A multi-functional photothermal-catalytic foam for cascade treatment of saline wastewater

Abstract

Saline organic wastewater (SOW) is more dangerous to the environment and difficult to clean as compared to ordinary wastewater. Traditional photothermal materials can extract distilled water from wastewater through interfacial solar evaporation. However, the condensed wastewater after evaporation accumulates high concentrations of organic pollutants, salts, and bacteria. Herein, for the first time we design a flexible multifunctional porous foam through in situ growth of rough CoNi₂S₄ nanoneedle array on a PVDF framework (SCoNi–pDA/PVDF foam), which can achieve a high evaporation rate of 2.63 kg m⁻² h⁻¹ under one-sun illumination. Meanwhile, SCoNi–pDA/PVDF foam exhibits significant enhancement in PMS activation for SOW degradation due to the coexistence of Co⁰ and Ni⁰. The super-hydrophilic CoNi₂S₄ nanoneedle array and intrinsic nature of metallic sulfides endow the SCoNi–pDA/PVDF foam with strong salt resistance and excellent antimicrobial properties. As a result, the catalytic and evaporation cascade system model proves the convenience of practical application of the SCoNi–pDA/PVDF foam, which can efficiently collect concentrated brine and freshwater (1.06 kg m⁻² h⁻¹) during long-term outdoor evaporation of SOW. This work provides an inspiration for the future development of high-performance and multifunctional wastewater treatment materials and devices.