Kinetics of adsorption-desorption of chromate on .gamma.-alumina surface using the pressure-jump technique

Adsorption of Cr(VI) on γ-alumina in the presence and absence of CO2: Comparison of three surface complexation models

“…The TLM requires more parameterization then either the CCM or the DLM, but it has the advantage of allowing sorbates to be explicitly described as inner-or outersphere by placing charges on either the "0" or the "b" plane, and thus allows explicit competition of sorbates with electrolyte cations and anions for adsorption on the "b" plane. Cr(VI) adsorption on substrates including c-alumina (Mikami et al, 1983;Wu et al, 2000;Alvarez-Ayuso et al, 2007), a-alumina (Musorrafiti et al, 2008;Elzinga et al, 2009) and iron oxides (Zachara et al, 1987;Ainsworth et al, 1989;Mesuere and Fish, 1992) is typically assumed to occur via outersphere complexation, although a few studies do suggest innersphere adsorption of Cr on goethite (Fendorf et al, 1997) or a combination of inner-and outersphere complexes (Villalobos et al, 2001). Three reaction stoichiometries were tested using a TLM, two forming outersphere complexes:…”

“…Furthermore, because c-alumina contains both octahedrally and tetrahedrally coordinated aluminum, it has been used as an analog for surface aluminol groups on aluminosilicate minerals (Brady and Walther, 1989;Casey et al, 1989). A few studies demonstrate significant Cr(VI) sorption on c-alumina (Mayer and Schick, 1981;Mikami et al, 1983;Wu et al, 2000;Fritzen et al, 2006;Elzinga et al, 2009), as well as on a-alumina (Honeyman, 1984;Ajouyed et al, 2007;Musorrafiti et al, 2008), which also has a high pH ZPC (5-9.3: Kosmulski, 2002Kosmulski, , 2004Kosmulski, , 2006 but contains only octahedrally-coordinated aluminum.…”

Adsorption of Cr(VI) from synthetic solutions and electroplating wastewaters on amorphous aluminium oxide

“…In this way, adsorption appears as a highly promising alternative to purify such wastewaters. Several studies have been reported using different low-cost adsorbents for the Cr(VI) removal, including activated carbon [8,9], wool [10], agricultural byproducts such as coconut husks and palm pressed fibres [11], sugar cane bagasse, sugar beet pulp, maize cob, saw dust, olive cake, pine needles, almond shell and cactus leaves [12,10], waste materials such as fly ashes [13], red mud [14,15] and biogas residual slurry [16] and minerals such as feldspar [17], hydrotalcite-like compounds [18][19][20][21][22], crystalline iron oxyhydroxides [23][24][25][26][27][28][29] and ␥-Al 2 O 3 [30,31]. From the light of these studies adsorption emerges as a robust and versatile method that could solve the problems of sludge handling and render the purification system more economically viable, especially if lowcost adsorbents are involved.…”

Thiocyanate removal from aqueous solution by a synthetic hydrotalcite sol

“…The formation of surface complexes in anion/hydrous solid systems, such as CrO 2À 4 /cAl 2 O 3 , AsO 3À 4 /a-FeOOH, PO 3À 4 /a-FeOOH, and CrO 2À 4 /MgO, was verified by previous studies [27][28][29], although there was controversy about the configuration of anions on hydrous oxide surfaces in past studies. The association between the positively charged surface of LDHC and the SCN À anions may be written as…”