Characterization of MX-80 bentonite and its sorption of radionickel in the presence of humic and fulvic acids

MX-80 bentonite is considered as one of the best backfill materials for high-level radioactive nuclear waste. Herein, the bentonite is characterized by using XRD and FTIR techniques. Sorption of radionickel to MX-80 bentonite in the presence/absence of humic acid (HA) or fulvic acid (FA) as a function of pH is investigated. The results indicate that the presence of HA or FA decreases the sorption of Ni²⁺ obviously. The different experimental processes do not affect the sorption of nickel to FA/HA bound bentonite. The sorption of Ni²⁺ on FA/HA-bound bentonite decreases with the increasing FA/HA content in the systems. The mechanism of nickel sorption is also discussed in detail.     

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.     

Interaction of radionickel with diatomite as a function of pH, ionic strength and temperature

Sequestration of Ni(II) on diatomite as a function of reaction time, pH, ionic strength, foreign ions and temperature were investigated by batch sorption technique. The results indicated that the sorption of Ni(II) on diatomite was quickly in the first contact time of 2 h and then slowly with increasing contact time. The interaction of Ni(II) with diatomite was strongly pH- and ionic strength-dependent at low pH values (i.e., which was dominated by ion exchange or outer-sphere surface complexation), while the pH-dependent and ionic strength-independent sorption at high pH suggested that inner-sphere or multinuclear surface complexation was the main sorption mechanism. With increasing temperature, the sorption of Ni(II) on diatomite increased and the experimental data were well fitted by Langmuir model. The sorption samples at pH 6.8 and 10.0 were also characterized by XPS spectroscopy, and the results suggested that Si atoms also participated in Ni(II) sorption on diatomite. The results are important to evaluate the physicochemical behavior of Ni(II) and other similar radionuclides and heavy metal ions in the environment.     

Correction to: Characterization of MX-80 bentonite and its sorption of radionickel in the presence of humic and fulvic acids

Journal of Radioanalytical and Nuclear Chemistry - The original publication of the article includes mistakes on instrument types of FTIR and XRD characterization in Page 702. The corrected...     

Influence of contact time, pH, soil humic/fulvic acids, ionic strength and temperature on sorption of U(VI) onto MX-80 bentonite

The sorption of U(VI) from aqueous solution on MX-80 bentonite was studied as a function of contact time, pH, ionic strength, solid contents, humic acid (HA), fulvic acid (FA) and temperature under ambient conditions using batch technique. The results indicate that sorption of U(VI) on MX-80 bentonite is strongly dependent on pH and ionic strength. The removal of U(VI) to MX-80 bentonite is rather quick and the kinetic sorption data is simulated well by a pseudo-second-order rate equation. The presence of HA enhances the sorption of U(VI) on MX-80 bentonite obviously, but the influence of FA on U(VI) sorption is not obvious. The thermodynamic parameters (ΔH ⁰, ΔS ⁰, and ΔG ⁰) for the sorption of U(VI) calculated from temperature dependent sorption suggest that the sorption reaction is endothermic and spontaneous.     

Sorption of Th(IV) on MX-80 bentonite: effect of pH and modeling

MX-80 bentonite was characterized by XRD and FTIR in detail. The sorption of Th(IV) on MX-80 bentonite was studied as a function of pH and ionic strength in the presence and absence of humic acid/fulvic acid. The results indicate that the sorption of Th(IV) on MX-80 bentonite increases from 0 to 95% at pH range of 0–4, and then maintains high level with increasing pH values. The sorption of Th(IV) on bentonite decreases with increasing ionic strength. The diffusion layer model (DLM) is applied to simulate the sorption of Th(IV) with the aid of FITEQL 3.1 mode. The species of Th(IV) adsorbed on bare MX-80 bentonite are consisted of “strong” species o \textYOHTh^{4 +} \equiv {\text{YOHTh}}^{4 + } at low pH and “weak” species o \textXOTh(OH)₃ \equiv {\text{XOTh(OH)}}_{3} at pH > 4. On HA bound MX-80 bentonite, the species of Th(IV) adsorbed on HA-bentonite hybrids are mainly consisted of o \textYOThL₃ \equiv {\text{YOThL}}_{3} and o \textXOThL₁ \equiv {\text{XOThL}}_{1} at pH < 4, and o \textXOTh(OH)₃ \equiv {\text{XOTh(OH)}}_{3} at pH > 4. Similar species of Th(IV) adsorbed on FA bound MX-80 bentonite are observed as on FA bound MX-80 bentonite. The sorption isotherm is simulated by Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models, respectively. The sorption mechanism of Th(IV) on MX-80 bentonite is discussed in detail.     

