Feasibility study on the application of coal gangue as landfill liner material

Coal gangue is one of the largest industrial solid waste all over the world, and many methods have been proposed for the recycling of coal gangue. In the present study, the feasibility of using coal gangue as landfill liner material is studied through a series of laboratory tests in terms of hydraulic conductivity, sorption characteristics and leaching behavior. The results indicated that the hydraulic conductivity of coal gangue could be smaller than the regulatory requirement 1×10^-7cm/s with a void ratio less than 0.60. The batch sorption experiments performed on Pb²⁺ and Zn²⁺ illustrated that the coal gangue showed remarkable sorption capacity for the two heavy metals, and the sorption capacity for Pb²⁺ was larger than that for Zn²⁺. Both the pseudo first-order and pseudo second-order models fitted well with the sorption kinetics data of the Pb²⁺ and Zn²⁺ on the coal gangue, and the Langmuir model was found to best-fit the sorption isotherms. The sorption capacity decreased in presence of multiple heavy metals, both for Pb²⁺ and Zn²⁺. Concentrations of heavy metals leached from the coal gangue were all below the regulatory limits from China MEP and U.S. EPA. These desirable characteristics indicated that the coal gangue has potential to be used as landfill liner materials.