Preparation and characterization of magnetic Fe3O4/CNT nanoparticles by RPO method to enhance the efficient removal of Cr(VI)

• Published in: Environmental science and pollution research international 2013-10, Vol.20 (10), p.7175-7185
• Main Authors: Chen, Runhua, Chai, Liyuan, Li, Qinzhu, Shi, Yan, Wang, Yangyang, Mohammad, Ali
• Format: Article
• Language: English
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Research Article; Waste Water Technology; Water Management; Water Pollution Control
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-013-1671-4

This work described a novel method for the synthesis of high-ferromagnetism nanoparticles (Fe 3 O 4 /CNTs) to efficiently remove Cr(VI) from aqueous solution. The Fe 3 O 4 /carbon nanotubes (CNTs) were prepared by in situ reduction with post-oxidation method by using cheap and environmentally friendly precursor under mild condition. Magnetic hysteresis loops revealed that Fe 3 O 4 /CNTs had superior saturation magnetization (152 emu/g), enabling the highly efficient recovery of Fe 3 O 4 /CNTs from aqueous solution by magnetic separation at low magnetic field gradients. FTIR, Raman, XPS, and TEM observations were employed to characterize the physical–chemical properties of Fe 3 O 4 /CNTs, demonstrating that CNTs were successfully coated with iron oxide matrix. The adsorption equilibrium of Cr(VI) on Fe 3 O 4 /CNTs was reached within 30 min. Langmuir, Freundlich, and Dubinin–Radushkevich isotherm were chosen to analyze the equilibrium data. The results indicated that Langmuir model can well describe the equilibrium data with the maximum adsorption capacity of 47.98 mg/g at room temperature and 83.54 mg/g at 353 K. The adsorption capacity of Fe 3 O 4 /CNTs for Cr(VI) was greatly improved as compared to raw CNTs and other similar adsorbents reported. The pseudo-second-order kinetic model provided the best description of Cr(VI) adsorption on Fe 3 O 4 /CNTs. Most importantly, possible synthesis mechanism and Cr(VI) removal mechanism were explored. The results suggest that large amounts of Cr(VI) were adsorbed on Fe 3 O 4 /CNTs surface by substituting the surface position of –OH and then reducing it to Cr(OH) 3 and Cr 2 O 3 .