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.     

Sorption of europium on a MX-80 bentonite sample: experimental and modelling results

The EDXRF technique offers simultaneous detection and determination of multiple trace elements in F₃ generation seed of Cicer arietinum L. plant, developed from irradiated group of 0.05, 0.10, 0.15 kGy and 0.20 kGy using ⁶⁰Co gamma source (0.12 kGy/h). The accumulations of elements in edible seeds were significantly different (p ≤ 0.05) in different absorbed dose. Out of 14 elementals (S, Cl, K, P, Ca, V, Mn, Fe, Co, Cu, Zn, Rb, Sr and Cd), the accumulations of K, P, Ca, S, Cu, Zn, Mn, Fe, Cd, Rb, Sr and Cl were increased in seed with in the dose range of 0.15–0.20 kGy, except V and Co. Also, the yielding potentials of seeds were increased with in the dose range of 0.15–0.20 kGy.     

Sorption of Eu(III) onto Gaomiaozi bentonite by batch technique as a function of pH, ionic strength, and humic acid

The bentonite from Gaomiaozi county (Inner Mongolia, China) (denoted as GMZ bentonite) was characterized by X-ray powder diffraction and Fourier transform infrared spectroscopy. The effect of pH, contact time, ionic strength, humic acid (HA) and Eu(III) concentrations on Eu(III) sorption to the GMZ bentonite was studied by batch technique under ambient conditions. The sorption of Eu(III) on GMZ bentonite was strongly dependent on pH and independent of ionic strength. The sorption of Eu(III) on GMZ bentonite was mainly dominated by surface complexation rather than by ion exchange. The presence of HA enhanced Eu(III) sorption at low pH values, but decreased Eu(III) sorption at high pH values. The enhanced sorption of Eu(III) on GMZ bentonite at low pH was attributed to the strong complexation of Eu(III) with surface adsorbed HA on GMZ bentonite and the reduced sorption of Eu(III) at high pH was attributed to the formation of soluble HA–Eu complexes in aqueous solution. The strong sorption of Eu(III) on GMZ bentonite suggested that the GMZ bentonite could be used as the backfill material in nuclear waste disposal.     

Effect of pH, ionic strength, foreign ions and humic substances on Th(IV) sorption to GMZ bentonite studied by batch experiments

Bentonite has been studied extensively because of its strong sorption and complexation ability. Herein, GMZ bentonite from Gaomiaozi county (Inner Mongolia, China) was investigated as the candidate of backfill material for the removal of Th(IV) ions from aqueous solutions. The results indicate that the sorption of Th(IV) is strongly dependent on pH and ionic strength at pH < 5, and independent of ionic strength at pH > 5. Outer-sphere surface complexation or ion-exchange are the main mechanism of Th(IV) sorption on GMZ bentonite at low pH values, whereas the sorption of Th(IV) at pH > 5 is mainly dominated by inner-sphere surface complexation or surface precipitation. Soil fulvic acid (FA) and humic acid (HA) have a positive influence on the sorption of Th(IV) on bentonite at pH < 5. The different addition sequences of HA and Th(IV) to GMZ bentonite suspensions have no obvious effect on Th(IV) sorption to HA-bentonite hybrids. The high sorption capacity of Th(IV) on GMZ bentonite suggests that the GMZ bentonite can remove Th(IV) ions from large volumes of aqueous solutions in real work.     

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.     

Effect of pH and ionic strength on U(IV) sorption to oxidized multiwalled carbon nanotubes

Multiwalled carbon nanotubes (MWCNTs) have attracted multidisciplinary study because of their unique physicochemical properties. Herein, the sorption of U(VI) from aqueous solution to oxidized MWCNTs was investigated as a function of contact time, pH and ionic strength. The results indicate that U(VI) sorption on oxidized MWCNTs is strongly dependent on pH and ionic strength. The sorption of U(VI) is mainly dominated by surface complexation and cation exchange. The sorption of U(VI) on oxidized MWCNTs is quickly to achieve the sorption equilibrium. The sorption capacity calculated from sorption isotherms suggests that oxidized MWCNTs are suitable material in the preconcentration and solidification of U(VI) from large volumes of aqueous solutions.     

