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伯胺及中性试剂从硫酸盐介质中萃取Fe(Ⅲ)的机理和动力学研究
孟锡泉
Subtype博士
Thesis Advisor陈家镛
1998
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline化学工艺
Other Abstract考查了伯胺N_(1923)单独从硫酸盐中萃取Fe(III)的行为。结果表明,萃取是按加成反应过程进行的,当平衡pH小于2.0时,铁基本上都以非水解的形式Fe~(3+)-SO_4~=被萃取。各种化学方法的实验结果及有机相的分析都表明此时萃合物中的胺-铁之比是3而不是2。对不同中性试剂对伯胺萃取铁的影响进行了考查。结果表明,中性试剂的给体性质在全面改善伯胺萃铁的性能方面起着关键的作用。加入具有给体性质的中性试剂后,可以在不同的pH条件下出现协萃或抑萃现象,选择官能团单一而且价格较为便宜、应用也更为广泛的TBP(磷酸三丁脂)作为协萃剂对伯胺N_(923)-中性给体体系萃铁的机理进行了深入的研究。光谱研究结果及有机相的分析结果都表明此时的铁是以部份水解了的形式Fe(OH)~(2+)被萃取的,斜率法、连续变量法及饱和容量法等大量实验结果也都表明此时的萃合物是Fe(OH)SO_4(RNH_3)_2SO_4(TBP)。通过对各种萃取现象及规律的比较和分析,可以认为是TBP的直接配位作用加强了伯胺对部份水解铁的萃取而是空间位阻效应抑制了对非水解铁的萃取,总的效果是使体系对部份水解了的铁有很好的选择性。在动力学研究中,首先对旋转圆盘扩散池进行了改进。用不锈钢的多孔薄膜取代滤纸膜,并通过研究KCl在膜池内的扩散传质对该膜及整个扩散池的适应性进行了考查。结果表明这种膜的有效扩散面积与路径之比比滤纸膜的大100倍左右,而且在不同转速下均可以精确确定。改进后的旋转圆盘扩散池除可以比较精确地研究传质在总过程中的作用外,更为准确判断过程的速率限制性步骤提供了可靠的手段。随后在标定过的扩散池中进行的伯胺-TBP萃铁的动力学研究是以三夹层(Sandwich)的形式进行的。实验研究结果表明,伯胺-TBP对铁的萃取受化学反应控制,在所研究范围内表观传质速率与池常数(或圆盘转速)无关,并且是理论扩散控制的传质速率大100倍左右。; With the purpose of stripping the iron (III) extracted in the organic phase back into the aqueous phase with dilute sulfuric acid solution, the extraction of iron (III) from sulfate solution with either primary amine N_(1923) or the mixtures of N_(1923) and neutral chemicals as solvent has been extensively studied from the point of view that the overall modification of the amine extraction system was achieved with proper addition of other extractants. In the first part of the work. The ratio of amine to iron in extracted species was 3 and the overall extraction reaction was: Fe~(3+) + 3SO_4~= + 3H~+ + 3RNH_2 = Fe(SO_4)_3(RNH_3)_3. The bonding behavour in extracted species can be summarized as: The dissociated form of amine sulfate was probably involved in extraction reaction and the dissociation was the rate-controlling step. Morever, the extraction behavour was not sensitive to the change of aqueous pH value, and for efficient stripping of iron (III) extracted it was necessary to treat the iron (III)-contained organic phase with extremly concentrated sulfuric acid solution to convert the amine sulfate into acidic amine sulfate. The partially hydrolyzed iron (III) was extracted in small amount when equlibrium pH was higher, which caused shift of absorbence peak in spectra of iron (III) in organic phase from 305nm to 295nm. With addition of neutral chemicals or not, the iron extraction differed greatly. The experimental results showed that the donor property of the additive played a very important role in modification of iron extraction by primary amine. When the mixtures of primary amine N_(1923) and neutral donors was used as solvent, enhancement was found in both rate and the efficiency of the extraction depending on the aqueous pH value, i.e. synergism appeared in higher pH (pH > 1.5 for [Fe] ~ 5gdm~(-3)) and anti-synergism in lower pH (pH < 1.3 for [Fe] ~ 5gdm~(-3)), which made it feasible to strip the iron extracted back into the aqueous solutions with dilute sulfuric acid solution. The octanol-2 was chosen as the synergistic agent for further study on iron removal in ZnSO_s4 solution. For both composed solution and high pressure leaching liquor of ZnS, satisfactory removal or separation of iron (III) from Zn were obtained, and the consumption of sulfuric acid was 10 times less than that of the traditional extraction process by primary amine, and separation factor of Fe-Zn was up to 10~6. In conclusion, the mixture of primary amine and donors constituted a potential extraction system for Zn-Fe separation in sulfate solution. Consequently, the mechanism of iron (III) extraction by primary amine N_(1923) and neutral donor has been investigated and TBP (tri-butyl phosphate) has been chosen as the synergistic agent for its simple function group and lower price. Both spectrometry studies and chemical analysis of the organic phases indicated that iron (III) was extracted in the partially hydrolyzed form of Fe(OH)~(2+)-SO_4~=. The results obtained by various methods (including slope method, the method of continuous variation and saturation capacity) showed that the extracted species was Fe(OH)SO_4(RNH_3)SO_4(TBP) and the overall extraction reaction was as follows: Fe~(3+) + SO_4~= + (RNH_3)SO_4+TBP+H_2O = Fe(OH)SO_4(RNH_3)_2SO_4(TBP)+H~+ The comparison of effects of TBP, TBPO (tri-butyl phosphine oxide), and TBenP (tri-benzyl phosphate) indicated that the TBP molecule bonded directly to iron (III) by oxygen in P = O group. The bonding form in extracted species can be represented by: It was the direct bonding of donors that made the extraction of partially hydrolyzed iron (III) much more effective, and the stereoselectivity of coordination that made the extraction of unhydrolyzed iron (III) depressed, so that the extraction system became selective to the partially hydrolyzed iron (III). In this case, the stripping behavour of the extraction system was improved in two aspects. Firstly, the iron (III) was extracted in the partially hydrolyzed form of Fe(OH)~(2+), which made the extraction be sensitive to the change of aqueous pH value and then possible to strip the iron (III) extracted quite effectively on condition that the hydrolyzed iron (III) was destroyed. Secondly, the amine's basicity was increased by its interaction with donors, which made it much easier to convert primary amine sulfate into acidic amine sulfate. In the second part of the work.
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8340
Collection湿法冶金清洁生产技术国家工程实验室
Recommended Citation
GB/T 7714
孟锡泉. 伯胺及中性试剂从硫酸盐介质中萃取Fe(Ⅲ)的机理和动力学研究[D]. 北京. 中国科学院研究生院,1998.
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