Magnesium ferrite nanoparticles as a magnetic sorbent for the removal of Mn2+, Co2+, Ni2+ and Cu2+ from aqueous solution

The aim of this research was to prepare magnesium ferrite (MgFe₂O₄) magnetic nanoparticles and to investigate their sorption characteristics towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions in aqueous solution. MgFe₂O₄ was synthesized by glycine-nitrate combustion method and was characterized by low crystallinity with crystallite size of 8.2?nm, particle aggregates of 13–25?nm, BET surface area of 14?m²/g and pore size of 8.0?nm. Sorption properties of MgFe₂O₄ towards Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ ions were studied using one-component model solutions and found to be dependent on metal ions concentration, contact time, pH and conditions of regeneration experiment. The highest sorption capacity of MgFe₂O₄ was detected towards Co²⁺ (2.30?mmol?g¹) and Mn²⁺ (1.56?mmol?g^?1) and the lowest towards Ni²⁺ (0.89?mmol?g^?1) and Cu²⁺ (0.46?mmol?g^?1). It was observed that sorption equilibrium occurs very quickly within 20–60?min. The pH_zpc of sorbent was calculated to be 6.58. At studied pH interval (3.0–7.0) the sorption capacity of MgFe₂O₄ was not significantly affected. Regeneration study showed that the metal loaded sorbent could be regenerated by aqueous solution of 10^?3 M MgCl₂ at pH 6.0 within 120?min of contact time. Regeneration test suggested that MgFe₂O₄ magnetic sorbent can be efficiently used at least for four adsorption-desorption cycles. The high sorption properties and kinetics of toxic metal ion sorption indicates good prospects of developed sorbent in practice for wastewater treatment.     

Chemically modified carbon nanotubes as efficient and selective sorbent for enrichment of trace amount of some metal ions

Multi-walled carbon nanotubes (MWCNT) was oxidized and chemically functionalized by 3-hydroxy-4-((3-silylpropylimino) methyl) phenol (HSPIMP) and characterized with FT-IR technique. This new sorbent was used for enrichment and preconcentration of Cu²⁺, Ni²⁺, Zn²⁺, Pb²⁺, Co²⁺, Fe³⁺ ions. Variables such as pH, amount of solid phase, eluting solution conditions (type, volume and concentrations) have significant effect on sorption and recoveries of analytes and the influence was optimized. At optimum value of conditions, the interference of other ions on understudy ions recoveries was investigated. The metal ions loaded on the solid phase via chelation with the new sorbent and subsequently efficiently eluted using 6 mL of 4 mol L^?1 HNO₃ solution. At each run, metal ions content was determined by flame atomic absorption spectrometry (FAAS). Relative standard deviation (N = 3) for determination of 0.2 μg mL^?1 of analytes was between 1.6 and 3.0%, while their detection limit was between 1.0 and 2.6 ng mL^?1 (3Sb, n = 10). The sorption capacity of HSPIMP–MWCNT for understudy ions was above 30 mg g^?1. The proposed method successfully applied for the extraction and determination of the understudy metal ions in different samples.     

Sorption of heavy metal ions from aqueous solution by a novel cast PVA/TiO2 nanohybrid adsorbent functionalized with amine groups

Sorption of Cd(II), Ni(II) and U(VI) ions onto a novel cast PVA/TiO₂/APTES nanohybrid adsorbent with variations in adsorbent dose, pH, contact time, initial metal concentration and temperature has been investigated. The adsorbent were characterized by SEM and FTIR analysis. BET surface area, pore diameter and pore volume of adsorbent were 35.98 m² g⁻¹, 3.08 nm and 0.059 cm³ g⁻¹, respectively. The kinetic and equilibrium data were accurately described by the double-exponential and Freundlich models for all metals. The maximum sorption capacities were 49.0, 13.1 and 36.1 mg g⁻¹ for Cd(II), Ni(II) and U(VI) ions with pH of 5.5, 5 and 4.5, respectively. Thermodynamic studies showed that the sorption process was favored at higher temperature. The adsorbent can be easily regenerated after 5 cycles of sorption–desorption.     

