TiO2 deposited dual functional hydrogel coatings with superhydrophilic and photocatalytic properties for efficient oil/water separation and dye photodegradation

Hydrogel coatings have been applied in oil/water separation owing to the underwater superoleophobic and anti-oil fouling property. However, the intrinsic relatively poor mechanical performance of hydrogel coatings and inevitably polluted by organic pollutants induce the separation performance reduction in the long-term operation and even possibly cause the coatings to peel off. In this work, we developed a simple and robust TiO2 deposited polyacrylamide-sodium alginate (TiO2@PAS) composite hydrogel coating with underwater superoleophobic and dye photodegradation abilities. PDA/TiO2 nanoparticles were deposited on the substrate surface through the mussel inspired chemistry strategy. Moreover, Polyacrylamide and calcium alginate were crosslinked into the double network hydrogel to enhance mechanical performance. The prepared hydrogel coating was introduced onto different substrates to endow the coated substrates with robust superwetting and anti-oil fouling properties. Separation efficiency of TiO2@PAS hydrogel coated copper mesh for oil/water mixtures reached 99.1% after 50 cycle separation tests. The hydrogel coated PVDF membrane was prepared through the same method and separation efficiency for oil-in-water emulsion keeps above 99.3% during multiple cycles separation. Moreover, the photocatalysis active TiO2 nanoparticles allowed the TiO2@PAS composite hydrogel coating to degrade the organic dye methylene blue (MB) through the photo-Fenton-like photodegradation process with degradation efficiency as high as 98.7%. Notedly, the TiO2@PAS hydrogel coating shows robust superwetting performance even underwent abrasion test and acid-base immersing, which has the potential for adapting extreme operating condition. Overall, the study on the TiO2@PAS composite hydrogel coatings provides a general and simple design strategy for superwetting and photocatalytic hydrogel coatings for multi-demand water treatment application.