氨氮在煤矿采空区充填矸石中的运移机制

我国西部多数煤矿区矿井水往往含有较多的生产污水，导致其氨氮含量较高，利用煤矿采空区充填矸石对矿井水进行预处理已成为矿井水及矸石资源化利用的重要措施。以神华神东煤炭集团公司保德矿矸石为充填介质、以矿井水中的氨氮为研究对象，通过模拟采空区的水文地质环境，开展柱模拟实验，结合CXTFIT 2.1软件，研究氨氮在充填矸石中的运移机制，这对于评价煤矿采空区充填矸石对矿井水的预处理效果具有重要意义。结果表明:达西流速3.12 cm/h、25℃时，Cl?在充填矸石中的运移可用CDE模型较好地表征(r2=0.999)，较高的纵向弥散系数(D)、溶质分子扩散系数(D_f)、机械弥散系数(D_h)和弥散度(λ)值与充填矸石较大粒径、较长运移距离有关，淋出液中总溶解性固体(TDS)和Cl?的质量浓度呈显著线性关系；双点位吸附溶质运移模型能够较好地表征氨氮的运移过程，氨氮的阻滞系数R为23.79，其在矸石上的平衡吸附点位仅占总吸附点位的46%，一级动力学吸附速率常数α为3.5×10?4 h?1；氨氮的孔隙流速及水动力弥散系数远低于Cl?的数值，这主要与高含量的黏土矿物高岭石对氨氮的吸附有关；在649 h的氨氮运移过程中，亚硝酸盐和硝酸盐氮以及pH值均无明显变化，实验中后期TDS稳定，这进一步证实氨氮在模拟的矸石柱运移过程中以对流、弥散迁移及吸附为主，生物转化作用可以忽略。研究结果可为评价我国煤矿采空区地下水库的水质预处理技术提供重要理论依据。 

Transport mechanism of ammonia nitrogen in the simulated gob area packed with coal gangue

In many coal mining areas in western China, waste water produced during coal mining is often dominant in mine water, resulting in high ammonia nitrogen content. The pretreatment of mine water by filling gangue in coal mine gob areas has become an important measure for the resource utilization of mine water and gangue. The research took the coal gangue from Baode Coal Mine of Shenhua Shendong Coal Group Corporation as the filling medium and the ammonia nitrogen in mine water as the research object. Based on CXTFIT2.1, column simulation experiments were carried out to study the migration mechanism of ammonia nitrogen in the filling gangue by simulating the hydrogeological environment of the studied gob area. The results show that the migration of Cl? through the filled gangue could be well described by the convection-dispersion equation (CDE) at a Darcy flux of 3.12 cm/h at 25℃(r2 =0.999). The high values of D, D_f, D_h and λ were related to the large grain size and long migration distance of the filling gangue. There was a significant linear relationship between the contents of total dissolved solids (TDS) and Cl? in the effluent samples. The two-site adsorption solute transport model could well describe the migration process of ammonia nitrogen in the filling coal gangue. The arrest coefficient R of ammonia nitrogen was 23.79, and its equilibrium adsorption points on the coal gangue only accounted for 46% of the total adsorption points. The first-order kinetic adsorption rate coefficient α was 3.5×10?4 h?1. The pore velocity and hydrodynamic dispersion coefficient of ammonia nitrogen were much lower than those of Cl?, which was mainly related to the adsorption of ammonia by the high content of clay mineral kaolinite in the studied matrix. The variations of nitrite and nitrate nitrogen contents and pH were not obvious during the test duration of 649 h. The TDS in the effluent samples was stable in the middle and later stages of the experiment. The above results indicate that the transport of ammonia nitrogen in the simulated gangue column was dominated by convection, dispersion and adsorption while the biotransformation of ammonium ion could be ignored. The findings could provide an important theoretical basis for evaluating the water quality pretreatment technology of underground reservoirs in the coal gob area in China.