Treatment of wastewater containing Pb and Fe using ion‐exchange techniques

Treatment of wastewater containing lead and iron was examined using two different ion‐exchange resins namely Duolite ES 467 (containing amino‐phosphonic functional groups) and a chelating ion‐exchange resin (containing hydroxamic acid functional groups). Initially different sorption parameters such as contact time, pH, concentrations of sorbent, sorbate and chloride ion were studied. The sorption kinetics was observed to be fast and equilibrium could be reached within 30 min. Lead sorption efficiency increased with increase in pH whereas the opposite trend was observed with iron. The presence of chloride ions greatly reduced the Pb sorption efficiency in the case of Duolite ES 467. Column studies were carried out to recover Pb and Fe individually using Duolite ES 467 resin. The maximum uptake of Pb at pH 2 and 3 was observed to be 11.63 and 33.96 g dm^?3 of resin respectively. Similarly, for Fe at pH 2 and 3 the uptake was observed to be 10.07 and 6.96 g dm^?3 of resin respectively. In the presence of chloride ions, column studies were carried out using Duolite ES 467 for iron and chelating ion‐exchange resin containing hydroxamic acid functional groups for lead sorption. Hydroxamic acid resin's loading capacity remains constant for at least up to 20 cycles. Copyright © 2005 Society of Chemical Industry     

Kinetics of the sorption of heavy-metal ions by a sorbent obtained from boric acid production waste

The results of studies of kinetic regularities of sorption of heavy-metals ions (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Mn²⁺) by a sorbent based on calcium hydrosilicate (hereinafter referred to as silicate sorbent) produced from manmade waste formed during the processing of the boron-containing mineral raw materials (boron–gypsum) have been presented.     

Dy(III) sorption from water solutions by mesoporous silicas functionalized with phosphonic acid groups

The sorption properties towards dysprosium(III) ions of three samples of mesoporous silicas functionalized with phosphonic groups????Si(CH₂)₂P(O)(OH)₂ were studied. It was found that for the sample synthesized by spray-drying using OTAB as a template both sorption and desorption rate of Dy³⁺ ions is high, due to the defined porosity of the sorbent. Sorption of Dy³⁺ ions by bridged silsesquioxane xerogels with disordered structure is significantly hindered by diffusion processes, due to the chaotic packing of globules. Using a model for the chemical reactions, the composition of dysprosium(III) complexes with surface phosphonic groups were determined, and their formation constants were calculated. It was shown that xerogels with higher surface concentration of ligand groups (L), can form complexes DyL₃ and DyL₄ ^?. Meanwhile, the sample synthesized by spray-drying method forms only DyL₂ ⁺ and DyL₃ complexes. For this sample, complexes DyL₃ are more stable than for xerogels. So, mesoporous silica derived by spray-drying method, with defined spatial porosity and relatively low surface concentration complexation groups, is characterized by the best sorption properties towards dysprosium(III) (adsorption and desorption kinetics, the value of the static sorption capacity).     

Adsorption of Eu(III), Th(IV), and U(VI) by mesoporous solid materials bearing sulfonic acid and sulfamic acid functionalities

ABSTRACT

SBA-15 mesoporous materials modified by sulfonic acid and sulfamic acid functionalities, abbreviated as SBA-15/SO₃H and SBA-15/NHSO₃H, were synthesized and applied for the removal–separation of Eu(III), Th(IV), and U(VI). SBA-15/NHSO₃H showed an excellent selectivity toward U(VI), while SBA-15/SO₃H was more efficient adsorbent for Eu(III) and Th(IV). It was found that in the presence of KNO₃ (1 mol L^?1), the separation of Eu(III)/Th(IV) from their mixtures is possible. The results of the sorption behavior indicated a high adsorption capacity toward U(VI) and Th(IV) ions (140.5 and 106.7 mg g^?1, respectively) and ultrafast kinetics (15 min) in Eu(III) adsorption.     

Removal of Lead from Water Samples by Sorption onto Powdered Limestone

Abstract

Bench scale batch adsorption experiments were performed, aiming at the removal of the Pb²⁺ ions from aqueous solutions and water samples by fine powdered Limestone (LS) as an effective inorganic sorbent, which is inexpensive, widespread, and cheap. The main parameters (i.e., solution pH, sorbent and lead concentrations, stirring times, and temperature) influencing the sorption process, in addition to the effect of some foreign ions, were investigated. The results obtained stated that the sorption of Pb²⁺ ions onto LS is well described by Freundlich model and deviated from that of Langmuir over the concentration range studied. Under the optimum experimental conditions employed, the removal of ca. 100% of Pb²⁺ ions was attained. The procedure was successfully applied to the removal of lead from aqueous and different natural water samples. Moreover, the adsorption mechanism is suggested.     

