Application of NKF-6 zeolite for the removal of U(VI) from aqueous solution

To better understand the application of NKF-6 zeolite as an adsorbent for the removal of U(VI) from radionuclides and heavy metal ions polluted water, herein, NKF-6 zeolite was employed to remove U(VI) at different experimental conditions. The influence of solid/liquid ratio, contact time, pH, ionic strength, humic substances and temperature on sorption of U(VI) to NKF-6 zeolite was investigated using batch technique under ambient conditions. The experimental results demonstrated that the sorption of U(VI) on NKF-6 zeolite was strongly dependent on pH. The sorption property of U(VI) was influenced by ionic strength at pH < 7.0, whereas was independent of ionic strength at pH > 7.0. The presence of fulvic acid or humic acid promoted the sorption of U(VI) on NKF-6 zeolite at low pH values while restrained the sorption at high pH values. The thermodynamic parameters (i.e., ΔS ⁰, ΔH ⁰, and ΔG ⁰) calculated from the temperature-dependent sorption isotherms demonstrated that the sorption process of U(VI) on NKF-6 zeolite was endothermic and spontaneous. At low pH values, the sorption of U(VI) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on NKF-6 zeolite surfaces, while inner-sphere surface complexation was the main sorption mechanism at high pH values. From the experimental results, one can conclude that NKF-6 zeolite can be used as a potential adsorbent for the preconcentration and solidification of U(VI) from large volumes of aqueous solutions.     

Interaction of U(VI) with Na-attapulgite in the presence and absence of humic acid as a function of pH, ionic strength and temperature

The interaction of U(VI) with Na-attapulgite was studied by using batch technique at different experimental conditions. The effect of contact time, solid content, pH, ionic strength and temperature on the sorption of U(VI) onto Na-attapulgite in the presence and absence of humic acid was also investigated. The results showed that the sorption of U(VI) on Na-attapulgite achieved sorption equilibrium quickly. Sorption of U(VI) on Na-attapulgite increased quickly with increasing pH at pH < 6.5, and then decreased with pH increasing at pH > 6.5. The sorption curves were shifted to left in low NaClO₄ solutions as compared those in high NaClO₄ solutions. The sorption was strongly dependent on pH and ionic strength. The sorption was dominated by ion exchange or outer-sphere surface complexation at low pH values, and by inner-sphere surface complexation or surface precipitation at high pH values. The thermodynamic parameters (i.e., ΔH ⁰, ΔS ⁰, and ΔG ⁰) for the sorption of U(VI) were calculated from the temperature dependent sorption isotherms, and the results suggested that the sorption reaction was an endothermic and spontaneous process. The Na-attapulgite is a suitable material in the removal and preconcentration of U(VI) from large volumes of aqueous solutions in nuclear waste management.     

Diethylenetriamine-functionalized chitosan magnetic nano-based particles for the sorption of rare earth metal ions [Nd(III), Dy(III) and Yb(III)]

The recovery of three rare earth (RE) metals ions [Yb(III), Dy(III) and Nd(III), belonging to heavy, mild and light REs, respectively] was investigated using hybrid chitosan-magnetic nano-based particles functionalized by diethylenetriamine (DETA). The effect of pH on sorption performance was analyzed: the optimum initial pH value was found close to 5 (equilibrium pH value close to 6.5). The nanometric size of sorbent particles (30–50 nm) minimized the contribution of resistance to intraparticle diffusion on the control of uptake kinetics, which is efficiently modeled using the pseudo-second order rate equation: under selected experimental conditions the contact time required for reaching equilibrium was less than 1 h. Sorption isotherms were efficiently modeled using the Langmuir equation: maximum sorption capacities reached about 50 mg metal g^?1, regardless of the RE. The temperature had a very limited effect on sorption capacity (in the range 300–320 K). The thermodynamic parameters were determined: the sorption was endothermic (positive values of ΔH°), spontaneous (negative values of ΔG°) and contributed to increasing the disorder of the system (positive values of ΔS°). The three REs have similar sorption properties on DETA-functionalized chitosan magnetic nano-based particles: the selective separation of these elements seems to be difficult. The sorbed metal ions can be removed from loaded sorbents using thiourea, and the sorbent can be recycled for at least five sorption/desorption cycles with a limited loss in sorption performance (by less than 6 %). The saturation magnetization was close to 20 emu g^?1; this means that nano-based superparamagnetic particles can be readily recovered by an external magnetic field, making the processing of these materials easy.     

