Uptake properties of Eu(III) on Na-attapulgite as a function of pH, ionic strength and temperature

Herein, the sorption properties of Eu(III) on Na-attapulgite were performed by using batch sorption experiments under different experimental conditions, such as contact time, pH, ionic strength, humic acid and temperatures. The results indicated that the sorption of Eu(III) on Na-attapulgite was strongly dependent on pH and temperature. At low pH values, the sorption of Eu(III) was influenced by ionic strength, whereas the sorption was not affected by ionic strength at high pH values. The sorption of Eu(III) was mainly 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 sorption of Eu(III) onto Na-attapulgite increased with increasing temperature. The Langmuir and Freundlich models were applied to simulate the sorption isotherms, and the results indicated that the Langmuir model simulated the sorption isotherms better than the Freundlich model. The thermodynamic parameters (∆G ^o, ∆S ^o, ∆H ^o) were calculated from the temperature dependent sorption isotherms at 293, 313 and 333 K, respectively, and the results indicated that the uptake of Eu(III) on Na-attapulgite was an endothermic and spontaneous process. The results of high Eu(III) sorption capacity on Na-attapulgite suggest that the attapulgite is a suitable material for the preconcentration and immobilization of Eu(III) ions from large volumes of aqueous solutions.     

Sorption of radiocobalt(II) from aqueous solutions to Na-attapulgite

The sorption of Co(II) on Na-attapulgite as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid (FA) and temperature under ambient conditions was studied. The kinetic of Co(II) sorption on Na-attapulgite was described well by pseudo-second-order model. The sorption of Co(II) on Na-attapulgite was strongly dependent on pH and ionic strength. The sorption of Co(II) was mainly dominated by outer-sphere surface complexation and/or ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The presence of FA did not affect Co(II) sorption obviously at pH <7, and a negative effect was observed at pH >7. The Langmuir and Freundlich models were used to simulate the sorption data at different temperatures, and the results indicated that the Langmuir model simulated the data better than the Freundlich isotherm model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on Na-attapulgite was an endothermic and spontaneous process. The results suggest that the attapulgite sample is a suitable material in the preconcentration and solidification of radiocobalt from large volumes of aqueous solutions.     

Effect of pH,ionic strength,foreign ions,humic acid and temperature on sorption of radionuclide <Superscript>60</Superscript>Co(II) on illite

In this article, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, solid content, pH, ionic strength, foreign ions, temperature and coexisting humic acid on the sorption behavior radionuclide ⁶⁰Co(II) on illite. The results indicated that the sorption of Co(II) was strongly dependent on pH, ionic strength and temperature. At low pH, the sorption was dominated by outer-sphere surface complexation and ion exchange on illite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic data (∆G ⁰, ∆S ⁰, ∆H ⁰) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Co(II) on illite was an endothermic and spontaneous process. The sorption test revealed that the illite can be as a cost-effective adsorbent suitable for pre-concentration of Co(II) from large volumes of aqueous solutions.     

Impact of environmental conditions on the sorption behavior of Co(II) on Na-rectorite studied by batch experiments

The sorption of Co(II) from aqueous solution on Na-rectorite 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 Co(II) was strongly dependent on pH. At low pH the sorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (∆G ⁰, ∆S ⁰, ∆H ⁰) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Co(II) on Na-rectorite was spontaneous and endothermic. Experimental results indicate that Na-rectorite is a suitable adsorbent for preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Adsorption of Eu(III) from aqueous solution using mesoporous molecular sieve

The adsorption behavior of Eu(III) from aqueous solution to mesoporous molecular sieves (Al-MCM-41) is investigated as a function of contact time, solid content, ionic strength, pH, foreign ions and temperature by using batch technique. The experimental results show that Eu(III) adsorption is strongly dependent on pH values, but independent of ionic strength and foreign cations under our experimental conditions. The kinetic process is described by a pseudo-second-order rate model very well. The adsorption isotherms are simulated by Langmuir model very well. The thermodynamic parameters (∆G°, ∆S°, ∆H°) are calculated from the temperature dependent adsorption isotherms at 293, 313 and 333 K, respectively, and the results suggest that the adsorption of Eu(III) on Al-MCM-41 is a spontaneous and endothermic process. Desorption studies indicate that the adsorbed Eu(III) is very difficult to be desorbed from the solid surface. Al-MCM-41 is a suitable material for the preconcentration and solidification of Eu(III) from large volumes of aqueous solutions.     

