Adsorption of Methyl Orange from Aqueous Solution using Chitin and Polystyrene-Modified Chitin: Kinetics and Isotherm Studies

Abstract

Chitin is a natural, biodegradable and non-toxic biopolymer. Batch adsorption experiments were conducted to remove methyl orange from aqueous solution. The influence of physicochemical parameters, such as solution pH, dye concentration, adsorbent dosage and contact time were investigated. The results showed that the modified chitin has improved adsorption capacity and the percentage dye removal strongly depends on pH, nature and structure of the dyes. The maximum adsorption of methyl orange by both raw chitin and polystyrenemodified chitin occurred at the pH of 6, with percentage dye removal of 26.38% and 35.20% respectively, for an initial concentration of 10 mg/L. The pseudo-first-order model gives poor fittings for both chitin and the modified chitin as indicated by the low coefficients of determination (R²). The pseudo-second-order model fits the experimental data well, having R² close to unity. The Langmuir isotherm was found to conform better than the Freundlich model in the adsorption of both dyes on both chitin and the modified chitin with R² of nearly unity.

Keywords: Adsorption, Chitin, Isotherms, Kinetics, Methyl orange, Modified chitin