Converting pomelo peel biowaste into multifunctional sponges integrated underwater superoleophobicity and catalytic ability for sewage treatment

Fabricating practical multitasking materials integrating efficient oil-water separation ability and excellent catalytic performance is significant for water remediation but challenging for substrates and subsequent surface modification causing high cost, high power consumption, and poor reusability. Herein, a multitasking sponge was designed for water purification by successively modifying the biomass pomelo peel (PP) with polypyrrole (PPy), Au nanoparticles (NPs), and polydopamine (PDA). The cost-effective and renewable PP substrates, facile surface decoration of PP with PPy coating, in-situ spontaneous growth of Au NPs, and the protection of the outermost PDA coating endowed the as-obtained PP/PPy-Au/PDA sponges high sewage treatment efficiency and the potential for large-scale preparation. The PP/PPy-Au/PDA sponges exhibited high catalytic reduction activity for 4-nitrophenol (4-NP) and excellent reusability without remarkable decline in catalytic activity even after 10 recycles due to the synergistic effect among PPy, Au NPs and PDA. In addition, this sponge also displayed superior separation efficiency and high filtration flux towards both immiscible oil-water mixtures and O/W emulsions due to its underwater superoleophobicity. Integrating above properties, the PP/PPy-Au/PDA sponge could perform catalytic degradation of organic molecules and meanwhile separation of oil-water mixtures.