Effect of Ionic Strength and Ion Pair Formation on the Adsorption of Nickel by Kaolinite

Abstract

Abstract---Adsorption of Ni(II) by Ca-and Na-saturated kaolinites was studied in equilibrating solutions with total Ni concentrations ranging from 118 to 946/xg/liter. Background electrolytes used in these :experiments were 0.005, 0,0l, 0.025, and 0.5 M Ca(NO3)~, 0.002 and 0.005 M CaSO4,0.0l and 0.1 M NaNO3, and 0.005 and 0.05 M Na2SO4. Ion speciation in equilibrium solutions was calculated by the computer program GEOCHEM. Computed Ni 2+ concentrations and activities at equilibrium were correlated with total Ni adsorbed by kaolinite. Increasing ionic strength resulted in decreasing Ni adsorption. Adsorption of Ni was greater from solutions when NO3 was the dominant anion. Based on adsorption data in SO4 medium, the standard free energy of adsorption of Ni 2* ion on kaolinite was computed to be -27 k J/mole.

Geochemical characterization of mangrove sediments of the Zuari estuarine system, West coast of India

“…Albee (1962) reported that in natural chlorites, small amounts of Cr do substitute Si. Mattigod et al (1979) studied the adsorption of Ni onto kaolinite and found that increasing ionic strength decreases adsorption of Ni. Thus, the low salinity in the upper middle estuary must be facilitating the adsorption of Ni onto kaolinite as compared to the other locations in the estuary.…”

Nickel adsorption by variable charge soils: effect of pH and ionic strength

“…The Ni 2+ cation is known to form complexes with various organic and inorganic ligands (Bowman et al, 1981). Many studies have considered the effect of cations and anions that constitute the electrolyte support on metal adsorption, principally regarding to the competitive effect of Ca 2+ for adsorption sites and by the action of Cl -in the formation of chloride complexes with less affinity for the surface (Mattigod et al, 1979;Bowman et al, 1981;Wang et al, 1997;Echeverría et al, 2003). Considering the nature of electrolyte support, the effect of the competition between Ca 2+ and Ni 2+ for the same adsorption sites probably justified the decrease in Ni adsorption with the increase in ionic strength, rather than the probable formation of complexes between Ni and the anion because NO 3 -has much less affinity than Cl -for this type of reaction in solution (Criscenty and Sverjensky, 1999).…”

“…This aspect is of particular interest for Ni adsorption, because there is no consensus yet on its retention mechanism by the soil. Nickel adsorption has been studied in pure systems, such as Fe, Al and Mn hydrated oxides (McKenzie, 1980;Beukes et al, 2000), clay minerals (Mattigod et al, 1979;Echeverría et al, 2003;Sen Gupta and Bhattacharyya, 2006) and organic matter (Mellis et al, 2004), and in complex systems such as the soil, under natural and agricultural conditions or with residue application (Camargo et al, 1989;Pombo et al, 1989;Mellis et al, 2004;Iglesias et al, 2007). However, sufficient data have not yet been gathered on Ni adsorption by weathered soils of the wet tropics to assure the implementation of efficient prevention techniques and remediation of soil contamination.…”

Adsorption of Cr(VI) from Aqueous Solutions by Staphylococcus aureus Biomass

“…Freundlich Langmuir Thermodynamic parameters [25,26]. These two solution effects cause decreasing adsorption of Cr(VI) to S. aureus biomass surfaces with a net positive charge.…”