Liu Lecheng, Zheng Tianyuan, Ma Haoran, Hao Yujie, Liu Guangfei, Guo Bo, Shi Qing, Zheng Xilai
Key Laboratory of Marine Environment and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China; Shandong Provincial Key Laboratory of Marine Environment and Geological Engineering, Ocean University of China, Qingdao 266100, China.
Key Laboratory of Industrial Ecology and Environmental Engineering, Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
Sci Total Environ. 2024 Nov 15;951:175635. doi: 10.1016/j.scitotenv.2024.175635. Epub 2024 Aug 20.
Chemical denitrification by redox-active Fe(II) species is pivotal in the coupled iron and nitrogen cycles. The reductive dissolution of ferric minerals by ligand can generate Fe(II)-ligand complexes, but their reducing capability for electrophilic pollutants like nitrate and nitrite remains uncertain. Here, biogenic secondary iron minerals (SIM) after dissimilatory iron reduction were reductively dissolved by oxalate and the siderophore desferrioxamine B, and subsequently the partially-dissolved SIM (SIMD) effectively removed NO from groundwater via reduction, while exhibiting much lower reactivity towards NO. The dissolution and removal processes were well-fitted with the Kabai model and the pseudo-second-order adsorption model, respectively. The equilibrium NO removal capacity (q) of SIMD reached 0.146-0.223 mmol/g, accompanied with the rate constants as 0.433-0.810 g/(mmol·h). The emission of NO and NO verified the occurrence of chemical denitrification during NO removal by SIMD. From the perspective of Fe(II) reactivity, SIMD exhibited higher densities of surface Fe(II) and more negative Eh values than SIM, and these two indicators showed linear correlations with the removal rates. Combined with microscopic, electrochemical and spectral analysis, our results indicated the redox reaction of adsorbed Fe(II)-complexes with NO on SIMD surface. The concurrent substance biochar was also considered, as it indirectly influenced dissolution and pollutant removal by shifting the iron mineral phase in SIM from magnetite to goethite. These findings highlight the significant role of reductive dissolution of iron mineral in N transformation, expand the electron pool available to support chemical denitrification, and have implications for Fe and N cycling coupling with pollutant reduction.
氧化还原活性铁（II）物种介导的化学反硝化作用在铁和氮的耦合循环中起着关键作用。配体对铁矿物的还原溶解可生成铁（II）-配体络合物，但其对硝酸盐和亚硝酸盐等亲电子污染物的还原能力仍不确定。在此，异化铁还原后的生物源次生铁矿物（SIM）被草酸盐和铁载体去铁胺B还原溶解，随后部分溶解的SIM（SIMD）通过还原作用有效去除地下水中的NO，而对NO的反应性则低得多。溶解和去除过程分别与Kabai模型和准二级吸附模型拟合良好。SIMD的平衡NO去除容量（q）达到0.146-0.223 mmol/g，速率常数为0.433-0.810 g/（mmol·h）。NO和NO的排放证实了SIMD去除NO过程中发生了化学反硝化作用。从铁（II）反应性的角度来看，SIMD的表面铁（II）密度更高，Eh值更负，这两个指标与去除率呈线性相关。结合微观、电化学和光谱分析，我们的结果表明吸附在SIMD表面的铁（II）络合物与NO发生了氧化还原反应。同时还考虑了共存物质生物炭，因为它通过将SIM中的铁矿物相从磁铁矿转变为针铁矿，间接影响了溶解和污染物去除。这些发现突出了铁矿物还原溶解在氮转化中的重要作用，扩大了支持化学反硝化作用的电子池，并对铁和氮循环与污染物还原的耦合具有启示意义。
