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铁是化工、冶金等工业过程常见杂质组份之一。化学沉淀、溶剂萃取及离子交换等常规除铁方法通常用于脱除溶液体系中较高浓度的铁杂质，对于微量或痕量铁杂质的脱除，常规除铁方法无法适用。离子印迹法凭借功能基团的选择性和模板离子的印迹效应，对目标离子具有较好的分离效果，已成为低浓度杂质离子分离脱除的新方法之一。离子印迹聚合物的制备与调控，是影响离子印迹法分离效果的关键因素。本论文以铁离子为模板离子，选择不同的功能单体，采用不同的方法制备了多种铁离子印迹聚合物，对其结构和吸附性能进行了表征和评价，并将其应用于钒、铬水溶液体系深度除铁工艺过程，对微量铁杂质获得了较好的脱除效果。本论文取得了如下进展：（1）采用本体聚合法制备了含羧酸功能基团的铁离子印迹聚合物，明确了功能单体与模板离子的作用方式，探究了功能单体与模板离子的比例对聚合物结构和性能的影响规律，研究了印迹聚合物对Fe(III)离子的吸附平衡和吸附动力学，确定了最佳吸附条件，并将其应用于Cr(III)溶液中微量铁杂质的深度脱除。结果表明，丙烯酸功能单体与Fe(III)离子的最佳摩尔比为9:1，印迹聚合物对Fe(III)离子的最大吸附容量为114.25 mg g-1，在Cr(III)离子存在的情况下对Fe(III)离子的选择性系数为492.18，相对选择性系数为50.87。铁离子印迹聚合物对溶液中Fe(III)离子的吸附符合Langmuir吸附等温式和准二级动力学方程。在pH为3.5、吸附温度为30 oC、吸附时间为18 h的优化条件下，该印迹聚合物对1.5 g L-1的Cr(III)溶液中铁杂质的去除率可达94.43%，除铁后溶液中铁杂质浓度仅为0.053 mg L-1，Cr(III)与Fe(III)的质量比达到26000:1。（2）以硅胶为基底，采用表面印迹法制备了含氨基或羧酸功能基团的铁离子印迹聚合物，并研究了其吸附性能。结果表明，通过硅胶表面氨基化制备的铁离子印迹聚合物，功能单体接枝率为4.46%，在Cr(III)离子存在的情况下对Fe(III)离子的选择性系数为81.88，相对选择性系数为8.06。然而，在Cr(III)离子和Fe(III)离子浓度均为50 mg L-1时，其对Fe(III)离子的吸附容量仅0.94 mg g-1。与本体聚合法制备的含羧酸功能基团铁离子印迹聚合物相比，通过硅胶表面接枝法制备的含羧酸功能基团铁离子印迹聚合物对Fe(III)离子的吸附速率明显加快。（3）制备并表征了含单膦酸功能基团的铁离子印迹聚合物，确定了功能单体与模板离子的最佳比例和作用方式，探究了其在较高浓度Cr(III)溶液中对Fe(III)离子的吸附条件、吸附平衡和吸附动力学。结果表明，在Cr(III)离子存在的情况下，含单膦酸功能基团的铁离子印迹聚合物对Fe(III)离子的选择性系数可达701.10，相对选择性系数为2.44。在pH为2.0、吸附温度为30 oC、吸附时间为3 h的优化条件下，含单膦酸功能基团的印迹聚合物在10 g L-1的Cr(III)溶液中对Fe(III)离子的吸附容量达到最大值15.71 mg g-1，且其吸附容量在Cr(III)浓度升高到12 g L-1时无明显下降。印迹聚合物和非印迹聚合物在Cr(III)溶液中对Fe(III)离子的吸附行为符合Freundlich吸附等温式和准二级动力学方程。（4）研究了含单膦酸功能基团的铁离子印迹聚合物对工业碱式硫酸铬样品中铁杂质的深度脱除工艺，讨论了铁离子在碱式硫酸铬溶液中的氧化还原规律，对比了铁离子印迹聚合物与两种商业离子交换树脂（Tulsion CH90Na和Tulsion CH93）的除铁效果。结果表明，含单膦酸功能基团的铁离子印迹聚合物可实现180 g L-1碱式硫酸铬溶液中铁杂质的深度去除，在优化的工艺条件下，除铁率可达98.16%。溶液经吸附和烘干后，碱式硫酸铬样品中铁杂质含量由处理前的111.31 mg kg-1降至4.33 mg kg-1，且样品的其它质量指标基本保持不变。碱式硫酸铬溶液中的Fe(II)离子经双氧水氧化后，可被残留的葡萄糖缓慢还原。与两种商业离子交换树脂相比，离子印迹聚合物除铁效果更好，铬的损失量更小，且铁的解吸更容易。（5）依次采用商业离子交换树脂（Tulsion CH93）和含单膦酸功能基团的铁离子印迹聚合物对含钒溶液中铁杂质进行了串联脱除工艺研究。结果表明，首先使用Tulsion CH93离子交换树脂进行除铁，在pH为1.25、吸附温度为30 oC、吸附时间为30 h、树脂与溶液体积比为0.07的优化条件下，可将3 g L-1的V(V)溶液中的铁杂质由1 g L-1降至30 mg L-1，去除率达96.39%。然后，在pH为2.5、吸附温度为30 oC、吸附时间为3 h的优化条件下，使用含单膦酸功能基团的铁离子印迹聚合物可将溶液中的铁杂质由30 mg L-1进一步降至2 mg L-1，去除率达92.70%。经两步串联脱除处理后，钒溶液中铁杂质的总体去除率达99.74%。;Iron is one of the most common impurities in chemical and metallurgical processes. Currently, the traditional iron removal methods, including chemical precipitation, solvent extraction and ion exchange, are only used to remove iron impurities in high content from aqueous solutions. However, for the aqueous solutions containing trace amount of iron impurities and large amount of coexisted ions, it is difficult to deeply remove iron impurities through the traditional methods. Ion imprinted polymers (IIPs), due to the selectivity of functional groups and the imprinting effect of template ions, have exhibited good performance in selective recognition of target ions and became one of the most promising methods for deep removal of impurity ions. However, the preparation and regulation of IIPs are the key factors affecting the separation efficiency of this method. In this paper, several Fe(III)-IIPs were synthesized through different methods by using the template