Sorption of strontium ions from aqueous solutions by oxidized multiwall carbon nanotubes

Multiwall carbon nanotubes (MWCNTs) oxidized by nitric acid solution were used to investigate the adsorption behavior of strontium from aqueous solutions similar to the nuclear waste media. The physical properties of both as produced and oxidized MWCNTs were studied by Boehm’s titration method and nitrogen adsorption/desorption. The results showed that the surface properties of MWCNTs such as specific surface area, functional groups and the total number of acid sites were improved after oxidation. Furthermore, the effect of solution conditions such as initial concentration of strontium(II), pH, ionic strength, MWCNT concentration and contact time were studied at room temperature. The results of this study showed that the adsorption of strontium(II) was significantly influenced by the pH value and the solution ionic strength. According to the Langmuir model, the maximum adsorption capacities of strontium(II) onto the as produced and oxidized MWCNTs were obtained as 1.62 and 6.62 mg g^?1, respectively. The contact time to reach equilibrium was 100 min. The good adsorption of strontium(II) on oxidized MWCNTs at the lower ionic strength, the relatively high pH and the short equilibrium time indicate that the oxidized MWCNTs have great potential applications in the field of the environmental protection.     

Sorption of arsenic onto inorganic sorbents modified with iron compounds

Granulated inorganic sorbents based on silica gel of KSKG grade and aluminum oxide and modified with Fe(III) compounds were developed for water treatment to remove As(V). The influence of the particle size of the modifying additive on the ability of silica gel to take up As(V) was examined. The KSKG-based sorbents modified with nanoparticles of Fe(III) compounds exhibit the highest sorption capacity. The capacity of silica gel based sorbents modified with nanoparticles of iron compounds for As(V) is higher than that of analogous sorbents modified with iron oxides prepared by thermal decomposition of Fe(III) nitrate.     

Sorption of anti-infective organic molecules from aqueous solutions onto zirconium phosphate

Amorphous zirconium phosphate (ZP), an inorganic ion exchange material of tetravalent metal acid (tma) salt, is synthesized by the sol-gel method and characterized by elemental analysis (ICP-AES), thermal analysis (TGA, DSC), FT-IR and X-ray diffraction studies. The resistivity of the material to acids, bases and organic solvents is assessed. The sorption behavior of the dyes acriflavin (AF) and brilliant green (BG) toward ZP was studied at 313, 323 and 333 K and the kinetic and thermodynamic parameters evaluated. Adsorption isotherms [Langmuir and Fruendlich], breakthrough capacity and elution behavior of these dyes are also studied. The sorption affinity of dyes towards ZP is BG > AF.     

Granulated sulfur-containing sorbents for recovery of heavy metal ions from aqueous solutions

Granulated sorbents that can recover zinc salts from aqueous solutions were produced by poly-condensation of organochlorine wastes from manufacture of epichlorohydrin with sodium polysulfide on the surface of ash-and-slag particles formed at thermal power plants in the system constituted by aqueous hydrazine and an alkali.     

Sorption of thallous ion from acidic aqueous solutions onto ETS-10 titanosilicate

The sorption of the thallous ion from aqueous acidic solution (pH = 1.5) onto as-synthesized and modified ETS-10 titanosilicates was studied by using an isotope dilution method and a batch-mode technique. The present results show that the thallium(I) sorption was effective onto all three considered materials and is enhanced by the porosity and acidity modification of the ETS-10 titanosilicate. The best uptake performance was achieved by the meso-ETS-10. This behavior is explained based on the newly created additional mesoporous system and enriching the external surface with silanol groups. Also, the presence of phosphorus enhanced the inherent porosity allowing thus better internal diffusion properties of crystalline material. However, the chemically modified surface seems to have a negative contribution to the kinetic uptake of thallous ion as shown by the positive value of the activation energy E _a, in comparison with the processes more favorable energetically for ETS-10 and meso-ETS-10 materials.     

