Removal of methylene blue from aqueous solution using porous starch-g-poly(acrylic acid) superadsorbents

Abstract

Porous starch-g-poly(acrylic acid) (St-g-PAA) superadsorbents have been prepared by free radical graft polymerization of AA onto potato starch in aqueous solutions in the presence of Triton X-100. The porous St-g-PAA superadsorbent was characterized by scanning electron microscopy. Batch adsorption experiments were carried out for the removal of methylene blue (MB) from aqueous solutions using the St-g-PAA superadsorbents. The effects of the pH of MB solutions and the weight ratio of AA to starch on the adsorption capacity were investigated. In addition, the adsorption kinetics and adsorption isotherms were analyzed by studying the effects of the adsorption time and the initial MB concentration on the adsorption capacity. The results indicates that the St-g-PAA superadsorbent prepared with an AA/starch weight ratio of 6 : 1 has a porous structure and has the highest adsorption capacity for MB (1532 mg g⁻¹). In addition, the adsorption capacity increases with increasing pH and MB concentration of the MB solutions. The adsorption equilibrium can be achieved in 30 min, which is faster than many of the previously reported adsorbents for MB. The adsorption behaviors of the St-g-PAA superadsorbent for MB indicate that the adsorption kinetics and isotherms are in good agreement with the pseudo-second-order equation and the Langmuir equation, respectively.