海绵铁及其组合材料PRB去除地下水中NO_3^--N的效果分析

Analysis on the effect of sponge iron and its composites PRB on NO_3^--N removal from groundwater

以海绵铁为可渗透性反应墙的介质,通过4组动态试验分析了海绵铁单层介质(1~#)、海绵铁+活性炭单层介质(2~#)、海绵铁+活性炭+沸石单层介质(3~#)、海绵铁+活性炭与沸石双层介质(4~#)对模拟地下水中NO_3^--N的去除效果。结果表明:在运行的8 d期间,1~#、2~#、3~#、4~#反应柱对NO_3^--N的去除率最高可分别达到91.1%、94.4%、87.9%、91.0%,且NO_3^--N质量浓度均能达标;4~#反应柱的出水中氨氮、NO_2^--N和总氮相较于其他反应柱均为最低,并且其NO_2-N质量浓度都在0.02 mg/L以下;电镜扫描和X射线衍射的分析表明,反应前后海绵铁表面形态和化学物质变化较大,反应后海绵铁表面产生了许多氧化物和氢氧化物,微孔隙被严重堵塞,阻碍了海绵铁与NO_3^--N的进一步反应。

Using sponge iron as permeable reactive barrier medium,the removal effect of nitrate nitrogen from the simulated groundwater is studied by four groups of dynamic test,including sponge iron monolayer medium（ 1^#）,sponge iron ＋ activated carbon monolayer medium（ 2^#）,sponge iron ＋ activated carbon and zeolite monolayer medium（ 3^#）,sponge iron ＋ activated carbon and zeolite double-deck medium（ 4^#）. The results indicate that during 8 days of running,the maximum removal rates of 1^#,2^#,3^#,4^#reaction column of nitrate nitrogen can reach 91. 1%,94. 4%,87. 9% and 94. 4%,respectively,and all the nitrate nitrogen concentration can meet the standard. In the effluent of 4^#reaction column,ammonia nitrogen,nitrite nitrogen and total nitrogen are the lowest in contrast with other reaction column,and the concentrations of nitrite nitrogen are below 0. 02 mg/Ls. Scanning Electron Microscope and X-ray diffraction analysis show that before and after reaction,a great change about the surface morphology and chemical composition of sponge iron is observed. After reaction,many new materials,such as oxides and hydroxides,are found on sponge iron surface,resulting in the blocking of the micro pore and hampering the further reaction of sponge iron and nitrate nitrogen.