Abstract
Ph.D. (Chemistry)
This study involves the synthesis of titania and silica nanocomposite derived from sodium
alginate and xanthan gum, respectively, for their application in the removal of cationic
dyes from aqueous media during the water treatment process. Acrylic acid grafted sodium
alginate based hydrogels were synthesized via a free radical polymerization process using
potassium persulphate as an initiator. A crosslinking agent N,N'-methylene-bis-acrylamide
was used in the polymerization step. With the view to obtaining crosslinked hydrogel
possessing high swelling and grafting behavior, various reaction parameters (time, solvent,
pH, crosslinker, initiator and monomer concentration) were optimized. The optimized
hydrogel sample with the greatest percentage swelling and grafting was employed for the
incorporation of TiO2 nanoparticles to form the hydrogel nanocomposite. The respective
xanthan gumsilica nanocomposite was synthesized using sol-gel method; the reaction
pathway proceeds via dehydroxylation and condensation reaction of tetraethoxysilane.
Ammonium hydroxide and ethanol were used as base catalyst and co-solvent, respectively.
The control silica oligomer was prepared in a similar manner, except for the presence of
xanthan gum. The resultant nanocomposites were characterized using different techniques
such as Dynamic Mechanical Analysis (DMA), Fourier Transform Infrared Spectroscopy
(FTIR), X-Ray Diffraction Studies (XRD), Thermogravimetric Analysis (TGA), Brunauer-
Emmett-Teller (BET), Scanning Electron Microscopy (SEM) and Transmission Electron
Microscopy (TEM). Finally, the nanocomposites were tested for their efficiency in the
extraction of cationic dyes from aqueous solution using the batch method. The kinetics and
the adsorption isotherms for the adsorption of dyes from aqueous solution were studied in
detail. The process for the adsorption of dyes is strongly dependent on the point of zero
charge of the nanocomposites, and the mechanism of adsorption of dyes by the...