Green Fabrication of a Multifunctional Sponge as an Absorbent for Highly Efficient and Ultrafast Oil-Water Separation

Oil leakage results in serious environmental pollution and severe waste of resources, which makes the development of low-cost, environmentally friendly, high-capacity, and durable oil absorbents an urgent task. In this paper, superhydrophobic coatings of activated carbon (AC)-TiO2-PDMS@PDMS were developed without using any fluorine-containing reagents. The TiO2 particles were grown on the AC surface to form AC-TiO2 powders. The hydrophilic AC-TiO2 powders were further grafted with polydimethylsiloxane (PDMS) molecules (AC- TiO2-PDMS) to achieve superhydrophobicity through covalent reaction between PDMS and TiO2 under UV light. The AC-TiO2-PDMS powder was mixed with a PDMS polymer to form a superhydrophobic coating solution, which made the commercial sponge obtain durable superhydrophobicity. It showed high liquid repellency and antifouling ability toward various liquids and drinks. Taking advantage of the large surface area and high absorption capacity of AC, the coated sponge showed superior high absorption capacity (up to 100-158 g/g) toward various oils and organic solvents with a high absorption speed. Besides, the sponge showed high reusability that could be repeatedly used to absorb various oils and organic solvents. Moreover, the sponge also presented photocatalytic capability, which could repeatedly photodegrade the oil contaminants without influencing the superhydrophobicity, therefore largely increasing the recyclability and lifetime of the sponge. It also could separate immiscible oil-water mixtures with high efficiency and continuously remove oils from water. It was chemically stable and mechanically durable and could resist various harsh conditions without losing its superhydrophobicity. This study developed a facile, cost-effective, and environmentally friendly method to fabricate very promising absorbents for large-scale oil and solvent cleanups and recovery.