【作者】 胡伟；

【导师】 李燕；

【作者基本信息】 吉林大学 ， 环境工程（专业学位）， 2022， 硕士

【摘要】 由于硝酸盐污染严重威胁着生态环境和人类健康,水体中硝酸盐去除成为了全球关心的问题,硝酸盐去除方法中最有效快速的方法之一是吸附。然而,现有大多数硝酸盐吸附剂存在吸附量低、选择性差、合成步骤繁琐及合成过程中产生有毒物质等问题。因此,研制具有显著硝酸盐吸附量和选择性且兼备合成单体少、时间短、过程环保的硝酸盐吸附剂是非常必要的。基于此,本研究采用共聚法快速合成了乙烯基咪唑/二溴癸烷/乙烯基吡啶聚合物（vinylimidazole/dibromodecane/vinylpyridine,VDV）硝酸盐吸附剂,提高有机吸附剂对硝酸盐的吸附量和选择性。此外,VDV与壳聚糖、碳多壁纳米管结合,制备了VDV/壳聚糖/碳多壁纳米管（VDV/chitosan/MWNT）硝酸盐检测电极,检测水中硝酸盐。本研究内容及结果如下:（1）确定吸附剂VDV中乙烯基咪唑、二溴癸烷和乙烯基吡啶单体间的最佳摩尔比为1:1:1,并对材料进行了扫描电子显微镜（SEM）、能谱分析（EDS）、傅里叶变换红外光谱仪（FTIR）、X射线光电子能谱（XPS）和同步热分析仪（TGA）表征分析。VDV对硝酸盐氮的最大吸附量可达52.6 mg/g,在热力学方面,吸附过程符合Freundlich模型（在温度15℃、25℃、35℃下的相关系数R²分别为0.998、0.997、0.995）。动力学方面,吸附过程符合准一级、准二级动力学模型（R²均大于0.99）,表明该吸附过程涉及化学和多层吸附。硝酸盐选择性方面,对于硫酸盐,当硫酸盐与硝酸盐氮浓度分别为350 mg/和56.45 mg/L时(SO₄^2-/NO₃^-浓度比为6.2),VDV对硝酸盐的选择性(K_e/c)仍可达到2.6（大于1）,说明吸附剂对硝酸盐具有选择性;对于碳酸氢根离子,当HCO₃^-/NO₃^-浓度比小于或等于6.2时,VDV的吸附量没有变化;对于氯离子,VDV硝酸盐吸附量随Cl^-/NO₃^-浓度比逐渐减小,当其浓度比等于6.2时,与硝酸盐单独存在的溶液相比,VDV吸附量下降了16.8%。VDV重复利用性方面,VDV在经过5次循环后,硝酸盐的吸附量依然稳定在VDV首次使用的91%,说明VDV具有稳定的重复利用性,解吸剂氯化钠最佳浓度为0.3 M。。在柱状动态实际废水吸附实验中,当污水处理厂二级出水硝酸盐氮浓度为20 mg/L,VDV对硝酸盐吸附量为13.51 mg/g,当工业废水硝酸盐氮浓度为100 mg/L时,其吸附量为25.04 mg/g,处理完的硝酸盐氮浓度均低于10 mg/L,表明VDV对低浓度二次出水和高浓度工业废水具有良好的处理效果。结合材料表征与实验结果,VDV对硝酸盐的选择性吸附机理主要包括VDV对硝酸盐的静电作用、VDV与硝酸盐间的离子交换和疏水作用。（2）在硝酸盐检测方面,利用VDV作为检测硝酸盐的活性层,与壳聚糖相结合（VDV与壳聚糖质量比为4:1）,碳多壁纳米管（浓度为200 mg/L）作为传导层,制备了VDV/chitosan/MWNT电极,用循环伏安法测得此电极的检出限范围为1～50 mg/L,相关系数R²为0.994。VDV/chitosan/MWNT电极相较于玻璃碳电极和VDV/chitosan电极来说,阻抗最小;进行优化条件时发现,p H为2时,VDV/chitosan/MWNT电极在检测时中显示出较高的电信号,且电极的富集时间在5分钟可达到稳定。在进行重复利用性时,发现电极在0.2 M Na Cl溶液中吸附/脱附6次,检测硝酸盐仍可保持较为稳定的电信号;VDV/chitosan/MWNT电极的检测范围为1 mg/L到50 mg/L,与相应的铁氰化钾氧化峰电流能显示出较好的线性关系（R²=0.994）。VDV/chitosan/MWNT电极进行共存离子实验时发现,在干扰离子/硝酸盐浓度都为50 mg/L的二元磷酸盐缓冲溶液中,SO₄^2-对检测电极产生电信号的干扰较大,而HCO₃^-和Cl^-对此电极的电信号没有影响。更多还原

