Valorization of rice by-products for carbon nanostructures synthesis in dye wastewater remediation

초록

A sustainable and cost-effective approach was developed for synthesizing carbon nanostructures namely carbon nanotubes (CNTs), carbon spheres (CSs), and carbon fibers (CFs). The process employed pyrolyzed hydrochar derived from treated rice straw, kaolin, zeolite or hydrochar as supports for Fe-Ni bimetallic catalysts, while hydrochar, camphor, or cotton fiber served as carbon sources. The resulting nanostructured materials were characterized using FE-SEM, XRD, FTIR, and N-2 adsorption analyses. These tools demonstrated that morphology and structure of the carbon materials produced are governed by the carbon precursor, catalyst support, and catalyst-carbon interactions. The resultant carbon nanostructures have distinctive graphitic characteristics and surface functions that improve adsorption performance. The adsorption performance of the synthesized nanostructures was evaluated using methylene blue (MB) as a model pollutant. Among them, CNTs exhibited the highest adsorption capacity (similar to 130 mg/g), which was attributed to its a large specific surface area and abundant pi-pi interaction sites. Adsorption behavior of MB dye followed the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer chemisorption with multiple rate-controlling steps. This work highlights an efficient route for valorizing agricultural waste into functional carbon nanostructures for wastewater remediation.

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