Preparation and Evaluation of Graphene-Agricultural Waste Biomass Nanocomposite for Removal of Cr(VI) Oxyanion from Aqueous Solutions

Adsorption is one of the promising techniques that use for removal of most toxic metals like chromium from industrial wastewater. Herein, the author concerned with the preparation of costly effective adsorbent for this process. A promising nanocomposite of reduced graphene oxide-sugarcane bagasse (rGOSC) was prepared for the first time using ultrasonic assisted method followed by freeze-drying technique. A facile and efficient modified Hummer method technique was used to prepare reduced graphene oxide (rGO). The prepared nanocomposite was characterized using different techniques such as; thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transforms infrared spectroscopy (FTIR). The morphological structure was also confirmed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The data confirmed the successful formation of rGOSC nanocomposite. The effectiveness of rGO/SC as an adsorbent is assessed for Cr(VI) oxyanion elimination from aquatic solutions and industrial wastewater. Different experimental conditions were studied (pH, adsorbent dosage, Cr(VI) initial concentration, contact time and adsorption temperature). The kinetic models were applied for adsorption of Cr(VI) on rGOSC and the data is fit with Pseudo-second order model. Both Langmuir and D-R models gave the best fit with the equilibrium isothermal data among the four isotherm models applied. The topmost sorption ability of 26.7 mg/g was achieved on rGOSC at pH 2. The value of adsorption energy from (D-R) isothermal pattern showed ion exchange-sorption of Cr(VI) ions on rGOSC. The parameters of thermodynamic studies demonstrated random, spontaneous and endothermic removal process. Desorption of Cr(VI) from loaded rGOSC was studied at different pHs, indicating the maximum desorption that was achieved is 69.8% at pH 10. The result clarified that the economic feasibility of rGOSC-nanocomposite that is synthesized from purchasing graphene powder is higher than rGOSC-nanocomposite that is prepared in this research. Accordingly, the prepared low-cost rGOSC-nanocomposite adsorbent was used as an environmentally friendly material in treating polluted industrial water.