Facile Fabrication of Robust and Fluorine-Free Superhydrophobic PDMS/STA-Coated Cotton Fabric for Highly Efficient Oil-Water Separation

Oil-water separation using special wettability materials has received much attention due to its low energy consumption and high separation efficiency. Herein, a fluorine-free superhydrophobic cotton fabric (PDMS/STA-coated cotton fabric) was successfully prepared by a simple impregnation method using hydroxyl-capped polydimethylsiloxane (PDMS-OH), tetraethoxysilane (TEOS), and stearic acid (STA) as precursors. The investigation found that the cross-linking reactions between the hydroxyl groups of PDMS-OH and hydrolyzed TEOS enabled a strong interaction between PDMS-OH and cotton fabric. Furthermore, a suitable roughness surface of coated cotton fabric was established by introducing STA due to its long chain structure. The contact angle of this composite can reach 158.7 degrees under optimal conditions due to its low surface energy and desired roughness. The oil/water separation efficiency of PDMS/STA-coated cotton fabric is higher than 90% even after 10 cycles of oil-water separation, and the oil flux can reach 11862.42 L m(-2) h(-1). In addition, PDMS/STA-coated cotton fabric exhibits excellent chemical stability and durability under extreme conditions such as strong acid (HCl, pH = 1 similar to 2) and alkali (NaOH, pH = 13 similar to 14), and the hydrophobicity of PDMS/STA-coated cotton fabric was decreased to 147 degrees after 300 cycles of abrasion testing.

Automated summary

This study successfully prepared a fluorine-free superhydrophobic cotton fabric with low energy consumption and high separation efficiency, using hydroxyl-capped polydimethylsiloxane (PDMS-OH), tetraethoxysilane (TEOS), and stearic acid (STA) as precursors. The cross-linking reactions between PDMS-OH and hydrolyzed TEOS enabled a strong interaction between PDMS-OH and cotton fabric, while the introduction of STA created a suitable roughness surface. The PDMS/STA-coated cotton fabric exhibited a contact angle of 158.7 degrees and showed excellent oil/water separation efficiency of over 90% even after 10 cycles of separation.