Kinetics and Thermodynamic Studies for Rhodamine B Dye Removal onto Graphene Oxide Nanosheets in Simulated Wastewater

This report describes for the first time the kinetics, thermodynamic and optimized conditions for maximum removal of Rhodamine B in aqueous solution onto nanosheets of graphene oxides. Results from the GONS characterizations: UV, TEM, FTIR, EDX and XRD, revealed successful introduction of oxygen functionalities on the pristine graphite lattices. Adsorptive behaviour of RhB dye onto GONS under different experimental conditions such as pH, initial concentrations, adsorbent dosage, temperature, and contact time, were fully discussed in this work. The study showed that ≈93% of RhB was removed from simulated wastewater at; sorbent mass of 16.67mg; pH of 6.5; temperature of 298K; contact time of 60min; and concentrations ranging from 2.5 to 30mg/L. Experimental data tested against results of the kinetics and adsorption isotherm models, revealed that the sorption of RhB were best described by pseudo-second order and Freundlich models, respectively. Regeneration of the spent adsorbent was investigated using water, methanol and methanol/acetic acid (9:1) solution, as desorbing eluents. Methanol solution of acetic acid was observed to remove up to 94% of adsorbed RhB from GO surface compared to water (71.36%), and methanol (45.52%). The ease at which RhB was eluted from RhB-loaded GO using methanol/acetic acid (9:1), methanol and water shows that the adsorption mechanism is best described by physisorption.