t-BAMBP分离铷钾萃取机理及热力学函数研究

Extraction Mechanism and Thermodynamic Functions of Rb^+ With t-BAMBP

为了提取稀有金属铷,研究了4-叔丁基-2-(α-甲苄基)酚(t-BAMBP,简称ROH)/二甲苯从高含量Na+,K+的碱性水溶液中萃取铷、钾的萃取机理。通过考察分配比D与pOH以及ROH浓度的关系,使用斜率法和饱和法测得萃取反应的萃合物组成为MOR.2ROH(M为K+,Rb+),证明了萃取机理为阳离子交换反应,确定萃取反应式为:M(+a)+OH(-a)+3ROH(o)MOR.2ROH(o)+H2O(a),进而计算得Rb,K的表观平衡常数K分别为2.729和1.317。由分配比与温度的关系,求得Rb,K的萃取热焓ΔH分别为-48.65,-23.99 kJ/mol,由ΔH以及表观平衡常数K计算得Rb,K的萃取反应的自由能ΔG分别为-2.487,-0.683 kJ/mol;熵变ΔS分别为-154.9,-78.21 J/(K.mol),证明萃取反应是放热反应。Rb的萃取能力大于K。

The extraction mechanism and thermodynamic functions of K^＋ and Rb^＋ with 4-t- butyl-2（a-methylbenzy） phenol （t-BAMBP, as ROH） - xylene extraction system were studied in alkali solution with high concentration of Na^＋ and K^＋. A modified hypothesis on mechanism was developed. The extraction balance reaction was determined by slope method and saturation method. By investigating the relation between coefficient of distribution （D） and pOH, concentration of ROH, temperature for the extraction of Rb^＋ and K^＋ , the extracted compound was determined as MOR· 2ROH （M for K^＋ , Rb^＋ ）, the extraction mechanism was determined as cation exchange mechanism, the extraction formula was determined as M（a）^＋ ＋ OH（a）^- ＋ 3ROH（o）←→MOR·2ROH（o）＋H2O（a）. The extraction apparent equilibrium constants （K） of Rb, K is 2. 729, 1. 317, respectivly. Meanwhile, the thermodynamic functions of Rb and K is. △H, -48.65, -23. 99 kJ/mol; △G, -2. 487, -0.683 kJ/mol; △S, -154. 9, -78.21J/ （K·mol）.