Abstract
Highly porous carbon-silica composites (CSC) were prepared for the first time through a simple wet impregnation process and subsequent pyrolysis of low-value sugarcane by-products, namely molasses. These CSC materials demonstrate a distinct range of functionalities, which significantly differ from similar materials published in the literature. Importantly, the carbon-silica composites prepared at 800°C exhibited exceptional adsorption capacities for the azo-dye congo red (445 mg g−1), due to the graphitic carbon coating and unique functionality including C-O-C within the porous structure. Congo red adsorption capacity of the highly mesoporous graphitic carbon-silica composites significantly exceeds that of commercial activated carbon and silica, these carbon-silica composites therefore represent an effective step towards the development of porous bio-derived adsorbent for remediation of dye wastewaters. Both the porous properties (surface area and pore size distribution) and the functionality of the carbon coating were dependent on the temperature of preparation. The sustainable synthetic methods employed led to a versatile material that inherited the mesoporosity characteristics from the parent silica, demonstrating mesoporous volumes greater than 90% (as calculated from the total pore volume). Adsorption on the 800°C prepared carbon-silica composites demonstrated an excellent fit with the Langmuir isotherm and the pseudo-first-order kinetic model.
Highlights
MaterialsMolasses was obtained from Mitr Phol Thailand Industry (18% water content)
This article has been edited by the Royal Society of Chemistry, including the commissioning, peer review process and editorial aspects up to the point of acceptance
Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and Raman indicated the potential formation of graphitic carbon layers on the internal surface of K60 silica gel through a simple, green and facile wet impregnation of molasses followed by pyrolysis
Summary
Molasses was obtained from Mitr Phol Thailand Industry (18% water content). Silica gel 60 (less than 0.063 mm) and ethanol were supplied by Merck. Methylene blue (C.I. 52 015), with the molecular formula C16H18CIN3S, molecular weight of 319.85 g mol−1 and the wavelength of maximum adsorption = 665 nm, was supplied by Ajax Finechem. Congo red (C.I. 22 120), with the molecular formula C32H22N6Na2O6S2, the molecular weight of 696.68 g mol−1 and the wavelength of maximum adsorption = 498 nm, was obtained from Merck, USA
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