Studies on Adsorption Characteristics of Al-Free and Al-Substituted Goethite for Heavy Metal Ion Cr(VI)
2017
Ni, Chunyan | Liu, Shan | Wang, Huanling | Liu, Hui | Chen, Rufen
In the present paper, α-FeOOH and α-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 SO₄ ²⁻, H₂PO₄ ⁻, C₂O₄ ²⁻, CO₃ ²⁻, and SiO₃ ²⁻ on the adsorption of Cr(VI) on α-FeOOH and α-Fe(Al)OOH was studied by batch techniques. The results show that the adsorption capacity of Cr(VI) on α-Fe(Al)OOH increases with the introduction of aluminum, but decreases with the increase of pH. The adsorption irreversibility of Cr(VI) on α-Fe(Al)OOH is much higher than that on pure α-FeOOH. The adsorbed Cr(VI) species mainly exists in the form of *Fe(wk)-OHCrO₄ ²⁻ on the surface of the samples. With the presence of SiO₃ ²⁻, CO₃ ²⁻, C₂O₄ ²⁻, SO₄ ²⁻, 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 α-FeOOH, Cr(VI) ions are preferentially adsorbed on Al sites rather than Fe sites on α-Fe(Al)OOH.
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