US EPA

7750781 

Journal Article 

Effect of perchlorate, nitrate, chloride and pH on sulfate adsorption by variable-charge soils 

Zhang, GY; Brummer, GM; Zhang, XN 

1996 

Yes 

Geoderma
ISSN: 0016-7061
EISSN: 1872-6259 

73 

3-4 

217-229 

English 

10.1016/0016-7061(96)00050-X 

WOS:A1996VL04400006 

The adsorption of sulfate at different pH in the presence of different concentrations of sodium perchlorate, sodium nitrate or sodium chloride by two variable charge soils with contrasting surface charge properties was studied. The adsorption decreased with the increase in pH. For the Ferralsol carrying net positive surface charge at natural pH increasing the concentration of NaClO4 or NaNO3 resulted in a decrease in sulfate adsorption at low pH and an increase in sulfate adsorption at high pH. There was an intermediate pH at which the salt concentration had no effect on adsorption. This point of zero salt effect (PZSE) on adsorption for NaClO4 and NaNO3 was 5.5 and 5.8, respectively. In the presence of NaCl the adsorption pH curves converged at pH 7 at which the soil practically did not adsorb sulfate. For the Ferric luvisol with a net negative surface charge at natural pH a PZSE on adsorption occurred at pH 5.7 only in the presence of NaClO4. The adsorption pH curves converged at pH 6.4 in the presence of NaNO3 and were nearly parallel to one another in the presence of NaCl. These results were explained by the combined effect of competitive adsorption and the change in electrical potential at the adsorption plane. It was suggested that the more abundant the positive surface charge relative to negative surface charge of a soil at natural pH, the more likely the occurrence of a point of zero salt effect on sulfate adsorption, and that chloride ions were more effective in inducing the increases in negative surface charge and surface potential of soils than nitrate and perchlorate ions. 

pH; PZSE on adsorption; sulfate adsorption; variable-charge soil