Chitosan-containing organoclays: Structural characterization and retention/removal of methylene blue

• Published in: Desalination and water treatment 2019-02, Vol.141, p.342-355
• Main Authors: Kabbadj, Sarra, Hajjaji, Mohamed, Alagui, Abdelhakim
• Format: Article
• Language: English
• Subjects: Adsorption; Chitosan; Desorption; Methylene blue; Organoclays; RSM
• ISSN: 1944-3986
• DOI: 10.5004/dwt.2019.23501

Organoclays, composed of chitosan and stevensite-rich clay (RH) or kaolinitic-illitic clay (BN2), were structurally characterized, and their adsorption abilities for methylene blue (MB) were investigated by XRD, FT-IR, UV-vis spectroscopy and SEM. The effects of pH, ionic strength (I) and temperature (T) on MB desorption were evaluated by using the response surface methodology (RSM). The results showed that the chitosan was placed within interlamellar spaces of swelling clay minerals, and around clay and ancillary particles, and the kinetics of MB adsorption was generally controlled by film-diffusion. MB adsorption occurred spontaneously (–41 < ∆G° < –32 kJ/mol), and the Langmuir maximum adsorption capacity of RH-based composite (138 mg/g at 298 K) was about three times higher than that of BN2-based composites. MB species were adsorbed by cation exchange, and they were located at surfaces of composite particles as MB+, (MB+)2 and (MB+)3. Also, they were attached to surficial chitosan mainly by means of amino-groups. The results of RSM showed that the increase of one among the above factors had a negative impact on MB desorption, and the weights of the effects of the factors followed the order pH > T > I.