Low cost synthesis of SiO2/C nanocomposite from corn cobs and its adsorption of uranium (VI), chromium (VI) and cationic dyes from wastewater

SiO2/carbon nanocomposite as well as nanoporous carbon has been synthesized using a simple, low cost, industry scalable method from corn cob biowaste. The composition and morphology of the materials have been confirmed via powder XRD, Raman, FTIR, TEM, EDS and XPS studies. The BET specific surface area of both samples has been obtained and the pore volume analyses has been done using BJH method. The prepared nanocomposites have been explored as a novel adsorbent for Methylene blue (MB) dye and U(VI)/Cr(VI) ions from aqueous solution. Different operating conditions of time, pH, initial dye/metal ion concentration and adsorbent amount have been investigated and the results indicate a promising adsorption capacity for all three pollutants. The kinetics data were fitted with pseudo-first order, pseudo-second order, Elovich, intraparticle diffusion and Bangham's kinetic models. The adsorption isotherms were tested with Langmuir, Freundlich, Tempkin and Dubinin & Radushkevich isotherm models. SiO2/carbon nanocomposite shows a maximum uptake capacity of 255.12 mg/g for U(VI) and 90.01 mg/g for Cr(VI) with adsorption efficiency of 94.2% and 98%, respectively. The uptake of Cr(VI) ions has also been tested in presence of interfering salts like NaCl/Na2SO4. The SiO2/carbon nanocomposite shows adequate reusability making it a cost effective alternative sorbent compared to commercial activated carbon.