Abstract
In this study, a new sulfidated nanoscale zero-valent iron (S-nZVI) supported on hydrogel (S-nZVI@H) was successfully synthesized for the removal of chromium (Cr) (VI) from groundwater. The surface morphology, dispersion phenomenon and functional groups of novel S-nZVI@H were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Box-Behnken design (BBD) optimization technology based on response surface methodology (RSM) is applied to demonstrate the influence of the interaction of S-nZVI@H dose, initial Cr(VI) concentration, contact time, and initial pH with the Cr(VI) removal efficiency. The analysis of variance results (F = 118.73, P < 0.0001, R2 = 0.9916) show that the quadratic polynomial model is significant enough to reflect the close relationship between the experimental and predicted values. The predicted optimum removal conditions are: S-nZVI@H dose 9.46 g/L, initial Cr(VI) concentration 30 mg/L, contact time 40.7 min, and initial pH 5.27, and the S-nZVI@H dose is the key factor affecting the removal of Cr(VI). The predicted value (99.76%) of Cr (VI) removal efficiency is in good agreement with the experimental value (97.75%), which verifies the validity of the quadratic polynomial model. This demonstrates that RSM with appropriate BBD can be utilized to optimize the design of experiments for removal of Cr(VI).
Highlights
As a metal pollutant, chromium (Cr) comes from industrial processes such as tanning, electroplating, metallurgy, and textile (Selvi et al 2001)
Two materials of nano zero-valent iron (nZVI)@H and sulfidated nanoscale zero-valent iron (S-nZVI)@H are successfully synthesized for Cr(VI) removal
With better removal effects confirmed by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) characterizations and comparable experiments, S-nZVI@H is selected as the material designed by response surface methodology (RSM) to further explore its removal efficiency of Cr(VI)
Summary
Chromium (Cr) comes from industrial processes such as tanning, electroplating, metallurgy, and textile (Selvi et al 2001). Cr usually exists in the environment in the form of trivalent chromium (Cr(III)) and hexavalent chromium (Cr(VI)) (Fendorf 1995). In order to effectively control the pollution of Cr, some methods of removing Cr(VI) have been developed, including activated carbon adsorption technology (Mohan & Pittman Jr 2006), polymer membrane filtration technology (Aroua et al 2007), ion exchange technology (Lin & Kiang 2003), electrochemical precipitation technology (Kongsricharoern & Polprasert 1995). In order to further improve the removal efficiency of Cr(VI) and reduce the impact of the treatment processes on the environment, it is necessary to develop a green material with high removal efficiency, low cost, and little secondary pollution
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