Adsorption studies of Malachite green on 5-sulphosalicylic acid doped tetraethoxysilane (SATEOS) composite material

• Published in: RSC advances 2015-01, Vol.5 (112), p.92788-92798
• Main Authors: Ahad, Sozia, Islam, Nasarul, Bashir, Arshid, Rehman, Suhail-ul, Pandith, Altaf Hussain
• Format: Article
• Language: English
• Subjects: Adsorption; Diffusion; Dyes; Malachite green; Mathematical analysis; Mathematical models; Tetraethoxysilane
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA17838J

We report batch adsorption studies for the removal of Malachite green from an aqueous solution using 5-sulphosalicylic acid doped tetraethoxysilane (SATEOS) composite material, prepared in our laboratory previously. Various variables studied were the initial dye concentration, adsorbent concentration, pH, contact time and temperature. The maximum percentage of colour was removed at the basic pH of 9. The removal data were fitted to Langmuir and Freundlich adsorption isotherm equations. The values of their corresponding constants were determined from the slope and intercepts of their respective plots. The monolayer adsorption capacity of SATEOS at 323 K was found to be 657.89 mg g −1 . The values of various thermodynamic parameters, such as Δ G °, Δ S ° and Δ H °, were also determined. A pseudo second-order kinetic model and Lagergren first-order kinetic model were also applied to study the adsorption process. The effective diffusion parameter D i values were estimated at different initial dye concentrations. The mechanism of adsorption was studied using Rechienberg's equation where a linearity test indicates a film diffusion controlled adsorption mechanism. The maximum interaction (IE = 1432.54 kJ mol −1 ) between SATEOS and the dye molecule, calculated using B3PW91 functional and LanL2MB basis set, was observed when the nitrogen atom of the dye lies at a distance of 1.57 Å from the hydrogen of the hydroxyl group present on SATEOS molecule.