Cd Adsorption Properties of Components in Different Freshwater Surface Coatings:  The Important Role of Ferromanganese Oxides

Abstract

Surface coatings developed in different natural waters were used to study the role of the composition of surface coatings in controlling Cd adsorption in aquatic environments. To investigate the adsorption property of each component, the method of extraction techniques followed by Cd adsorption and statistical analysis were employed. Hydroxylamine hydrochloride was used to remove Mn oxides selectively, sodium dithionite was used to remove Mn and Fe oxides, and oxalic acid was used to remove most metal oxides and part of the organic material. Adsorption of Cd to surface coatings was measured before and after extraction under controlled laboratory conditions. The observed Cd adsorptions to unextracted and extracted surface coatings were analyzed using nonlinear least-squares fitting to estimate the adsorption property of each surface coating constituent. In different waters, the relative contribution to Cd adsorption of each component was different, but in all the waters studied, ferromanganese oxides contributed most with lesser roles indicated for organic phase and Al oxides. The Cd adsorption ability of manganese oxides was significantly higher than that of the other components.

Cadmium complexation by bacteriogenic iron oxides from a subterranean environment

“…The results from ICP-OES analysis showed that 95.1% of the iron originally present in the BIOS (6.55 ± 0.09 mg/L) was removed in the bacteria fraction by NH 2 OH·HCl treatment. As reported by Dong et al [20], processing of the BIOS with hydroxylamine hydrochloride (NH 2 OH·HCl) avoids substantial damage to the cells of microorganisms, as inferred from microscopic examination [20]. This process should then be suitable for the preparation of a representative sample of intact and fragmented Gallionella ferruguinea cells for subsequent potentiometric metal sorption experiments (Fig.…”

“…The process was repeated for BIOS bacterial cell fractions by treating 30-ml whole sample pellets with 0.04 M NH 2 OH·HCl in 25% (v/v) acetic acid to reductively dissolve the iron oxyhydroxide phase, as described above, before washing it by centrifugation. Hydroxylamine hydrochloride, NH 2 OH·HCl, is a potent reducing agent; however, Dong et al [20] have concluded from microscopic examination that treatment with hydroxylamine hydrochloride does not cause any substantial damage to the cells of microorganisms or in turn to the organic (bacterial) matter present in the BIOS sample [20].…”

Use of speciation and complexation models to estimate heavy metal sorption in soils

“…A possible candidate is complexation by manganese oxides, which is not included in these model calculations, because data for sorption to manganese oxides are rare and generic parameter values for sorption to manganese oxides are consequently not available. Yet, several authors have found that Pb is strongly complexed by manganese oxides (Lofts and Tipping, 1998;Trivedi and Axe, 2001;Cancès et al, 2003;Dong et al, 2003). A different explanation is suggested by Schröder et al (2005) who used the formation of a ternary leadphosphate species on goethite to improve estimates of Pb sorption.…”

Modeling Pb sorption to microporous amorphous oxides as discrete particles and coatings

“…Amorphous oxide minerals of aluminum, iron, and manganese occur as coatings on other mineral surfaces or as discrete particles, and are persistent in aquatic environments [5,[7][8][9][10]. They have large surface areas, porous structures, and an abundance of binding sites; therefore, they have a significant impact on contaminant mobility [11,12].…”

“…Many studies have also revealed that hydrous iron, manganese, and aluminum oxide coatings substantially affect sorption behavior [3][4][5]10,[30][31][32][33][34][35][36][37][38]. For example, Levy and Tamura [30] observed that aluminum oxide-coated montmorillonite exhibited calcium-magnesium exchange properties different from those of pure montmorillonite.…”