One-step carbothermal synthesis of super nanoadsorbents for rapid and recyclable wastewater treatment

As a potential magnetic super adsorbent in wastewater treatment, Fe₃O₄ has been re-searched intensively up to date. However, its key problem of poor comprehensive magnetic properties is still challenging. In this work, an effective solution to this problem has been developed by a one-step carbothermal synthesis of Fe₃O₄ crystals, which are merited with pure-stoichiometry (FeO-phase free), high crystallinity, small-size (~10 nm), strong magnetism and sensitive magnetic response. The unveiled saturation magnetization of Fe₃O₄ nanoparticles reaches as high as 90.32 emu·g⁻¹, and the fastest magnetic response time is as short as only 5 s. Such magnetic Fe₃O₄ super adsorbents exhibit outstanding performance when applied as an adsorbent for wastewater treatment. They can quickly and effectively adsorb methylene blue with an adsorption capacity of 62.5 mg·g⁻¹, which is much higher than that of Fe₃O₄ adsorbents prepared by other methods reported in the literature. Importantly, this capacity is refreshable after removing the adsorbed methylene blue just by ultrasonic cleaning. With such combined outstanding magnetic properties and recyclable adsorption capacity, the problems associated with the conventional adsorbent solid–liquid separation could be resolved, thus making a forward development towards industrial wastewater treatment.