Comparative study on lanthanum(III) sorption onto Lewatit TP 207 and Lewatit TP 260

Batch experiments are carried out for the sorption of La(III) onto commercial macroporous resins containing iminodiacetic (Lewatit TP 207) and aminomethylphosphonic acid groups (Lewatit TP 260). The operating variables studied are initial La(III) concentration, pH, temperature and contact time. Since the extraction kinetics were fast, with a mixture of 0.1 g of resin and 5 mL of lanthanum ions 0.5 × 10^?3 mol L^?1 solution, extraction equilibrium was reached within 30 min of mixing. The optimum pH values level for quantitative sorption were between 1.5 and 4.6 with Lewatit 207 and about 5.2 with Lewatit TP 260. The sorption capacities of Lewatit TP 207 and Lewatit TP 260 resins are 114.7 and 106.7 mg g^?1, respectively. Adsorption equilibrium data were calculated for Langmuir and Freundlich isotherms. It was found that the sorption of La(III) on Lewatit TP 207 was better suited to the Langmuir adsorption model while Freundlich adsorption model fitted better sorption on Lewatit TP 260. Thermodynamics data leads to endothermic and spontaneous process. ΔG° decreases with increasing temperature indicating that sorption process of La(III) on both Lewatit TP 207 and Lewatit TP 260 was more favored at high temperature.     

Impact of environmental conditions on the sorption behavior of 60Co(II) on illite

In this work, a naturally occurring illite was characterized by using FT-IR and XRD technique to determine its surface functional groups and crystal structure. Sorption of ⁶⁰Co(II) on illite as a function of contact time, pH, ionic strength, foreign ions, humic substances and temperature was studied under ambient condition using batch technique. The results indicated that the sorption of ⁶⁰Co(II) on illite is strongly affected by pH values (2–9) and ionic strength. A positive effect of humic substances on ⁶⁰Co(II) sorption was found at pH < 7.0, whereas a negative effect was observed at pH > 7.0. At low pH, the sorption of ⁶⁰Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir and Freundlich models were used to simulate the sorption isotherms of ⁶⁰Co(II) at three different temperatures of 298.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) calculated from the temperature dependent sorption isotherms indicated that the sorption process of ⁶⁰Co(II) on illite was endothermic and spontaneous.     

Removal of radiocobalt ions from aqueous solutions by natural halloysite nanotubes

In this study, natural halloysite nanotubes (HNTs) were applied to remove radiocobalt from wastewaters under various environmental parameters such as contact time, pH, ionic strength, foreign ions and temperature by using batch technique. The results indicated that the sorption of Co(II) on HNTs was dependent on ionic strength at pH < 8.5 and independent of ionic strength at pH > 8.5. Langmuir and Freundlich models were applied to simulate the sorption isotherms of Co(II) at three different temperatures of 293, 313 and 333 K. Langmuir model fitted the sorption isotherms of Co(II) on HNTs better than Freundlich model. The thermodynamic parameters (ΔG ⁰, ΔS ⁰ and ΔH ⁰) calculated from the temperature-dependent sorption isotherms manifested that the sorption of Co(II) on HNTs was an endothermic and spontaneous process. The sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange at low pH, whereas inner-sphere surface complexation or precipitation was the main sorption mechanism at high pH. The experimental results show that HNTs have good potentialities for cost-effective disposal of cobalt-bearing wastewaters.     

