Surface characterization and thermodynamics of adsorption of Sr2+, Ce3+, Sm3+, Gd3+, Th4+, UO 2 2+ on activated charcoal from aqueous solution

Surface parameters of the activated charcoal were measured using precise instrumental techniques for dehydration, carbon content, trace metals impurities, anions, bulk, tap and true densities, surface area, pore volume, porosity and average particle diameter. The adsorption of Sr²⁺, Ce³⁺, Sm³⁺, Gd³⁺, Th⁴⁺ and UO ₂ ²⁺ ions on activated charcoal from aqueous solution was studied as a function of temperature. Thermodynamic parameters such as HH ⁰ and S ⁰ were calculated from the slopes and intercepts of the linear variation of lnK ₁ vs. 1/T, whereK ₃ is obtained from Langmuir equation. The results show endothermic heats of adsorption, but negative free energy values indicate that the adsorption process of metal ions on activated charcoal is favored at high temperature. The value of isosteric heat of adsorption, calculated from the Clausius-Clapeyron equation, shows that the surface of the activated charcoal is heterogeneous with respect to activity. A wavelength dispersive x-ray fluorescence spectrometer was used for measuring the concentration of metal ions.     

Adsorption of UO2 2+, Tl+, Pb2+, Ra2+ and Ac3+ onto polyacrylamide-bentonite composite

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerization in a suspension of bentonite (B), the composite was then modified by phytic acid (PAA-B-Phy). The parameters related to adsorption of UO₂ ²⁺ in absence and presence of 0.01M CaCl₂ and of natural radionuclides (Tl⁺, Pb²⁺, Ra²⁺ and Ac³⁺ in a leaching solution) onto PAA-B and PAA-B-Phy, and thermodynamics of the adsorption were investigated. Adsorption isotherms were of L and H types for the adsorption of UO₂ ²⁺ onto PAA-B and PAA-B-Phy, whilst for Tl⁺, Pb²⁺, Ra²⁺ and Ac³⁺ they were of C type for both adsorbents. Langmuir equilibrium constants for the adsorption of all studied ions onto PAA-B-Phy were significantly higher than those found for PAA-B. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy. The composite of PAA-B and its modification by Phy have been used for the first time in this study. It is concluded that the composites can be practically used for adsorption and applied as adsorbent of radionuclides.     

UO2 2+, Tl+, Pb2+, Ra2+, Bi3+ and Ac3+ adsorption onto polyacrylamide-zeolite composite and its modified composition by phytic acid

The adsorption of naturally occurring radionuclides (UO₂ ²⁺, Tl⁺, Pb²⁺, Ra²⁺, Bi³⁺ and Ac³⁺) onto zeolite (Z) and polyacrylamide-zeolite composite (PAA-Z) and its modified composition by phytic acid (Z-Phy and PAA-Z-Phy) were investigated. Adsorption parameters were derived from the Langmuir and Freundlich fits to adsorption isotherms of the ions studied. The adsorption isotherms were of L and H types. The adsorption capacity of Z decreased by PAA inclusion, but the Phy modification of PAA-Z increased the capacity back to that of Z. The Phy modification made the adsorption spontaneity at least ten times better than in the absence of Phy. This investigation showed that the zeolite, as one of the most abundant natural materials and commonly used adsorbent can also be used for the removal of UO₂ ²⁺ and, in the PAA-Z form, of the studied radionuclides. The usage of Z, as PAA-Z and its Phy modification provide research materials which possess adequate practicality and effectiveness in studies of adsorption. This revised version was published online in July 2006 with corrections to the Cover Date.     

Study on the controllable synthesis of SH-MCM-41 mesoporous materials and their adsorption properties of the La3+, Gd3+ and Yb3+

