Modeling the adsorption of Cd(II) onto kaolinite and Muloorina illite in the presence of citric acid

A surface complexation and ion exchange model of Pb and Cd competitive sorption on natural soils

“…Randall et al (1999) corroborated this study by showing the adsorption of Cd on goethite as bidentate surface complexes. Prior studies (Schindler et al, 1987;Lackovic et al, 2004b;Bhattacharyya and Gupta, 2007;Gu and Evans, 2007) suggested specific Cd retention on clay mineral hydroxyl sites, although no spectroscopic studies have been published to date to our knowledge for Cd sorption on clay minerals.…”

“…In addition to specific metal sorption, previous studies indicate that retention of Pb and Cd on permanent charge sites of the siloxane surfaces of phyllosilicate minerals also occurs through ion exchange reactions in which the sorbed ion is assumed to retain its inner hydration sphere (Dzombak and Morel, 1990;Lackovic et al, 2004b). Electrostatically bound Pb and Cd can be displaced by other cations present in solution through exchange reactions that are assumed to be reversible (Ziper et al, 1988;Kraepiel et al, 1999;Bradbury and Baeyens, 2005;Srivastava et al, 2005;Gu and Evans, 2007).…”

Competitive sorption of cadmium and lead in acid soils of Central Spain

“…As described above, the mineralogical composition of soils S1, S2, and S3 is dominated by kaolinite and illite, whereas, the clay fraction of soil S4 is dominated by smectite. Metal sorption on kaolinite and illite does not differ much (Lackovic et al, 2004) and it is known to be a rapid reaction since their exchange capacities are mainly due to external surface and edge sites readily accessible to cation exchange . In fact, cation exchange on clays without narrow interlayer space such as kaolinite appears to be instantaneous in comparison to exchange on smectite which can be related to its freely expanding interlayer space and limited by the rate of cation diffusion through this region (McBride, 1994).…”

Modelling the adsorption of Cd(II), Cu(II), Ni(II), Pb(II), and Zn(II) onto Fithian illite

“…Although their model fitted the experimental data well, the model contains many fitting parameters making it difficult to use practically. Recently, Lackovic et al [8][9][10] used a twosite model containing edge sites, ≡SOH and a basal surface site, ≡X − , to describe the adsorption of Cd(II), citric acid and a mixture of them onto illite. Echeverría et al [11,12] found out that at the lower pH, the main adsorption mechanism of retention of Ni(II) and Pb(II) onto illite was ion exchange which was affected by ionic strength, and at higher pH, the effect of ionic strength on the retention decreased with pH.…”