Removal of Cr(VI) Oxy‐anions from Aqueous Solution by Sorption into Poly(Acrylamide‐Co‐Maleic Acid) Hydrogels

Abstract

The dynamic removal of hexavalent chromiuim by poly(acrylamide‐co‐maleic acid) hydrogels was studied by a batch equilibrium technique at 35°C. Various kinetic and adsorption parameters such as rate constant for sorption, intraparticle diffusion rate constant, Langmuir constant, and adsorption capacity have been evaluated. The sorption process follows the Langmuir‐type behavior and extent of sorption of Cr(VI) ions depends upon the composition of co‐polymeric gels, presence of other ions in the solution, and temperature of the system. Relatively higher temperature favors the sorption process. The activation energy was found to be ?20.369 kJ mol^?1. Finally, various thermodynamic parameters have also been calculated to elucidate the mechanism involved in the sorption process. The positive enthalpy change indicates the endothermic nature of the process. The presence of fluoride ions causes a decrease in the degree of sorption of Cr(VI). Finally, the sorption of Cr(VI) into the copolymeric sorbent has been explained on the basis of coordination between electron rich O and N atoms of sorbent molecules and the Cr(III) molecules. Moreover, H‐bonding interactions also seem to contribute to the sorption process.     

Synthesis and characterization of poly(hydroxamic acid)–poly(amidoxime) chelating ligands from polymer‐grafted acacia cellulose

Graft copolymerization of methyl acrylate (MA) and acrylonitrile (AN) onto acacia cellulose was carried out using free radical initiating process in which ceric ammonium nitrate (CAN) was used as an initiator. The optimum grafting yield was determined by the certain amount of acacia cellulose (AGU), mineral acid (H₂SO₄), CAN, MA, and AN at 0.062, 0.120, 0.016, 0.397, and 0.550 mol L^?1, respectively. The poly(methyl acrylate‐co‐acrylonitrile)‐grafted acacia cellulose was obtained at 55°C after 2‐h stirring, and purified acrylic polymer‐grafted cellulose was characterized by FTIR and TG analysis. Therein, the ester and nitrile functional groups of the grafted copolymers were reacted with hydroxylamine solution for conversion into the hydroxamic acid and amidoxime ligands. The chelating behavior of the prepared ligands toward some metal ions was investigated using batch technique. The metal ions sorption capacities of the ligands were pH dependent, and the sorption capacity toward the metal ions was in the following order: Zn²⁺ > Fe³⁺ > Cr³⁺ > Cu²⁺ > Ni²⁺. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Extraction of Uranium(VI) and Thorium(IV) from Nitric Acid Solution by N,N,N′,N′ – Tetraoctylglutaricamide

Synthesis and characterization of N,N,N′,N′-tetraoctylglutaricamide (TOGA) was carried out and used for extraction of U(VI) and Th(IV) from nitric acid solutions. The processes of extraction were determined by the slope analysis and by analyzing a function that allows the simultaneous treatment of all the experimental points obtained in different conditions. The different factors affecting the extraction distribution ratio(D) of U(VI) and Th(IV) (extraction concentration, concentrations of nitric acid, salting-out agent NaNO₃ concentration, equilibration time, temperature, and types of diluents) were investigated. The results obtained indicated that the extraction species of U(VI) and Th(IV) are mainly extracted as UO₂(NO₃)₂·1.0TOGA and Th(NO₃)₄·1.5TOGA. The apparent equilibrium constant of U(VI) and Th(IV) extraction determined are 3.35 ± 0.03 L³/mol³ and 1.87 ± 0.01 L⁵/mol⁵ at 298 ± 1 K. Thermodynamic parameters such as the free energy(ΔG), enthalpy(ΔH), and entropy(ΔS) changes associated with the extraction processes could be evaluated. Back-extraction of U(VI) and Th(IV) from organic phases was also studied.     

Hydrous iron oxide for removal of inorganic contaminants in simulated stormwater: A batch sorption kinetics study

Urban stormwater runoff, which consists of inorganic and organic contaminants, is a major source of pollutants to receiving waters and therefore they need to be removed. Simultaneous removal of contaminants, Cd²⁺, Cu²⁺, Ni²⁺, Zn²⁺ (heavy metal cations), and SeO₄²⁻ (oxyanion) from a simulated stormwater by a hydrous ferric oxide (HFO) was studied in batch and column sorption experiments. In the batch experiment the rate of sorption of the ions was rapid at the beginning and reached equilibrium in approximately 300 min. The amounts of ions sorbed were proportionate to the respective initial concentration of the ions added to the HFO. Cluster analysis showed that all heavy metals had similar sorption behavior, whereas Se had a distinctly different sorption process. Of the three different kinetic models tested the pseudo-first order kinetic model fitted the data the best. The column experimental results beyond 180 min were consistent with those of the batch experiment that the removal efficiencies of the ions were in proportion to the ion concentration in the feed. Below 180 min, Cu appeared to be preferentially removed than Zn.     

