煤矸石中无机和有机氮的溶出规律研究

Release of inorganic and organic nitrogen from coal gangue

在我国生态脆弱煤矿区,地下采空区多以煤矸石为填充材料用于矿井水的临时储存和净化,然而,煤矸石中溶出的氮素对矿井水水质的影响研究报道却很少。文中以保德矿区采集的煤矸石为研究对象,在温度为25℃,达西流量0.25mL/min条件下通过柱模拟试验研究了地下采空区充填煤矸石无机和有机氮的溶出规律,这对于评价地下采空区预处理矿井水效果具有重要意义。研究结果表明:煤矸石溶出的氮素主要为氨氮,其次为有机氮。在整个实验过程中,煤矸石中氨氮、总氮(TN)及有机氮的溶出具有间歇性特点,这与所研究煤矸石的岩石成分、矿物成分和化学成分有关,且氨氮的间歇性溶出对淋出液中pH值的变化也有一定影响。淋出液中氨氮(NH+4-N)、硝态氮(NO-3-N)、亚硝态氮(NO-2-N)、总氮(TN)和溶解性总固体(TDS)浓度的最大值均出现在实验初始取样点18h;其中硝态氮、亚硝态氮和TDS均经过了快速下降、缓慢下降至稳定三个阶段。实验开始时淋出液中硝态氮浓度约为实验结束时的42倍左右,亚硝态氮浓度约为结束时的600倍左右。总体上,煤矸石中各类氮素在前期溶出速度较快,但溶出量随时间的推移而减小并趋于稳定。

In ecologically fragile coal mine area of China, coal gangue is used as filling material for the temporary storage and purification of mine water in underground goaf. However, little information is available on the impact of nitrogen released from the coal gangue on the quality of the mine water. Taking coal gangue collected in Baode mining area as the research object, the dissolution rule of inorganic and organic nitrogen of coal gangue filled in the underground goaf was studied by the column experiment at 25℃ and the Darcy flow of 0.25 mL/min, which was of great significance to evaluate the effect of pretreatment of mine water in underground goaf. The results showed that the nitrogen dissolved from coal gangue was mainly ammonia nitrogen, followed by organic nitrogen. In the whole experiment process, the dissolution of ammonia nitrogen, total nitrogen(TN) and organic nitrogen from coal gangue had intermittent characteristics, which was related to the rock composition, mineral composition and chemical composition of the studied coal gangue, and the intermittent dissolution of ammonia nitrogen also had certain influence on the effluent pH. The maximum concentrations of ammonia nitrogen(NH+4-N), nitrate nitrogen(NO-3-N), nitrite nitrogen(NO-2-N), total nitrogen(TN) and total dissolved solids(TDS) in the effluent all appeared at the initial sampling point of the experiment for 18 h. The NO-3-N, NO-2-N, TN and TDS through decreased rapidly, decreased slowly and tended to become stable during the column experiments. At the beginning of the experiment, the effluent NO-3-N concentration was about 42 times of that at the end of the experiment, and the NO-2-N concentration was about 600 times of that at the end of the experiment. On the whole, the dissolution rate of all kinds of nitrogen in coal gangue was faster in the early stage, while the dissolution rate decreased with time and tended to be stable.