the adsorption kinetics was best described by the pseudo-second-order model. The fiber's selectivity was investigated in a solution mixture of Cu(II), Zn(II), Pb(II), Ni(II), and Cd(II) ions and the calculated parameters revealed the creation of a remarkable affinity for the Cd(II) ions compared to the other coexisting metal ions.

Sorption of silver (I) ions from aqueous solutions using the synthetic sorbent

We study the sorption of silver ions from aqueous solutions by a synthetic chelating sorbent. In the presence of formaldehyde, a polymeric sorbent based on a copolymer of styrene with maleic anhydride, modified with N,N’-diphenylguanidine, was synthesized and further used for extracting Ag(I) ions. The composition and structure of the synthesized polymeric chelating sorbent were studied using IR and UV spectroscopy methods. A simple, inexpensive, and efficient method for extracting Ag(I) ions from aqueous solutions was used. The effect of various parameters on the sorption process was studied, including the acidity of the medium (pH), the initial concentration of the metal ion, the time required to establish complete sorption equilibrium, and ionic strength. The optimum pH value for the extraction of Ag(I) was found to be 6. The process is characterized by a high adsorption capacity reaching 547.2 mg/g. The research results showed that the time required to establish a complete sorption equilibrium for the sorbent modified with N,N’- diphenylguanidine is 60 min. Ag(I) adsorption increases up to the value of ionic strength of μ = 1, after which its intensity decreases. At the final stage, the process of desorption of absorbed silver ions was carried out. During desorption, the best eluting agent for the extraction of Ag(I) was determined to be 0.5 M HNO3. The sorbent can be re-used after regeneration. The copolymer of styrene and maleic anhydride modified with N,N’-diphenylguanidine has a high sorption capacity and, therefore, can be used as a potential adsorbent for the extraction of silver (I) from aqueous solutions.

New Magnetic Chelating Sorbent for Chromium Speciation by Magnetic Solid Phase Extraction On-Line with Inductively Coupled Plasma Optical Emission Spectrometry

New Magnetic Chelating Sorbent for Chromium Speciation by Magnetic Solid Phase Extraction On-Line with Inductively Coupled Plasma Optical Emission Spectrometry

Применение хелатообразующего сорбента, содержащего фрагменты 4-амино-тиоурацила, для сорбционного извлечения тория(IV) из глины

The article considers the danger of thorium due to its radioactive toxicity. There has been proved the diversity of thorium compounds and the influence of thorium on a human body and the environment. A polymer chelating sorbent containing fragments of 4-amino - thiouracil has been investigated. An isotherm of thorium sorption with the sorbent is constructed and the optimal concentration conditions are determined: pH = 4; = 6 • 10–3 mol/l; Vob = 25 ml; msorb = 0.03 g; sorptive capacity (CE) = 1 163 mg/g. The degree of extraction of thorium(IV) ions under optimal conditions exceeds 95%. The developed technique was applied to extract thorium from clay. Studying sorption was carried out under static conditions using special equipment.

Synthesis of bi-functional chelating sorbent for recovery of uranium from aqueous solution: sorption, kinetics and reusability studies

Synthesis of bi-functional chelating sorbent for recovery of uranium from aqueous solution: sorption, kinetics and reusability studies

Titration of chelating fibrous sorbent in the presence of complex-forming divalent cations

Titration curves of H-forms of the fibrous chelating sorbent with iminodiacetic groups based on industrial polyacrylonitrile fiber Nitron with potassium hydroxide in 1M KCl solution in the presence of Ni2+, Co2+, Cu2+ and Ca2+ chlorides were obtained. The method used made it possible to simultaneously measure the pH of the solution and the concentration of the divalent cation at each point of the titration curve. From these data, the dependences of their sorption values on the pH of the equilibrium solution were calculated. The curves of direct and back titration practically coincided in all cases. As the pH changed during titration, precipitation was observed at pH values of precipitation of the corresponding hydroxides. In this case, the increase in pH was suspended or greatly slowed down by adding alkali to the titration cell. The formation of a precipitate occurred mainly in a solution for Co2+ and Ni2+ (pH 8), when the ion exchanger was saturated with a metal ion. In the case of Cu2+ (precipitate formation pH 4), Cu2+ sorption occurs at both lower and higher pH due to ionization of carboxyl groups and partial dissolution of the precipitate. In all cases, the maximum sorption of Ni2+, Co2+, Cu2+, Ca2+ corresponded to the formation of sorption complexes of the R–N(CH2COO-)2Me2+ type.

