Preparation, structural changes and adsorption performance of heavy metal ions on sulfonated cellulose with varying degrees of substitution

Abstract Sulfonated cellulose (SC) with varying degrees of substitution (DS) were prepared with the pyridine sulfur trioxide complex (Py-SO 3 ) as a sulfonation reagent (as a source of sulfur trioxide) in dimethyl formamide (DMF) as a solvent, where the DS was primarily affected by the molar ratio between Py-SO 3 and the anhydroglucose (AHG) unit. Sulfonation temperature and residence time have less effect on DS. The ratio of the crystalline domain of SC decreased gradually with incremental DS, and the crystalline cellulose I of SC at DS 0.81 nearly disappeared, and the moiety of the paracrystalline SC with high hydrophilicity increased. The thermostability decreased with increasing DS as a consequence of crystalline domain decrement. The adsorption performance of SC to metal ions was enhanced with increasing DS. However, above DS 0.62, the adsorption capacity enhancement is negligible. For an economic adsorption of heavy meatal ions in effluents, the DS of SC must be optimized.