Development of a Scalable Method for Manufacturing High‐Temperature CO2 Capture Sorbents

An engineered process for scalable manufacture of a calcium aluminum carbonate CO₂ sorbent with production amounts of about 1000 g per hour has been developed. The process includes mixing and heating, solid‐liquid separation, drying and extrusion, crushing and conveying, and calcined molding steps. The sorbent preparation involves the coprecipitation of Ca²⁺, Al³⁺, and CO₃^2– under alkaline conditions. By adjusting the Ca:Al molar ratio, a series of Ca‐rich materials could be synthesized for use as CO₂ sorbents at 750 °C. A calcium acetate‐derived sorbent exhibited better cyclic stability than sorbents originating from CaCl₂ and Ca(NO₃)₂. The initial sorption capacity increased with CaO concentration. High stability of more than 90 % was maintained by the Ca:Al sorbents after 40 looping tests.     

Retention,Thermodynamics and Adsorption Profile of Th(IV) Ions onto 1‐(2‐Pyridylazo)‐2‐Naphthol (PAN) Loaded Polyurethane Foam from Acetate Media and its Separation from Rare Earths

Abstract

The sorption behavior of 2.7×10^?5 M solution of Th(IV) ions on 1‐(2‐pyridylazo)‐2‐naphthol (PAN) loaded polyurethane foam (PUF) has been investigated. The quantitative sorption was occurred from pH 6 to 9 from acetate buffer solutions. The sorption conditions were optimized with respect to pH, shaking time, and weight of sorbent. The sorption data followed the Freundlich, Langmuir, and Dubinin‐Radushkevich (D‐R) isotherms very successfully at low metal ions concentration. The Freundlich isotherm constant (1/n) is estimated to be 0.22±0.01, and reflects the surface heterogeneity of the sorbent. The Langmuir isotherm gives the maximum monolayer coverage is to be 8.61×10^?6 mol g^?1. The sorption free energy of the D‐R isotherm was 17.85±0.33 kJ mol^?1, suggesting chemisorption involving chemical bonding was responsible for the adsorption process. The numerical values of thermodynamic parameters such as enthalpy (ΔH), entropy (ΔS), and Gibbs free energy (ΔG) indicate that sorption is endothermic, entropy driven, and spontaneous in nature. The adsorption free energy (ΔG_ads) and effective free energy (ΔG_eff) are also evaluated and discussed. The effect of different anions on the sorption of Th(IV) ions onto PAN loaded PUF was studied. The possible sorption mechanism on the basis of experimental finding was discussed. A new separation procedure of Th(IV) from synthetic rare earth mixture using batch, column chromatography, and squeezing techniques were reported.     

Modern hybrid sorbents – New ways of heavy metal removal from waters

The possibility of hybrid ion exchanger (HIX) application in the simultaneous removal of heavy metal ions such as Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) was presented. The ion exchanger in question combines the unique properties of hydrated metal oxides with the mechanical and thermal stability of synthetic ion exchangers. The kinetics of the sorption process of Cr(VI), Cu(II) and Zn(II) as well as Cd(II) and Pb(II) in the presence of Cl⁻, NO₃⁻ and SO₄²⁻ as well as EDDS (ethylenediaminedisuccinic acid) was also analyzed. Additionally, the effect of initial concentration, phase contact time and pH was also studied. Taking into account the possibility of its application on a large scale, the parameters of the adsorption process were estimated based on the linear form of the Langmuir and Freundlich isotherms.     

Sorption of copper ions by granulated chitosan

The features of sorption of Cu²⁺ ions from aqueous solutions of CuSO₄ by granulated chitosan sorbent in static conditions and the different contribution of surface and bulk amino groups in the sorbent to complexation are discussed. Sorption with freshly formed swollen and maximally amorphized granules with accessible bulk amino groups can be described by Langmuir’s equation; it attains 5.6 mmole/g of dry sorbent, which is close to the sorption calculated from the equimolar composition of the amino-copper complex. Sorption of initially dry granules with less accessible bulk amino groups does not obey Langmuir’s equation due to precipitation of copper hydroxide and hydrosulfate on the surface of the sorbent. __________ Translated from Khimicheskie Volokna, No. 2, pp. 11–14, March–April, 2006.     

