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题名:
基于离子液体和生物质吸附剂的钒铬分离性能研究
作者: 胡乔宇
学位类别: 硕士
答辩日期: 2014-04
授予单位: 中国科学院研究生院
导师: 刘会洲  ;  赵君梅
关键词: 钒铬分离  ;  离子液体  ;  生物质吸附剂  ;  萃取  ;  吸附
其他题名: Studies on the separation properties of Vanadium (V) and Chromium (VI) Based on Ionic Liquids and Biomass Adsorbents
学位专业: 化学工艺
中文摘要: 钒和铬均为十分重要的金属资源,在催化、冶金、电镀、金属陶瓷等领域都具有非常重要的应用价值。同时,钒铬在工业上的广泛应用导致大量钒铬废渣和含钒铬废水的产生,从这些含钒铬废渣、废水中回收钒、铬具有资源化和环保双重意义。由于钒铬的物化性质相近,如何有效地从含钒铬共存资源中分离钒铬目前仍然是钒铬资源回收过程中的一个关键问题。 近年来,以离子液体和生物质吸附剂为代表的金属离子的绿色分离体系越来越受到研究者的广泛关注。离子液体(Ionic Liquids,ILs)是在室温下完全以离子状态存在的低温熔融盐,它的众多优良特性如不挥发性、不易燃性、低毒性、较宽的液程范围、对众多有机和无机物质良好的溶解能力、热稳定性和化学稳定性等使得ILs在分离金属方面具有代替传统挥发性有机溶剂(Volatile Organic Compounds,VOCs)的潜力。此外,以生物质为原料的吸附剂由于其低廉的价格、简单的合成步骤和良好的吸附效果也被广泛应用于金属分离领域。本论文从分离金属的绿色体系出发,系统地研究了离子液体和生物质吸附剂在钒铬分离方面的应用。 实验首先从七种疏水性咪唑型离子液体中筛选出了一种对钒铬分离效果良好的IL - [C8mim][PF6],系统地研究了纯离子液体[C8mim][PF6]从含有Cr(VI)的水相中萃取V(V)的行为及其他多种因素对萃取的影响。结果表明,[C8mim][PF6]对V(V)和Cr(VI)的分离系数βV/Cr在pHe = 3.5时达到最大值100.58,优于很多传统的溶剂萃取体系。由于V(V)和Cr(VI)在水溶液中主要以钒酸根和铬酸根阴离子的形式存在,研究表明[C8mim][PF6]萃取V(V)和Cr(VI)的机理为阴离子交换机理。相比于Cr(VI),[C8mim][PF6]对V(V)有较高的萃取能力与钒酸根阴离子具有较强的亲核性有关。钒的萃取在40 s内即可达到平衡,萃取过程符合拟二级反应动力学模型;升高温度会使钒铬的萃取率增加,萃取过程为吸热熵增的过程。虽然阴离子交换会导致IL损失到水相,但是反萃过程中使用碱性条件下的KPF6作为反萃剂,可以弥补IL的损失,且使V(V)的反萃率达到97.66%。经过9次循环萃取,IL对钒的萃取率仍然接近100%。 此外,初步研究了离子液体([A336][NO3])和酸化后的伯胺N1923(RNH3NO3)组成的混合萃取体系[A336][NO3] - RNH3NO3从水相中萃取分离钒铬的行为。研究表明,相比于单一的[A336][NO3]体系,[A336][NO3] - RNH3NO3混合体系对V(V)的萃取分配比有明显的提高,尤其在pHe = 3 - 5和pHe = 8 - 10两个区域内增幅更为显著;而对Cr(VI)的萃取几乎没有影响,仍维持在较低的水平。因此混合萃取体系可以提高钒铬的分离系数βV/Cr。而且碱性条件下的钒铬分离系数βV/Cr大于酸性条件下的βV/Cr。[A336][NO3] - RNH3NO3混合体系对V(V)和Cr(VI)的萃取在1 h内可以达到平衡,萃取动力学符合拟二级反应动力学模型。 最后,以干燥的橘子废渣为原料,负载Zr(IV)离子,制备生物质吸附剂Zr(IV)-SOW用于从水溶液吸附分离钒铬。Zr(IV)-SOW粒径均一(200 - 300 μm之间),在水溶液中的等电点为pH = 2.0左右。Zr(IV)-SOW对V(V)的吸附率在pHe = 2.85时达到最大值68%,而其对Cr(VI)的吸附率小于10%,此时钒铬分离系数βV/Cr计算值为12,高于传统的商业树脂D201。经过FTIR和XPS等表征证实,Zr(IV)-SOW吸附V(V)和Cr(VI)的机理属于阴离子交换机理。Zr(IV)-SOW对 V(V)和Cr(VI)的吸附在24 h内可以达到吸附平衡,吸附动力学均符合拟二级反应动力学模型;升高温度,金属离子在吸附剂上的吸附量增加,说明吸附反应是吸热反应。共存离子Cl-、NO3-对V(V)的吸附几乎没有影响,SO42-使V(V)的吸附率有一定程度的降低,PO43-的存在则显著降低了金属离子的吸附量。0.1 M的NaOH溶液可以将负载在吸附剂上的V(V)完全洗脱。Zr(IV)-SOW的动态柱连续吸附分离钒铬的实验表明,钒可以实现较高的富集因子,而铬的富集因子只有钒的1/12。 本论文的工作为离子液体和生物质吸附剂分离钒铬的基础研究提供了必要的基础数据,并预测了这些新型绿色的钒铬分离体系的可能的应用前景。
英文摘要: Both of vanadium and chromium are extremely important metallic resources, which have many practical applications in the fields of catalysis, metallurgy, electroplating, metal ceramic and so on. In addition, the wide applications of vanadium and chromium in industries result in the production of large amount of residue and wastewater containing V(V) and Cr(VI). Recovery of vanadium and chromium from those residue and wastewater is very significant in terms of both resourcfulization and environmental protection. As a result, how to effectively separate vanadium and chromium from V/Cr associated resources is still a key problem on the recovery of metallic resources due to the similarity of physical and chemical properties of V(V) and Cr(VI). Recently, the green separation systems of metal ions respresented by ionic liquids and biomass adsorbents have attracted more and more attentions. Ionic liquids (ILs) are a series of molten salts in low temperature that can exist completely in ionic state. They have great potentials to