Preparation and application synthesis of magnetic nanocomposite using waste toner for the removal of Cr(vi).

In this study, a novel magnetic nanocomposite was prepared using waste toner (WT) through high temperature decomposition, and calcination was conducted in different atmospheres (air, ammonia, and vacuum). WT calcined in ammonia (WT(NH 3 )), and it was then utilized as an efficient absorbent for the reduction of Cr(vi) in aqueous solutions; a batch experiment with different conditions was performed to investigate its Cr(vi) removal ability. The effects of two pH-regulating acid (HCl and H 2 SO 4 ) treatments were also studied. It was found that WT(NH 3 ) could remove about 99% Cr(vi) at pH 2 under H 2 SO 4 treatment. The XRD and TEM results coupled with VSM results confirmed that WT(NH 3 ) is an Fe 3 O 4 /Fe 2 N nanohybrid, which possesses excellent water-dispersibility and remarkable magnetic properties. XPS analysis showed the presence of Cr(vi) and Cr(iii) on the surface of WT(NH 3 ), which indicated that Cr(vi) was reduced to Cr(iii). Furthermore, H 2 SO 4 regulation also promoted the reduction of Cr(vi) by WT(NH 3 ), and this reduction was higher than that obtained by HCl regulation.