Lime-treated montmorillonite clay for immobilizing zinc

摘要

In this dissertation I studied (1) the effects of the different Zn(II) concentrations and different quantities of lime on capture of Zn(II) by montmorillonite K10, and (2) the effects of Zn(II) and lime on changing adsorptive, hydraulic, and mechanic properties of montmorillonite K10.;Column and batch tests were conducted in this study. For the batch tests, 5 grams of montmorillonite K10 were mixed with 7 different lime contents and 8 different initial Zn(II) concentrations in stirred batch reactors. For the column tests, every permeameter column contained 100 grams of montmorillonite K10 and 400 grams of Ottawa standard sand, 20 $sim$ 30 mesh, with different lime contents. One series of column tests used deionized water and one series used 1000 $mu$g/ml Zn(II) solution for percolation. The zinc concentration of samples collected from clay-Zn(II) suspensions in batch tests and the percolated solutions from the column tests were analyzed for zinc using atomic absorption spectrophotometry.;The batch test results indicate that the mass of Zn(II) adsorbed by montmorillonite K10 can not be modeled by Freundlich or Langmuir isotherms. However, it can be accurately modeled by the two-term Freundlich isotherm.;The column test results show that the hydraulic conductivities for the mixture of montmorillonite K10 and sand with different lime contents are highest at 2% of lime for Zn(II) solution and 5% of lime for deionized water. The lowest hydraulic conductivity occurs with 5% of lime, the highest lime addition tested. The breakthrough curves indicate that the Zn(II) capture and Zn(II) breakthrough of the clay-sand mixtures with different lime contents increase with increasing lime addition. Based upon the effects of lime on Zn(II) captured by montmorillonite K10, a description for the interacting effects of lime and Zn(II) capture on changing hydraulic conductivity is suggested.;A comparison was made between Zn(II) adsorption in batch and column tests. The result shows that the Zn(II) adsorption in micrograms per gram of clay is the same for both batch and column tests. This result suggests that Zn(II) captured by clay can be estimated using batch tests and the more cumbersome and expensive column tests with permeameters are not necessary.;The results of this research demonstrate a potential application of lime-treated clay liner for landfill having lower hydraulic conductivity and better Zn(II) capture ability.