Modeling the adsorption of Cd(II) onto Muloorina illite and related clay minerals

Abstract

The adsorption of Cd(II) onto goethite, kaolinite, and illite was measured as a function of pH (adsorption edges) and concentration (adsorption isotherms) at 25 degrees C. As the pH was increased, adsorption onto goethite occurred mainly in the pH range 5.5-8, whereas adsorption onto kaolinite occurred in two stages, separated by a plateau in the pH region 5.5 to 7. Adsorption onto illite increased steadily as the pH was increased, with far less Cd(II) adsorbing onto illite than onto goethite or kaolinite per m(2) of mineral surface area. Potentiometric titrations of suspensions of each mineral, with and without Cd(II) present, were also completed. Results from all three types of experiments were modeled using an extended constant- capacitance surface complexation model. The reactions [Formula: see text] [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto goethite, while [Formula: see text] and [Formula: see text] best described Cd(II) adsorption onto kaolinite. A combination of the first, second, and fourth of these reactions best fitted the data for Cd(II) adsorption onto illite. In each case the model fitted all experimental data well. The results suggest that adsorption onto the variable charge (SOH) sites on illite more closely resembles adsorption onto goethite than onto kaolinite.

New insights into the sorption mechanism of cadmium on red mud

“…Thus, the XANES spectra of the sorption samples were fitted using a least-squares algorithm to obtain linear combinations of edge spectra from the three spectra. Cd(OH)Cl was chosen as a reference compound because many studies have proposed that Cd(OH)Cl-like compound was formed on clay minerals during Cd sorption (Lackovic et al, 2002;Gräfe et al, 2007;Serrano et al, 2009). Additionally, the experimental spectrum shape of the compound was well reproduced by FEFF calculation: intensities and positions of the features are satisfactory (Fig.…”

“…It was proposed that Cd 2þ could be sorbed to surface hydroxyl groups in Fe-and Al-oxyhydroxide minerals at neutral pH based on surface complexation model via the following reactions (Lackovic et al, 2002;Srivastava et al, 2005;Serrano et al, 2009):…”

“…The greater affinity of hydroxyl metal ions from dissociation over metal ions is also apparent due to the lower degree of hydration of the former which leads to both steric and electrostatic favoritism in the sorption process (Ma and Uren, 1998;Naidu et al, 1994). It is necessary to note that formation of the two complexes could occur simultaneously (Lackovic et al, 2002;Serrano et al, 2009).…”

Research Project on CO2 Geological Storage and Groundwater Resources: Water Quality Effects Caused by CO2 Intrusion into Shallow Groundwater

“…The values developed in Xu et al (2006 are typically two orders of magnitude smaller than measured surface areas based on surface roughness evaluation, because only part of the total mineral surface is involved in the chemical reaction, due to coatings, reduced exposure to the aqueous phase, and channeling of reactive flow. The reactive surface areas of illite, kaolinite, smectite and goethite are taken from published BET surface areas (Bradbury and Baeyens, 2005;Gu and Evans, 2007;Lackovic et al, 2003;Muller and Sigg, 1991) in conformity with the surface area used for surface complexation reaction involved in adsorption/desorption. Kinetic rate parameters for most minerals are taken from Xu et al (2006, which are based on work by Palandri and Kharaka (2004), with the exception of galena and arsenopyrite.…”

Competitive adsorption of metal ions onto goethite–humic acid-modified kaolinite clay

“…The interaction of HS (Saada et al 2003;Wang and Xing 2005;Alekseeva and Zolotareva 2013) and goethite (Grossi and Sparks 1994;Jung et al 1998;Lackovic et al 2003;Gimenez et al 2007) with clays has been well studied. Wang and Xing (2005) pointed out in their study that the aliphatic fraction of humic acid is preferentially adsorbed by clay minerals, while the aromatic fractions are left in solution.…”