Adsorption of textile dyes with ultrasonic assistance using green reduced graphene oxide: An in-depth investigation on sonochemical factors

This study reports adsorption of Methylene Blue (MB) and Basic Fuchsin (BF) on green reduced graphene oxide. Using modified Hummer's method, Graphene Oxide (GO) was synthesised and reduced using Tamaridus Indica. The synthesised GO and RGO were characterized using XRD, UV-vis spectroscopy, TEM, XPS, FT-IR and BET analysis. Through XRD result, the reduction in a peak corresponding to (001) plane and appearance of new peak at (002) plane confirmed the reduction process. TEM results displayed a hexagonal SAED and lamellar structure in RGO with a d-spacing of 0.346 nm in the (002) plane. Effect of variables such as pH, initial dye concentration, dosage, temperature, sonication time, ultrasonic power and frequency were studied and optimum conditions for the removal of MB and BF were found. From the Langmuir isotherm model, the maximum adsorption capacity was noticed to be 238.095 and 243.90 mg/g respectively for MB and BF. Further, the presence of humic acid and various ions decreased the removal efficiency for both the dyes. The experimental results indicated that the pseudo second order suited well than other kinetic models. Among various error analysis, ARE model provided minimum error for Langmuir isotherm (MB: 7.52, BF: 9.82) and kinetic study (MB: 10.47, BF: 6.04). FTIR and XPS analysis indicated that electrostatic attraction, hydrogen bonding, n-pi and pi-pi interactions played significantly during adsorption process. The facile synthesis and higher adsorption capacity indicates that the material could be a potential candidate for the removal of textile effluents.