Sustainable and Optimized Microwave-assisted Hydrothermal Method for Production of Dual-Adsorptive Reduced Graphene Nanomaterials for Wastewater Remediation

In this study, a facile, low cost and eco-friendly microwave-assisted hydrothermal method has been used and optimized for large-scale production of reduced graphene oxide (rGO) nanosheets. Different rGO samples have been prepared by the modified Hummers method, followed by microwave-assisted reduction at different MW temperatures of 190, 200, 210, 250 °C for 3, 10, 15, 17, 20 and 25 min irradiation time. The morphological, crystallographic and structural analyses of the different produced rGO samples have been investigated using surface area S_BET, TEM and XRD techniques. The HRTEM images confirm the formation of rGO nanosheets with few lots of wrinkles. The XRD confirmed the complete transformation of GO into rGO after only 15 min of microwave irradiation. The surface area analyses showed a remarkable increase in the S_BET and the total pore volume by reduction of GO into rGO (from 0.7 to 26.3 m².g^-1 and from 0.012 to 0.17 cm².g^-1). The produced rGO samples have been tested for dual adsorptive removal of Fe³⁺ metal ions and methylene blue (MB) dye pollutant. A high adsorptive removal efficiency of 95.5% and 99.5% for Fe³⁺ and MB has been achieved using rGO-17 min, 200 °C optimum sample. The Langmuir isotherm model highlighted adsorption capacities (qm values of 126.1 mg.g^-1 for Fe³⁺ and 27.24 mg.g^-1 for MB), confirming the effectiveness of the optimized rGO sample. Additionally, Form the practical point of view and for the first time, the optimized rGO sample has been tested on real wastewater sample. The removal efficiency of both Fe³⁺ and dye content was approximately 57% after 8 h and 49% after only 2 hours, respectively. This demonstrates an optimized low-cost and sustainable method for wastewater remediation.

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