Surface-coating montmorillonite nanoclay by water-soluble proteins extracted from hominy feed

Montmorillonite (MMT) nanoclay was surface-coated by water-soluble proteins precipitated from hominy feed extract at pH 6.0, 5.5, and 4.3 to modify its native structure. Surface-coating was performed at 60 °C, pH 2.0-10.0, and MMT:protein mass ratios from 49:1 to 2:1, followed by lyophilizing the triple-washed precipitate for characterization. Proteins precipitated at pH 5.5 were the most effective in creating intercalated and/or exfoliated MMT structures that were also impacted by the protein level and pH during coating. At pH 2.0, X-ray diffraction peaks of pristine MMT were no longer observed at an MMT:protein mass ratio of 4:1 or lower, while different degrees of intercalation were achieved at other pH conditions. The adsorption of proteins on MMT at all studied pH conditions was confirmed by FTIR, analysis of adsorbed proteins, and zeta-potential. These results suggest that interactions involved in coating MMT include coulombic and non-coulombic forces.