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  • Author or Editor: Zhiqiang Guo x
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Abstract  

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
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{YOHTh}}^{4 + }$$ \end{document}
at low pH and “weak” species
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOTh(OH)}}_{3}$$ \end{document}
at pH > 4. On HA bound MX-80 bentonite, the species of Th(IV) adsorbed on HA-bentonite hybrids are mainly consisted of
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{YOThL}}_{3}$$ \end{document}
and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOThL}}_{1}$$ \end{document}
at pH < 4, and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\equiv {\text{XOTh(OH)}}_{3}$$ \end{document}
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.
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Abstract  

In this study, the adsorption of U(VI) from aqueous solution on Na-rectorite was studied as a function of various environmental conditions such as contact time, pH, ionic strength, soil humic acid (HA)/fulvic acid (FA), solid contents, and temperature under ambient conditions by using batch technique. The kinetic adsorption is fitted by the pseudo-second-order model very well. The adsorption of U(VI) on Na-rectorite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on U(VI) adsorption was found at low pH, whereas a negative effect was observed at high pH. The presence of HA/FA enhanced the U(VI) adsorption at low pH values, but reduced U(VI) adsorption at high pH. The thermodynamic parameters (ΔH 0, ΔS 0, and ΔG 0) were also calculated from the temperature dependent adsorption isotherms, and the results suggested that the adsorption of U(VI) on Na-rectorite was a spontaneous and endothermic process.

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Abstract  

This work contributed to the adsorption of radiocobalt on goethite as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of fulvic acid (FA) under ambient conditions. The results indicated that adsorption of Co(II) was dependent on ionic strength and foreign ions at low pH values (pH < 7.8), and independent of ionic strength and foreign ions at high pH values (pH > 7.8). Outer-sphere surface complexation and/or ion exchange were the main mechanisms of Co(II) adsorption on goethite at low pH values, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH values. The presence of FA enhanced Co(II) adsorption at low pH values, but reduced Co(II) adsorption at high pH values. The thermodynamic data (ΔH 0, ΔS 0, ΔG 0) were calculated from the temperature dependent adsorption isotherms, and the results suggested that adsorption process of Co(II) on goethite was spontaneous and endothermic. The results are crucial to understand the physicochemical behavior of Co(II) in the nature environment.

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Abstract  

In this work, a series of batch experiments were carried out to investigate the effect of various environmental factors such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances and temperature on the sorption behavior of illite towards 64Cu(II). The results indicated that 64Cu(II) sorption on illite achieved equilibrium quickly. The pH- and ionic strength-dependent sorption suggested that 64Cu(II) sorption on illite was dominated by ion exchange or outer-sphere surface complexation at pH < 7, whereas the pH-dependent and ionic strength-independent sorption indicated that the sorption process was mainly attributed to inner-sphere surface complexation at pH > 7. A positive effect of humic substances on 64Cu(II) sorption was found at pH < 6.5, whereas a negative effect was observed at pH > 6.5. The Langmuir and Freundlich models were used to simulate the sorption isotherms of 64Cu(II) at three different temperatures of 293, 313, and 333 K. The thermodynamic parameters (ΔH 0, ΔS 0, and ΔG 0) of 64Cu(II) sorption on illite were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption of 64Cu(II) on illite was endothermic and spontaneous. From the experimental results, it is possible to conclude that illite has good potentialities for cost-effective treatments of 64Cu(II)-contaminated wastewaters.

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Abstract  

Carbonate hydroxylapatite (CHAP), prepared from eggshell waste, was used to remove 60Co(II) from aqueous solutions. The sorption of 60Co(II) on CHAP as a function of contact time, pH, ionic strength and foreign ions in the absence and presence of humic acid and fulvic acid under ambient conditions was studied. The sorption of 60Co(II) on CHAP was strongly dependent on pH and ionic strength. The thermodynamic parameters (ΔH 0, ΔS 0, ΔG 0) of 60Co(II) sorption on CHAP were calculated from the temperature-dependent sorption isotherms, and the results indicated that the sorption process of 60Co(II) on CHAP was endothermic and spontaneous. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on CHAP surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. Experimental results also indicated that CHAP was a suitable low-cost adsorbent for pre-concentration and solidification of 60Co(II) from large volumes of aqueous solutions.

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Abstract  

In this study, the removal of radionuclide 60Co(II) from wastewater by Ca-rectorite was studied as a function of various environmental parameters such as contact time, pH, ionic strength, coexisting electrolyte ions, humic substances (HS) and temperature under ambient conditions. The results indicated that the sorption of Co(II) on Ca-rectorite was strongly dependent on pH and ionic strength. The Langmuir and Freundlich models were used to simulate the sorption isotherms of Co(II) at three different temperatures of 298.15, 318.15 and 338.15 K. The thermodynamic parameters (
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Updelta H^{0} ,\,\Updelta S^{0}$$ \end{document}
and
\documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{upgreek} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} $$\Updelta G^{0}$$ \end{document}
) calculated from the temperature-dependent sorption isotherms indicated that the sorption process of Co(II) on Ca-rectorite was spontaneous and endothermic. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange with Ca+/H+ on Ca-rectorite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, it is possible to conclude that Ca-rectorite has good potentialities for cost-effective disposal of radiocobalt bearing wastewaters.
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Abstract  

A novel adsorbent, TiO2/eggshell composite, was synthesized by sol–gel method, and characterized by XRD and FTIR. The removal of 60Co(II) from aqueous solution by TiO2/eggshell was studied as a function of contact time, pH, ionic strength, foreign ions, humic substances and temperature. The results indicated that the sorption of 60Co(II) on TiO2/eggshell was strongly dependent on pH and ionic strength. The Langmuir, Freundlich and D-R models were applied to simulate the sorption of 60Co(II) at temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH 0, ΔS 0, ΔG 0) calculated from the temperature dependent sorption isotherms indicated that the sorption process of 60Co(II) on TiO2/eggshell was endothermic and spontaneous. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. TiO2/eggshell composites have good potentialities for cost-effective disposal of 60Co(II) bearing wastewaters.

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Abstract  

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., ΔH 0, ΔS 0, ΔG 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.

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