Kinetics Investigation on Removal of Hexavalent Chromium by Tannic Acid Stabilized Nanoscale Zero-valent Iron
Tannic acid stabilized nanoscale zero-valent iron(TA-nZVI)with molar ratios of tannic acid and nanoscale zero-valent iron of 0.012 5,0.025 0,0.050 0,0.100 0 and 0.200 0 was prepared by adding different doses of tannic acid.TEM,UV-Vis,XRD,GT methods were used to analyze the morphology,particle size,composition,and thermal stability of TA-nZVI in different proportions.TA-nZVI is a special cluster structure with size of distributing between 40～70 nm,whose specific surface area can be as high as 180.1 m2·g-1.So TA-nZVI has extremely high reactivity,and the removal rate of Cr(Ⅵ)can reach 100％within 30 min.The reduction of Cr(Ⅵ)by TA-nZVI synthesized in different conditions fits the pseudo first-order model quite well.Under the same conditions,the apparent rate constant and surface area normalized rate constant of TA-nZVI are 1119 times and 70.64 times higher than that of Bare-nZVI,respectively.Therefore,the efficient removal of Cr(Ⅵ)by TA-nZVI is related to its huge specific surface area and its Fe0 activity per unit volume surface area.
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