A Preliminary Study On Remediation Of A Mining Tailings Contaminated Soil Using Natural Bentonite

Soil contaminated by heavy metals has been of worldwide concerns in past years, the pollution of soil calls for an immediate action to remediate these contaminated sites. Various physiochemical and biological processes, including soil washing, thermal desorption, electrochemical remediation, supercritical fluid extraction, bioremediation, and phytoremediation, have been used to restore the heavy metal contaminated soils. However, the remediation techniques used for clean-up processes are generally time consuming and expensive, and up to date there is still scarce of cost-effective and reliable remediation technology on a large scale. Therefore, we should find high efficient, low cost, and "environmentally friendly" materials to treat the contaminated soils.Because of large specific surface areas, low cost, high cation exchange capacity and ubiquitous presence in soils, bentonite is chosen to prevent heavy metals being released into the environment. Main original conclusions are shown as follows:1,Bentonite could effectively reduce the release of the heavy metals in the contaminated soil. The adsorption isotherm could be described using Langmuir-type model. The sorption of heavy metals by bentonite was related to the solution pH values, and the best pH value was 5.02,Bentonite could effectively reduce the release of Pb and Zn in the contaminated soil at different pH values. The observed concentrations of Pb and Zn in solution for the bentonite treatment were 44% and 58% lower than the control(no bentonite) respectively.3,Bentonite could effectively reduce the release of Pb and Zn in the contaminated soil at different ratio of bentonite to the contaminated soil. While the ratio of bentonite to the contaminated soil was 0.2, the observed concentrations of Pb and Zn in solution for the bentonite treatment were 33% and 78% lower than the control(no bentonite) respectively.4,The inhibition of the release of Pb and Zn from the contaminated soil was clearly enhanced with the increment of the added bentonite. When the added bentonite reached to a certain amount, the observed concentrations of Pb and Zn in solution were below detection limits.