Center for Environmental Systems, Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, 1 Castle Point Terrace, Hoboken, NJ 07030, United States.
Center for Environmental Systems, Department of Civil, Environmental and Ocean Engineering, Stevens Institute of Technology, 1 Castle Point Terrace, Hoboken, NJ 07030, United States.
Environ Res. 2022 Dec;215(Pt 2):114368. doi: 10.1016/j.envres.2022.114368. Epub 2022 Sep 20.
Amine-modified wheat straw (AMWS) has already been reported as a promising adsorbent for nitrate (NO) removal due to its cost-effectiveness and high efficiency. However, the NO removal mechanism has not been well understood, especially in the presence of co-existing ions. Here, the effect of co-existing anions on NO removal by AMWS was investigated and the underlying mechanisms were revealed using a combination of in-situ infrared (IR) spectroscopy and computational modeling. The in-situ IR results indicated that NO, sulfate (SO), and phosphate (PO) are all adsorbed as outer-sphere complexes on AMWS. The two-dimensional-correlation spectroscopy analysis implied the adsorption sequence of SO > PO > NO. The adsorption energies obtained from density functional theory calculation range from -0.24 to 0.51 eV (-23.2 to 49.2 kJ/mol), confirming that these anions adsorb on AMWS as outer-sphere complexes. For the first time, this study provides direct spectroscopic evidence of the outer-sphere adsorption of NO on AMWS, as well as identifies the adsorption sequence, confirmed by computational modeling. The competitive mechanism of NO SO, and PO revealed in this study is helpful to understand and predict the applications of AMWS.
胺改性麦草（AMWS）由于其成本效益和高效率，已被报道为一种很有前途的硝酸盐（NO）去除吸附剂。然而，NO 去除机制尚未得到很好的理解，特别是在存在共存离子的情况下。在这里，采用原位红外（IR）光谱和计算建模相结合的方法，研究了共存阴离子对 AMWS 去除 NO 的影响，并揭示了其潜在的机制。原位 IR 结果表明，NO、硫酸盐（SO）和磷酸盐（PO）均作为外配位络合物吸附在 AMWS 上。二维相关光谱分析表明吸附顺序为 SO>PO>NO。从密度泛函理论计算得到的吸附能范围为-0.24 至 0.51 eV（-23.2 至 49.2 kJ/mol），证实这些阴离子以外配位络合物的形式吸附在 AMWS 上。本研究首次提供了 NO 在 AMWS 上发生外配位吸附的直接光谱证据，并通过计算建模确认了吸附顺序。本研究中揭示的 NO、SO 和 PO 的竞争机制有助于理解和预测 AMWS 的应用。
