The use of polysaccharides for acid red 18 anionic dye removal from aqueous solutions

In the paper, the adsorption of Acid Red 18 (AR18) on chitosan (CHs), sodium carboxymethyl cellulose (CMC) and agar (AGA) was researched. The adsorption capability of biosorbents was examined as a function of initial pH, time of contact and influence of initial concentration of dye. The adsorption kinetics was compared with the pseudo 1. and 2. order models. It was found that the dye adsorption occurred in accordance with the pseudo 2. order model. The experimental data of adsorption in the equilibrium state was analysed with the use of isotherms of the Freundlich, Langmuir and double-Langmuir models. It was found that for the description of dye adsorption on adsorbents, the double-Langmuir model was suitable, which was demonstrated by the determined values of the average relative error (ARE). The highest adsorption capacity and affinity to AR 18 was obtained for CHs, at 81.7 mg/g d.w and 0.997 L/mg, respectively. The experimental results show that CHs seems to be a promising biosorbent for AR 18 dye removal from aqueous solutions.