Deep and efficient removal of vanadium from molybdate solution using magnetic γ-Fe2O3 nanoparticles

It is urgently desired to develop a promising method for deep removal of vanadium from molybdate solution for the efficient recycle of spent hydrodesulfurization (HDS) catalyst. In this paper, a novel method was investigated to deeply remove vanadium using gamma-Fe2O3 particles as adsorbent. The properties of synthesized adsorbent were analyzed by a series of characterization methods. The adsorbent composed of gamma-Fe2O3 nanoparticles with a diameter of 10-15 nm shows superparamagnetism and the saturation magnetization is about 56 emu center dot g(-1). The performance of this adsorbent including the vanadium removal efficiency and adsorbent stability was evaluated. The vanadium removal rate is up to 97.6% and the co-adsorbed Mo is lower than 5% at a pH of 10 within only 30 min. Furthermore, both magnetism and adsorption capacity of the gamma-Fe2O3 adsorbent are nearly unchanged after 30 days storage. The adsorption mechanism was revealed that polymeric vanadium ions exhibit higher affinity with gamma-Fe2O3 than MoO42-, and the adsorption follows ion exchange mechanism between hydroxyls covered on the adsorbent. The gamma-Fe2O3 adsorbent presents a series of advantages of excellent V-removal performance, good recyclability, excellent stability, which may have significant potential for industrial-scale applications.