Adsorption and desorption of Ni2+ on Na-montmorillonite: Effect of pH, ionic strength, fulvic acid, humic acid and addition sequences
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.
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ABSTRACT: Interlamellar space organization of low-charge montmorillonite was studied by modeling of X-ray diffraction (XRD) patterns recorded under controlled relative humidity (RH) conditions on Ni saturated specimens. The quantitative XRD investigation, based on an indirect method consisting of the comparison of experimental reflections with the other calculated from structural models, is used to characterize eventual nanostructural changes along axis of Ni-exchanged montmorillonite. This method allowed us to determine, respectively, the relative layer types contribution, the layer thickness, nanoconfiguration of the interlamellar space, and position, amount, and organization of water molecules and exchangeable cations. Obtained theoretical models exhibit heterogeneous hydration state which is the dominating character detected all over studied cycles. Along RH cycle a modification in the main structure of the host materials is performed and the presence of a mixed layer structure (MLS) is noted. The hydration hysteresis at the low and the high RH range can be explained by fluctuations in the water retention mechanism and hydration heterogeneities created within the smectite crystalliteJournal of Nanomaterials 11/2014; 2014. · 1.61 Impact Factor
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ABSTRACT: This study investigated the removal of Sb(III) and Sb(V) from aqueous media through their adsorption onto oxide minerals (goethite) under a set of conditions (initial Sb concentration, pH, reaction time, and interaction temperature). The kinetic studies suggested that the adsorption equilibriums for both Sb(III) and Sb(V) were achieved within 24 h. The adsorption data collected at three different temperatures were successfully modeled using both the Langmuir and Freundlich isotherms. The adsorption of Sb(III) onto goethite was greater than that of Sb(V) at the three investigated temperatures. The thermodynamic parameters (Delta G degrees, Delta H degrees, and Delta S degrees) were calculated from the dependence of the adsorption process on the reaction temperature, and the calculated parameters suggest that the adsorption of both Sb(III) and Sb(V) onto goethite is spontaneously endothermic. The adsorption of Sb(III) and Sb(V) on goethite was dependent on pH within the investigated pH range.Water Quality Research Journal of Canada 08/2013; 48(3):223. DOI:10.2166/wqrjc.2013.030 · 0.33 Impact Factor
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ABSTRACT: Montmorillonite and vermiculite as solid phases for the preconcentration of trace elements in natural waters: Adsorption and desorption studies of As, An evaluation of the feasibility of vermiculite and K10 montmorillonite for use as adsorbent in the separation and/or preconcentration of elements prior to their determination was performed for As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sr, V and Zn. The adsorption of elements onto both clay minerals was studied using a multi-element solu-tion in trace concentrations by batch technique, and no stirring under ambient conditions. Effects of adsorbent concentration, pH and ionic strength were also investigated. The desorption process of the previously adsorbed elements onto clay minerals was studied using HCl and HNO 3 as extractors. In general, the adsorbents exhibited excellent sorption properties for most of the elements. The content of adsorption obtained was higher than 70% for almost all cases. On average, at low salt concentration (b 0.05 mol L −1) the sorption efficiency was only slight-ly higher in montmorillonite when compared to vermiculite, however the reverse is true at high salt concentra-tion. The adsorption of metal ions onto vermiculite and montmorillonite reduces with decreasing pH and increasing ionic strength. An opposite behavior was observed in the adsorption of oxi-anionic species of arsenic and vanadium. The results of desorption experiments indicated that a single extraction with 1.0 mol L −1 HNO 3 or HCl was sufficient for the recovery of most elements with an average desorption of 82% and 90% for K10 mont-morillonite and vermiculite, respectively.Applied Clay Science 07/2014; 99:289. DOI:10.1016/j.clay.2014.07.013 · 2.70 Impact Factor