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Home  >  Volume 32 (Nov. 2015)

Studies in the Removal of Anionic Dye (Bromocresol Purple) From Acidic Solution Using Chemically Crosslinked Chitosan Beads by G. Okunzuwa, I.S. Okunzuwa, O. Moses and A. Jideonwo (pages 299-308)
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Chitosan was prepared by deacetylation of chitin from gaint snail shells. The chitosan was used to prepare glutaraldehyde chitosan beads with varying degrees of crosslinking densities of 0.8 and 0.4.  These materials including the uncrosslinked chitosan were applied for the removal of anionic dye, bromocresol purple from aqueous solution at pH4. The adsorption capacity of these materials depended on adsorbent (dye) dosage, contact time, crosslink densities and pH.  FTIR  analysis of this material was also carried out. The result obtained from the adsorption showed that chitosan removed 91.20%, gluteraldehyde chitosan 0.8 and 0.4 removed 71.64% and 53.30% of the dye respectively. The percentage removal of the dye was of  the order:  chitosan >glutaraldehyde chitosan 0.8 > glutaraldehyde chitosan 0.4. FTIR reveals that the uncrosslinked chitosan shows a band at  3480cm-1 which is due to the OH stretching and the band at 1632cm-1 which is assigned for the NH bending of the amino group NH2. The absorption of Glutraldehyde chitosan at 2387.19cm-1 and 2352.7cm-1 are due to NH3+ stretching and the absorption at 1409cm-1 represent the -CH bending of –CH2 in glutaraldehyde. The absorption at 1604cm-1 for glutraldehyde chitosan is owing to (CH2)3HC=N- stretching which is a characteristic absorption for Chitosan crosslinking with glutaraldehyde as a result of the reaction of glutaraldehyde with  NH2 group in chitosan to form a crosslink. Results obtained were evaluated with the use of adsorption isotherms − Langmuir and freundlich adsorption isotherm. The chitosan data fitted best with the Langmuir model while the glutaraldehyde chitosan 0.8 and 0.4 data  fitted best with the freundlich model, these were predicted by the highest correlation coefficient- R2 value. The R2 value are regarded as a measure of the best  fit  of experimental data on the isotherm model. This indicates that adsorption of chitosan proved uptake onto homogenous adsorbent surface while that of glutaraldehyde chitosan proved uptake onto heterogeneous adsorbent surfaces.

 Keywords: Chitosan, Glutaraldehyde chitosan, Anionic dye, adsorption isotherm; Langmuir and freundlich isotherm