Preparation of calcium alginate-graphene oxide composite and its application for the removal of Maxilon Blue

Although graphene oxide (GO) showed excellent adsorption capacities for a few model dyes and heavy metals, its application is limited due to high dispersibility in an aqueous system. In this article preparation of non-dispersible calcium alginate-graphene oxide (CA-GO) composite, its characterization and application for adsorption of an industrial dye have been presented. The CA-GO composite was prepared by adding a mixture of GO with sodium alginate and CaCO3 (SA:CaCO3:GO = 10:2.5:1) to 2% HCl. The prepared composite was characterized by scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy analysis. The surface charge of the composite was also determined by zeta potential analysis. The adsorption properties of the composite were investigated for an industrially used cationic dye, Maxilon Blue (GRL) (MBG). Effects of dye concentration, contact time, adsorbent dosage, pH of dye solution and temperature on adsorption capacity of the composite were studied. The equilibrium of the process preferably followed the Langmuir model. The theoretical maximum adsorption capacity was 1,253.13 mg/g at pH 7.0. For the mechanism of dye adsorption, the data fitted perfectly with a pseudo-second-order kinetic model. Thermodynamic studies revealed that the adsorption of MBG on CA-GO composite was spontaneous and physical in nature. The exhausted adsorbent was regenerated by simple treatment with 2% HCl followed by washing with demineralized water and the regenerated composite showed almost similar adsorption capacity.