Adsorption of gelatin to a polystyrene/water interface as a function of concentration, pH, and ionic strength

The technique of neutron reflection has been used to investigate the adsorption of alpha-enriched gelatin from aqueous solution onto spun polystyrene substrates. Neutron reflection can provide information about the distribution of material perpendicular to an interface as well as total adsorbed amounts. The adsorbed layers were found to have maximum density at the surface, decaying with distance into solution. The adsorbed amount, layer thickness, and density were all seen to increase with solution concentration. Temperature was found to have little effect on adsorption. Thicker, less dense layers were observed at high pH and thinner, denser layers were observed at low pH, but the total adsorbed amount did not change significantly. The presence of sodium chloride had little effect on the adsorbed layers. The results are discussed in the context of other studies and the known amino acid sequence of alpha-gelatin.     

Adsorption of La(III) onto GMZ bentonite: effect of contact time,bentonite content,pH value and ionic strength

Bentonite has been studied extensively because of its strong adsorption capacity. A local Na-bentonite named GMZ bentonite, collected from Gaomiaozi County (Inner Mongolia, China), was selected as the first choice of buffer/backfill material for the high-level radioactive waste repository in China. In this research, the adsorption of La (ΙΙΙ) onto GMZ bentonite was performed as a function of contact time, pH, solid content and metal ion concentrations by using the batch experiments. The results indicate that the adsorption of La (III) on GMZ bentonite achieves equilibration quickly and the kinetic adsorption follows the pseudo-second-order model; the adsorption of La (III) on the adsorbent is strongly dependent on pH and solid content, the adsorption process follows Langmuir isotherm. The equilibrium batch experiment data demonstrate that GMZ bentonite is effective adsorbent for the removal of La (III) from aqueous solution with the maximum adsorption capacity of 26.8 mg g⁻¹ under the given experimental conditions.     

Effect of pH, ionic strength and temperature on sorption characteristics of Th(IV) on oxidized multiwalled carbon nanotubes

Oxidized multiwalled carbon nanotubes (MWCNTs) were characterized by SEM and FTIR. The sorption of Th(IV) on MWCNTs was studied as a function of contact time, pH, ionic strength, Th(IV) concentration and temperature. The results indicate that the sorption of Th(IV) on MWCNTs is strongly dependent on pH and weakly dependent on ionic strength. The sorption thermodynamics of Th(IV) on MWCNTs was carried out at 293.15, 313.15 and 333.15 K, respectively, and the thermodynamic parameters (standard free energy changes (??G ⁰), standard enthalpy change (??H ⁰) and standard entropy change (??S ⁰)) were calculated from the temperature dependent sorption isotherms. The sorption of Th(IV) on MWCNTs is a spontaneous and endothermic process. The oxidized MWCNTs may be a promising candidate for the preconcentration and solidification of Th(IV), or its analogue actinides from large volumes of aqueous solutions.     

Effect of pH,ionic strength,fulvic acid and humic acid on sorption of Th(IV) on Na-rectorite

Sorption of Th(IV) on Na-rectorite as a function of pH, ionic strength, soil humic acid (HA) and fulvic acid (FA) are studied under ambient conditions by using a batch technique. The results indicate that the sorption of Th(IV) on Na-rectorite is not only dependent on medium pH values, but also dependent on medium ionic strength and humic substances. Surface complexation and cation competition exchange account for Th(IV) sorption on Na-rectorite. The sorption of Th(IV) on Na-rectorite decreases with the increase on the concentration of NaNO₃, Mg(NO₃)₂ and Ca(NO₃)₂, and increases with the increasing amount of HA/FA in the suspension/adsorbed on rectorite. Soil HA/FA enhances the sorption of Th(IV) on rectorite at medium pH<4 drastically, but the presence of FA reduces the sorption of Th(IV) at medium pH>6, and HA has no effect on Th(IV) sorption at medium pH>6. An interpretation for the results is attempted, considering the occurrence of different sorption mechanisms.