of Fe(III) ions and corresponding functional monomers. The prepared polymers were analyzed and characterized, and their adsorption performance was also evaluated. The Fe(III)-IIPs were applied to remove trace iron impurities from aqueous solutions containing chromium or vanadium and high iron removal efficiencies were achieved.The main innovative progress is summarized as follows:(1) An Fe(III)-IIP with carboxylic groups was synthesized by bulk polymerization and the interaction between functional groups and template ions was determined. After that, the effects of the ratio of functional monomers to template ions on the structure and adsorption performance of the polymers were studied. Subsequently, the suitable adsorption conditions, adsorption equilibrium and adsorption kinetics of the prepared Fe(III)-IIP were studied. Finally, the prepared Fe(III)-IIP was used to deeply remove trace Fe(III) ions from Cr(III)-containing solutions. The experimental results indicated that the suitable molar ratio of functional monomers to template ions was 9:1. For the Fe(III)-IIP prepared under the optimized ratio, the selectivity coefficient and relative selectivity coefficient for Fe(III) ions were 492.18 and 50.87 in the binary solution containing Fe(III) ions and Cr(III) ions, respectively, and the maximum adsorption capacity of the prepared Fe(III)-IIP was 114.25 mg g-1. The adsorption processes could be well fitted by the Langmuir isotherm model and the pseudo-second-order equation. Under the optimized adsorption conditions of pH 3.5, 30 oC and adsorption for 18 h, 94.43% of iron impurities could be removed by the prepared Fe(III)-IIP when the initial concentration of Cr(III) ions was 1.5 g L-1. The residual iron concentration was only 0.053 mg L-1, and the mass ratio of Cr(III) to Fe(III) could reach 26000:1 in the treated solutions.(2) Fe(III)-IIPs with amino or carboxyl functional groups were prepared on the surface of silica gel by surface imprinting method and the adsorption performances of the prepared particles were studied. For the Fe(III)-IIP with amino groups, the grafting rate of amino groups on silica gel was 4.46%, and the values of selective coefficient and relative selective coefficient for Fe(III) ions were 81.88 and 8.06 in the binary solution containing Fe(III) ions and Cr(III) ions, respectively. However, its adsorption capacity was only 0.94 mg g-1 when the concentrations of Cr(III) and Fe(III) were both 50 mg L-1. For the Fe(III)-IIP with carboxylic acid functional groups prepared on the surface of silica gel through the surface initiation method, the adsorption rate was much faster than the Fe(III)-IIP prepared through the bulk polymerization method.