Reclamation of Acid Pickling Waste: Preparation of Nano α‑Fe₂O₃ and Its Catalytic Performance

Nano α-Fe₂O₃ materials with various size and morphology were prepared from acid pickling waste using nonionic surfactant polyethylene glycol (PEG-400) as dispersant and ultrasonic enhancement, as proved by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis, and inductively coupled plasma mass spectrometry (ICP-MS), respectively. The results showed that high purity (96.89%) α-Fe₂O₃ nanoparticles were well-crystallized with different size and morphology, mainly including a web-like structure linked by about 25 nm spherical particles (Fe-w), a nanorod with about a 45 nm width diameter (Fe-r), and daylily bud-like materials with a 50 nm width leaf (Fe-l). The Fe-w, as well as other nanosized α-Fe₂O₃, was found to be very active for benzylation of aromatics by benzyl chloride, exhibiting turn over frequency (TOF) of 35.2 h^–1 for anisole, 65.1 h^–1 for aniline, 33.3 h^–1 for phenol, and 1776 h^–1 for benzene, respectively. The catalyst could be recycled at least three times without appreciable loss of catalytic activity