Adsorption isotherm studies of chromium (VI) from aqueous solutions using sol–gel hydrotalcite-like compounds

Isotherms and thermodynamics for the sorption of heavy metal ions onto functionalized sporopollenin

“…Theoretically, the sorbent has a finite capacity for the sorbate. The Langmuir isotherm assumes that metal ions are chemically adsorbed at a fixed number of welldefined sites, where each site can hold only one ion, and all sites are energetically equivalent without any interaction between the ions [18]. Freundlich isotherm is an empirical isotherm model used for the adsorption on heterogeneous surfaces or surfaces supporting sites of varied affinities [19].…”

The influence of ferric iron in calcined nano-Mg/Al hydrotalcite on adsorption of Cr (VI) from aqueous solution

“…However, if the calcined temperature is too high such as higher than 600 • C, stable M III M II 2 O 4 spinel and M II O phases are formed and hydrotalcites can not be reconstructed [5]. Recently, the high anion exchange capacity and "memory effect" make hydrotalcites and their calcined products as the promising adsorption materials for anions removal, such as the removal of chromium (VI) [6,7].…”

Removal of chromium(VI) using nano-hydrotalcite/SiO2 composite

“…Indeed, the most polluting species are the 14 chromates formed with chromium (VI) and chromium(III) cation. 15 Cr(VI) exposure causes marked irritation of the respiratory track 16 and ulceration and perforation of the nasal septum in workers in 17 the chromate producing and using industries and it may induce 18 cancer [2].…”

“…Furthermore there is a possibility to recover the metal 32 or even the retained chromium to be disposed for some useful 33 application such as catalysis [9,10]. 34 An original and recent approach has been the use of ionic 35 exchangers such as hydrotalcites (HT) [11][12][13][14][15]. Hydrotalcites, also 36 known as layered double hydroxides (LDH), are anionic clays with 37 positively charged octahedral hydroxide layers, which are neutral- where M 2+ and M 3+ are di-and tri-valent cations, respectively, A 41 mÀ is an anion whose charge is mÀ.…”