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本文采用火焰原子吸收光谱法,对碳纤维中碱金属,碱土金属离子的含量及试样中共存金属离子的干扰影响作了研究。由于碳纤维中钾、钠、钙、镁等离子在高温下易电离,会降低原子吸收的灵敏度(其中钙原子吸收灵敏度下降趋势尤为显著)。为了提高钙原子吸收的灵敏度,本文选用了氯化锶、氯化铯、氧化镧等抑制剂抑制待测金属离子的电离,提高钙原子吸收的灵敏度。抑制剂既能消除共存金属离子的干扰影响,又能提高分析结果的准确度。 相似文献
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选择性催化还原法(SCR)是目前治理NOx比较成熟和有效的手段,催化剂是SCR烟气脱硝系统中重要的组成部分,其性能会直接影响到SCR系统的整体脱硝效果和脱硝成本.在水泥、玻璃窑中,烟气成分中含有Na、K、Ca等碱及碱土金属,它们进入到SCR脱硝系统中后,会吸附于催化剂上,引起催化剂中毒,导致催化剂的使用寿命和催化效率显著降低,同时增加了SCR脱硝成本.本文介绍了碱及碱土金属对钒基和锰基脱硝催化剂的中毒研究情况,总结了其中毒作用机理、抗中毒能力提升及循环再生的相关研究工作进展. 相似文献
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Lithium may be recovered from the Dead Sea brines by a process which combines membrane separation with ion-exchange. Solvent-polymeric membranes based on alkyl-arylphosphates cause selective permeation of lithium ions with Br−3 as counter ions. Addition of the derivatives of neutral “crown” ethers did not improve their performance and an adverse effect, due to the decrease in the fluidity of the membrane system, was observed. Incorporation of ionizable “crown” ethers compatible with the system may, however, be advantageous; pH gradients could act as a driving force for transport of lithium in such systems. Membranes prepared with (2-ethylhexyl)-diphenyl phosphate (Santicizer 141) gave the best results from the point of view of selectivity of Li+ transport vs. Mg2+ and Ca2+. Maintenance of ca. 10−3 M concentrations of Br2 in the end-brine solutions gives optimal membrane performance. No significant change in membrane permeability and selectivity occurred during six months of their operation. Lithium ions in the product solution of the membrane separation process may be further separated from the residual Mg2+ and Ca2+ ions and concentrated up to 1 M by ion exchange processes. Lithium may be precipitated from such solutions, free from alkaline earth ions, as Li2CO3. 相似文献
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《分离科学与技术》2012,47(12):2077-2085
Abstract A simple method for rapid and selective separation of Ba2+ ion from alkali and alkaline earth metal ions by using octadecyl silica membrane disks modified with dibenzo-18-crown-6 in the presence of 0.01 M picric acid is presented. The influence of picric acid concentration, nature of the macrocyclic ligands, flow rates, and nature of the stripping acid have been investigated. Maximum capacity of the membrane disks modified by 10 mg crown ether was found to be 900 μg of Ba2+ ions. The method was applied to the recovery of barium ion from three different water samples and a certified reference material. 相似文献
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快速热解是生物质高效转化利用的重要方法之一,然而其目标产物生物油因含氧量高、组分复杂等不足而难以直接利用。通过在热解体系中引入碱土金属氧化物基催化剂,可以将热解产物中的氧元素以CO2和H2O等方式脱除,从而实现生物油品质的提升。总结了典型碱土金属氧化物基催化剂对生物质催化热解过程中发生的酮基化、羟醛缩合、开环和侧链断裂反应及机理,讨论了催化剂类型(CaO、MgO、基于碱土金属氧化物的分子筛和活性炭等)、生物质原料、温度、催化剂用量、停留时间、催化方式、催化剂失活等因素对生物油产率与品质的影响,并对生物质催化热解制备高品质生物油及其应用进行了展望。 相似文献
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杯芳烃作为继冠醚和环糊精之后的第三代超分子主体化合物,其应用领域日益广泛。本文综述了杯芳烃及其衍生物在医药、分子离子识别、模拟酶、相转移催化剂等方面的研究进展。 相似文献
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《溶剂提取与离子交换》2013,31(5):707-715
Abstract N,N,N′,N′‐Tetraoctyl‐3‐oxapentane diamide (TODGA) and its homologues were shown to be usefully applied to the extraction of divalent alkaline earth metal: M(II) ions from aqueous solutions of high nitric acid concentration, specifically around 3 M. The stoichiometry of the extracted Sr(II)‐DGA species was found to depend mainly on the concentration of nitric acid and molecular structure of DGA. The degree of extraction of M(II) by TODGA decreases in the order of Ca(II) > Sr(II) > Ba(II). 相似文献
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荧光型杯芳烃作为一类能发出荧光的物质被用作荧光探针,而杯芳烃带上荧光基团萘后,可利用其荧光发射光谱和荧光强度的不同,对有机分子和金属阳/阴离子等加以识别.荧光型杯芳烃的合成颇具价值.综述了国内外以荧光基团萘环的杯芳烃衍生物用作传感器的最新研究和应用进展. 相似文献