Effect of chemical modification of palygorskite and sepiolite by 3-aminopropyltriethoxisilane on adsorption of cationic and anionic dyes

A study has been performed on the removal of representative cationic and anionic dyes, methylene blue and metanil yellow, from aqueous solutions using fibrous clay minerals grafted with amine groups using (3-aminopropyl)triethoxysilane as functionalizing agent. Parameters affecting dye uptake, including contact time and dye concentration, the desorption process, pH and the recovery of both the dyes and the adsorbents, were evaluated. The adsorption capacities were 49.48 and 47.03 mg/g for grafted palygorskite and 60.00 and 59.78 mg/g for grafted sepiolite, for methylene blue and metanil yellow dyes, respectively. Adsorption of the anionic dye was enhanced by the grafting process. Grafted clay mineral adsorbents proved to be efficient to remove the contaminants from a real wastewater from textile industry within 30 min. Both adsorbents showed good reusability and the maximum adsorption capacity was maintained stable after a 2-cycle test. Thus, hybrid adsorbents based on fibrous clay minerals can efficiently be applied in adsorption/desorption cycles for removal of dyes. (C) 2016 Elsevier B.V. All rights reserved.