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P204从盐酸体系中萃取铝的动力学
马赟
Subtype硕士
Thesis Advisor朱屯
1989-06-30
Degree Grantor中国科学院研究生院
Abstract利用恒界面池考察了二(2-乙基已基)磷酸(DEHPA,简写为HA)从HCl体系中萃取铝的动力学行为。稀释剂为正庚烷。料液用HCl-KC_8H_5O_4(邻苯二甲酸氢钾)缓冲溶液配制,以保证萃取过程中水相酸度不变。离子强度用KCl调节。P204浓度范围0.0075-0.06M,水相铝的总浓度0.01-0.06M, pH=2.47-3.22. 实验结果表明:1。尽管萃取反应对[Al~(3+)]或[AlL~+]应为一级,但由于水相酸度随铝浓度的改变而改变,萃取速率与水相铝的总浓度之间并不存在正比关系。2。萃取速率R∝[H~+]~(-2)。3。当[HA]=0.0075-0.03M时,R∝[HA]~(0.5)。当[HA]=0.03-0.06M时,R∝[HA]~(1.5)。4。当[HA]=0.0075M时,R∝S(界面积)。当[HA]=0.045M时,R≈constant。分析计算了Al~(3+)在水溶液中的主要存在形态,同时考虑了萃取在水相及界面发生的可能性,用最小二乘法对实验结果进行回归处理,推测本体系有两条反应途径:1。从Al(H_2O)_6~(3+)出发 (a) Al(H_2O)_6~(3+) + A~- <-> Al(H_2O)_5A~(2+) + H_2O (b) Al(H_2O)_5A~(2+) + A~- <-> Al(H_2O)_4A_2~+ + H_2O (c) Al(H_2O)_4A_2~+ + A~- <-> Al(H_2O)_3A_3 + H_2O (d) Al(H_2O)_3A_3 + HA <-> Al(H_2O)_2A_3(HA) + H_2O (e) Al(H_2O)_2A_3(HA) + HA <-> Al(H_2O)A_3(HA)_2 + H_2O (f) Al(H_2O)A_3(HA)_2 + HA → AlA_3(HA)_3 + H_2O 其中,反应(f)因为位阻最大,为速度控制步骤。2。从Al(H_2O)_4L~+出发(L~(2-)为邻苯二甲酸根.) (a) Al(H_2O)_4L~+ + A~- <-> Al(H_2O)_3LA + H_2O (b) Al(H_2O)_3LA + HA <-> Al(H_2O)_2LA(HA) + H_2O (c) Al(H_2O)_2LA(HA) + HA <-> Al(H_2O)LA(HA)_2 + H_2O (d) Al(H_2O)LA(HA)_2 + HA <-> AlLA(HA)_3 + H_2O (e) AlLA(HA)_3 <-> Al(HL)A_2(HA)_2 (f) Al(HL)A_2(HA)_2 + HA <-> Al(HL)A_2(HA)_3 (g) Al(HL)A_2(HA)_3 + A~- → AlA_3(HA)_3 + HL~-因为螯合配位的稳定性,反应(e)为速度控制步骤。萃取条件不同会使反应的主通道发生变化。1。萃取剂浓度[HA]<0.03M时,萃取为界面反应控制。2。萃取剂浓度[HA]<0.03M时,萃取为水面反应控制。
Other AbstractIn constant interfacical area cell(Lewis cell), a study has been made on the rate of aluminium extraction from hydrochloric acid solution with di-2-ethylhexyl phosphoric acid (DEHPA, HA) in n-heptane. The [H~+] in aqueous phase was maintained by adding HCl-KC_8H_5O_4 (potassium biphthalate) buffer solution, and the ionic strength of all aqueous phase was kept constant by adding KCl. Extractant concentrations were changed from 0.0075 to 0.06 kmol/m~3, pH was varied from 2.47 to 3.22, and aluminium concentrations were between 0.01 and 0.06 kmol/m~3. Following results were obtained. 1. Although the reaction rate should be the first order to [Al~(3+)] or [AlL~+], there wasn't a definite order with respect to the sum of the concentrations of all aluminium species in aqueous phase because of effect of aluminium concentration on pH. 2. The extraction rate R ∝ [H~+]~(-2). 3. As [HA] = 0.0075 - 0.03M, R ∝ [HA]~(0.5). As [HA] = 0.03 - 0.06M, R ∝ [HA]~(1.5). 4. As [HA] = 0.0075M, R ∝ S (interfacial area). As [HA] = 0.045M, R ≈ constant. Based on the calculation of the coordination states of the aluminium ions and the consideration of the different reaction egion, a reaction mechanism has been proposed to describe the process, which includes two main reaction paths as following. It can fit the experimental results quite well by using the linear least square regression with computer. 1. One is a path from Al(H_2O)_6~(3+) (a) Al(H_2O)_6~(3+) + A~- <-> Al(H_2O)_5A~(2+) + H_2O (b) Al(H_2O)_5A~(2+) + A~- <-> Al(H_2O)_4A_2~+ + H_2O (c) Al(H_2O)_4A_2~+ + A~- <-> Al(H_2O)_3A_3 + H_2O (d) Al(H_2O)_3A_3 + HA <-> Al(H_2O)_2A_3(HA) + H_2O (e) Al(H_2O)_2A_3(HA) + HA <-> Al(H_2O)A_3(HA)_2 + H_2O (f) Al(H_2O)A_3(HA)_2 + HA → AlA_3(HA)_3 + H_2O Equation (f) is the rate determing step becouse of the strongest steric effect. 2. The other one is a path from Al(H_2O)_4L~+ (L~(2-) = C_8H_4O_4~(2-)) (a) Al(H_2O)_4L~+ + A~- <-> Al(H_2O)_3LA + H_2O (b) Al(H_2O)_3LA + HA <-> Al(H_2O)_2LA(HA) + H_2O (c) Al(H_2O)_2LA(HA) + HA <-> Al(H_2O)LA(HA)_2 + H_2O (d) Al(H_2O)LA(HA)_2 + HA <-> AlLA(HA)_3 + H_2O (e) AlLA(HA)_3 <-> Al(HL)A_2(HA)_2 (f) Al(HL)A_2(HA)_2 + HA <-> Al(HL)A_2(HA)_3 (g) Al(HL)A_2(HA)_3 + A~- → AlA_3(HA)_3 + HL~- Equation (e) is the rate determing step because of the stability of chelating bond. The reaction region can be changed as the condition of extraction changed. 1. When [HA] < 0.03M, the extraction is contributed by interfacial reaction. 2. When [HA] > 0.03M, the extraction is contributed by aqueous phase reaction.
Pages71
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8385
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
马赟. P204从盐酸体系中萃取铝的动力学[D]. 中国科学院研究生院,1989.
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