Investigation of radionuclide <Superscript>63</Superscript>Ni(II) sorption on ZSM-5 zeolite

The sorption of ⁶³Ni(II) from aqueous solution using ZSM-5 zeolite was investigated by batch technique under ambient conditions. ZSM-5 zeolite was characterized by point of zero net proton charge (PZNPC) titration. The sorption was investigated as a function of shaking time, pH, ionic strength, foreign ions, humic acid (HA), fulvic acid (FA) and temperature. The results indicate that the sorption of ⁶³Ni(II) on ZSM-5 zeolite is strongly dependent on pH. The sorption is dependent on ionic strength at low pH, but independent of ionic strength at high pH values. The presence of HA/FA enhances ⁶³Ni(II) sorption at low pH values, whereas reduces ⁶³Ni(II) sorption at high pH values. The sorption isotherms are simulated by Langmuir model very well. The thermodynamic parameters (i.e., ∆H ⁰, ∆S ⁰ and ∆G ⁰) for the sorption of ⁶³Ni(II) are determined from the temperature dependent sorption isotherms at 293.15, 313.15 and 333.15 K, respectively, and the results indicate that the sorption process of ⁶³Ni(II) on ZSM-5 zeolite is spontaneous and endothermic.     

Impact of environmental conditions on the removal of Ni(II) from aqueous solution to bentonite/iron oxide magnetic composites

The sorption of radionuclide ⁶³Ni(II) on bentonite/iron oxide magnetic composites was investigated by batch technique under ambient conditions. The effect of contact time, solid content, pH, coexistent electrolyte ions, fulvic acid, and temperature on Ni(II) sorption to bentonite/iron oxide magnetic composites was examined. The results demonstrated that the sorption of Ni(II) was strongly dependent on pH and ionic strength at pH <8.0, and was independent of pH and ionic strength at high pH values. The sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange at low pH, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The experimental data were well fitted by Langmuir model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Ni(II) on bentonite/iron oxide magnetic composites was an endothermic and spontaneous processes. The results show that bentonite/iron oxide magnetic composites are promising magnetic materials for the preconcentration and separation of radionickel from aqueous solutions in environmental pollution.     

Investigation of Co(II) sorption on GMZ bentonite from aqueous solutions by batch experiments

In this study, a local bentonite from Gaomiaozi county (Inner Mongolia, China) was converted to Na-bentonite and was characterized by FTIR and XRD to determine its chemical constituents and micro-structure. The removal of cobalt from aqueous solutions by Na-bentonite was investigated as a function of contact time, pH, ionic strength, foreign ions and temperature by batch technique under ambient conditions. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Co(II) at the temperatures of 293.15, 313.15 and 333.15 K, respectively. The thermodynamic parameters (∆G°, ∆S°, ∆H°) of Co(II) sorption on GMZ bentonite calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on GMZ bentonite was an exothermic and spontaneous process. The Na-bentonite is a suitable material for the preconcentration and solidification of Co(II) from aqueous solutions.     

