A two-step organic modification strategy for improving surface hydrophobicity of zeolites

The organic modification using a silane coupling agent can significantly improve the surface hydrophobicity of zeolite powders. However, insufficient hydroxyl group content on surface of the zeolites greatly limits the immobilization dosage of the agent, making the samples less hydrophobic. In this study, a two-step organic modification strategy using 1,2-bis(triethoxysilyl)ethane (BTESE) and dodecyltrimethoxysilane (DTMS) was adopted and developed to synthesize highly hydrophobic organic modified zeolite powders. The results showed that the BTESE modification could significantly increase the hydroxyl group content on the surface of zeolite powders, and relatively higher amount of DTMS could be then modified on the BTESE-modified samples. The mean critical surface tension, water vapor adsorption capacity, and water drop contact angle/penetration time of the 0.5% DTMS modified 10% BTESE-zeolite powders were 46.20 mN /m, 27 mg/g, and 142°/˃25 s, while those of the 0.5% DTMS modified zeolite powders were > 71.60 mN/m, 45 mg/g, and 124°/19.48 s, respectively, indicating that the sample synthesized by this two-step method was much more hydrophobic than the sample synthesized by traditional method. This two-step organic modification method appears to be a simple and effective way to prepare highly hydrophobic zeolite powders.