Thermoluminescence, infrared reflectivity and electron paramagnetic resonance properties of hemimorphite

Hemimorphite as a natural sink for arsenic in zinc deposits and related mine tailings: Evidence from single-crystal EPR spectroscopy and hydrothermal synthesis

“…Two previous EPR studies of natural hemimorphite reported the following paramagnetic centers: Cu 2+ , Mn 2+ , Fe 3+ and E 0 (Vassilikou-Dova and Eftaxias, 1991; Gallegos et al, 2009). These centers, except for E 0 , have been observed in samples of hemimorphite examined by our reconnaissance EPR measurements.…”

“…In either case, incorporation of As in the hemimorphite lattice attenuates its mobility and bioavailability. Similarly, hemimorphite may play important roles in the transport and bioavailability of heavy metals (Pb, Cu and Cd) in Zn mine tailings (Table 1; Schaider et al, 2007;Cabala et al, 2009;Chen et al, 2009;Gallegos et al, 2009).…”

Nature of Heavy Metals in Hemimorphite: A Cation-Exchange and Single-Crystal Epr Study

“…Previous EPR studies (Vassilikou-Dova & Eftaxias 1991, Gallegos et al 2009, Mao et al 2010 reported the presence of Cu 2+ , Fe 3+ , E', Mn 2+ , [AsO 4 ] 4-, [AsO 4 ] 2-, and Pb 3+ centers in hemimorphite. Our reconnaissance EPR measurements of both as-is and gamma-rayirradiated hemimorphite from the 10 samples confirmed the common presence of the Fe 3+ , Mn 2+ , Cu 2+ , [AsO 4 ] 4-, [AsO 4 ] 2and several unknown centers (see also Gallegos et al 2009).…”

“…Single-crystal electron paramagnetic resonance (EPR) spectra of gamma-ray-irradiated hemimorphite revealed the presence of two arsenic-associated oxygen radicals, [AsO 4 ] 4and [AsO 4 ] 2-, derived from substitutional [AsO 4 ] 3groups at the Si site and provided unambiguous evidence for the sequestration of arsenate in its structure. Similarly, using powder EPR data, Gallegos et al (2009) reported paramagnetic Cu 2+ and Pb 3+ ions in natural and gamma-ray-irradiated hemimorphite, respectively, and interpreted them to reside at interstitial sites in the crystal structure on the basis of their ionic radii.…”

“…Specifically, cation-exchange experiments were intended to test whether or not Cu, Cd and Pb reside at the channel sites, as proposed by Gallegos et al (2009). Single-crystal EPR measurements were designed for identification and quantitative analysis of paramagnetic Cu, Cd and Pb centers ).…”