Macroporous monoliths with tailorable hydrophobicity for oil–water separation

Separation of oil/water mixtures using monolithic porous materials is an attractive approach for absorbing a variety of polar and apolar solvents from their mixtures. In our work, we report a simple and low-cost fabrication of macroporous monolith followed by hydrophobization with adsorption of candle soot particles (CSPs). This modification makes it omniphilic and substantially enhance its hydrophobic nature by packing of CSPs into the polymeric walls of the monolith as confirmed by scanning electron micrographs. Water contact angle (WCA) and solvent absorption behaviour of CSP-adsorbed monoliths were studied and subsequently, were employed for the separation of floating oil/water mixture. Unmodified monolith S0 is hydrophilic in nature and absorbs over 30 times its weight when dipped in water. WCA study reveals that the contact angle increases systematically from 0 to ∼ 130° with an increase in CSP concentration and monolith S5 can absorb chloroform more than 38 times its weight. Monoliths possess high mechanical strength and can be used for repetitive compression/absorption cycle for solvent absorption. These high porosity sponges provide an effective strategy, high-performance controllable absorbability, and can be used as a separation tool for floating oil/water mixtures.