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Fast and Highly Efficient Removal of Chromate from Aqueous Solution Using Nanoscale Zero-Valent Iron/Activated Carbon (NZVI/AC)

Xu, Chun-Hua, Zhu, Liu-jia, Wang, Xiao-Hong, Lin, Sheng, Chen, Ya-ming
Water, air, and soil pollution 2014 v.225 no.2 pp. 1845
X-ray diffraction, activated carbon, chromium, ions, iron, pollution, potassium, reaction kinetics, surface area, temperature, transmission electron microscopy
Nanoscale zero-valent iron supported on activated carbon (NZVI/AC) was synthesized by a modified potassium borohydride reduction method and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and specific surface area (SSA). The effects of NZVI loading on AC, NZVI/AC dosage, pH, the initial concentration of Cr(VI), and temperature on the removal of Cr(VI) were investigated. XRD confirmed the existence of Fe⁰and TEM revealed that the material consisted of mainly spherical bead-like particles aggregated into chains of individual units. The SSA of the iron particles and the removal efficiency of Cr(VI) indicated that the optimum iron loading was 25 %. Increase of NZVI/AC dosage and reaction concentration abated the removal of Cr(VI). Kinetics studies showed that removal of Cr(VI) is a two-step reaction and each step could be expressed by pseudo-first-order reaction kinetics, with initial Cr(VI) and temperature as variables. Total Cr was always almost equal to that of Cr(VI) under all tested conditions, which indicated that little Cr(III) existed in solution. Iron ions, which could cause secondary pollution in the environment, are almost not released from this system. These results demonstrated that NZVI/AC could potentially be used for Cr(VI) removal.