Ceria decorated biochar derived from rice straw for cadmium removal

This study examines the modification of ceria decorated biochar (ce-bc) using pyrolyzed rice straw. After initial pyrolysis, the biochar was impregnated with Ce(NO3)3·6H2O before being thermally activated again. Several characterization methods like proximate analysis, Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray Spectroscopy (EDX) were applied to evaluate the structural and surface changes induced by cerium loading. Proximate analysis that the Ce inclusion raised ash content to 28.42% and fixed carbon to 17.93%, while moisture was reduced to 2.78%, indicating better thermal stability and hydrophobicity. FTIR spectra revealed abundant hydroxyl and amino groups on both rice-straw biochar and Ce-BC, and distinct Ce-O peaks confirmed cerium oxide formation. XRD patterns showed new diffraction peaks corresponding to cubic CeO₂, and SEM micrographs displayed increased surface roughness and porosity after impregnation. EDX analysis detected additional cerium with 3.18wt% and an elevated oxygen ratio, corroborating the successful deposition of cerium oxide. Ce-BC was tested in Cd removal in 50mL of 50ppm, with pH 5.5 and soaking time 6h, reaching a maximum uptake of 7.77 mg/g compared to 6.24 mg/g for the unmodified biochar. Overall, the results suggest that decorating biochar with ceria creates more reactive surface sites and enhances its suitability for heavy-metal remediation.