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 treatment of wastewater with high salinity due to its eco-friendliness, abundance, and sustainability. However, caused by salt contamination, it is difficult for the evaporator to maintain durable stability and high efficiency. Herein, Fe3C@ enteromorpha doped graphene aerogel (GEF) is synthesized by a one-step hydrothermal reduction method for the simultaneous recovery of fresh water and salt in high salinity wastewater. In which, most of Fe3C are 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. And enteromorpha is doped between graphene lamellae to construct the structural basis for the rapid water evaporation and salt resistance of aerogel. The rich microporous structure with super hydrophilicity endows the GEF with exceptional evaporation performance. Impressively, the water evaporation rate and photothermal conversion efficiency can reach 3.76 kg·m-2·h-1 and 127%, respectively, under 1 sun irradiation. Besides, the multi-layer structure of GEF makes the salt precipitation on the side, so that the evaporation and crystallization surface can be separated without any other operation, which further enhanced the salt tolerance of the GEF aerogel. GEF has a stable evaporation rate of 3.2 kg·m-2·h-1 for 20% NaCl solution during 10 hours of continuous evaporation and remains stable for 5 days. In this study, the aerogel with excellent photothermal properties and salt resistance is synthesized, which is expected to recover clean water and salt resources from the actual treatment of high-salt wastewater.

Keywords: Solar-driven, Magnetic field assisted, High salinity wastewater, Super-hydrophilic, salt tolerance