Sulfhydryl MCM-41 (SH-MCM-41) mesoporous materials were prepared via a hydrothermal method, and -SH was successfully imported by a post-grafting method. The structure and surface properties of the materials were characterized using Fourier Transform infrared spectroscopy, X-ray diffraction and Transmission Electron Microscopy analysis. The low concentrations of La³⁺, Gd³⁺ and Yb³⁺ adsorption on the material were investigated. This paper discusses the effects of system factors, such as pH and the solid-liquid ratio, on the performance of the adsorption process. The adsorption thermodynamics and kinetics were also explored. Experimental results indicated that the materials were in good order and had high specific surface area (956 m²/g) with an average pore diameter of 2.1 nm; the mercapto groups were successfully grafted onto a molecular sieve, and the best grafted amount was 1.46 × 10^?3 mol/g. The materials showed preferable adsorption of La³⁺, Gd³⁺ and Yb³⁺ with maximum adsorption capacities of 560.56 mg/g, 467.60 mg/g and 540.68 mg/g, respectively. The adsorption process can be described by the Freundlich isotherm model, and the adsorption data fits pseudo-second-order kinetics. After repeating the elution-regeneration cycle four times, the adsorption capacity of rare earth ions was mostly maintained, indicating that the adsorbent can be regenerated well and recycled to save costs. It has potential in practical application.     

Thermodynamic parameters of TI+, Ra2+, Bi3+and Ac3+ adsorption onto polyhydroxyethylmethacrylate-hydroxyapatite composite

In this research, a new composite, poly (hydroxyethylmethacrylate-hydroxyapatite) [P(HEMA-Hap)], was synthesized and its adsorptive features for natural radionuclides (TI⁺, Ra²⁺, Bi³⁺and Ac³⁺ in a leaching solution) were investigated at differing initial pH, concentration and temperature ranges. The natural radionuclides were counted by gamma spectrometer using a type NAI (Tl) detector. The adsorption data obtained were well represented by Langmuir and Freundlich type isotherms. The magnitude of determined monolayer adsorption capacities (X _L) for the adsorbed radionuclides were TI⁺ = Ac³⁺ > Ra²⁺ = Bi³⁺. These results demonstrated that P(HEMA-Hap) had high affinity to the natural radionuclide. The thermodynamic parameters indicated that the adsorption mechanisms were spontaneous (ΔG < 0) in terms of adsorption free enthalpy, and changes in the enthalpy and entropy values showed that the overall adsorption process was endothermic (ΔH > 0), thus increasing entropy (ΔS > 0).     

Investigations for Modification of Polyacrylamide-Bentonite by Phytic Acid and its Usability in Fe3+, Zn2+ and UO2 2+ Adsorption

Composite of polyacrylamide-bentonite (PAA-B) was prepared by direct polymerisation of PAA in a suspension of bentonite (B). Adsorption and thermodynamic features of phytic acid (Phy) adsorption onto B, PAA and PAA-B, and those of Fe³⁺, Zn²⁺, UO₂ ²⁺ adsorption onto PAA-B and its modification by Phy (PAA-B-Phy) have been investigated. The reusability, storagability, ion selectivity and recoverability of sorbed ions with 1 M HCl have also been considered.The chemical and physical structure of adsorbents has been characterised by means of FT-IR and XRD. All adsorption isotherms for Phy and the ions were L-type of the Giles classification except, the one which is S type for adsorption of Phy onto PAA. The maximum adsorption capacities for the ions adsorbed were in order of UO₂ ²⁺ > Fe³⁺ > Zn²⁺ for PAA-B and Zn²⁺ > Fe³⁺ > UO₂ ²⁺ for PAA-B-Phy. Langmuir equilibrium constants for the adsorption of ions onto PAA-B-Phy were significantly higher than those found for PAA-B; the magnitude of increase for UO₂ ²⁺ was about 100. The thermodynamic parameters indicated that adsorption reactions are spontaneous in terms of adsorption free enthalpy.The chemical structure of PAA-B-Phy was not changed at the end of the studies of reusability and storagability. The composite was selective for UO₂ ²⁺ of the ions of interest.The composite of PAA-B and its modification by Phy have been used for the first time in this investigation. It is proposed that the composites can be practically used in the investigations and applications of adsorption.     

Chemically modified kapok fiber for fast adsorption of Pb2+, Cd2+, Cu2+ from aqueous solution

Kapok fiber, a natural hollow fiber with thin shell and large cavity, has rarely been used as adsorbent for heavy metal ions. In this paper, kapok fibers were modified with diethylenetriamine pentaacetic acid (DTPA) after hydrophilicity treatment. The adsorption behavior of the resultant kapok-DTPA influenced by pH, adsorption time and initial concentration of metal ion was investigated. The results demonstrate that adsorption equilibrium was reached within 2 min for Pb²⁺ and Cd²⁺. Adsorption kinetics showed that the adsorption rate was well fitted by pseudo-second-order rate model. The adsorption isotherms were studied, and the best fit was obtained in the Langmuir model. The maximum adsorption capacities of kapok-DTPA were 310.6 mg g^?1 for Pb²⁺, 163.7 mg g^?1 for Cd²⁺, 101.0 mg g^?1 for Cu²⁺, respectively. After eight desorption and re-adsorption loops, the lost adsorption capacities for Pb²⁺ and Cu²⁺ were less than 10 %. Because of the large specific area derived from the hollow fiber structure, kapok-DTPA exhibited much better adsorption capacity compared with many other reported adsorbents based on natural materials.     

