Green synthesis of mesoporous graphene oxide/silica nanocomposites from rich husk ash: Characterization and adsorption performance

Rice husk is an agricultural waste. Rice husk ash (RHA) is the main residue when rice husk is burned to produce biomass energy. The conversion of RHA into high-valueadded products is a sustainable method and can help develop a circular economy. In this study, a graphene oxide/SBA-15 composite was synthesized from RHA. Experimental investigations revealed that the various oxygen-containing functional groups of the graphene oxide/SBA-15 composite resulted in considerably enhanced adsorption capacity. Furthermore, the composite possessed a pore volume of 0.978 cm(3)/g, pore size of 10.5 nm, and surface area of 625 m(2)/g. The pore structure of the composite was mainly a hexagonal array of mesopores, which did not change with the addition of GO. TEM images revealed that the SBA-15 surface was homogeneously covered with GO flakes. Raman spectroscopy demonstrated that composite contained disordered carbon with a high degree of oxidation. The effects of adsorption conditions - adsorbent dosage, initial dye concentration, adsorption temperature, and solution pH - on the Rhodamine B adsorption of the graphene oxide/SBA-15 composite were investigated. The composite exhibited the highest adsorption capacity of 151.28 mg/g at 80 degrees C. The adsorption was endothermic with enthalpy of 11.83 kJ/mol. The isotherm adsorption experiment revealed that the Langmuir model was the best fit for the adsorption results. Kinetic investigations revealed that the adsorption process followed the pseudo-secondorder model. The adsorption rate was mainly controlled by the intraparticle diffusion step. Commercially available SBA-15 materials are expensive. This study provides an economically viable method of treating RHA that improves its potential for applications involving removal of dyes from wastewater. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study investigates the synthesis of a graphene oxide/SBA-15 composite from rice husk ash and its adsorption properties for Rhodamine B dye. The composite showed enhanced adsorption capacity due to the various oxygen-containing functional groups. The adsorption process followed the pseudo-second-order model, with the adsorption rate mainly controlled by the intraparticle diffusion step.