The current study attempted to couple acid-treated thermal power station waste fly ash with different weight percentages of phenyltriethoxysilane and deposited on the cotton fabric surfaces in order to get superhydrophobic/superoleophilic materials (TPSWFA/PTES-CF). The contact angle measurements were carried out along with other physiochemical and morphological studies for TPSWFA/PTES-CF materials using a goniometer and showed an average static water angle value of 158.5°. The wetting behavior of corrosive liquids such as coffee, milk, tea, water-dyed methylene blue, strong acids (HCl), strong alkali (NaOH), and saturated salt solution (NaCl) was assessed for the fabricated TPSWFA/PTES-CF superhydrophobic/superoleophilic substrates using an optical contact angle meter. The wash durability, mechanical stability, oil/water separation, and self-cleaning ability through flushed water were also carried out for the newly developed high-value superhydrophobic TPSWFA/PTES-CFS filter and reported. The results obtained from oil-water separation shows exceptional separation efficiency with oil purity of ≥99.97 wt %, and high permeation flux values up to 11,100 ± 22 L m