Novel fabrication of flame-retardant melamine sponge for all-weather cleanup of viscous oil spills by Joule heat and photothermal effects

Abstract

Fast and effective cleanup of viscous crude oil spills remains a global challenge. Herein, by coating the melamine sponge (MS) with a bio-based flame retardant, reduced graphene oxide (rGO) and carbon nanotubes (CNTs), we prepared a flame-retardant and photo/electrothermal conversion absorbent (rGO/CNTs/FRMS) for rapid oil/water separation. The multifunctional sponge demonstrates remarkable hydrophobicity (the water contact angle: 140.0°), high oil absorption capacity (48.2–114.9 g g⁻¹) and recyclability (89.5% after 20 cycles). Notably, rGO/CNTs/FRMS exhibits excellent thermal stability, flame retardancy and photo/electrothermal conversion performance. Under 1 sun irradiation or 9 V, the surface temperatures of rGO/CNTs/FRMS rise to 98.8 °C or 123.2 °C within 60 s, respectively. The solar-assisted and Joule-heating rGO/CNTs/FRMS drastically reduces the viscosity of silicon oil, and thus saves absorption time by 29% under 1 sun or 47% under 9 V, respectively. The proposed all-weather oil absorbent design provides a sustainable and promising solution for crude oil spill clean-up.