(3) An Fe(III)-IIP with monophosphonic functional groups was synthesized and characterized. The suitable molar ratio of functional monomers to template ions and their interaction were determined. The suitable adsorption conditions, adsorption equilibrium and adsorption kinetics for the prepared polymers adsorbing Fe(III) ions from high concentration Cr(III)-containing solutions were studied. The results showed that the selectivity coefficient and relative selectivity coefficient for Fe(III) ions were 701.10 and 2.44 in the binary solution containing Fe(III) ions and Cr(III) ions, respectively. Under the optimized adsorption conditions of pH 2.0, 30 oC and adsorption for 3 h, the adsorption capacity of the Fe(III)-IIP for Fe(III) ions could reach 15.71 mg g-1 in solutions containing 10 g L-1 of Cr(III) ions, and the adsorption capacity did not decrease obviously with the concentration of Cr(III) ions increased to 12 g L-1. The adsorption processes could be well fitted by the Freundlich isotherm model and the pseudo-second-order equation.(4) The deep removal process of iron impurities from industrial basic chromium sulfate samples through the Fe(III)-IIP with monophosphonic functional groups was studied, and the redox behaviors of iron ions in basic chromium sulfate solutions were also discussed. Furthermore, the iron removal efficiencies of the prepared Fe(III)-IIP were compared with those of commercial Tulsion CH90Na and Tulsion CH93 cation exchange resins. The results showed that the iron impurities could be deeply removed from solutions containing 180 g L-1 of basic chromium sulfate by the Fe(III)-IIP with monophosphonic functional groups. Under the optimized conditions, iron removal efficiency could reach 98.16%. After adsorption and drying, the content of iron impurities in samples could be reduced from 111.31 mg kg-1 to 4.33 mg kg-1, and no obvious change of other quality indexes was found after the iron removal process. The Fe(II) ions could be selectively oxidized by H2O2 and then slowly reduced by the glucose remained in industrial basic chromium sulfate samples. Compared with the selected commercial ion exchange resins, the prepared Fe(III)-IIP could achieve a better performance on iron impurity removal, a lower loss of trivalent chromium and an easier process for desorbing the removed iron.(5) The removal of iron impurities from vanadium-containing solutions was studied through a continuous adsorption process by using the commercial Tulsion CH93 cation exchange resins and the Fe(III)-IIP with monophosphonic groups in order. The results showed that under the optimized adsorption conditions of pH 1.25, 30 oC and adsorption for 30 h, 96.39% of the iron impurities could be removed by using the commercial Tulsion CH93 ion exchange resin when the volume ratio of resins to solution was 0.07, and the content of iron impurities in solutions could be reduced from 1 g L-1 to 30 mg L-1. Subsequently, under the optimized adsorption conditions of pH 2.5, 30 oC and adsorption for 3 h, 92.70% of the iron impurities could be deeply removed by using the prepared Fe(III)-IIP, and the content of iron impurities could be reduced from 30 mg L-1 to 2 mg L-1. Therefore, by using the commercial Tulsion CH93 cation exchange resins and the Fe(III)-IIP with monophosphonic groups in order, the total removal rate of iron impurities could be achieved as high as 99.74%.
|朱光锦. 铁离子印迹聚合物的制备及其在钒、铬溶液深度除铁中的应用[D]. 中国科学院大学,2020.|
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