Separation of strontium from simulated waste in K2SO4/Nitrate medium containing Sr2+, Eu3+, Ce3+, Pd2+, Rh3+, Ru3+, UO 2 2+ , Fe3+, Cr3+, Ni2+, Al3+, Ca2+ and Cs+, by strongly basic anion exchanger

In this work Strontium was separated selectively form, Pd²⁺, Ni²⁺ and Ca³⁺ using anionic resins of Amberlite type IRA-900 and IRA-410 from nitrate medium. The Separation of strontium by strongly basic anion exchangers IRA-410 and IRA-900 from simulated waste containing, Sr²⁺, Eu³⁺, Ce³⁺, Pd²⁺, Rh³⁺, Ru³⁺, VO₂ ²⁺, Fe³⁺, Cr³⁺, Ni²⁺, Al³⁺, Ca²⁺, and Cs⁺, in K₂SO₄/nitrate medium which adsorbed as strontium sulphate complex was achieved through ligand- ligan exchange. The elution of strontium carried out via “loading” the column with a solution of 0.03N EDTA in presence of 0.1N NaNO₃ at pH7 where Sr²⁺ has low K_d value. An inductively Coubled Plasma — Optical Emission Spectrometry (ICP — OES) of ARL type model 3520, was used for elemental analysis.     

Tunable luminescence and energy transfer process between Tb3+ and Eu3+ in GYAG:Bi3+, Tb3+, Eu3+ phosphors

A series of Eu³⁺ ions co-doped (Gd_0.9Y_0.1)₃Al₅O₁₂:Bi³⁺, Tb³⁺ (GYAG) phosphors have been synthesized by means of solvothermal reaction method. The XRD pattern of GYAG phosphor sintered at 1500 °C confirms their garnet phase. The luminescence properties of these phosphors have been explored by analyzing their excitation and emission spectra along with their decay curves. The excitation spectra of the GYAG:Bi³⁺, Tb³⁺, Eu³⁺ phosphors consists of broad bands in the shorter wavelength region due to 4f⁸ → 4f⁷5d¹ transition of Tb³⁺ ions overlapped with 6s² → 6s¹6p¹ (¹S₀ → ³P₁) transition of Bi³⁺ ions and the charge transfer band of Eu³⁺–O^2?. The present phosphors exhibit green and red colors due to ⁵D₄ → ⁷F₅ transition of Tb³⁺ ions and ⁵D₀ → ⁷F₁ transition of Eu³⁺ ions, respectively. The emission was shifted from green to red color by co-doping with Eu³⁺ ions, which indicate that the energy transfer probability from Tb³⁺ to Eu³⁺ ions are dependent strongly on the concentration of Eu³⁺ ions.     

Sorption of microamounts of Ce3+, Pm3+, Eu3+, Gd3+ and Yb3+ on aluminium hydroxide

The sorption of microamounts of trivalent lanthanides (Ln³⁺) on freshly precipitated Al(OH)₃ has been measured in dependence on pH and the time of sorption. Also, the influence of organic complexing ligands and inorganic electrolytes on the sorption process has been investigated. The mechanism of sorption is discussed. Freshly precipitated Al(OH)₃ can be used for the preconcentration of microamounts of trivalent lanthanides. However, the preconcentration is not quantitative in the presence of high concentrations of complexing ligands (citrate and similar) which form strong complexes with Ln³⁺ ions.     

