Adsorption and desorption of Ni2+ on Na-montmorillonite: Effect of pH, ionic strength, fulvic acid, humic acid and addition sequences

ArticleinApplied Clay Science 39(3-4):133-141 · May 2008with12 Reads
DOI: 10.1016/j.clay.2007.05.006
Humic substances and clay minerals have been studied intensively because of their strong complexation and adsorption capacities. In this work, adsorption of Ni2+ on Na-montmorillonite was studied using batch technique under ambient conditions. Effect of pH, ionic strength, solid content, humic acid (HA), fulvic acid (FA) and the addition sequences of fulvic acid/Ni2+/montmorillonite on Ni2+ adsorption was also investigated. The results indicate that adsorption of Ni2+ on montmorillonite are strongly dependent on pH and ionic strength. The adsorption of Ni2+ is mainly dominated by surface complexation and ion exchange. The adsorption–desorption hysteresis suggests that the adsorption of Ni2+ is irreversible. The thermodynamic parameters (ΔH, ΔS, and ΔG) are calculated from the temperature dependence, and the results suggest that the adsorption reaction is endothermic and spontaneous. The presence of FA and the addition sequences of FA/Ni2+/montmorillonite do not influence the adsorption of Ni2+ on FA bound montmorillonite hybrids. Montmorillonite is a suitable candidate for pre-concentration and solidification of Ni2+ from large volume of solutions.
    • "The addition sequences of HA and Th(IV) to solid adsorbent suspension effect the metal ion adsorption must be discussed controversially. Some authors reported the influence of addition sequences on adsorption on solid surfaces (Reiller et al., 2005; Xu et al., 2006a Xu et al., , 2008 ). However , other results indicated no noticeable effect of addition sequences of HA/metal ions on the adsorption of metal ions at solid surfaces (Xu et al., 2006b; Wang et al., 2009). "
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    • "In addition , intracellular metal ions should account for the biosorption capacity difference between living and nonliving Mucoromycote sp. XLC. Xu et al. 2008; Yee et al. 2004). The spectrum of native living and nonliving biosorbents showed broad and strong bands at 3433.86 cm ¡1 and 3437.78 "
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    • "In contrast, the sorption of U(VI) became an irreversible process in the presence of HA, indicating that the ternary surface complexes were mainly Table 3. Thermodynamic Parameters for U(VI) Sorption on SONPs. Temperature ΔH 0 (kJ/mol) ΔG 0 (kJ/mol) ΔS 0 (J/(molÁK)) Interactions between Silicon Oxide Nanoparticles (SONPs) and U(VI) Contaminations contributed to U(VI) sorption as Type A complexes, where HA played a role of " bridge " between SONPs and U(VI) [1,43]. As shown in Table 4 , the positive value of HC% was consistent with the irreversible process, and the values of both K dðsorbÞ and K dðdesorbÞ for the ternary SONPs/U(VI)/HA system are much bigger than those for the binary SONPs/U(VI) system, which suggested that much more U(VI) was restrained in solids. "
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