Reduction and Sorption of Chromium by Fe(II)-Bearing Phyllosilicates: Chemical Treatments and X-Ray Absorption Spectroscopy (XAS) Studies

Abstract

Abstract--The reduction of hexavalent chromium species in aqueous solutions by interaction with Fe(lI)-bearing solid surfaces was studied using a 0.96 • l0 3 M Cr(VI) solution and iron-rich clays with different Fe(lI)/Fe(III) ratios, layer charge, and exchange properties, i.e., chlorite, corrensite, and montmorillonite. Experimental studies demonstrated that Fe(lI)-bearing phyllosilicates reduce aqueous Cr(VI) ions at acidic pH. Chlorite and corrensite, owing to the high Fe(II)/Fe(III) ratio, are electrochemically reactive, as rapid Cr(VI) reduction indicated. In contrast, montmorillonite showed minimum to nil reactivity towards Cr(VI). Furthermore, corrensite, which is high in both Fe(II)~'e(III) ratio and exchange capacity, adsorbs the greatest amount of chromium.X-ray absorption spectroscopy at A1, Mg, Fe, and Cr K-edges was used to investigate the adsorbed chromium species. The montmorillonite sample, unaffected by treatment with Cr(VI) solution, displays no change at any investigated edge. Edge shape and energy also do not change for the Mg and A1 spectra in corrensite, and changes are minor in chlorite. By contrast, the Fe K-edge changes both in chlorite and corrensite, and indicates an increase of Fe(III) in treated samples at the expense of pre-existing Fe(II). Cr K-edge spectra show that chlorite and corrensite sorb Cr(III), which implies its reduction from Cr(VI) in the interacting solution.

Transient and quasi-steady-state dissolution of biotite at 22–25°C in high pH, sodium, nitrate, and aluminate solutions

“…The oxidized forms, chromate, CrO 4 2Ϫ , and pertechnetate, TcO 4 Ϫ , are soluble and mobile, whereas reduced forms are sparingly soluble solids that may be less mobile (e.g., Jardine et al, 1999;Wharton et al, 2000). Ferrous iron can reduce these anions (e.g., Ilton and Veblen, 1994;Cui and Eriksen, 1996;Peterson et al, 1996;Buerge and Hug, 1997;Buerge and Hug, 1999;Brigatti et al, 2000;Loyaux-Lawniczak et al, 2001), and biotite is the most abundant source of Fe 2ϩ in the Hanford sediments (10 wt% average mica as biotite or muscovite, McKinley et al, 2002).…”

Environmentally benign Fe(III)–montmorillonite for rapid adsorption of methylene blue dye in aqueous medium under ambient conditions

“…Later, solid sample was dried at room temp (RT ~25 °C), ground to powder form and stored in a vacuum desiccator. In order to estimate the interlayer iron, Fe(III)-Mt was subjected for cation exchange with 0.05 M H 2 SO 4 for about 24 h. The ratio of ferrous to ferric ions (Fe 2+ /Fe total where Fe total = Fe 2+ + Fe 3+ ) released was determined by 1,10 phenanthroline method (Brigatti et al 2000) using UV-Vis spectrophotometer (λ max = 510 nm).…”

“…It is obvious that the development of new method which involves heterogeneous reaction would be suitable for large-scale synthesis. Fe-pillared montmorillonite or Fe(III) incorporated clay minerals has been extensively used in heterogeneous catalytic systems and were proved to be advantageous in both economic and environmental point of view (Vinoda and Manjanna 2014;Brigatti et al 2000). There are only a few reports on natural (Parthasarathy et al 2003;Shi et al 2011) and modified clay minerals (Manjanna et al 2009;Wu et al 2012;Vinuth et al 2015) for Cr(VI) reduction.…”

Asbestiform tremolite within the Holocene late pyroclastic deposits of Colli Albani volcano (Latium, Italy): occurrence and crystal chemistry

“…Efforts to overcome those problems have been described by several authors (e.g. Brigatti et al, 2000;Laskin and Cowin, 2003;Ro et al, 2003;Paoletti et al, 2008), who dealt in particular with the improvement of techniques for EDS analysis of amphibole fibres.…”