Effect of pH,fulvic acid and temperature on sorption of Th(IV) on zirconium oxophosphate

Sorption of Th(IV) on Zr₂O(PO₄)₂ as a function of contact time, reaction temperature, pH, ionic strength and solid-to-liquid ratio (m/V) is studied under ambient condition by using batch technique. Effects of fulvic acid (FA), phosphate, sulfate and citrate on Th(IV) sorption are investigated in detail. A pseudo-second-order rate equation is used to simulate the kinetic sorption. The removal of Th(IV) increases with increasing pH and hardly depends on ionic strength. Sorption of Th(IV) increases with increasing m/V and reaction temperature. The presence of FA and phosphate enhances the sorption of Th(IV) on Zr₂O(PO₄)₂ while sulfate and citrate decrease the sorption. The Langmuir and Freundlich models are used to simulate the sorption isotherm of Th(IV) on Zr₂O(PO₄)₂ at different temperatures. The thermodynamic data (i.e., ∆H ⁰, ∆S ⁰, ∆G ⁰) are calculated from temperature dependent sorption isotherms. The results suggest that the sorption process of Th(IV) on Zr₂O(PO₄)₂ is 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.     

Sorption of radiocobalt(II) onto Ca-montmorillonite: effect of contact time, solid content, pH, ionic strength and temperature

In this paper, the sorption of Co(II) from aqueous solution to Ca-montmorillonite was studied under ambient conditions by using batch technique. The effects of contact time, solid content, pH, ionic strength and temperature on the sorption of Co(II) to Ca-montmorillonite was also investigated. The results indicated that the sorption of Co(II) was strongly dependent on pH values. The sorption was dependent on ionic strength at low pH values, but independent of ionic strength at high pH values. Outer-sphere surface complexes were formed on the surface of Ca-montmorillonite at low pH values, whereas inner-sphere surface complexes were formed at high pH values. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms of Co(II) at three different temperatures. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption reaction of Co(II) to Ca-montmorillonite was an endothermic and spontaneous process. The high sorption capacity of Co(II) on Ca-montmorillonite suggests that the Ca-montmorillonite is a suitable material for the preconcentration and solidification of radiocobalt from aqueous solutions.     

Characterization of Co(II) removal from aqueous solution using bentonite/iron oxide magnetic composites

The bentonite/iron oxide magnetic composites were prepared by co-precipitation method, and characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscope. The prepared bentonite/iron oxide magnetic composites were used as a sorbent for the removal of Co(II) 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. The sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange at low pH whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of iron oxide in the composites also contributes to the sorption of Co(II) ions on the magnetic composites. The experimental data were well described by Langmuir model. The thermodynamic parameters (∆G ^°, ∆S ^°, ∆H ^°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on bentonite/iron oxide magnetic composites was an endothermic and spontaneous processes.     

Sorption of Th(IV) on goethite: effects of pH,ionic strength,FA and phosphate

Sorption of thorium (IV) on goethite was investigated as a function of contact time, pH, ionic strength, anions, solid-to-liquid ratio (m/V) and Th(IV) concentration using batch technique. The results showed that the sorption of Th(IV) was strong pH-dependence, and increased from ~10 to ~100% over the pH range of 2.0–4.0, and then kept a constant level in the higher pH range. The sorption of Th(IV) increased with increasing m/V and independent of ionic strength. It was clear that phosphate and FA significantly enhanced Th(IV) sorption on goethite. The sorption and desorption isotherms were investigated at pH 2.90 ± 0.05 and analyzed with Freundlich and Langmuir models, respectively. Compared to Langmuir model, Freundlich model could fit the experimental data better, according to the high relative coefficients.     

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.     

Effect of pH, ionic strength, foreign ions, fulvic acid and temperature on 109Cd(II) sorption to γ-Al2O3

The sorption of Cd(II) from aqueous solution on γ-Al₂O₃ 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 γ-Al₂O₃ surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) 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 γ-Al₂O₃ was an spontaneous and endothermic process.     

