A five-year performance review of field-scale, slow-release permanganate candles with recommendations for second-generation improvements.
A five-year performance review of field-scale, slow-release permanganate candles with recommendations for second-generation improvements.
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DOI：
10.1016/j.chemosphere.2016.01.125
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发表时间：
2016-05
期刊：
影响因子：
8.8
通讯作者：
Brunner L
中科院分区：
文献类型：
--
作者：
Christenson M;Kambhu A;Reece J;Comfort S;Brunner L
2009年，我们在一个位于低渗透粉质粘土含水层的废弃垃圾填埋场发现了TCE羽流。为了治疗TCE，我们制作了直径为5.1或7.6 cm，长91.4 cm的高锰酸钾缓释瓶（氧化蜡烛）。2010年，我们通过插入同等质量的氧化蜡烛（7.6 cm和5.1 cm直径），比较了两种蜡烛安装方法。直径为5.1 cm的蜡烛用直推杆插入，而直径为7.6 cm的蜡烛则放置在屏风中，并放入10个永久井中。自安装以来，7.6厘米的氧化蜡烛大约每年翻新一次，轻轻地刮掉表面的氧化物。2012年，我们报告了初步结果；在本文中，我们提供了自安装以来的5年性能回顾。时间采样显示，放置在井中的氧化蜡烛稳定地降低了迁移的TCE浓度。此外，这些蜡烛仍然保持着氧化剂的内核，尚未有助于溶解前线，应该提供几年的服务。通过直接推动插入的氧化蜡烛已经停止降低TCE浓度，因为蜡烛外部形成了二氧化锰垢。为了抵消氧化垢，我们制造了含有六偏磷酸钠的第二代氧化蜡烛。实验室实验（批量和流动）表明，这些第二代高锰酸盐蜡烛具有更好的释放特性，不易氧化结垢。这一改进将减少对放置在井中的蜡烛进行维护的需求，并延长直接推入蜡烛的使用寿命。
In 2009, we identified a TCE plume at an abandoned landfill that was located in a low permeable silty-clay aquifer. To treat the TCE, we manufactured slow-release potassium permanganate cylinders (oxidant candles) that had diameters of either 5.1 or 7.6 cm and were 91.4 cm long. In 2010, we compared two methods of candle installation by inserting equal masses of the oxidant candles (7.6-cm vs 5.1-cm dia). The 5.1-cm dia candles were inserted with direct-push rods while the 7.6-cm candles were housed in screens and lowered into 10 permanent wells. Since installation, the 7.6-cm oxidant candles have been refurbished approximately once per year by gently scraping off surface oxides. In 2012, we reported initial results; in this paper, we provide a 5-yr performance review since installation. Temporal sampling shows oxidant candles placed in wells have steadily reduced migrating TCE concentrations. Moreover, these candles still maintain an inner core of oxidant that has yet to contribute to the dissolution front and should provide several more years of service. Oxidant candles inserted by direct-push have stopped reducing TCE concentrations because a MnO2 scale developed on the outside of the candles. To counteract oxide scaling, we fabricated a second generation of oxidant candles that contain sodium hexametaphosphate. Laboratory experiments (batch and flow-through) show that these second-generation permanganate candles have better release characteristics and are less prone to oxide scaling. This improvement should reduce the need to perform maintenance on candles placed in wells and provide greater longevity for candles inserted by direct-push.