Experimental Study On Removal Of Heavy Metal Pb From Groundwater By Carbonate Rock

Groundwater is seriously polluted with the industrialization and urbanization.Especially in the areas of mineral exploitation,The seepage of wastewater into the aquifer causes serious heave metals groundwater pollution,which is produced during mining and leachate of tailings stacking.Experimental study on removal of heavy metal pollution,it will contribute to the environmental protection research of heavy metal pollutants and to provide scientific basis for groundwater governance and remediation of heavy metal pollution.this paper selects Carbonate rocks in karst area of Southwest China and Heavy Metal Pb for the research object,then adopt the method of indoor batch test and column test to study removal of heavy metal Pb from water by carbonate.The main conclusions are as follows:(1)The removal of heavy metal Pb by carbonate rocks is affected by temperature,solution pH,initial concentration of solution and particle size of limestone.The increase of temperature will lead to the decrease of the ability of carbonate to remove heavy metal Pb in water.Carbonate can effectively change pH of acid solution.The ability of carbonate to remove Pb is enhanced with the increase of specific surface area.(2)The Langmuir isothermal adsorption model can be used to fit the batch test data and the fitting correlation coefficient is higher than 0.99.Carbonate rocks' ability of deal with heavy metal Pb in acidic environments are increased with the decrease of the particle size.Maximum adsorption quantity Qmax and K were increased with the decrease of the particle size.It was found that pseudo-2nd-order kinetic model could better describe the dynamic process of the removal of heavy metal Pb by carbonate rocks.(3)Four kinds of particle size of limestone isothermal adsorption test results found that:Under the condition of low concentration,the amount of heavy metals removed by limestone is almost the same.At this point,the amount of Pb removed by carbonate rocks depends on the amount of heavy metal Pb ion in the solution.Comparison of static and seismic dynamic test results can find that under vibration condition the removal rate and the maximum removal rate are improved.Under static conditions,Precipitation leads to limestone's surface passivation,then the ability to remove heavy metal Pb from aqueous solution was weakened.(4)The study on the removal of heavy metal Pb from aqueous solution by six different kinds of carbonate samples shows that the ability of carbonate to treat heavy metal Pb is closely related to the composition of rock.The content of calcium carbonate and hydrolysis capacity of carbonate rocks obviously affect the ability of removing heavy metals.The increase of soluble components can enhance the ability of carbonate rocks to remove Pb.(5)Through the column experiment phenomena show that:In the closed cycle test system,the increase of the flow velocity will significantly enhance the treatment ability of carbonate rocks to heavy metal Pb.In the closed cycle system of test,the increase of the flow rate substantially increases the contact time between the sample and the heavy metal solution.At the same time,the increase of flow velocity enhances the erosion of water flow to carbonate rock samples,the enhancement of erosion action can take away the precipitate on carbonate surface and enhanced the ability of carbonate to remove heavy metal Pb.