Studies on Synthetic Inorganic Ion Exchangers-III Quantitative Separations of Mg2+ -Pb2+, Zn2+ - Pb2+ Cu2+ - Pb2+, Al3+ - Pb2+, Zn2+ - Cd2+, and Mg2+ - Cd2+ on Lead Antimonate Columns

Abstract

A new inorganic ion exchanger, lead antimonate has been synthesized having an Pb:Sb ratio of 1:5 and cation exchange capacity of 1.46 mequiv./g. It is fairly stable in water and dilute solutions of acids, bases and salts. Ion distribution studies on twenty metal ions have been determined on this gel at pH 1,2,3 and 5. The following mixtures have been separated: Mg²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Zn²⁺ - Pb²⁺, Cu²⁺ - Pb²⁺, Al³⁺ - Pb²⁺, Zn²⁺ - Cd²⁺ and Mg²⁺ - Cd²⁺. Mg²⁺ and Al³⁺ were removed with 0.4 M ammonium nitrate, Cu²⁺ and Zn²⁺ with 0.4 M ammonium nitrate + 0.1M nitric acid (1:1), Pb²⁺ with 0.5M nitric acid and Cd²⁺ with 0.25M nitric acid. A tentative structure of this material is proposed on the basis of chemical analysis, pH titrations, thermogravimetry and IR spectrophotometry.     

Study of sorption of Pb2+, Cd2+, Zn2+ and Cu2+ from wastewater on synthetic analogues of clintonite

The study describes a sorption of metal ions Pb²⁺, Cd²⁺, Zn²⁺ and Cu²⁺ on a synthetic mica clintonite. Synthesis of analogues of clintonite was carried out by using inorganic salts as sources of silicon and aluminum in the hydrothermal method. Alkaline conditions were applied to increase the nucleation rate. Powdered clintonite obtained after mechanical grinding was used for the removal of metal ions from the wastewater. The sorption experiments were done under batch process to measure the concentrations of metal ions. Effects of pH, contact time between sorbent and sorbate solution, amount of sorbent and temperature on the sorption of metal ions were studied. The sorption was shown to increase with the pH of the medium. The optimal conditions for sorption of metal ions on synthetic analogues of clintonite were determined.     

Study of the adsorption capacity to Co2+, Ni2+ and Cu2+ ions of an active carbon/functionalized polyamine hybrid material

The retention of Co²⁺, Ni²⁺ and Cu²⁺ metal ions from aqueous solution, on a functionalized hybrid material obtained by the anchorage of N-(4-amino-1,6-dihydro-1-methyl-5-nitroso-6-oxopyrimidin-2-yl)-N′-[bis(2-aminoethyl)] ethylenediamine ligand on a low-functionalized activated carbon, at pH 4.5 has been studied. The adsorption isotherms fit the Langmuir equation and the calculated maximum adsorption capacities were compared to those obtained by using the un-functionalized activated carbon as well as to other analogous hybrid materials as adsorbent of the same metal ions. These studies were carried out by rationalizing the resulting adsorption data regarding the stability constant values of the complexes formed by the three metal ions with the free tri-amine function of the ligand. The results demonstrate that the adsorption capacities of the activated carbon–ligand hybrid material towards the three metal-ions studied correlated with the stabilities of the tri-amine-metal-ion bonds formed during the adsorption processes.     

A thermometric titration study of the interaction of Al3+, Co2+, Ni2+ and Zr4+ with xylenol orange

A thermometric titrimetry study of the interaction in aqueous solution of A1³⁺, Co²⁺, Ni²⁺ and Zr⁴⁺ with xylenol orange has revealed in each case a linear reaction heat/[Mⁿ⁺] relationship at a specified pH, thereby suggesting the potential of metallochromic indicators for the analytical determination of these metals in water. The effect of pH on the reaction heat is investigated and is interpreted in terms of the ability of these metal cations to complex with the known xylenol orange species existing at the various pH studied. An interference study, involving transition and non-transition metal ions, is also reported and the interference effect, as measured by the deviation ofQ/Q from unity (Q andQ are the relevant reaction heats in the presence and absence of interfering ion), is partially explained in terms of the coordination numbers, relative sizes and crystal field stabilization energies of the cations studied and the known behaviour of xylenol orange in aqueous solution.     

Chelation Ion Chromatography on DMSO Impregnated Silica Gel-G Layers: Specific Separation of Cd2+, W6+, and Zr4+ from Transitional Metal Ions

Abstract

Chelation ion chromatography of metal ions on DMSO impregnated silica gel-G layers in ether; DMSO: 1M HNO₃ (1:1); n-butanol: acetone: HNO₃ (6:6:1) and di-isopropyl ether: DMSO: THF systems having varying compositions, was performed. The zero R_f for a number of cations is explained in terms of precipitation and strong adsorption. It was possible to separate Cd²⁺, W⁶⁺, Zr⁴⁺, Zn²⁺ and VO²⁺ from numerous metal ions. A number of analytically important binary and ternary separations were also achieved and were found useful in synthetic alloy analysis.     

