Adsorption of water-soluble dyes on chitin and chitosan

Abstract

Effects of various parameters on the adsorption of four dyes on three adsorbents were investigated. The adsorption of acid dye, reactive dye and direct dye was highly effective in acidic solutions at pH 5 or less, of which chitosan could adsob more than chitin and shrimp shells. On the contrary, the amounts of basic dye adsorbed on adsorbents were very effective in alkaline solutions at pH 10 or higher, especially on shrimp shells. The amounts of adsorbed dye increased with increasing adsorption time and initial dye concentration but decreased with increasing particle size. The adsorbed amounts of all dyes except the basic dye increased with increasing degree of deacetylation. The ionic interaction was the main force that involved in the dye adsorption on adsorbents. Desorption of dyes at different pHs and temperatures was also studied. Desorption of dyes from adsorbents was highly effective at 80 ํC and pH>=10 except the basic dye which highly desorbed at pH<=3. The least desorption was found in the reactive dye. The removal of dyes from textile effluents was shown similar tendency to those from the synthetic dye solutions. The amounts of acid dye, reactive dye and direct dye adsorbed on chitosan reach almost 72%, 61% and 94%, respectively, shrimp shells could adsorb basic dye from effluents up to 43%. The amounts of dye removal depend on the type of dyes in effluents