Synergistic pyrolysis of Cellulose/Fe-MOF Composite: A Combined experimental and DFT study on dye removal

Abstract

We propose the development of an innovative composite material formed through the pyrolysis of oxidized cellulose derived from sawdust, utilizing iron-based MOF as a precursor. This novel material incorporates multiple iron-based components (Fe₃O₄, Fe₃C and Fe⁰) within a biochar matrix. We employed the composite to adsorb a cationic dye from aqueous solution. Batch adsorption studies explored the effects of pH, contact time, and initial dye concentration. The experimental data fitted well with the pseudo-second-order kinetic model, suggesting chemisorption as the primary mechanism, while equilibrium adsorption results fitted to the Langmuir isotherm model, described monolayer adsorption displaying the highest adsorption capacity (106 mg/g). A fixed-bed column experiment further demonstrated effective removal of methylene blue (MB) dye, achieving an initial breakthrough time of approximately 12 h, and exhibiting an adsorption capacity (q_e = 71.14 mg/g) surpassing batch adsorption capacity at the same concentration (q_e batch = 52.53 mg/g), signifying the practical utility of the materials. In addition, pyrolysis-derived biochar samples displayed improved total organic carbon (TOC) removal efficiency, with P-Cell-MOF achieving 93 % TOC removal. Density functional theory (DFT) calculations were employed to investigate the binding of MB on the various materials derived from the pyrolysis of cellulose with MOF. The calculations show that MB chemisorbs on both Fe (110) and Fe₃C (001) surfaces while only physisorption was observed on Fe₃O₄(111) and graphene. These computational findings align well with the experimental data and provide an explanation for the enhanced TOC removal observed with the P-Cell-MOF.