Studies on the Effects of Sodium Hydroxide on Hydrogen Bonding of Water and Ionic Liquid/H2O Systems by ATR-IR Analyses
NI Liu-fang1, 2, YU Jing1, WANG Xin-ping1, WANG Jun1, CAO Xiao-xia2, CAO Shi-lin1*, MA Xiao-juan1*
1. College of Materials Engineering, Fujian Agriculture and Forestry University, Fuzhou 350108, China
2. School of Ecological Environment and Urban Construction, Fujian University of Technology, Fuzhou 350108, China
Abstract：In this study, attenuated total reflection spectroscopy (ATR-IR) was used to analyze the influence of NaOH on the hydrogen bonding network of H2O and 1-ethyl-3-methylimidazolium acetate ionic liquid aqueous solution (EmimAc/H2O). The results showed that the addition of NaOH affected the symmetry and type of hydrogen bond of water aqueous solution. The symmetric hydrogen bond bands Ⅰ (3 218 cm-1) and Ⅱ (3 375 cm-1) decreased with NaOH concentration. The hydrogen bonds of the water were polarized in the presence of NaOH, thus producing continuous absorption bands; moreover, the absorptions of the continuous bands were enhanced with increasing NaOH concentration. In the case of the EmimAc, water affects both the cation and anion. The OH of H2O interacts strongly with COO- of EmimAc and generates a wide absorption band between 3 400 and 3 200 cm-1, while the interaction of proton on H2O and COO- makes the C═O absorption band red-shift. H2O addition could cause a blue shift or a decrease of the absorption between the band 1 600～1 200 cm-1, which is referred that water could damage the original hydrogen bond network of EmimAc and form “anion…HOH…anion” and weaken the interaction between cation and anion of ionic liquid. When water was substituted by NaOH and mixed with EmimAc, the absorption strengthened. It is probably that destruction of the EmimAc hydrogen bond network by NaOH aqueous solution is not as significant as water. In summary, the EmimAc/NaOH system can be used to reduce the viscosity of the ionic liquid system and the application cost of EmimAc, which has a specific guiding significance for the pretreatment of lignocellulosic biomass.
Key words：1-ethyl-3-methylimidazolium acetate; Sodium hydroxide solution; Attenuated total reflection spectroscopy
倪柳芳，余 璟，汪心娉，王 俊，曹小霞，曹石林，马晓娟. ATR-IR分析氢氧化钠对水及离子液体/水体系氢键作用的影响[J]. 光谱学与光谱分析, 2021, 41(10): 3106-3110.
NI Liu-fang, YU Jing, WANG Xin-ping, WANG Jun, CAO Xiao-xia, CAO Shi-lin, MA Xiao-juan. Studies on the Effects of Sodium Hydroxide on Hydrogen Bonding of Water and Ionic Liquid/H2O Systems by ATR-IR Analyses. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2021, 41(10): 3106-3110.
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