Studies on Adsorption Characteristics of Al-Free and Al-Substituted Goethite for Heavy Metal Ion Cr(VI)

摘要

In the present paper, alpha-FeOOH and alpha-Fe(Al)OOH were prepared, and the adsorption of Cr(VI) on the two samples was investigated. The influence of pH, initial concentration, and some anions such as SO42-, H2PO4-, C2O42-, CO32-, and SiO32- on the adsorption of Cr(VI) on alpha-FeOOH and alpha-Fe(Al)OOH was studied by batch techniques. The results show that the adsorption capacity of Cr(VI) on alpha-Fe(Al)OOH increases with the introduction of aluminum, but decreases with the increase of pH. The adsorption irreversibility of Cr(VI) on alpha-Fe(Al)OOH is much higher than that on pure alpha-FeOOH. The adsorbed Cr(VI) species mainly exists in the form of *Fe(wk)-OHCrO42- on the surface of the samples. With the presence of SiO32-, CO32-, C2O42-, SO42-, and H2PO4- , the binding of Cr(VI) is inhibited by different degree. The inhibition of those anions is larger in the pure goethite than that in the Al-substituted goethite system. After Al was introduced into alpha-FeOOH, Cr(VI) ions are preferentially adsorbed on Al sites rather than Fe sites on alpha-Fe(Al)OOH.