Adsorption And Desorption Of Behaviors Of Lead And Contaminated Soil For Remediation By Thiol-Functionalized Bentonite

Thiol-functionalized bentonite was investigated by experiment in laboratory in this thesis. The effect of solid-liquid ratio, pH value, ionic strength, temperature and time of the adsorption of lead on thiol-functionalized bentonite has been studied. In the meantime, the acidity, ionic strength of simulant acid rain, the temperature and time of desorption also have been studied. In addition, the adsorption-desorption kinetics and thermodynamics of thiol-functionalized bentonite were analyzed. The remediation of thiol-functionalized bentonite on lead polluted soil was studied by means of batch extractions, which provided scientific evidence for further recognition of the action of lead and remediation of soil polluted by them. The main research results are as followes:1. A comparative analysis of the functional groups and surface structure of the Ca-bentonite and before-after adsorption thiol-functionalized bentonite were characterized by means of Infrared Spectrometry (IR). The vibration band confirmed the presence of the grafted-SH and the presence of lead ion complexation by the-SH group.2. The adsorption conditions of lead on thiol-functionalized bentonite has been studied.The adsorption rate of lead could reach more than98%, when the initial lead concentration was100mg/L, the liquid-solid ratio was1:200, pH was6.0, KNO3concentration was0.10mol/L and adsorption period was60min at25℃. Desorption experiments of lead from thiol-functionalized bentonite and Ca-bentonite with simulated acid rain (pH=3.50), ionic strength of simulant acid rain and the temperature and time of desorption have been done, the desorption rate was nearly0on thiol-functionalized bentonite. The result shows that the adsorption of lead on thiol-functionalized bentonite is not affected by simulant acid rain, but the Ca-bentonite was affected by it.3. The study of the adsorption kinetics and thermodynamics showed that the adsorption of lead on thiol-functionalized bentonite followed Langmuir and Dubinin-Radushkevich(D-R) isotherm models well which indicated that the adsorption was taken place at the functional groups/binding sites on the surface of the adsorbent which was regarded as monolayer adsorption at20℃、30℃、408、50℃. Pseudo second order model describe the reaction rate best, adsorption capacity calculated by the model is consistent with that actual measurement, which the linear correlation coefficient (R2) is more than0.999. The study of the desorption kinetics showed that desorption kinetics of thiol-functionalized bentonite fitted the pseudo second order model at20℃、30℃、40℃、50℃.4. Effects of the thiol-functionalized bentonite for remediation of lead and lead-cadmium polluted soils were studied. The simulated acid rain (pH=3.50) was used as extracting agent, the amount of desorption of lead is less than0.05%, it shows that the fixation capacity for lead has a little different if application or no-application the thiol-functionalized bentonite on the condition of the natural acid rain. The desorption amount of lead is substantially increased by using the mixed extracting agent0.005mol/L DTPA+0.01mol/L CaCl2+0.1mol/L TEA, the desorption amount of lead increased with increase of the concentration of lead, then at the same concentration of lead, the desorption amount of lead is lowest when the contaminated soil was added the thiol-functionalized bentonite.