title: Chromium(VI) adsorption from aqueous solution onto Moroccan Al-pillared and cationic surfactant stevensite.
abstract: Batch adsorption of the chromium(VI) onto Moroccan stevensite pillared by Keggin aluminium hydroxypolycation (Al-stevensite) and cationic surfactant cetyltrimethylammoniumbromide (CTA-stevensite) was investigated. The results showed that the CTA-stevensite has a higher affinity than that of Al-stevensite for chromium(VI) adsorption. The adsorption capacities for natural stevensite, Al-stevensite and CTA-stevensite calculated according to the Dubinin-Kaganer-Radushkevich isotherm (DKR) are 13.7, 75.4 and 195.6mmolkg(-1), respectively. The study of the pH effect showed that the optimal range corresponding to the Cr(VI) maximum adsorption on Al-stevensite is pH 3.5-6 and that on CTA-stevensite is pH 2-6. The adsorption rates evaluated according to the pseudo-second-order model are 7.2, 207.2 and 178.5mmolkg(-1)min(-1) for the natural stevensite, Al-stevensite and CTA-stevensite, respectively. The low values of the adsorption energy calculated by (DKR) suggest that anion exchange is the main mechanism that governs the chromate adsorption.
authors.affiliation: Faculté des Sciences Semlalia, Avenue My Abdellah, BP-2390, Marrakech, Morocco. Benhammou_ab@yahaoo.fr
authors.forename: Abdelaziz
authors.initials: A
authors.lastname: Benhammou
authors.forename: Abdelrani
authors.initials: A
authors.lastname: Yaacoubi
authors.forename: Lahbib
authors.initials: L
authors.lastname: Nibou
authors.forename: Boumediane
authors.initials: B
authors.lastname: Tanouti
mesh_terms: D000327:Adsorption; D000535:Aluminum; D002412:Cations; D002857:Chromium / Q000302:isolation & purification*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D012996:Solutions; D013501:Surface-Active Agents / Q000737:chemistry*; D014867:Water; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*
chemical_list: D002412:Cations; D012996:Solutions; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical; D014867:Water; D002857:Chromium; D000535:Aluminum