Removal of heavy metal ions from aqueous solutions using low-cost sorbents obtained from ash

This study’s main objective was the development of effective low-cost sorbents for the removal of heavy metal ions from aqueous solutions. The influence of different factors on the sorption capacity of ash and modified ash as low-cost sorbents obtained by different methods was investigated. The synthesis of new ash-based materials was carried out at ambient temperature (20°C), 70°C, and 90°C, respectively, in an alkaline medium with NaOH concentrations of 2 M and 5 M, respectively, corresponding to a mixture with solid/liquid ratios of 1: 3 and 1: 5, respectively. The prepared materials (sorbents) were characterised by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), X-ray diffraction, and BET surface measurement. Adsorption isotherms were determined using the batch equilibrium method. The results showed that these types of new materials displayed a good capacity to remove copper, nickel, and lead ions (29.97 mg of Cu²⁺ per g of sorbent, 303 mg of Ni²⁺ per g of sorbent, and 1111 mg of Pb²⁺ per g of sorbent) from aqueous solutions. The modified materials were prepared using an alkaline attack (a recognised method used in previous studies), but Romanian ash from a thermal power plant was studied for the above purpose for the first time. Hence, the factors which affect the sorption capacity of the prepared low-cost sorbents were determined and their behaviour was explained, taking into account the composition and structure of the new materials.     

Sorption profile and chromatographic separation of uranium (VI) ions from aqueous solutions onto date pits solid sorbent

The retention profile of uranium (VI) as uranyl ions (UO(2)(2+)) from the aqueous media onto the solid sorbent date pits has been investigated. The sorption of UO(2)(2+) ions onto the date pits was achieved quantitatively (98+/-3.4%, n=5) after 15 min of shaking at pH 6-7. The sorption of UO(2)(2+) onto the used sorbent was found fast, followed by a first order rate equation with an overall rate constant, k of 4.8+/-0.05 s(-1). The sorption data were explained in a manner consistent with a "solvent extraction" mechanism. The sorption data were also subjected to Freundlich isotherm model over a wide range of equilibrium concentration (1-20 microgmL(-1)) of UO(2)(2+). The results revealed that, a "dual-mode" of sorption mechanism involving absorption related to "solvent extraction" and an added component for "surface adsorption" is most likely operated simultaneously for uranyl ions uptaking the solid sorbent. The thermodynamic parameters (-DeltaH, DeltaS and DeltaG) of the uranyl ions uptake onto the date pits indicated that, the process is endothermic and proceeds spontaneously. The interference of some diverse ions on the sorption UO(2)(2+) from the aqueous media onto the date pits packed column was critically investigated and the data revealed quantitative collection of UO(2)(2+) at 5 mLmin(-1) flow rate. The retained UO(2)(2+) was recovered quantitatively with HCl (3.0 molL(-1)) from the column at 5 mLmin(-1) flow rate. The mode of binding of the date pits with UO(2)(2+) was determined from the IR spectral date bits before and after extraction of uranium (VI). The height equivalent (HETP) and the number (N) of theoretical plates of the date pits packed column were determined from the chromatograms. Complete retention and recovery of UO(2)(2+) spiked to wastewater samples by the date pits packed column was successfully achieved. The capacity of the used sorbent towards retention of uranium (VI) from aqueous solutions was much better than the most common sorbents.     

Sorption of metal ions from multicomponent aqueous solutions by activated carbons produced from waste

Activated carbons produced by thermal treatment of a mixture of sunflower husks, low-grade coal, and refinery waste were studied as adsorbents of transition ion metals from aqueous solutions of various compositions. The optimal conditions and the mechanism of sorption, as well as the structure of the sorbents, were studied.     

Sorption characteristics and separation of tellurium ions from aqueous solutions using nano-TiO2

Titanium dioxide nanoparticles (nano-TiO₂) were employed for the sorption of Te(IV) ions from aqueous solution. A detailed study of the process was performed by varying the sorption time, pH, and temperature. The sorption was found to be fast, equilibrium was reached within 8 min. When the concentration of Te(IV) was below 40 mg L⁻¹, at least 97% of tellurium was adsorbed by nano-TiO₂ in the pH range of 1-2 and 8-9. The sorbed Te(IV) ions were desorbed with 2.0 mL of 0.5 mol L⁻¹ NaOH. The sorption data could be well interpreted by the Langmuir model with the maximum adsorption capacity of 32.75 mg g⁻¹ (20 ± 0.1 °C) of Te(IV) on nano-TiO₂. The kinetics and thermodynamics of the sorption of Te(IV) onto nano-TiO₂ were also studied. The kinetic experimental data properly correlated with the second-order kinetic model (k₂ = 0.0368 g mg⁻¹ min⁻¹, 293 K). The overall rate process appeared to be influenced by both boundary layer diffusion and intra-particle diffusion. The mean energy of adsorption was calculated to be 17.41 kJ mol⁻¹ from the Dubinin-Radushkevich (D-R) adsorption isotherm at room temperature. Moreover, the thermodynamic parameters for the sorption were estimated, and the ΔH⁰ and ΔG⁰ values indicated the exothermic and spontaneous nature of the sorption process, respectively. Finally, Nano-TiO₂ as sorbent was successfully applied to the separation of Te(IV) from the environmental samples with satisfactory results (recoveries >95%, relative standard deviations was 2.0%).     

