摘要
An analysis of Cr (Ⅵ)-sorbed surface of the soils by using a scanning electron microscope and an electron probe microscope has proved that aluminium is the chief element affecting Cr (Ⅵ) adsoption. As the ionic strength of the solution increased, the amounts of Cr (Ⅵ) adsorbed by goethite and soils decreased. Cr (Ⅵ) adsorption was greatly depressed in the presence of SO42-, WO42-, MoO42-, HPO42- and H2PO4- which competed for anion adsorption sites. The depressing extent of these anions was found to follow the sequence: HPO42-, H2PO4-> MoO42-> WO42-> SO42-> > Cl-, NO3-. The amounts of Cr (Ⅵ) desorption varied with different extractants. 0.5 M NH4F and 0.1 M KH2PO4 could be regarded as the best extractants for Cr (Ⅵ) sorbed in the soils. The mechanism of Cr (Ⅵ) adsorption by goethite and soils seemed to be similar to that of phosphate. Basically, Cr (Ⅵ) was adsorbed through specific adsorption and could not be desorbed by Cl- and NO3-. Cr (Ⅵ) adsorption on goethite released OH-. There was a significant correlation between the amounts of Cr (Ⅵ) adsorbed and pH variation in goethite suspension.
An analysis of Cr(Ⅵ)-sorbed surface of the soils by using a scanning electron microscope and an electron probe microscope has proved that aluminium is the chief element affecting Cr(Ⅵ）adsoption.As the ionic strength of the solution increased,the amounts of Cr(Ⅵ) adsorbed by goethite and soils decreased.Cr(Ⅵ) absorption was greatly depressed in the presence of SO4^2-,WO4^2-,MoO4^2-,HPO4^1- and H2PO4^- which competed for anion adsorption sites.The depressing extent of these anions was found to follow the sequence:HPO4^2-,H2PO4^-> MoO4^2-> WO4^2->SO4^2->> Cl^-,NO3^-.The amounts of Cr(Ⅵ) desorption varied with different extractants.0.5M NH4F and 0.1M KH2PO4 could be regarded as the best extractants for Cr(Ⅵ) sorbed in the soils.The mechanism of Cr(Ⅵ) adsorption by goethite and soils seemed to be similar to that of phosphate.Basically,Cr(Ⅵ) was adsorbed through specific adsorption and could not be desorbed by Cl^- and NO3^-.Cr(Ⅵ) adsorption on goethite released OH^-.There was a significant correlation between the amounts of Cr(Ⅵ) adsorbed and pH variation in goethite suspension.
