Sulfonated graphene oxide impregnated cellulose acetate floated beads for adsorption of methylene blue dye: optimization using response surface methodology

Abstract

New multi-featured adsorbent beads were fabricated through impregnation of sulfonated graphene (SGO) oxide into cellulose acetate (CA) beads for fast adsorption of cationic methylene blue (MB) dye. The formulated SGO@CA composite beads were thoroughly characterized by several tools including FTIR, TGA, SEM, XRD, XPS and zeta potential. The optimal levels of the most significant identified variables affecting the adsorption process were sequential determined by the response surface methodology (RSM) using Plackett–Burman and Box–Behnken designs. The gained results denoted that the surface of SGO@CA beads displayed the higher negative charges (− 42.2 mV) compared to − 35.7 and − 38.7 mV for pristine CA and SGO, respectively. In addition, the floated SGO@CA beads demonstrated excellent floating property, fast adsorption and easy separation. The adsorption performance was accomplished rapidly, since the adsorption equilibrium was closely gotten within 30 min. Furthermore, the adsorption capacity was greatly improved with increasing SGO content from 10 to 30%. The obtained data were followed the pseudo-second order kinetic model and agreed with Langmuir adsorption isotherm model with a maximum adsorption capacity reached 234.74 mg g−1. The thermodynamic studies designated the spontaneity and endothermic nature of MB dye adsorption. Besides, the floated beads exposed acceptable adsorption characteristics for six successive reuse cycles, in addition to their better adsorption selectivity towards MB dye compared to cationic crystal violet and anionic Congo red dyes. These findings assume that the formulated SGO@CA floated beads could be used effectively as highly efficient, easy separable and reusable adsorbents for the fast removal of toxic cationic dyes.