Silica gel matrix immobilized Chlorophyta hydrodictyon africanum for the removal of methylene blue from aqueous solutions: Equilibrium and kinetic studies

Abstract

Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results from sorption studies show that 124.11 mg·g^-1 of MB could be adsorbed at an optimum pH of 8 and immobilization of 300 mg per gram silica. Maximum immobilization was 400 mg biomass per gram silica. Sorption capacity increased with an increase in initial dye concentration and reached equilibrium within 30 min. Three models were used to  simulate kinetic data and the pseudo–second order model gave a better fit with R² greater than 0.98 in all cases. Equilibrium studies revealed that the adsorption of MB followed Freundlich isotherm (R²=1.00).

Key words: Adsorbent, algae, Langmuir model, Freundlich isotherm.