Separation of Y from Sr by zirconium vanadate gel ion-exchanger sorbent: kinetics and thermodynamic study

A new zirconium vanadate (Zr–V) ion-exchanger was synthesized and characterized for fast and selective separation procedure of ⁹⁰Y from ⁸⁹Sr. The method was based on ⁹⁰Y(III) sorption from aqueous HCl solution containing ⁸⁹Sr(II) onto Zr–V gel exchanger. The kinetics of Y(III) sorption from HCl solution by Zr–V exchanger was subjected to Weber–Morris, Lagergren, Bhattacharya and Venkobachar, and Bt models. Initially, the uptake of Y(III) onto the exchanger was fast followed by kinetically first-order sorption with an overall rate constant, K _Lager = (3.55 ± 0.03) × 10^?4 min^?1. Film and intraparticle transport are the two steps that might influence Y(III) sorption. The negative values of ΔG of ⁹⁰Y retention dictate that, the process is a spontaneous. The negative values of ΔH and ΔS reflect the exothermic nature of ⁹⁰Y(IIsorption and the random uptake of ⁹⁰Y(III) onto Zr–V sorbent. Zr–V exchanger offers unique advantages of ⁹⁰Y(III) retention over conventional solid sorbents in rapid and effective separation of traces of ⁹⁰Y(III) from Sr. The exchanger was successfully packed in column for an effective separation of ⁹⁰Y.     

Solution chemistry effects on sorption behavior of 109Cd(II) on Ca-montmorillonite

The sorption of radiocadmium on Ca-montmorillonite as a function of contact time, pH, ionic strength, foreign ions, humic acid (HA) and fulvic acid (FA) was studied using batch technique. The results demonstrated that the sorption of Cd(II) was dependent on ionic strength at pH < 9, and was independent of ionic strength at pH > 9. Outer-sphere surface complexation and/or ion exchange were the main mechanism of Cd(II) sorption on Ca-montmorillonite at low pH, whereas the sorption at high pH was mainly dominated via inner-sphere surface complexation. The sorption of Cd(II) on Ca-montmorillonite was dependent on foreign ions at low pH values, but was independent of foreign ions at high pH values. A positive effect of HA/FA on Cd(II) sorption was found at low pH values, whereas a negative effect was observed at high pH values. The thermodynamic parameters (i.e., ??H ⁰, ??S ⁰, ??G ⁰) were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption process of Cd(II) on Ca-montmorillonite was spontaneous and endothermic.     

Effect of pH, ionic strength, foreign ions and temperatures on the sorption of Eu(III) on attapulgite-iron oxide magnetic composites

In this paper, the attapulgite-iron oxide magnetic composites were synthesized by coprecipitation method and were characterized by SEM, XRD and FTIR in detail. The characterization results indicated that the iron oxide was successfully formed on the surface of attapulgite. The prepared attapulgite-iron oxide magnetic composites were applied as adsorbents to remove Eu(III) from aqueous solutions by using batch sorption experiments under different experimental conditions. The sorption properties of Eu(III) on bare attapulgite were also performed as comparison. The results indicated that the sorption of Eu(III) on attapulgite-iron oxide magnetic composites was strongly dependent on pH and temperature. The attapulgite-iron oxide magnetic composites can be separated from aqueous solutions using magnetic separation method in large scale. At low pH values, the sorption of Eu(III) was influenced by ionic strength and pH obviously, while the sorption of Eu(III) was not affected by ionic strength at high pH values. The sorption of Eu(III) was dominated by ion exchange or outer-sphere surface complexation at low pH values, and mainly by inner-sphere surface complexation at high pH values. The thermodynamic parameters (i.e., ?G ^°, ?S ^°, ?H ^°) calculated from the temperature dependent sorption isotherms indicated that the sorption of Eu(III) on attapulgite-iron oxide magnetic composites was an endothermic and spontaneous process. Although the sorption capacities of Eu(III) on attapulgite-iron oxide magnetic composites were a little lower than those of Eu(III) on bare attapulgite, the magnetic separation in large scale is suitable for the application of the magnetic composites in the preconcentration of Eu(III) from large volumes of aqueous solutions in possible real applications.     

