The role of anatase impurity in the leaching of Cd(II) from contaminated kaolinite. Issue 1 (February 2019)

• Record Type: Journal Article
• Authors: Suzuki, Tasuma; Nakase, Kisyo; Kakoyama, Satoshi; Takamuro, Junko; Okita, Miyu; Niinae, Masakazu
• Is Part Of: Journal of environmental chemical engineering. Volume 7:Issue 1(2019)
• Publication Date: 2019-02
• Subjects: Cadmium(II) -- Kaolinite -- Anatase -- Leaching -- Outer-sphere complex formation -- Inner-sphere complex formation; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2018.102851
• Languages: English
• ISSNs: 2213-2929

Abstract

Graphical abstract: Highlights: Anatase shows higher Cd(II) adsorption capability than that of kaolinite. Anatase dominantly absorbs Cd(II) via inner-sphere complex formation. At pH < 6.0, kaolinite absorbs Cd(II) via outer-sphere complex formation. Leaching of Cd(II) decreased with increasing amounts of anatase impurity. Anatase content in kaolinite is a factor controlling the leaching extent of Cd(II). Abstract: This study was performed to enhance the understanding of the Cd(II) leaching mechanism from contaminated kaolinite with a focus on the role of anatase impurities. Experimental data obtained from titration and batch Cd(II) adsorption experiments were analyzed using a surface complexation model coupled with ion exchange reaction. Anatase showed significantly higher Cd(II) adsorption capability than those of kaolinite and goethite (α-FeOOH), with inner-sphere complex formation as the dominant adsorption mechanism. Under acidic and near-neutral conditions, kaolinite absorbs Cd(II) mainly via outer-sphere complex formation, while both outer-sphere and inner-sphere complex formation are important at higher pH. Binding constants obtained from modeling analyses were then used to predict the leaching extent of Cd(II) from contaminated kaolinite with different contents of anatase impurity at pH 4.0–7.0. The experimental data and model predictions consistently showed that the leaching of Cd(II) decreased with increasing anatase content and this trend was more significant under acidic conditions. These results showed that the content of anatase impurity is a factor controlling the leaching extent of Cd(II) from kaolinite when exposed to acid rain.