Synthesis of multifunctional superwettable zinc nanoparticle with pH-bidirectional responsive for efficient emulsion separation

Abstract

Smart pH-bidirectional responsive material has been presented based on zinc nanoparticles with smart surfaces adaptably transform wettability in mutual directions between the superhydrophobicity-superoleophilicity and the superhydrophilicity-underwater superoleophobicity depending on the pH. The smart material fabrication was prepared by immersing the fabric in AA-co-VTES-ZnO (composite A) and APTES-FOTS-ZnO (composite B) reactions. The material was synthesized by free radical polymerization. Characterization by FTIR, and SEM/EDX explained that the chemical compositions were uniformly distributed through the smart fabric surface caused by the strong chelating bond between the hydroxide, carboxylates, and silane active surfaces. The chemical stability, mechanical durability, and separation test results revealed selective separation efficiency for oil/water separation with efficacy ≥99 % and high satisfactory oil flux 7000–8000 L.h−1.m−2 and water flux (5500–6500 L.h−1.m−2). Moreover, the water contact angle (WCA) for neutral water was showing at 167° indicating powerful superhydrophobic properties, and for acidic/basic water was absorbing from 143/153° to 0° over time indicating superhydrophylic properties. Underwater treatment showed that the smart fabric has superoleophobic behavior with around 150° oil contact angle (OAC). Various weights and % NaCl immersion tests also have been applied for mechanical and chemical stability tests. The results displayed brilliant stability under severe conditions confirming great WCA after repeating and increasing mass and concentration. For oil removal and emulsion test, dyed oil was rapidly absorbed within 2 s and oil/water emulsions were easily separated by developed fabric with a good flux and separation efficacy of over 97 %. Interestingly, the prepared materials can also be efficiently and continuously separated for complicated oil/water/oil mixtures without particular treatment.