Electrosorption of ions from aqueous solutions by nanostructured carbon aerogel

Electrosorption is generally defined as potential-induced adsorption on the surface of charged electrodes. After polarization of the electrodes, ions are removed from the electrolyte solution by the imposed electric field and adsorbed onto the surface of the electrodes. Experimental and modeling studies were conducted using two types of carbon aerogel composites of different surface areas to provide a better understanding on the mechanisms of electrosorption. The experimental results revealed that no significant specific adsorption of F- ions occurred, while strong specific adsorption was observed for NO3- and Cu2+ ions. In addition, although the two types of carbon aerogel electrodes had different surface areas, their capacities were found to be very similar because of the electrical double-layer overlapping effect in micropores. An electrical double-layer model developed in our previous work (16), in which the electrical double-layer overlapping correction is included, is expanded in the present work by considering the effect of the specific adsorption on the electrosorption process. Modeling results were compared with experimental data obtained under various conditions. When the overlapping effect and specific adsorption were considered, the model provided results that were in good agreement with experimental data.     

Recovery of heavy metal ions from aqueous solutions using modified organosilicas

Sorption of Cu(II), Pb(II), Cd(II), and Zn(II) from aqueous solutions on two-component organosilicas was studied as influenced by sorbent composition, contact time, ratio of solid and liquid phases, solution pH, nature and concentration of heavy metal ions, and content of modifying agent. The degrees of sorption of these metal ions from aqueous solutions using organosilicas modified with aluminum(III) added into the siloxane matrix or with copper(II) grafted to the sorbent surface layer were compared.     

Sorption of copper ions by cellulose sorbents modified with a dichlorotriazine compound and polyvinylpyrrolidone

Sorption of copper ions by cellulose sorbents: pinewood sawdust and cotton and flax fibers, both untreated and chemically modified with a polyfunctional compound, followed by fixation with polyvinylpyrrolidone, was studied.     

Complexing sorbents based on dispersed minerals for recovery of heavy metal ions from aqueous solutions

We have obtained sorbents for recovery of heavy metal ions from aqueous solutions by modification of kaolinite and metakaolinite, aluminum oxyhydroxide and aluminum hydroxide by polyphosphates. Using sorption of Ni²⁺, Co²⁺ and Cr³⁺ as an example, we have shown that the sorbents have high sorption capacity and distribution coefficient with respect to heavy metal ions. We have studied the composition of the complexes formed. We have developed methods for granulation of the sorbents with a binder and for regeneration of the sorbents. A. V. Dumanskii Institute of Colloid Chemistry and Chemistry of Water, National Academy of Sciences of Ukraine, 42 Bul'var Akademika Vernadskogo, Kiev-142 252680, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 3, pp. 167–170, May–June, 1999.     

Sorption of thallium(III) ions from aqueous solutions using titanium dioxide nanoparticles

Titanium dioxide nanoparticles (NPs) were employed for the sorption of Tl(III) ions from aqueous solution. The process was studied in detail by varying the sorption time, pH, Tl(III) concentration, temperature, and amount of sorbent. The sorption was found to be fast and to reach equilibrium within 2 min, to be less efficient at low pH values, and to increase with pH and temperature. The sorption fits the Langmuir equation and follows a pseudo second order model. The mean energy of the sorption is approximately 15 kJ mol^?1 as calculated from the Dubinin–Radushkevich isotherm. The thermodynamic parameters for the sorption were also determined, and the ΔH ⁰ and ΔG ⁰ values indicate endothermic behavior.     

Sorption of norfloxacin from aqueous solutions by activated carbon developed from Trapa natans husk

The low-cost activated carbon was prepared from a renewable aquatic plant residue,Trapa natans husk,and tested for its ability to remove norfloxacin (NOR) from aqueous solutions. Physical and chemical properties of the Trapa natans husk activated carbon (TAC) were characterized. TAC has a large surface area of 1274 m2/g and mesoporous structure. Carboxylic and hydroxyl groups contributed to the sorption of NOR onto TAC but they were not the most important factors in the sorption process. The rates of adsorp...     

Sorption of 60Co(II) from aqueous solutions onto biosynthesized zinc oxide nanocomposites

Journal of Radioanalytical and Nuclear Chemistry - Nano ZnO is biosynthesized using Lactobcillus sp. Poly Acrylic acid-co-Acrylonitrile/ZnO, PAACAN/ZnO, and poly Acrylic acid-co-Maleic acid/ZnO,...     

