Characteristics Of Panxie Mine Water Quality And Application Of Nanofiltration Separation

In recent years,in order to meet the requirements of protecting ecology and environment,the coagulation sedimentation has been uesd to purge mine water to remove suspended solids（SS）,chemical oxygen demand（COD）and other pollutants.However,the purged mine water has possessed the disadvantages of high salinity,high sulfate content and high hardness,resulting in scaling and blockage in the mine water circulation system.It has seriously restricted the comprehensive utilization of mine water.The nanofiltration（NF）is a separation process of membrane by pressure.It intercepts the component with the molecular weight between 200 and 1000 Da.The nanofiltration membranes have a lot of surface and internal electric charges which are provided with selectivity for solute interception,and possess the advantages of high flux,low pressure and low energy consumption.In this paper,the effects of operating pressure,solution concentration and mass ratio of solute on nanofiltration were studied,as well as the relationship among Na⁺,Mg²⁺,Cl^-,SO₄^2-in the single salt solution,the simulated mine water and the mine water.The main results obtained are as follows.（1）In Huainan Panxie Mining Area,the main types of middle aquifer of cenozoic loose layer are the Cl-Na type and the Cl·SO₄-Na type,the lower aquifer of cenozoic loose layer is the Cl-Na Cl,the sandstone water are the Cl-Na,HCO₃·Cl-Na and Cl·HCO₃-Na,the Taihui water are the Cl·HCO₃-Na and Cl-Na,the Ordovician limestone water are the Cl-Na and Cl·SO₄-Na.（2）The membrane fluxes increased with the decrease of solute concentration and the increase of operat pressure regardless of the single salt solution,the simulated mine water or really mine water.It was according to the solvent permeation flux equation in the non-equilibrium thermodynamic model.（3）SO₄^2-not only promoted Cl^-to penetrate the nanofiltration membrane but also reduces the rejection rate of Cl^-in the simulated mine water.SO₄^2-played an important part in inhibiting the rejection rate of Cl^-.Mg²⁺not only promoted Na⁺to penetrate the nanofiltration membrane,but also reduced the rejection rate of Na⁺in the simulated mine water.Mg²⁺played a part in inhibiting the rejection rate of Na⁺.When Mg²⁺played a part in inhibiting the rejection rate of Na⁺,Na⁺promoted the rejection rate of Mg²⁺.The intensity of interaction between ions is related to the solubility of Mg²⁺.（4）The retention rates of K⁺,Na⁺,Mg²⁺,Ca²⁺and Cl^-increased firstly then tended to be constant with the increase of operating pressure in the Guqiao and Pan’er mine water.The retention rate of SO₄^2-kept stable and maintained a high level.It didn’t have obvious changing trend in the mine water.（5）Filtrating the mine water by nanofiltration,more than 90%of SO₄^2-could be removed,more than 60%of Mg²⁺and Ca²⁺could be removed.The content of scaling ions could be reduced greatly.There was a significant effect on separating sulfate and reducing the content of calcium and magnesium.