Investigation On The Adsorption Mechanism And Effects Of Removal Of Ammonia Nitrogen In Mine Water By Coal Gangue From Baode Coal Mine

The No.8 coal seam of Baode coal mine in shendong mining area was taken as the research area,and the underground reservoir and the coal gangue obtained from the working face in the second mining area were taken as the research objects.The physical and chemical characteristics of coal gangue were analyzed by scanning electron microscope,X-ray fluorescence spectrometer and low temperature liquid nitrogen adsorption method.The adsorption kinetics and isothermal adsorption of ammonia nitrogen by coal gangue were analyzed through batch experiments,and the adsorption mechanism and treatment effect of ammonia nitrogen by coal gangue under the hydrogeological conditions of the underground reservoir in the study area were further studied by 2016 h column simulation experiment.The results were as follows:(1)The mineral composition of coal gangue in Baode mine was kaolinite,aluminum ore and quartz,which contained 64.5%clay mineral kaolinite.The surface of coal gangue showed flaky rock mass and clastic particles,among which the pores and micropores were relatively abundant,with an average pore diameter of 13.57 nm and the specific surface area was 9.25 m~2/g.The large specific surface area and high content of clay minerals made gangue have good adsorption performance.The influent concentrations of ammonia nitrogen and chloride ion in the underground reservoir in the mining area were 20.97 mg/L and 415.69 mg/L,respectively.After the mine water was purified in the underground reservoir,the removal rates of TDS and ammonia nitrogen were 49.17%and 62.47%,and the effluent concentrations was 124.51 mg/L and 7.87mg/L respectively.(2)The quasi second-order kinetic model and the Banham channel diffusion model could well simulate the adsorption mechanism of ammonia nitrogen by coal gangue,and the correlation coefficients R~2 were 1 and 0.994,respectively.The diffusion and adsorption of ammonia nitrogen in coal gangue pore was obvious.The adsorption process of ammonia nitrogen by coal gangue had chemical bond,which was mainly controlled by chemical adsorption mechanism.The isothermal adsorption process of ammonia nitrogen by coal gangue could be well characterized by Langmuir model(R~2=0.99),which indicated that the adsorption of ammonia nitrogen by coal gangue was mainly single-molecule layer adsorption,and the adsorption surface had both physical and chemical effects.In a certain time,the increase of initial concentration of ammonia nitrogen could improve the adsorption capacity of coal gangue to ammonia nitrogen.(3)At a Darcy flow rate of 0.32-0.40 cm/h and 25℃,the retardation coefficient(R_d)of ammonia nitrogen migration in coal gangue was 13.90,the hydrodynamic dispersion coefficient(R_L)was 1.33 cm~2/h,and the complete breakthrough time was1945 h.Within 278h,the ammonia nitrogen in leaching solution could be absorbed completely.The adsorption capacity of coal gangue to ammonia nitrogen reached 34.04mg/kg,and the adsorption capacity of coal gangue to ammonia nitrogen reached saturation at 1945 h.The corresponding maximum adsorption capacity was 113.05mg/kg,slightly lower than the saturated adsorption capacity of 126 mg/kg obtained in the oscillation adsorption experiment.The effluent p H decreased and increased alternately between 7.52-8.10,which might be related to the cationic exchange in the simulated water-rock system and the breeding of microorganisms.The research was of great significance to the promotion and application of underground reservoir technology,the efficient and comprehensive utilization of mine water,the resource utilization of coal gangue and the protection of ecological environment.It could also provide important theoretical basis for the research and development of gangue water treatment agent.