Synthesis of reduced graphene oxide using gamma radiation and its application for treatment of bisphenol a present in solution: batch and optimisation using response surface methodology

In this study, Graphene Oxide (GO) was irradiated with gamma rays in order to reduce the GO to form a graphene like material. The synthesised material was termed reduced Graphene Oxide (rGO) which was then utilised for adsorbing Bisphenol A (BPA) from water. The synthesised rGO was characterised by Ultraviolet Visible (UV-Vis) adsorption spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD) and Brunner Emmet Teller (BET) analysis. From the UV–Vis spectra, FTIR and XRD analysis it was inferred that the GO was indeed reduced by the gamma radiation and from the BET analysis it was found that the rGO had a surface area of 17.32 m2/g. From the batch study results, the highest removal was observed to be 98.63% which was attained under the conditions of 10 mg/L concentration of BPA, 2 g/L dosage of rGO, pH 7, temperature 303 K and contact time of 120 min. In order to understand the interaction between the experimental parameters and to further optimise the experimental process, a Response Surface Methodology (RSM) study was performed. From the result of the RSM study, the highest removal was found to be 85.58% which was attained at pH 6, rGO dosage of 3 g/L and contact time of 90 min. The adsorption process was best described by Langmuir isotherm and pseudo-second order kinetics. From the thermodynamic analysis, it was inferred that the adsorption process was spontaneous and endothermic in nature. The activation energy was calculated to be 2.75 kJ/mole thereby denoting that the adsorption was physical in nature. The rGO also exhibited high reusability potential. Overall, from the outcome of the present study, it was inferred that the rGO was a stable and efficient adsorbent capable of effectively adsorbing BPA from water.