Investigation of sequestration mechanisms of radionuclide 63Ni(II) on kaolinite in aqueous solutions

To better understand the application of kaolinite as an adsorbent for the decontamination of Ni(II) from radionuclide contaminated aqueous systems, herein, the sorption behavior of radionuclide ⁶³Ni(II) on kaolinite as a function of contacting time, pH, coexistent electrolyte ions, adsorbent concentration, fulvic acid and humic acid was investigated using batch technique. At low pH values, ion exchange and/or outer-sphere surface complexation was the main mechanism of Ni(II) sorption on kaolinite, whereas, the sorption of Ni(II) was dominated by inner-sphere surface complexation at high pH values. The presence of different electrolyte ions can enhance or inhibit the sorption of Ni(II) on kaolinite to some extent. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Ni(II) at three different temperatures of 288, 313 and 338 K. The thermodynamic parameters (i.e., ΔS°, ΔH°, and ΔG°) calculated from the temperature-dependent sorption isotherms indicated that the sorption reaction of Ni(II) on kaolinite was endothermic and spontaneous. The findings in this present study demonstrates that the kaolinite can be used as a cost-effective adsorbent for the solidification and pre-concentration of Ni(II) from large volumes of aqueous systems.     

Impact of environmental conditions on the sorption behavior of Pb(II) onto attapulgite

This paper examined the application of attapulgite as an adsorbent for the removal of Pb(II) from heavy metal-contaminated water under various conditions. The sorption results indicated that the sorption of Pb(II) on attapulgite was strongly dependent on ionic strength at pH < 7.0. Outer-sphere surface complexation or ion exchange may be the main sorption mechanism of Pb(II) on attapulgite at low pH values. No drastic difference of Pb(II) sorption was observed at pH 7.0–10.0, and the sorption at pH > 10.0 was mainly dominated by inner-sphere surface complexation. The sorption of Pb(II) on attapulgite was affected by foreign ions in solution at pH < 7.0, and was not affected by foreign ions at pH > 7.0. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) were evaluated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of Pb(II) on attapulgite was spontaneous and endothermic in nature.     

Sorption of americium from low-level liquid wastes by nanocrystalline MnO2

Nanocrystalline MnO₂, synthesized by alcoholic hydrolysis of KMnO₄, has been studied as a sorbent for removal of americium from low level liquid waste solutions. The synthesized MnO₂ was found to have BET surface area of 230 m² g^?1. Am(III) was found to be sorbed by MnO₂ quantitatively within 15 min at pH 5. The sorption was found to be more than 90 % at as low a pH as 1.2 and reached to near 100 % at all pH values above pH 3.0 There was no effect of ionic strength (0.01–1.0 M NaCl, CaCl₂) on the sorption suggesting the sorption following inner sphere complexation mechanism at all the pH values. Adsorption isotherm studies were carried out using Eu(III) as a chemical analogue of Am(III). These studies showed the isotherm data to follow Langmuir adsorption isotherm.     

Effect of pH,foreign ions and temperature on radionickel sorption onto bentonite from Inner Mongolia,China

The development of nuclear power releases large amounts of radionuclides into the natural environment. Herein, the sorption of radionuclide ⁶³Ni on bentonite from Gaomiaozi county (Inner Mongolia, China) at different experimental conditions such as pH, contact time, ionic strength, foreign cations and anions, and temperatures were investigated by using batch technique. The results indicated that the sorption of ⁶³Ni on the bentonite was quickly at first contact time and then increased slowly with increasing contact time. The sorption of ⁶³Ni was strongly dependent on ionic strength at low pH values and independent of ionic strength at high pH values. The sorption of ⁶³Ni on bentonite was mainly dominated by outer-sphere surface complexation or ion exchange at low pH values, whereas inner-sphere surface complexation was the main sorption mechanism at high pH values. The Langmuir, Freundlich, and D–R models were applied to simulate the sorption isotherms of ⁶³Ni at three different temperatures, and the thermodynamic parameters (i.e., ΔH°, ΔS° and ΔG°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of ⁶³Ni on bentonite was an endothermic and spontaneous process. Experimental results indicate that the bentonite is a suitable material for the preconcentration and solidification of ⁶³Ni from large volume of solutions in radionickel pollution cleanup.     

