Chemical Engineering Department, EEBE, Universitat Politècnica de Catalunya (UPC)-BarcelonaTech, c/Eduard Maristany 10-14, Barcelona 08019, Spain; Barcelona Research Center in Multiscale Science and Engineering, EEBE, Universitat Politècnica de Catalunya (UPC)-BarcelonaTech, c/Eduard Maristany 10-14, Barcelona 08019, Spain.
Chemical Engineering Department, EEBE, Universitat Politècnica de Catalunya (UPC)-BarcelonaTech, c/Eduard Maristany 10-14, Barcelona 08019, Spain; Barcelona Research Center in Multiscale Science and Engineering, EEBE, Universitat Politècnica de Catalunya (UPC)-BarcelonaTech, c/Eduard Maristany 10-14, Barcelona 08019, Spain.
Sci Total Environ. 2022 Mar 1;810:152300. doi: 10.1016/j.scitotenv.2021.152300. Epub 2021 Dec 10.
Injection of zero-valent iron nanoparticles (nZVI) into aquifers has gained increasing attention of researchers for in-situ treatment of NO-contaminated groundwater. nZVI has proved efficient in chemically reducing NO and, according to recent research efforts, in supporting biological denitrification under favoured conditions. Given the scarce research on nZVI pulsed injection in continuous-flow systems, the objective of this study was to evaluate the effect of nZVI pulses on the removal of NO from groundwater in packed soil columns and, more particularly, to elucidate whether or not biotic NO removal processes were promoted by nZVI. Three identical columns were filled with aquifer soil samples and fed with the same nitrate polluted groundwater but operated under different conditions: (A) with application of nZVI pulses and biocide spiked in groundwater, (B) without application of nZVI pulses and (C) with application of nZVI pulses. Results showed that the application of nZVI (at 30 mg/L and 78 mg/L doses) resulted in an immediate and sharp removal of NO (88-94%), accompanied by an increase in pH (from 7.0 to 9.0-10.0), a drop in redox potential (Eh) (from +420 mV to <100 mV) and a release of Fe(II) and Total Organic Carbon (TOC) in the effluent (to 200 mg/L and 150-200 mg/L, respectively). The released TOC came from the organic polymer used as stabilizer of the nZVI particles. Comparison against the sterilized control column revealed that, under the experimental conditions, no biological denitrification developed and that the removal of NO was due to chemical reduction by nZVI. The main by-product of the NO removal was NH, which at the prevailing pH was partially converted to NH, which dissipated from the aqueous solution resulting in a net removal of total dissolved N. A mass balance of Fe permitted to quantify the percentage of injected nZVI trapped in the column (>98%) and the NO retention capacity of the nZVI particles (13.2-85.5 mg NO/g nZVI).
将零价铁纳米颗粒（nZVI）注入含水层引起了研究人员的广泛关注，因为它可用于原位处理受污染的地下水。nZVI 已被证明可有效化学还原 NO，并且根据最近的研究结果，在有利条件下还可支持生物反硝化。鉴于关于连续流系统中 nZVI 脉冲注入的研究很少，因此本研究的目的是评估 nZVI 脉冲对填充土壤柱中地下水 NO 去除的影响，更具体地说，要阐明 nZVI 是否促进了生物 NO 去除过程。三个相同的柱子中填充了含水层土壤样本，并使用相同的硝酸盐污染地下水，但在不同条件下运行：（A）施加 nZVI 脉冲和地下水的杀生物剂，（B）不施加 nZVI 脉冲，（C）施加 nZVI 脉冲。结果表明，施加 nZVI（剂量为 30 mg/L 和 78 mg/L）会立即急剧去除 NO（88-94%），同时 pH 值升高（从 7.0 增加到 9.0-10.0），氧化还原电位（Eh）降低（从+420 mV 降低至<100 mV），并在流出物中释放 Fe(II)和总有机碳（TOC）（分别增加到 200 mg/L 和 150-200 mg/L）。释放的 TOC 来自用作 nZVI 颗粒稳定剂的有机聚合物。与灭菌对照柱进行比较表明，在实验条件下，没有发生生物反硝化作用，NO 的去除是由于 nZVI 的化学还原作用所致。NO 去除的主要副产物是 NH，在当前 pH 条件下，NH 部分转化为 NH，从水溶液中逸出，导致总溶解氮的净去除。Fe 的质量平衡可定量计算（>98%）注入的 nZVI 在柱中截留的百分比和 nZVI 颗粒的 NO 保留能力（13.2-85.5 mg NO/g nZVI）。
