Magnetic field assisted synthesis of JANUS Fe3C@ Enteromorpha doped graphene aerogels for simultaneous recovery of fresh water and salt in high salinity wastewater

Abstract

Solar-driven evaporation technology has captured great attention in the fields of desalination and separation due to its eco-friendliness and minor energy costs. It is difficult to maintain durable stability and high efficiency for the evaporation process due to salt contamination. Herein, Fe3C@ Enteromorpha doped graphene aerogel (GEF) was synthesized by a one-step hydrothermal reduction method for the simultaneous recovery of fresh water and salt in high salinity wastewater. Enteromorpha was doped between graphene lamellae to construct the structural basis for the rapid water evaporation and salt resistance of aerogel. Fe3C was concentrated on the surface of aerogel with the assist of magnetic field, which not only improves the hydrophilicity of GEF by increasing the roughness and increasing hydrophilic groups, but also concentrates the heat on the evaporation surface. The rich microporous structure with super hydrophilicity endows the GEF with exceptional evaporation performance. Water evaporation rate and photothermal conversion efficiency can reach 3.76 kg·m−2·h−1 and 127 %, respectively, under 1 sun irradiation. The multi-layer structure of GEF enables the salt precipitation on the side, assisting the evaporation and crystallization. GEF has a stable evaporation rate of 3.2 kg·m−2·h−1 for 20 % NaCl solution during 10 h continuous evaporation for 5 days. The GEF aerogel shows excellent photothermal properties and salt resistance, and practical ability to recover clean water and salt resources from the actual treatment of high-salt wastewater.