Facile immobilization of polyaspartate onto silica gels via poly(dopamine) for the removal of methylene blue from aqueous solution

Abstract

In the present work, a facile two-step approach using polydopamine (pD) as a platform was developed to immobilize polyaspartate onto silica gels (SG) for enhancing the removal of methylene blue (MB) from aqueous solution. The chemical structures of the native and modified SG were characterized by FT-IR, SEM, and TGA. The adsorption behaviors of MB on SG, the pD-coated silica gels (SG-pD), and the polyaspartate-conjugated silica gels (SG-pA) were also compared. The results demonstrated that at pristine solution pH 6.2 SG-pA showed the highest adsorption capacity toward MB, the adsorption process on SG-pA was spontaneous, and the adsorption capacity of MB was reduced with temperature increasing. The kinetics studies indicated that SG-pA had the shortest equilibrium time of 540min toward MB adsorption and the adsorption process followed the pseudo-second-order model. Furthermore, the data of the equilibrium isotherms for MB adsorption on SG-pA were in good agreement with the Langmuir isotherm model, and the maximum adsorption capacity for MB was 90.2mgg−1. In addition, SG-pA still displayed high adsorption capacity after three times of cyclic adsorption tests, implying that SG-pA was a potential reusable adsorbent for the removal of MB from effluent water relative to pristine silica gels.