Removal of water-soluble dyes by adsorption using chitosan

Abstract

In this study, removal of water-soluble dyes from aqueous solution by adsorption was investigated. Adsorbents were chitosan having degree of deacetylaiton of 79% 87% and 95%. A set of experiments was conducted at atmospheric pressure initial solution pH of 5, 7 and 9, and temperatures of 30 ํC, 40 ํC and 50 ํC. Water-soluble dyes in this study are acid, direct, reactive and basic dyes. Each types of dye were dissolved in distilled water to obtain feedstock solution having initial concentration of 100 milligram per liter.The results show that all three types of chitosan can be used to remove all types of dye from aqueous solution. Removal of water-soluble dye depends on type of dye, initial pH, temperature, degree of deacetylation of chitosan, initial dye concentration, and particle size of adsorbent. Acid, direct, and reactive dyes can be adsorbed on chitosan better in acidic solution (low pH value) and basic dye can be adsorbed better in alkalinesolution. Adsorption ability of acid dye is independent of temperature. Adsorption ability of direct dye increases with increasing operating temperature but adsorption ability of basic dye decreases with increasing operating temperature. Acid, direct, and reactive dyes can be adsorbed on chitosan better at low degree of deacetylation (79%DD) and basic dye can be adsorbed better at high degree of deacetylation (95%DD). Adsorption ability of each type of dye slightly increases with increasing of initial concentration and decreases with increasing particle size of chitosan.