Adsorption behavior of methylene blue onto gellan gum-bentonite composite beads for bioremediation application

Abstract

Biopolymer Gellan Gum (GG) was made into insoluble composite bead using Bentonite (BT), a clay material. This insoluble composite formation was carried out using ionotropic gelation method where calcium chloride was a cross-linker to hold the organic polymer GG and inorganic material BT together. The composite (GG-BT) beads thus formed were used to study the adsorption behavior of cationic dye Methylene Blue (MB) from aqueous solution. The investigation incorporates initial dye concentrations (100-500 mg/L), contact time (15-45 minutes) and adsorbent dosage (25-100 mg) effects on adsorption process. It was observed that initial MB concentration of 500 mg/L showed maximum adsorption after 30 minutes contact time at adsorbent dosage of 25 mg. Maximum adsorption capacity was found to be 1140 mg/gm at room temperature. The experimental data’s were analyzed by Langmuir, Freundlich and BET models of adsorption isotherms. The adsorption data for MB, best fits to Langmuir isotherm at room temperature with coefficient of correlation (R²) value of 0.961. The results suggest that GG-BT beads provide a homogeneous surface for chemisorption of MB and irreversible in nature. Hence conclusion may be made that GG-BT composite can be utilized as adsorbent for MB and could be used in dye removal bioremediation application.