Adsorption of copper on specifically modified polyamide sorbent

A novel, specific sorbent based on polyamide covalently immobilized with dead yeast cells by glutaraldehyde was prepared and characterized. This sorbent exhibits a high capacity for metal complexation based on multifunctional groups of dead cells, as well as a good stability for reuse based on the crosslinking agent, glutaraldehyde. The Cu²⁺ sorption characteristics of the polyamide modified with immobilized dead cells were studied and compared to those of the polyamide chemically modified without cells. The adsorption capacity of specifically modified polyamide was about 19‐fold higher than the chemically modified polymer. The adsorption isotherms of Langmuir and Freundlich for the new specific sorbent were determined. The effect of pH, temperature and co‐ions (Zn²⁺, Pb²⁺, Co²⁺, Ca²⁺ and Mg²⁺) on the Cu²⁺ sorption capacity were studied. The effectiveness of heavy metal desorption and the coefficient of recovery of sorption ability were determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 80–85, 2003     

Selective Separation of Uranium using Alizarin Red S (ARS)-Modified Anion-Exchange Resin or by Flotation of U-ARS Chelate

ABSTRACT

An alizarin red S (ARS)-modified anion-exchange resin was prepared by a simple reaction of ARS with the anion exchanger Doulite A101 and used for the efficient sorption of uranium from aqueous media. The effect of various parameters on the sorption of U(VI) (pH effect, sorption kinetics, resin capacity and breakthrough curves) was investigated. The modified resin sorbs U(VI) over a wide range of pH (2·8–5) with a maximum sorption capacity of 0·68 mmol.g^?1 at pH 3·2 to 4·0. Iron (III), Zr(IV), Ti(IV), Cu(II), and Th(IV) ions are also sorbed to different extents, but Be(II), Bi(III), Ca(II), Mg(II), Pb(II), Hg(II), Zn(II), Cd(II), AI(III), Mn(II), Co(II) and Ni(II) are not sorbed; thus, conditions for separating U(VI) from these metal ions have been identified. For eluting U(VI) from the resin, 0·2 mol.L^?1 HCl was used and the recovery recorded was as high as 99.9%. The use of ARS is extended to float uranium quantitatively and selectively from aqueous media at pH = 4 by using oleic acid as a surfactant. The different parameters affecting the flotation process have also been investigated. Uranium(VI) has been effectively separated from natural water samples and certified uranium ores using both procedures.     

Composite Fe3O4/Humic Acid Magnetic Sorbent and its Sorption Ability for Chlorophenols and some other Aromatic Compounds

A composite magnetic sorbent with a relatively high content of humic substances (above 35% of organic carbon) was prepared by co-precipitation of Fe²⁺/Fe³⁺ salts with commercially available alkaline humate concentrate. Magnetite (Fe₃O₄) was identified as the main crystalline phase bearing the magnetic properties of the sorbent. Scanning electron microscope (SEM) images revealed the presence of uniform sub-micron structures on the surface of the sorbent grains. Due to the presence of humic substances, the sorbent exhibited good sorption ability towards low-polarity organic pollutants, namely chlorophenols. The sorption efficiency increased in the order of 4-mono- < 2,4-di- < 2,4,5-trichlorophenol in accordance with growing hydrophobicity of these compounds, confirming a hydrophobic nature of the interactions involved in the sorption process. Similar trends were found in the desorption study utilizing water and methanol as leachants. Some polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, fluoranthene, pyrene) were also retained on the sorbent. The chemical composition as well as the main physical characteristics (surface area, phase composition) of the sorbent remained virtually unchanged during the sorption process. The sorbent retained its magnetic properties during the sorption of organic substances from aqueous solutions, which provides an opportunity for its regeneration.     

Iron incorporated rice husk silica as a sorbent for hexavalent chromium attenuation in aqueous system

An environmentally benign metal oxide, Fe, was incorporated into silica derived from rice husk via the sol gel route and the physiognomies of both the modified (IRS) and raw rice husk derived silica (RHS) were studied via FTIR and XRD analysis and pH_PZC and surface area determinations. The stability of the Fe incorporated into the silica matrix, determined via the toxicity characteristic leaching procedure, showed that the integrity of the sorbent was intact only in basic medium but got vitiated in acidic medium. The sorption process conformed to the pseudo second order model than reversible first order and pseudo first order kinetic models and the rate of sorption of Cr(VI) onto either sorbents was determined by film diffusion. Process variables optimization showed that the amount of Cr(VI) removed per gram of sorbent reduced with increase in initial solution pH and the negative impact of the anionic interference was more in the presence of SO₃²⁻ than NO₃²⁻ and Cl⁻. The predicted Langmuir monolayer sorption capacity (mg/g) of the IRS (63.69) was higher than that of the RHS (61.35). The value of the mean free energy (kJ/mol) of sorption, obtained for IRS (267.26) and RHS (100.00), and the significant changes in the peak positions of specific functional groups on the Cr(VI) laden sorbents showed that chemisorption was the dominant mechanism of Cr(VI) uptake.