SYNTHESIS AND RESEARCH OF CHELATE FORMING SORBENT BASED ON CARBAMIDE, FORMALDEHYDE, DITIZONE

The purpose of this study is the synthesis and study of a chelating sorbent for the extraction of ions of non-ferrous and noble metals. To achieve this goal, a sulfur-containing chelating sorbent based on carbamide, formaldehyde, and dithizone was synthesized and studied. The optimal conditions for the synthesis of the sorbent have been determined and studies have been carried out on the influence of the molar ratios of the starting materials on the composition, and physicochemical properties of the synthesized sorbent. The optimum temperature of polycondensation was taken as 90 °C, the reaction time is 2.5-3 hours, as a result, the reaction is more uniform and the exchange capacity for a 0.1 N HCl solution reaches 3.8 mg-eq/g. As a result of the studies carried out, the sorbent with the best performance was obtained at a 1: 2: 0.5 ratio of carbamide, formaldehyde, and dithizone, respectively. Based on the results of IR spectroscopy, the reaction of sorbent formation is proposed. The static exchange capacity of the synthesized sorbent for metal ions was determined, mg-eq/g: Cu (II) – 2,75; Zn (II) – 2,83; Ni (II) – 2.72; Ag (I) – 3.12

Recyclable Functionalized Polymer for Cu(II) Decontamination from Aqueous Media

In the endeavor to explore more and more materials, this work is focused on the study of the potential applicability of a chelating sorbent based on an acrylic copolymer functionalized with amidoethylenamine groups in Cu(II) removal from wastewaters in batch and dynamic conditions. The proposed sorbent was synthesized by the chemical transformation reaction of ethylacrylate (EA): acrylonitrile (AN):2% divinylbenzene (DVB) copolymer with ethylenediamine (EDA). Batch sorption results pointed out that the Cu(II) retention by the acrylic copolymer functionalized with amidoethylen-amine groups was dependent on the initial solution pH, initial metal concentration and contact time. The sorption of Cu (II) on the tested chelating copolymer obeyed both Langmuir and Freundlich isotherms. The Langmuir maximum sorption capacity was 65.21mg Cu (II)/g of polymer. The kinetic experimental data fitted well with the pseudo - second order model. The dynamic behavior of a fixed bed column filled with the acrylic copolymer functionalized with amidoethylenamine groups has been studied in terms of breakthrough curve. The experimental breakthrough data have been well described by Thomas model. The tested chelating copolymer is suitable for multiple processes of Cu(II) sorption-desorption. The column studies with real wastewater sample presented a removal efficiency of 100% for Cu (II) and a significant improvement of the wastewater quality. The acrylic copolymer functionalized with amidoethyleneamine groups can be successfuly applied for the Cu (II) removal - recovery - recycling.

Functionalization of Magnetic-Chitosan Nanocomposite for Enhancing Th(IV) Ions Sorption.

Designing new chelating sorbents for the sorption of thorium as (Th4+) has become an impending challenge. This study describes a simple one-pot in situ co-precipitation method was used to synthesize a multifunctional magnetic-chitosan nanocomposite core-shell for enhanced Th4+ ions sorption from aqueous solutions. The synthesized biosorbent was well characterized by various techniques such as FTIR, XRD, pHzpc, TEM, VSM and elemental analysis. The sorption behavior of magnetic-chitosan nanocomposite (R-I) is systematically compared to the performance of functionalized magnetic-chitosan nanocomposite (R-II). The magnetic nanocomposites sizes around 25.0 nm. The grafting of methylene phosphonic groups on chitosan increased Th4+ sorption efficiency. Maximum sorption capacities reach 89.7 and 142.3 mg Th g−1 for R-I, and R-II sorbents, respectively at pH 3.5. Kinetics, isotherms, and thermodynamic behaviors of Th4+ ions sorption into the synthesized nanocomposite from an aqueous solution were studied in detail. The studies showed that the Langmuir isotherm and pseudo-second order model gave a better description for the sorption process. The sorption is spontaneous, endothermic and controlled by entropic change. EDTA solutions (0.25 M) can be efficiently used for metal recovery and sorbent can be recycled for at least 5 cycles without significant loss in sorption/desorption performances.

