Preparation of excellent magnetic superhydrophobic photothermal sponge based on Zif (Fe) for oil–water separation

The frequent leakage of crude oil and the illegal discharge of industrial organic pollutants have caused serious damage to the ecological environment and the loss of valuable resources. In this paper, we introduce a sponge with magnetic and photothermal properties. Polydopamine and ferric oxide (Fe₃O₄) were grafted onto the sponge, self-assembled on the three-dimensional (3D) skeleton surface by Zif material, and grafted with cetyltrimethoxysilane to make the modified sponge highly hydrophobic (water contact angle = 155°). Moreover, due to the dual photothermal conversion properties of polydopamine and ferric oxide (Fe₃O₄), the modified sponge can be quickly heated to 110 °C under light (1.25 kw/m²). The modified sponge demonstrated excellent crude oil adsorption capacity (44 g/g) and recyclability. Due to its magnetic properties (saturated magnetization = 4.43 emu/g), derived from the incorporation of Fe₃O₄, the sponge could be remotely controlled for adsorption. Moreover, it demonstrated the ability to continuously adsorb and collect light oil from the water surface with the aid of a peristaltic pump. The sponge also functioned as an efficient filter for separating heavy oil underwater through liquid gravity, achieving a separation efficiency of 97.2%. Therefore, this composite sponge not only presents a promising solution for crude oil spill remediation but also holds significant potential for industrial wastewater treatment, making it highly relevant for practical environmental applications.