Underwater superoleophobic APTES-SiO2/PVA organohydrogel for low-temperature tolerant, self-healing, recoverable oil/water separation mesh

Hydrogel is attracting more and more interest in the field of oil-water separation because of its hydrophilicity and underwater oleophobicity. However, most traditional hydrogel composites have poor recycling performance, can not achieve self-repairing effect in the case of external mechanical damage, and inevitably freeze and at subzero temperatures because of a lot of water-soluble solvents in the gel network. These properties limit its application in the oil-water separation field. Therefore, it is still a challenge to prepare self-repairing and recyclable gel-based materials for oil/water separation in multiple environments. Here, superhydrophilic/underwater superoleophobic anti-freezing (3-aminopropyl) triethoxysilane-functionalized silica/polyvinyl alcohol (APTES-SiO2/PVA) organohydrogel and the related gel-coated mesh were successfully synthesized through a low-cost and simple process. The gel-coated mesh can separate oil-water mixtures in various water environments (including deionized water, HCl solution (1 M), NaOH solution (1 M), saturated NaCl solution, artificial seawater and saturated NaCl solution (−20 °C)) with a separation efficiency of above 99%. Impressively, they can achieve self-repairing and the recycling of raw materials through the excellent remoldability of organohydrogel (sol-gel transformation). The low-cost and easy fabrication, harsh-environment tolerance, self-repairing and recyclable features make the organohydrogel-based mesh promising toward oil/water separation under practical conditions.