X-Ray Absorption and Diffraction Studies of Pr3+, Tb3+ and Er3+-Activated Silica Gels

Rare-earth (Pr³⁺, Tb³⁺, Er³⁺) doped silica xerogels were studied by x-ray absorption spectroscopy and x-ray diffraction. A change of the local environment around rare-earth ions upon xerogel densification at 900–950°C and co-doping with aluminum ions was determined from the rare-earths L₃-edge EXAFS signals. The densification process induces a decrease of the coordination number and a compression and deformation of the first coordination shell, composed of oxygen atoms. The second coordination shell, composed of silicon and/or aluminum ions, also experiences some modification, which is attributed mainly to a shortening of the shell radius. No evidence of clustering of rare-earth ions upon densification was observed. X-ray diffraction data on Tb-doped gels confirm the EXAFS results.     

Complex formation and adsorption of V3+, Cr3+ and Fe3+ ions with poly(N-vinylimidazole)

The complex formation of soluble poly (N-vinylimidazole) (PVIm) with trivalent metal ions in aqueous solution was studied by using UV–vis spectroscopy. Formation constants of PVIm–metal complexes were calculated by applying the “molar ratio” method. It was found that the interaction between PVIm and trivalent metal ions follows 4(base unit):1(metal ion) stoichiometry. The stability constants for the complexes of PVIm with trivalent transition-metal ions were in agreement with the Irving– William series. The biggest formation constant was found for the PVIm–Fe³⁺ complex system. The capacity of adsorption for these metal ions was investigated using cross-linked PVIm. Cross-linked PVIm hydrogels were prepared by irradiating binary mixture of N-vinylimidazole–water with a ⁶⁰Co γ-ray source having a dose rate of 4.5 kGy/h. Adsorption studies were performed at different pH and metal ion concentrations at room temperature. It was observed that the same sequence for the metal ions was verified by adsorption studies. Received: 28 May 2001 Accepted: 29 July     

Transport of Ca2+, Sr2+, Ba2+, Na+, K+ and Cs+ through hollow fiber supported liquid membrane

The transport of metal ions (Ca²⁺, Sr²⁺, Ba²⁺, Na⁺, K⁺, Cs⁺) through hollow fiber supported dichlorobenzene liquid membrane has been studied. The transport of cations using 8-crown-6 ether as a carrier and picrate as co-counter ion as well as a pertraction device and capillary isotachophoresis (ITP) measurement of the cation concentration is described.     

Preparation of core-shell magnetic Fe3O4@SiO2-dithiocarbamate nanoparticle and its application for the Ni2+, Cu2+ removal

A typical superparamagnetic nanoparticles-based dithiocarbamate absorbent (Fe₃O₄@SiO₂-DTC) with core-shell structure was applied for aqueous solution heavy metal ions Ni²⁺, Cu²⁺ removal.     

Novel nanostructured dendrimer based on 1,3-bis(4,6-dichloro-1,3,5-triazine-2-yl)urea as an excellent adsorbent for Pb2+, Ni2+, Co2+ and Zn2+ metal ions

Human health is seriously harmed by the consumption of poor-quality water. Due to high toxicity and water solubility, heavy metals are present in wastewater discharged from numerous industries. In the environmental realm, metal-containing water must be treated before being released. A dendrimer is a superior adsorbent for the removal of heavy metal ions due to its nanostructure and hydrophilic end group. In this work, a novel triazine-based hydroxy-terminated dendrimer up to generation three is designed employing a carbamide core. The dendrimer's structure was explored using FT-IR and ¹H NMR studies. Full generation dendrimers UG1.0, UG2.0, and UG3.0 were utilized as an adsorbent for Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ion removal from water in a series of tests. The ability of dendrimers to uptake Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions was investigated under various pH, time interval and dendrimer generation parameters. The presence of metal in the dendrimer was confirmed by FT-IR studies of dendrimer-metal complexes. The overall results show that Pb²⁺, Ni²⁺, Co²⁺ and Zn²⁺ metal ions uptake increases with the generation, time, and pH.