Preparation of biochar derived from waste cotton woven by low-dosage Fe(NO3)3 activation: characterization, pore development, and adsorption.

Currently, researchers are looking for efficient and sustainable methods to synthesize biochar for the adsorption of pollutants. In this study, biochar with high specific surface area, tunable pore structure, and abundant functional groups were prepared from waste cotton woven (WCW) using low-dosage Fe(NO3)3 activation at 400-900 °C. The biochar obtained at 800 °C possessed the excellent specific surface area of 1167.37 m2/g with a unique micro-mesoporous structure. XRD analysis showed that the Fe species changed from Fe2O3 to Fe3O4 and then Fe0 with the increase of pyrolysis temperature. TEM images further confirmed the template effect of iron oxides for mesoporous formation. The effect of Fe(NO3)3 on the pyrolysis pathway of waste cotton woven was systematically investigated by TG and XPS analyses to explore the pore development of biochar. The results indicated that Fe(NO3)3 could enhance the dehydration, decarbonylation and dehydroxylation of WCW components, thereby reducing the temperature required for WCW pyrolysis. Moreover, the synergistic effect of Fe and N species improved the development of microporous and mesoporous structure through carbon structure corrosion and reorganization, and volatile release. Additionally, satisfactory adsorption capacity for Eriochrome Black T (456.01 mg/g) of the prepared biochar was obtained at 25 °C. This study demonstrated that low-dosage Fe(NO3)3 activation of waste cotton woven could be used as a facile method to prepare promising inexpensive biochar for contaminants removal.