Effect of environmental conditions on 109Cd(II) sorption to MnO2

The sorption of Cd(II) from aqueous solution on MnO₂ was investigated under ambient conditions. Experiments were carried out as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid and temperature. The results indicated that the sorption of Cd(II) was strongly dependent on pH and ionic strength. At low pH, the sorption of Cd(II) was dominated by outer-sphere surface complexation and ion exchange with Na⁺/H⁺ on MnO₂ surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (ΔG ⁰, ΔS ⁰, ΔH ⁰) calculated from the temperature dependent sorption isotherms suggested that the sorption of Cd(II) on MnO₂ was an spontaneous and endothermic process.     

Kinetics and Equilibrium Models for Sorption of Cu(II) onto a Novel Manganese Nano-adsorbent

The studies of kinetics and equilibrium sorption of Cu(II) were undertaken using nanoscale zerovalent manganese (nZVMn) synthesized by chemical reduction in a single pot system. nZVMn was characterized using scanning electron microscopy, energy dispersive x-ray, and surface area determined by Brunauer–Emmett–Teller. The effect of pH, contact time, adsorbent dose, agitation speed, initial Cu(II) concentrations, temperature, and ionic strength on the sorption of Cu(II) onto nZVMn were investigated in a batch system. The kinetic data followed pseudo-second-order. The mechanism was governed by pore diffusion. The equilibrium sorption data were tested by Freundlich, Langmuir, Temkin, Dubinin–Kaganer–Raduskevich, and Halsey isotherm models. The Langmuir monolayer adsorption capacity (Q_max = 181.818 mg/g) is much greater compared to other nano-adsorbents used in sorption of Cu(II). The thermodynamic parameters (ΔH⁰, ΔS⁰, ΔG⁰) revealed a feasible, spontaneous, and endothermic adsorption process. nZVMn has a great potential for effective removal of copper (II) in aqueous solution.     

Hydrophobic Interaction Between Domain I of Albumin and B Chain of Detemir May Support Myristate-Dependent Detemir-Albumin Binding

The bindings of detemir [LysB29(Nε-tetradecanoyl)des(B30)-insulin] with two highly homologous albumins, HSA (human serum albumin) and BSA (bovine serum albumin), were investigated through CD, spectrofluorophotometry, and molecular docking analysis. The absence of any tryptophanyl residue in detemir makes albumin binding study possible by exclusive tryptophanyl spectral quenching at 340 nm (λem = 296 nm). The interactions found to be static (Kq > 10¹⁰ M^?1 s^?1) with Stern–Volmer constants ≈10³ M^?1. The observed ΔG ⁰ that was negative in all cases concludes the reactions were spontaneous. Domains I and III of an albumin unfold with 5.0 M urea at pH 7.4, although domain II remains intact. Significant decreases in ΔH ⁰ and ΔS ⁰ were due to unfolding explicit that detemir binding may involve domains I and III of albumins. Temperature-dependent changes in binding were higher in HSA than BSA but after unfolding such changes were very less, further indicating the role of domains I and III in detemir binding. Pro28 and Tyr26 of insulin were found to be interacting with Arg114 and Val116 of HSA domain I, while myristate segment of detemir binds to Lys519 of domain III. Interactions seem to be predominantly hydrophobic and entropy driven. Although detemir binds to albumin through myristate, the peptide part shows involvement in binding.     

Study of the gadolinium sorption on the C100 ion-exchange resin for the development of the antineutrino detector targets

Adsorption of the gadolinium from H₂O and HCl solutions on the ion-exchange resin C100 is investigated. The experiments were carried out by varying the acidity of the liquid phase, the amount of sorbent, and the temperature. The maximal sorption of the ions Gd³⁺ is observed from the solution 0–0.2 M HCl under optimal conditions, the sorption reaches more than 99.5%. Sorption of Gd³⁺ on C100 from H₂O solution occurs most intensively during the first 3 min then for 30 min the system smoothly comes to equilibrium. The maximal sorption capacity of the resin C100 amounted to 1.2 ± 0.1 mmol g^?1. The thermodynamic parameters of sorption: ΔG = ? 24.20 kJ mol^?1, ΔS = ? 90.27 J mol^?1 K^?1, ?H = ? 50.93 kJ mol^?1 were evaluated. It is shown that the sorption of gadolinium on the ion-exchange resin C100 is described by models of kinetically pseudo-first and pseudo-second order. It is established that the Gd³⁺ sorption on the C100 resin is reversible second order chemical reaction.     