【Abstract】 As nitrate pollution is a serious threat to the ecological environment and human health,nitrate removal from water bodies has become a global concern.Among the nitrate treatment methods,one of the most effective and rapid methods is adsorption.However,most of the existing nitrate adsorbents suffer from low adsorption capacity,poor selectivity,cumbersome synthesis steps and toxic substances generated during the synthesis process.Therefore,it is necessary to develop a nitrate adsorbent with excellent nitrate adsorption capacity and selectivity,and at the same time with less synthesis monomer,shorter time,and environmentally friendly process.Based on this,a polymeric sorbent vinylimidazole/dibromodecane/vinylpyridine（VDV）was synthesized by rapid copolymerization method to improve the nitrate sorption capacity and selectivity of organic adsorbent.In addition,VDV was combined with chitosan and carbon multi-walled nanotubes to prepare a VDV/chitosan/carbon multi-walled nanotube（VDV/chitosan/MWNT）nitrate detection electrode to detect nitrate in water.The contents and results of this study are as follows:（1）The optimal molar ratio between the adsorbent materials vinylimidazole,dibromodecane and vinyl pyridine monomers was determined to be 1:1:1,and the materials were characterized and analyzed by scanning electron microscopy（SEM）,energy spectrum analysis（EDS）,Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）and simultaneous thermal analyzer（TGA）.The maximum adsorption capacity of VDV for nitrate nitrogen was up to 52.6 mg/g.Thermodynamically,the adsorption process was in accordance with the Freundlich model（correlation coefficients R² of 0.998,0.997 and 0.995 at temperatures of 15℃,25℃and 35℃,respectively）.In terms of kinetics,the adsorption process conformed to the quasi-primary and quasi-secondary kinetic models（R² are greater than 0.99）,indicating that the adsorption process involves chemical and multilayer adsorption;In terms of nitrate selectivity,for sulfate,when the sulfate and nitrate nitrogen concentrations were 350 mg/and 56.45 mg/L respectively(SO₄^2-/NO₃^-concentration ratio was 6.2),the selectivity(K_e/c)of VDV for nitrate still reached 2.6（greater than1）,indicating that the adsorbent is selective for nitrate;for bicarbonate,when the HCO₃^-/NO₃^-concentration ratio was less than or equal to 6.2,the adsorption amount of VDV did not change;for chloride,when the Cl^-/NO₃^-concentration ratio was less than 6.2,the adsorption capacity of VDV for nitrate slightly decreased and when its concentration ratio was equal to 6.2,the adsorption capacity decreased by 16.8%compared with the solution in which nitrate was present alone;In terms of VDV reusability,the adsorption capacity of nitrate by VDV remained stable at 91%of the first use of VDV after five cycles,indicating that VDV has stable reusability,where the optimal concentration of desorbent in sodium chloride is 0.3 M.In the column dynamic actual wastewater adsorption experiment,when the nitrate nitrogen concentration of secondary effluent from wastewater treatment plant was 20 mg/L,the VDV adsorption capacity of nitrate was 13.51 mg/g,and when the nitrate nitrogen concentration of industrial wastewater was 100 mg/L,the adsorption capacity was25.04 mg/g.The concentration of nitrate nitrogen after treatment was less than 10mg/L,which showed that VDV has good treatment effect on low concentration secondary effluent and high concentration industrial wastewater.Combining the material characterization and experimental results,the selective adsorption mechanism of VDV on nitrate mainly included the electrostatic effect of VDV on nitrate,ion exchange and hydrophobic effect between VDV and nitrate.（2）For nitrate detection,the VDV/chitosan/MWNT electrode was prepared using VDV as the active layer part for nitrate detection,combined with chitosan（VDV to chitosan mass ratio of 4:1）and carbon multi-walled nanotubes（concentration of 200mg/L）as the conduction layer,and the detection limits of this electrode were measured by cyclic voltammetry in the range of 1～50 mg/L with a correlation R² of0.994.The VDV/chitosan/MWNT electrode showed the lowest impedance compared to the glassy carbon electrode and the VDV/chitosan electrode;when optimizing the conditions,it was found that the VDV/chitosan/MWNT electrode showed a high electrical signal at p H=2 and the enrichment time of the electrode was stable at 5 min.The VDV/chitosan/MWNT electrode showed good linearity（R²=0.994）in the detection range of 1 mg/L to 50 mg/L with the corresponding oxidation peak current of potassium ferricyanide.The VDV/chitosan/MWNT electrode showed good linearity in the detection range of 1 mg/L to 50 mg/L with the corresponding oxidation peak current of potassium ferricyanide;the VDV/chitosan/MWNT electrode showed good linearity in the detection range of 1 mg/L to 50 mg/L with the corresponding oxidation peak current of potassium ferricyanide.The coexistence ion experiment with the electrode revealed that SO₄^2-interfered more with the electrical signal generated by the detection electrode in the binary phosphate buffer solution with both interfering ion/nitrate concentration of 50 mg/L,while HCO₃^-and Cl^-had no effect on the electrical signal of this electrode.更多还原