SORPTION OF ALIZARIN RED AND CRYSTAL VIOLET FROM THEIR AQUEOUS SOLUTION USING CHITOSAN-CHARCOAL COMPOSITE

Abstract

In this work the removal efficiency of Alizarin Red S and Crystal violet from aqueous solution using chitosan charcoal composite as adsorbent was investigated using batch adsorption studies. Deproteination was carried out by placing 200g of powdered snail shell in 4% w/v NaOH for 2hours. The sample was then placed in 1% HCl for 24h to remove CaCO3. Deacetylation was done by boiling in 50% NaOH for 2h. 10% Oxalic acid was used to dissolve the chitosan before mixing it with commercial activated charcoal at 550C to form the composite The prepared composite was characterized by Fourier Transform Infra-Red and Scanning Electron Microscopy measurements. The efficiency of adsorption was evaluated by varying pH of the solution, contact time, initial concentration and adsorbent dose. Maximum alizarin removal was achieved at pH 4 for composite while pH 2 and 5 was obtained for chitosan and charcoal respectively. Maximum removal of crystal violet by composite and charcoal was attained at pH10 while maximum removal of crystal violet by chitosan was achieved at pH 8. The results showed that adsorption of both dyes followed the pseudo-second –order rate equation and fit the Langmuir and Freundlich isotherms. The data showed that composite was best suited for crystal violet removal and also did relatively well in the removal of alizarin red. Thermodynamic parameters such as enthalpy change (ΔHº), free energy change (ΔGº) and entropy change (ΔSº) were studied, and the adsorption process of Alizarin red and Crystal violet was found to be endothermic, spontaneous and feasible.