serve as substitutes of Volatile Organic Compounds (VOCs) because of ILs’ various unique properties including low vapor pressure, nonflammability, low toxicity, broad liquid range, excellent solubilities to inorganic and organic materials, excellent thermal and chemical stability and so on. What’s more, adsorbents based on biomass are also widely used in separating metal ions due to their low cost, simple synthesis and good adsorption performance. In brief, based on the green systems of metal separation, this thesis systematically investigates the separation of vanadium and chromium based on ILs and bioadsorbent. Firstly, IL - [C8mim][PF6] was screened from seven hydrophobic imidazolium ionic liquids due to it’s excellent performance in separating vanadium from chromium. Then the partition behavior of V(V) from Cr(VI) - including aqueous solution by pure ionic liquid [C8mim][PF6] as well as the influences of many factors on the extraction were systematically studied. The results showed that the separation coefficient of V(V) and Cr(VI) (βV/Cr) by [C8mim][PF6] can reach maximum value 100.58 at pHe 3.5, which is higher than βV/Cr of many traditional solvent extraction systems. In current experimental conditions, V(V) and Cr(VI) in aqueous solutions mainly exist as vanadate and chromate anions, thus the extraction mechanism of V(V) and Cr(VI) by [C8mim][PF6] was confirmed as anion exchange mechanism. Compared with Cr(VI), the higher extraction ability toward V(V) by [C8mim][PF6] was related with the stronger nucleophilicity of vanadate anions. The extraction of V(V) could reach equilibrium in 40 s, which followed the pseudo-second-order kinetic model. The increase of extraction efficiencies of V(V) and Cr(VI) with increasing temperatures showed that the extraction was a endothermic and entropy-increase process. Although the anion exchange mechanism would lead to the loss of IL’s anion to aqueous phase, the employment of KPF6 in alkaline condition as strippant could not only offset the loss of IL, but also make the stripping rate of V(V) reach 97.66%. After 9 cycles of consective operations, the extraction efficiency of V(V) can still remain nearly 100%. Additionally, the extraction and separation behaviors of V(V) and Cr(VI) by the mixed extractants composed of quaternary ammonium IL ([A336][NO3]) and acidulated primary amine N1923 (RNH3NO3) were investigated. The studies showed that the mixture [A336][NO3] - RNH3NO3 exhibited higher extraction distribution ratio towards V(V) compared with single [A336][NO3], especially in the pHe range of 3 - 5 and 8 - 10, while there is no obvious increase on the distributio ratio of Cr(VI). The extraction of Cr(VI) remained at a low level in both of the cases. Hence, the separation coefficient (βV/Cr) has also been improved in the mixed system of [A336][NO3] - RNH3NO3. Moreover, the values of βV/Cr is higher in alkaline solution than in acidic solution. The extraction equili
语种: 中文
内容类型: 学位论文
URI标识: http://ir.ipe.ac.cn/handle/122111/15560
Appears in Collections:研究所(批量导入)_学位论文

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Recommended Citation:
胡乔宇. 基于离子液体和生物质吸附剂的钒铬分离性能研究[D]. 中国科学院研究生院. 2014.
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