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
Abstract
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). "
    [Show abstract] [Hide abstract] ABSTRACT: The adsorption experiments of Th(IV) on illite as a function of time, pH, ionic strength, temperature and humic acid (HA) were investigated using batch experiments. The results showed that adsorption of Th(IV) on illite was strongly dependent on contact time, pH, and temperature and independent on humic acid(HA). The Th(IV) adsorption on illite increases with increasing pH (pH < 4.5) and temperature, but decreases with increasing ionic strength at pH < 4.5. Th(IV) adsorption data were successfully described by the pseudo second-order kinetic model and the intraparticle diffusion equation. Langmuir adsorption isotherm model simulated the adsorption process better than Freundlich model. The thermodynamic parameters of enthalpy, entropy and free energy change were calculated and thermodynamic parameters revealed the spontaneity and exothermic nature of adsorption Th(IV) on illite. Th(IV) of adsorption mechanism on illite is outer-sphere surface complexation and ion exchange with Na+/H+ on illite at low pH, whereas inner-sphere surface complexation was the main adsorption mechanism at high pH.
    Full-text · Article · Jul 2016
    • "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 "
    [Show abstract] [Hide abstract] ABSTRACT: The biosorption of cadmium (Cd2+) and nickel (Ni2+) using living and nonliving biomass of Mucoromycote sp. XLC as a biosorbent was investigated in this study. The optimum conditions were established with batch biosorption experiments. The data from equilibrium experiments showed that all kinds of biosorbents fitted the Langmuir model. For the living and nonliving biosorbent, the predicted maximum Cd2+ uptake capacity was 79.65 mg g−1 and 56.51 mg g−1, while the maximum Ni2+ uptake capacity was 51.26 mg g−1 and 44.32 mg g−1, respectively. Acid digestion results indicated that intracellular metal ions might be the main reason for the metal uptake capacity difference between living and nonliving biosorbents. FTIR analysis and potentiometric titration indicated freeze dehydration-autoclaving treatment of nonliving biomass slightly changed the surface structure of the cell wall and the functional groups involved in biosorption were carboxylic, phosphoryl, amine and hydroxyl groups. Our results suggest the living biosorbent had a second biosorption process by intracellularly accumulating metal ions, hence possessing a higher Cd2+or Ni2+ uptake capacity than nonliving biosorbent.
    Full-text · Article · Mar 2016
    • "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. "
    [Show abstract] [Hide abstract] ABSTRACT: The interactions between contaminations of U(VI) and silicon oxide nanoparticles (SONPs), both of which have been widely used in modern industry and induced serious environmental challenge due to their high mobility, bioavailability, and toxicity, were studied under different environmental conditions such as pH, temperature, and natural organic matters (NOMs) by using both batch and spectroscopic approaches. The results showed that the accumulation process, i.e., sorption, of U(VI) on SONPs was strongly dependent on pH and ionic strength, demonstrating that possible outer- and/or inner-sphere complexes were controlling the sorption process of U(VI) on SONPs in the observed pH range. Humic acid (HA), one dominated component of NOMs, bounded SONPs can enhance U(VI) sorption below pH~4.5, whereas restrain at high pH range. The reversible sorption of U(VI) on SONPs possibly indicated that the outer-sphere complexes were prevalent at pH 5. However, an irreversible interaction of U(VI) was observed in the presence of HA (Fig 1). It was mainly due to the ternary SONPs-HA-U(VI) complexes (Type A Complexes). After SONPs adsorbed U(VI), the particle size in suspension was apparently increased from ~240 nm to ~350 nm. These results showed that toxicity of both SONPs and U(VI) will decrease to some extent after the interaction in the environment. These findings are key for providing useful information on the possible mutual interactions among different contaminants in the environment.
    Full-text · Article · Mar 2016
Show more