Optimization of factors affecting hexavalent chromium removal from simulated electroplating wastewater by synthesized magnetite nanoparticles

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Abstract
Hexavalent chromium is a mutagen and carcinogen that is of significant concern in water and wastewater. In the present study, magnetite nanoparticles (n-Mag) were investigated as a potential remediation technology for the decontamination of Cr (VI)-contaminated wastewater. Synthesized n-Mag was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and BET-N2 technology. To screen and optimize the factors affecting Cr (VI) removal efficiency by synthesized nanoparticles, Plackett-Burman (PB) and Taguchi experimental designs were used respectively. The crystalline produced n-Mag was in the size range of 60–70 nm and had a specific surface area (SSA) of 31.55 m2 g−1. Results of PB design showed that the most significant factors affecting Cr (VI) removal efficiency were initial Cr (VI) concentration, pH, n-Mag dosage, and temperature. In a pH of 2, 20 mg L−1 of Cr (VI) concentration, 4 g L−1of n-Mag, temperature of 40 °C, 220 rpm of shaking speed, and 60 min of contact time, the complete removal efficiency of Cr (VI) was achieved. Batch experiments revealed that the removal of Cr (VI) by n-Mag was consistent with pseudo-second order reaction kinetics. The competition from common coexisting ions such as NO3 −, SO4 2−, and Cl− were not considerable, unless in the higher concentration of SO4 2−. These results indicated that the readily synthesized magnetite nanoparticles have promising applications for the removal of Cr (VI) from aqueous solution.

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