DETERMINATION OF VANADIUM (V) TRACE AMOUNTS IN OIL SLUDGE AFTER PRELIMINARY CONCENTRATION WITH POLYMER SORBENT

A modified sorbent based on copolymer of maleic anhydride with methacrylic acid was proposed for sorption of vanadium (V) concentration. A polymer chelating sorbent with fragments of para-amino salicylic acid was used in the work. Optimal sorption conditions were determined and the dependence of sorption capacity on the acidity of the solution studied. At pH 5, the degree of sorption attains its maximum. The effect of ionic strength on vanadium sorption was studied. Studies have shown that the ionic strength up to 0.6 mol/l does not affect the sorption, after 0.6 mol/l the increase in the ionic strength at the beginning gradually, and then sharply decreases the sorption. The effect of ionic strength on vanadium sorption was studied to show that the ionic strength up to 0.6 mol/l does not affect the sorption, and after 0.6 mol/l the increase in the ionic strength at the beginning gradually, and then sharply decreases the sorption. All further experiments were carried out in the solutions with an ionic strength of 0.6. It was found that as the concentration of vanadium rises in the solution, the amount of sorbed metal increases, and at a concentration of 8.10-3 mol/l it becomes maximum (pH = 5, CV5+ = 8.10-3 mol/l, vtotal = 20 ml, msorb. = 0.03 g, SC = 243 mg/g). The isotherm of vanadium (V) sorption with the synthesized sorbent was constructed. Sorption equilibrium is achieved within 1 hour of contact between the solution and the sorbent. Further growth in the sorption time does not change sorbent’s characteristics. The sorbent extracts vanadium (V) from solutions with a recovery rate of 93%. The effect of different mineral acids (HClO4, H2SO4, HNO3, HCl) of identical concentrations on vanadium (V) desorption from the sorbent was also studied. The results of the analysis showed that the maximum desorption of vanadium (V) occurs in perchlorate acid. The developed method was applied to determine the trace amounts of vanadium in oil sludge with preliminary concentration.

Chelating polymers with valuable sorption potential for development of precious metal recycling technologies

Abstract A special attention is currently focused on the recovery of Au, Ag, Pt, Pd and Rh from both primary and secondary sources. From the wide range of sorbents that have been used in this respect, the required selectivity is proved only by the chelating polymers containing donor N, O and S atoms in their functional groups. This work presents the recent published researches on this topic, pointing out the capabilities of chelating sorbents based on organic synthetic polymers for a sustainable development. The chelating sorbents are differentiated and reviewed according to their synthesis strategy and compatibility with synthetic and real matrices. First, an overview on the novel functionalized polymers and impregnated resins with good selectivity for the recovery of most valuable precious metals from synthetic leach solutions is given. Subsequently, the performances of these materials in the selective and preconcentrative recovery of Au, Ag, Pt, Pd and Rh from simulated and real leachates are discussed. The viability of an integrated approach for the determination of precious metals from simulated solutions by solid phase spectrometry is highlighted. The transposition of chelating polymers’ potential in challenging technologies for precious metal recovery-reuse-recycling needs further research on directions that are proposed.

Lead (II) concentration by a chelating sorbent containing meta-phenylenediamine fragments

A sorbent based on a copolymer of maleic anhydride with styrene, containing m-phenylenediamine fragments was synthesised. After drying at 50–60 ° С , the obtained sorbent was identified using IR spectroscopy. Further, a study of lead sorption by a synthesised sorbent was conducted. For this purpose, the effect of pH, time, ionic strength and metal concentration on sorption was determined. According to the experiment, the maximum sorption was established at рН = 6. Complete sorption of lead (II) wasobtained following 3 hours of metal contact with the sorbent. The effect of increase in ionic strength to 0.6 mol/L on sorption was shown to be insignificant, with a subsequent increase leading to a critical decrease in sorption value. The isotherm of lead sorption by the synthesised sorbent was constructed and the optimal concentration conditions studied. The analysis results demonstrated an increase in the concentration of lead (II) ions in the solution to provide higher values of sorbed metal concentration with the maximum occurring at a concentration of 6·10 -3 mol/L (pH = 6, С Pb +2 = 6·10 -3 mol/L, V sample = 20 mL, m sorb. = 0.05 g, CE = 405 mg/g). Under optimal conditions, the extraction degree of lead (II) ions exceeds 95 %. The study of sorption was carried out both under static and dynamic conditions. Additionally, the effect of various mineral acids (HClO 4 , H 2 SO 4 , HNO 3 , HCl) of the equal concentration on the desorption of lead (II) from the sorbent was studied. The maximum desorption of lead (II) was obtained in sulphuric acid. Thus, the proposed express technique including preliminary concentration of lead (II) with a synthesised sorbent provides quantitative isolation of lead (II) from a large sample volume with a complex background composition.

Effect of Amino- and Phosphorus-Containing Alkylene Substituents on the Complexing Ability of Phosphorus-Containing Cationites with Respect to Indium and Gallium Cations

The coordination properties of additional basic and acidic groups in phosphinic acid macroporous ionites are controlled by varying their nature and mutual arrangement during the sorption of indium and gallium cations. Patterns of the targeted change in the acidic and electron-donating properties of polydentate moieties are determined along with its effect on the sorption-selective characteristics of ionites, excluding that of matrix selectivity. It is shown how substituents in the form of proton-accepting anionogenic and phosphinic acid groups influence the sorbability of trace elements by raising the ion-coordinating strength of the phosphoryl system. It is established that the advantageous spatial structure of diphosphonic cationites and the effect of an additional ring increase the degree of sorption, especially for gallium in sulfuric acid solutions. Modifying ionites by replacing substituents in the phosphine center is an effective way of creating new chelating sorbents.