Zinc adsorption studies on Ethiopian Soils.
2002
Dawit Deguefu and Ellis,Boyd G.
Adsorption studies of Zn2+ on a Vertisolic and a Nitosolic soil from Ethiopia were conducted using several matrices, pH levels, and levels of initial Zn concentration, ([Nn)]. The matrices were 0.005 x 10-5 MAICI3 at pH 3.5 and 0.01 x 10-5 MCacl2, 0.01 x 10-5 M Mgcl2, o.03 x 10-5 MKCl, or 0.03 x 10-5 M NaCl, each at pH 5.0 and 7.0. The initial [Zn] was 0.25, 0.40, 0.50, 0.60, 0.75, and 1.00 x 10-5 M. The adsorption data fit Langmuir isotherms for both soils at pH 5.0 and 7.0. Adsorption increased with increasing initial [Zn] and was slightly greater at pH 7.0 than pH 5.0 for both soils. Generally, adsorption was greater for the Vertisol than for the Nitosol due, perhaps, to the greater CEC and higher clay and organic matter content of the Vertisol. As pH increased from 5.0 to 7.0, Ca and Mg appeared to be better competitors than K or Na with Zn for the adsorption complex site. Although there was little adsorption of Zn2+ with increasing rate and initial concentration in the Vertisol, this adsorption was very low at pH 3.5. No Zn adsorption occurred in the Nitosol at pH 3.5, suggesting that Al3+ competes with Zn2+ for the same adsorption site.
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