Sorption behavior of Sn(II) onto Haro river sand from aqueous acidic solutions

The sorption behavior of Sn(II) onto Haro river sand has been examined with respect to nature of electrolyte, agitation time, dosage of sorbent and concentration of sorbate. Maximum sorption (95.5%) has been achieved from 0.034M hydrochloric acid solution after equilibrating sorbate (2·10⁻⁵M) and sorbent (50 mg) for 120 minutes at aV/W ratio of 90 cm³·g⁻¹. The kinetic data have been subjected to Morris-Weber and Lagergren equations. The kinetics of sorption proceeds a two stage process consisting of a relatively slow initial uptake followed by a much rapid increase in the sorption. The rate constant of intraparticle transport, K_d, comes out to be 8.75·10⁻⁸ mol·g⁻¹·min^−1/2 and the first order rate constant for sorption is 0.0416 min⁻¹. The sorption data of Sn(II) onto Haro river sand followed Langmuir, Freundlich and Dubinin-Radushkevich (D-R) type isotherms. The Langmuir constant,Q, related to sorption capacity and,b, related to sorption energy are computed to be 10.6±1.1 μmol·g⁻¹ and 1123±137 dm³·mol⁻¹, respectively. The D-R isotherm yields the values ofC _m=348±151 μmol·g⁻¹ and β=−0.01044±0.0008 mol²·kJ⁻² and ofE=6.9±0.3 kJ·mol⁻¹. In all three isotherms correlation factor (γ) is ≥0.99. The influence of common anions and cations on the sorption has been investigated. Zn(II), Mg(II), oxalate, Pb(II), Mn(II) and tartrate reduce the sorption significantly whereas Fe(II) causes substantial increase in the sorption. It is essential that all ions causing a decrease in the sorption of Sn(II) must be absent from the sorptive solution otherwise low sorption yields would result.     

Removal of pentachlorophenol from aqueous solutions by dolomitic sorbents

The partial decomposition of dolomite carried out within the temperature range 600-1000 degrees C provides new sorbents, called dolomitic sorbents. Their surface properties and identification by X-ray diffraction are discussed. The lowest specific surface area value was found for the raw dolomite, while the highest value was achieved by the D-1000 sample. The adsorption equilibrium of pentachlorophenol from aqueous solutions on the examined sorbents was investigated at 30, 40, and 50 degrees C via a bath process. Langmuir, Freundlich, Langmuir-Freundlich, and Redlich-Petersen models were fitted to experimental equilibrium data, and their goodnesses of fit are compared. The adjustable parameters of Langmuir-Freundlich and Redlich-Petersen isotherms were estimated by nonlinear least-squares analysis. Langmuir and Freundlich models were found insufficient to explain the adsorption equilibrium, while Langmuir-Freundlich and Redlich-Petersen isotherms provide the best correlation of the pentachlorophenol adsorption onto dolomitic sorbents.     

Competitive adsorption of aqueous metal ions on an oxidized nanoporous activated carbon

Competitive adsorption is the usual situation in real applications, and it is of critical importance in determining the overall performance of an adsorbent. In this study, the competitive adsorption characteristics of all the combinations of binary mixtures of aqueous metal ion species Ca2+(aq), Cd2+(aq), Pb2+(aq), and Hg2+(aq) on a functionalized activated carbon were investigated. The porous structure of the functionalized active carbon was characterized using N2 (77 K) and CO2 (273 K) adsorption. The surface group characteristics were examined by temperature-programmed desorption, Fourier transform infrared spectroscopy, Raman spectroscopy, acid/base titrations, and measurement of the point of zero charge (pHpzc). The adsorption of aqueous metal ion species, M2+(aq), on acidic oxygen functional group sites mainly involves an ion exchange mechanism. The ratios of protons displaced to the amount of M2+(aq) metal species adsorbed have a linear relationship for both single-ion and binary mixtures of these species. Hydrolysis of metal species in solution may affect the adsorption, and this is the case for adsorption of Hg2+(aq) and Pb2+(aq). Competitive adsorption decreases the amounts of individual metal ions adsorbed, but the maximum amounts adsorbed still follow the order Hg2+(aq) > Pb2+(aq) > Cd2+(aq) > Ca2+(aq) obtained for single metal ion adsorption. The adsorption isotherms for single metal ion species were used to develop a model for competitive adsorption in binary mixtures, involving exchange of ions in solution with surface proton sites and adsorbed metal ions, with the species having different accessibilities to the porous structure. The model was validated against the experimental data.