Highly active nanoscale zero-valent iron (nZVI)–Fe3O4 nanocomposites for the removal of chromium(VI) from aqueous solutions

• Published in: Journal of colloid and interface science Vol. 369; no. 1; pp. 460 - 469
• Main Authors: Lv, Xiaoshu, Xu, Jiang, Jiang, Guangming, Tang, Jie, Xu, Xinhua
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01-03-2012; Elsevier
• Subjects: adsorption; aqueous solutions; Chemistry; Chromium; Concentration (composition); Cr(VI) removal; electron transfer; energy; Exact sciences and technology; General and physical chemistry; Iron; iron oxides; Magnetite; Mathematical models; Nanocomposites; Nanomaterials; Nanoscale zero-valent iron; Nanostructure; reaction kinetics; sorption isotherms; Surface physical chemistry; thermodynamics; Nanoscale zero-valent iron; Cr(VI) removal; Magnetite; Nanocomposites; Binary compound; Iron oxide; In situ; Electron transfer; Iron; Thermodynamics; Efficiency; Reaction mechanism; pH; Nanocomposite; Composition; Experimental data; Transition element compounds; Transition metal; Reaction rate; Free energy; Reduction method; Adsorption; Environment; Models; Kinetics; Aqueous solution; Thermodynamic properties; Chromium VI
• ISSN: 0021-9797; 1095-7103
• DOI: 10.1016/j.jcis.2011.11.049

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► Fe0–Fe3O4 nanocomposites were synthesized and used for Cr(VI) removal. ► The synthesized nanocomposites were observed by SEM, HRTEM, XRD, and XPS. ► Effects of mass composition, pH, and initial Cr(VI) concentration were investigated. ► Kinetics and adsorption isotherms of such system were firstly described. ► Reaction mechanism has been deeply discussed and clearly presented in the figures.
For the first time, nanoscale zero-valent iron (nZVI)–Fe3O4 nanocomposites, prepared by an in situ reduction method, are employed for chromium(VI) removal in aqueous environment. 96.4% Cr(VI) could be removed by these novel materials within 2h under pH of 8.0 and initial Cr concentration of 20mgL−1, compared with 48.8% by bare nFe3O4 and 18.8% by bare nZVI. Effects of several factors, including mass composition of nZVI–Fe3O4 nanocomposites, initial pH and Cr(VI) concentration, were evaluated. The optimal ratio of nFe3O4 to nZVI mass lies at 12:1 with a fixed nZVI concentration of 0.05gL−1. Low pH and initial Cr(VI) concentration could increase both the Cr(VI) removal efficiency and reaction rate. Corresponding reaction kinetics fitted well with the pseudo second-order adsorption model. Free energy change (ΔG) of this reaction was calculated to be −4.6kJmol−1 by thermodynamic study, which confirmed its spontaneous and endothermic characteristic. The experimental data could be well described by the Langmuir and Freundlich model, and the maximum capacity (qmax) obtained from the Langmuir model was 100 and 29.43mgg−1 at pH 3.0 and 8.0, respectively. The reaction mechanism was discussed in terms of the mutual benefit brought by the electron transfer from Fe0 to Fe3O4.