Preparation of organo-modified kaolinite sorbents: The effect of surface functionalization on protein adsorption performance

摘要

Kaolinite organic derivatives were obtained by functionalization of kaolinite (kaol), in order to improve its removal capacity with respect to polypeptides present in dairy industry effluents. Functionalization was carried out by grafting two organosilanes, namely tert-butyldimethylchlorosilane (TBSCl) and 3-aminopropyltriethoxysilane (APTES), onto the kaol surface, and by intercalation of the small polar molecules dimethyl sulfoxide (DMSO) and potassium acetate. FTIR spectroscopy provided qualitative evidence about the presence of organosilane molecules grafted on the kaol outer surface, as well as information about the organo-kaol intercalates. Quantitative data about the amount of grafted or intercalated organic molecules was also obtained by means of elemental and thermogravimetric analysis. Textural characterization of the samples was carried out by N-2 adsorption- desorption at 77 K and by mercury intrusion porosimetry. SEM microscopy was used to study the microscopic topography. Protein adsorption experiments were carried out in batch mode, using bovine serum albumin (BSA) as a model protein to test the removal capacity of the materials obtained. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms for kaol and its organic-derivatives, respectively. The results obtained showed that surface functionalization of kaol considerably improved its protein removal capacity.