Kinetic studies of graphene oxide towards the removal of rhodamine B and congo red

Batch adsorption experiments were performed to determine the effect of salt, temperature, initial dye concentration, contact time and adsorbent dosage on the removal of the rhodamine B and congo red dyes from aqueous solution on graphene oxide. It was observed that the adsorption of rhodamine B and congo red onto graphene oxide increased as the temperature was increased, indicating that adsorption is endothermic in nature. The equilibrium time for the removal of rhodamine B and congo red was observed to be 50 min and 120 min, respectively. The pseudo-first-order and pseudo-second-order equations were employed for the kinetics studies of adsorption to determine the rate-controlling step. The results showed that adsorption process followed the pseudo-second-order kinetics model. Further, it was noticed that the uptake of rhodamine B dye onto graphene oxide was greater than congo red due to the interaction between rhodamine B and graphene oxide. The regeneration tests indicated that the graphene oxide could be regenerated efficiently and used repeatedly.