Durable underwater superoleophobic hydrogels for oil- and Cu(II)-containing water purification

Purifying oily and Cu2+ ions-containing waste waters is still a challenge over the world. Traditional adsorption materials struggle to efficiently remove both pollutants. In this study, an underwater superoleophobic polyvinyl alcohol (PVA) and tannic acid (TA) based PVA-TA hydrogel was first prepared for the removal of both oils and Cu(II) ions. CaCO3 was subsequently incorporated to enhance the mechanical properties and Cu2+ adsorption capacities through electrostatic attractions. Both PVA-TA and PVA-TA/CaCO3 hydrogel-intermediated materials exhibited underwater superoleophobic and can be used to purify oily water, achieving separation efficiencies exceeding 99.20 % even after 60 cycles. Furthermore, these materials demonstrated excellent self-cleaning performance against viscous oil. The addition of CaCO3 can also improve the mechanical durability and chemical resistance of the PVA-TA under robbing, varying pH levels, and saline conditions. Moreover, the maximum Cu(II) adsorption capacity and removal efficiency of the PVA-TA/CaCO3 are 62.11 mg g−1 and 86.71 %, respectively; surpassing those of the PVA-TA due to increased micro-hole density and electrostatic interactions between CaCO3 and Cu(II). These porous materials can be further applied to purify real-life wastewater, indicating their potential for efficient practical wastewater treatment. This work not only provides effective porous materials for purifying oily and Cu2+-containing waste waters but also improves a simple method for preparing underwater superoleophobic hydrogel-intermediated materials. [Display omitted] •Mechanical durable hydrogel-intermediated porous materials were prepared.•The materials can be used to purify oily and Cu(II)-containing water.•The materials were underwater superoleophobic and durable under harsh conditions.•The materials are effective for more than 60 cycles.•The synthesis process is simple and environment-friendly.