Preparation of Silica-Supported Biosorbents for Copper(II) Removal Rattiya Singhon, Je ´ro ˆme Husson, Michael Knorr, and Myriam Euvrard Institut UTINAM, UMR 6213, Equipe Mate ´riaux et Surfaces Structure ´s, Universite ´ de Franche-Comte ´, Besanc ¸ on, France The objective of this study is the preparation of various types of functionalized silica particles for the capture of Cu(II) ions. Amino-functionalized silica and hybrid chitosan/silica particles have been prepared by grafting silica with amino groups and/or adsorption of chitosan on the surface of silica to develop efficient adsorbents for heavy metals ions in water. The adsorption of Cu(II) on these materials was carried out at pH 5 at 298 K. The kinetics were evaluated utilizing pseudo-first-order and pseudo-second-order models. The best interpretation for equilibrium data was given by both Langmuir and Freundlich isotherm models. The adsorption kinetics followed the mechanism of the pseudo-second-order equation for all systems studied. This study demon- strates that the adsorption capacities for Cu(II) ions are more efficient for the bio-hybrid material compared to amino-functionalized silica. Keywords Adsorption, biopolymer, chitosan, Cu(II), silica INTRODUCTION Both alumina- or silica-nanoparticles as well as chitin- or chitosan-functionalized microparticles open potential applications in applied sciences and diverse industrial sectors. Examples are their use as composite coatings, [1,2] filtration membranes, [3] capillary column fillers, [4] as adsorbent, and as water purification materials. [5,6] In phar- maceuticals and medicals domains they have successfully been used for drug delivery. [7,8] Nickel-Platinum-doped silica-supported chitosan has also been employed for the catalytic hydrogenation of nitriles. [9] The ease of functiona- lization of these particles via this strategy can realistically lead to the formulation of new materials with innovative features. In this context, the design and study of novel composites such as silica-supported low-cost and environ- mentally friendly biosorbents appears very interesting. Chitosan (CS) is the second most abundant natural amino-polysaccharides (Figure 1). This N-deacetylated chi- tin derivative constitutes the major component of arthro- pod and crustacean shells stemming from lobsters, crabs, shrimps, and cuttlefishes which are waste products of seafood processing industries. [10-12] CS possesses reactive amino and hydroxyl groups, amenable to chemical modifications. [13] Due to the presence of amino groups, chitosan may also act as cationic polyelectrolyte (pKa  6.5) and may bear a high positive charge due to presence of NH þ 3 groups. Therefore it adheres to negatively charged surfaces and it aggregates with polyanionic compounds. Not surprisingly, it has been reported that heavy metal ions could be effec- tively removed by complexation with chitosan. [14–19,39] CS also appears to be an economically attractive sorbent. [20] In order to widen its potential applications, many attempts have been undertaken to modify and optimize its pro- perties, such as by cross-linking, [21–25] chitosan layer coating, [26–27] deposition of hydroxyapatite, [28] grafting chitosan on stearic acid, [29] and finally various chemical functionalizations of chitosan. [30–35] In order to improve its mechanical and surface proper- ties, CS may also be grafted on a mineral support such as SiO 2 . Silica is known as a good supporting material because of its large surface area, high mass exchange char- acteristics, nonswelling, and excellent mechanical resist- ance. Amorphous silica, which often constitutes the supporting material for surface coating, is an inorganic polymer bearing reactive silanol groups (Si–OH) on its sur- face. The presence of these reactive silanol groups on the surface permits the covalent modification of this inorganic polymer by introduction of new functional groups. [36,37] When the silica surface is functionalized with amino groups, it is expected that the basic character of these func- tions would affect the overall chemical stability and Received 17 November 2010; accepted 22 November 2010. From the Proceedings from Formula VI in Stockholm 2010. Address correspondence to Myriam Euvrard, Institut UTINAM, UMR 6213, Equipe Mate ´riaux et Surfaces Structure ´s, Universite ´ de Franche-Comte ´, 16 route de Gray, Besanc ¸ on 25030, France. E-mail: myriam.euvrard@univ-fcomte.fr Journal of Dispersion Science and Technology, 32:1735–1741, 2011 Copyright # Taylor & Francis Group, LLC ISSN: 0193-2691 print=1532-2351 online DOI: 10.1080/01932691.2011.616133 1735 Downloaded by [SCD DE L'Universite De Franche Comte], [Myriam EUVRARD] at 05:18 21 November 2011