Sorption study of radionickel on attapulgite as a function of pH, ionic strength and temperature

Sorption of radionickel on attapulgite is studied as a function of contact time, ionic strength, pH and temperature. The results indicate that the sorption of Ni(II) on attapulgite is strongly ionic strength-dependent at pH <8, and independent of ionic strength at pH >8. Outer-sphere surface complexation or ion exchange contributes to Ni(II) sorption on attapulgite at pH <8, whereas the sorption of Ni(II) is mainly dominated by inner-sphere surface complexation at pH >8. The sorption of Ni(II) on attapulgite increases with increasing temperature, and the thermodynamic parameters (??H ⁰, ??G ⁰ and ??S ⁰) calculated from the temperature dependent sorption isotherms suggest that the sorption of Ni(II) on attapulgite is a spontaneous and endothermic process. The high sorption capacity of attapulgite suggests that attapulgite is a suitable material for the preconcentration and solidification of radionickel from large volumes of aqueous solutions.     

Removal of Zn(II) from aqueous solution by natural halloysite nanotubes

Clay minerals have been widely used in wastewater disposal due to their strong sorption and complexation ability towards various environmental pollutants. In this study, the removal of Zn(II) from aqueous solution by natural halloysite nanotubes (HNTs) was studied as a function of various solution chemistry conditions such as contact time, pH, ionic strength, coexisting electrolyte ions and temperature under ambient conditions. The results indicated that the removal of Zn(II) by HNTs was strongly dependent on pH and ionic strength. Langmuir and Freundlich models were used to simulate the sorption isotherms of Zn(II) at three different temperatures of 293, 313 and 333 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) calculated from the temperature dependent sorption isotherms indicated that the removal process of Zn(II) by HNTs was endothermic and spontaneous. At low pH, the removal of Zn(II) was dominated by outer-sphere surface complexation and/or cation exchange with Na⁺/H⁺ on HNT surfaces, whereas inner-sphere surface complexation was the main removal mechanism at high pH. From the experimental results, one can conclude that HNTs may have a good potentiality for the disposal of Zn(II)-bearing wastewaters.     

Separation of no-carrier-added radioactive scandium from neutron irradiated titanium

In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na⁺/H⁺ on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH.     

Impact of environmental conditions on the sorption behavior of radionuclide <Superscript>60</Superscript>Co(II) on MnO<Subscript>2</Subscript>

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions. The removal of ⁶⁰Co(II) from wastewaters by MnO₂ was studied as a function of various environmental parameters such as shaking time, pH, ionic strength, foreign ions, and humic substances under ambient conditions. The results indicated that the sorption of ⁶⁰Co(II) on MnO₂ was strongly dependent on pH and ionic strength. At low pH, the sorption of ⁶⁰Co(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 presence of HA/FA enhances ⁶⁰Co(II) sorption at low pH values, whereas reduces ⁶⁰Co(II) sorption at high pH values. The Langmuir and Freundlich models were used to simulate the sorption isotherms of ⁶⁰Co(II) at three different temperatures of 298.15, 318.15 and 338.15 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 MnO₂ was endothermic and spontaneous.     

Sorption efficiency of a new sorbent towards uranyl: phosphonic acid grafted Merrifield resin

A novel sorbent resin consisting of a Phosphonic Acid grafted on Merrifield Resin (PA-MR) for the extraction of uranyl from nitrate media is described. The sorption behaviour of uranyl cation on PA-MR was investigated using batch equilibrium technique. The effects of parameters such as shaking speed, pH levels, contact time, metal concentrations, ionic strength and temperature were reported. The results show that the sorption capacity increases with increasing both initial uranyl ion concentration and temperature and decreases with increasing ionic strength. Therefore, the optimum condition for the present study should be using 6.6 mg adsorbent per 1.0 mg uranyl in solution with pH 3.6 and shaking at 250 rpm for 180 min. The adsorption behavior of the system was also investigated and found to be in line with Langmuir isotherm. The kinetic data was well described by the pseudo second-order. Thermodynamics data leads to endothermic process ∆H = + 31.03 kJ⁻¹ mol⁻¹, ∆S = + 146.64 J mol⁻¹ K⁻¹ and ∆G = −11.96 kJ mol⁻¹ at 20 K. ∆G decreased to negatives values with increasing temperature indicating that the process was more favoured at high temperature.