Synthesis of nano-magnetic MnFe2O4 to remove Cr(III) and Cr(VI) from aqueous solution: A comprehensive study

• Published in: Environmental pollution (1987) 2020-10, Vol.265, p.113685-113685, Article 113685
• Main Authors: Eyvazi, Behzad, Jamshidi-Zanjani, Ahmad, Darban, Ahmad Khodadadi
• Format: Article
• Language: English
• Subjects: Chromium adsorption; Intra-particle diffusion model; Nano-adsorbent MnFe2O4; Thermodynamics
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2019.113685

The co-precipitation method was used to synthesize nano-magnetic adsorbent MnFe2O4 (nMFO), characterized through XRD, SEM, EDS, and BET techniques. The synthesized nMFO was used for hexavalent and trivalent chromium ions elimination from the aqueous phase. The optimum pH for the adsorption of Cr (VI) and Cr (III) was determined as 2 and 5, respectively. The chromium ions adsorption behavior was well interpreted through the pseudo-second order kinetics model. Furthermore, isotherm studies were conducted, and the obtained results indicated that Langmuir isotherm model could well justify the chromium ions adsorption process. Quick removal (less than 10 min) of both chromium ions and high removal efficiency were occurred using nMFO. The utmost adsorption capacity of trivalent and hexavalent chromium ions were determined as 39.6 and 34.84 mg g−1, respectively. Thermodynamic studies on chromium adsorption revealed positive value for ΔH and negative value for ΔG, representing that chromium ions adsorption was an endothermic and spontaneous process. The multilinearity in the graphs of chromium ions adsorption was observed using intra-particle diffusion model. In this regard, the external mass transfer of chromium ions on synthesized nanoparticles was the important and controlling step in the adsorption process. [Display omitted] •The high adsorption efficiency of Cr(VI) and Cr(III) was obtained using nMFO.•Rapid removal (less than 10 min) of both chromium ions was occurred using nMFO.•Electrostatic phenomena was the probable mechanism of Cr(VI) elimination.•Cation exchange was the main mechanism for the elimination of Cr(III).•The external mass transfer of chromium ions was the controlling step of the adsorption. Main finding: Rapid removal (less than 10 min) of both chromium ions was occurred using nMFO. Moreover, Electrostatic phenomena and cation exchange were the main mechanism for the elimination of Cr(VI) and Cr(III), respectively.