Insights into sorption species of Eu(III) on γ-Al2O3 and bentonite under different pH: Studies at macro- and micro-scales

The sorption species of Eu(III) on γ-Al₂O₃ and bentonite was investigated by batch, surface complexation model (SCM), and X-ray absorption spectroscopy (XAS). The results showed that sorption edges of Eu(III) on γ-Al₂O₃ and bentonite were as expected shifted forward high pH with the increasing in Eu(III) concentration, and sorption of Eu(III) was strongly dependent on pH. In γ-Al₂O₃ system, sorption of Eu(III) was decreased above pH 8.5 at low concentration of Eu(III) because of water soluble carbonate species of Eu(III), however the decline did not appear at high concentration of Eu(III) possibly due to a offset effect of surface precipitation. Actually, the sorption species of Eu(III) on bentonite mainly referred to at least four kinds of species including ion exchange (>X₃Eu⁰) at low pH, inner-sphere complexes (>AlOEu²⁺ and >SiOEu²⁺) at neutral condition, and hydrolysis species (>SiOEu(OH) ₂ ⁰ ) at alkaline condition. Linear combination fitting (LCF) in k space testified that hydrolysis of Eu(OH)₃(s) and oxide of Eu₂O₃ species were major for Eu(III) sorption on γ-Al₂O₃, whereas Eu³⁺(aq) and hydrolysis species comprised sorption species on bentonite. Extended X-ray absorption fine structure (EXAFS) analysis further confirmed the prediction from SCM and LCF. In addition, the typical shells of Eu–Al in R range of 3.0–3.4 Å and Eu–Si at ~4.0 Å were found in radial structure functions, which was possibly identified to edge-shared bidentate of Eu(III) on Al₂O₃ and bentonite.     

Removal of radiocobalt from aqueous solutions by kaolinite affected by solid content, pH, ionic strength, contact time and temperature

The kaolinite sample was characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray powder diffraction, and was applied as adsorbent for the removal of radiocobalt ions from radioactive wastewater. The results demonstrated that the sorption of Co(II) was strongly dependent on pH and ionic strength at low pH values, and independent of pH and ionic strength at high pH values. The sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange at low pH values, whereas inner-sphere surface complexation was the main sorption mechanism at high pH values. The sorption isotherms were well described by Langmuir, Freundlich and Dubinin–Radushkevich models. The thermodynamic parameters (i.e., ΔG°, ΔS°, ΔH°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on kaolinite was an endothermic and spontaneous process. The results of high sorption capacity of kaolinite suggested that the kaolinite sample was a suitable material for the preconcentration of Co(II) from large volumes of aqueous solutions and as backfill materials in nuclear waste management.     

Octadecylamine cobalt(III) dimethyl glyoximato complexes: synthesis,thermodynamics of micellization,steady-state photolysis and biological activities

A new class of surfactant–cobalt(III) complexes of the type trans-[Co(DH)₂(OA)X], where DH = dimethylglyoxime, OA = octadecylamine, X = Cl^?, Br^?, I^?, N₃ ^?, NO₂ ^?, SCN^? or OA, were synthesized and characterized by physicochemical and spectroscopic methods. The critical micelle concentration (CMC) values of these surfactant–cobalt(III) complexes in ethanol solution were obtained by measuring absorption at ~250 nm. Specific conductivity data (at 303–313 K) served for the evaluation of the temperature-dependent CMC and the thermodynamics of micellization (ΔG _m ⁰ , ΔH _m ⁰ and ΔS _m ⁰ ). Steady-state photolysis and cyclic voltammetry of the complexes were studied. The surfactant–cobalt(III) complexes were screened for their antibacterial and antifungal activities against various microorganisms.