Processing Cellulose Acetate into Hierarchically Porous Monoliths via Thermally Impacted Nonsolvent-induced Phase Separation with Octanol: Application in Dye Adsorption

This study reports the fabrication of hierarchically porous cellulose acetate (CA) monoliths via thermally impacted nonsolvent-induced phase separation (TIPS/NIPS), employing <i>n</i>-octanol as a novel nonsolvent. A ternary phase diagram (TPD) of the CA/DMF/<i>n</i>-octanol system was constructed to define optimal processing conditions in the metastable region, enabling the formation of continuous monolithic structures. The resulting CA monoliths exhibited a sponge-like morphology with interconnected meso- and macropores, a specific surface area of 34.33 m² g^-1, a high porosity of 90.68 ± 0.66%, and a low density of 103.12 mg cm^-3. Adsorption studies using crystal violet (CV) as a model contaminant demonstrated efficient dye removal (∼90%) within 180 min, reaching the highest adsorption capacity of 0.92948 mg g^-1, as determined by the Langmuir model. Kinetic modeling indicated that the adsorption followed a pseudo-second-order mechanism, suggesting chemisorption, whereas the equilibrium data fit best to the Langmuir isotherm model, indicating monolayer adsorption. Desorption studies showed that methanol and ethanol enabled CV recovery with efficiencies of up to 70%. These results confirm that the combination of TIPS/NIPS and <i>n</i>-octanol provides a promising, tunable platform for producing sustainable CA-based monoliths for wastewater treatment and dye removal.