【作者】 吕建华；

【导师】 李春利；

【作者基本信息】 河北工业大学 ， 化学工艺， 2009， 博士

【摘要】 本文以异辛醇为络合剂,甲苯为稀释剂,对从强酸性高镁低硼卤水中络合萃取硼酸的过程进行了研究,建立了硼酸络合萃取液-液平衡模型,并开发了低浓度硼酸的络合萃取工艺。论文研究了络合剂异辛醇浓度、不同稀释剂(煤油、甲苯、甲基苯酚)对萃取率、分配系数和分相时间的影响,当甲苯作为稀释剂,络合剂异辛醇浓度为0.5(v/v)时萃取效果最好。采用络合剂浓度0.5(v/v),萃取相比O/A=1:1 (有机相:水相),研究了卤水溶液pH值和镁离子浓度对萃取相平衡的影响,当pH<3,且镁离子浓度在3.3 mol·L-1以上时,硼酸在两相中的分配系数较大,有利于硼酸络合萃取过程的进行。同时采用纯水对萃取剂的再生进行了研究,确定了相比A/O=0.7:1(水相:有机相)、六级逆流萃取的再生条件。采用了红外光谱和斜率法相结合的分析手段,对于硼酸络合萃取机理进行了研究。首先采用红外光谱定性分析了萃合物的组分,然后采用斜率法确定了萃合物的组成。结果表明:异辛醇和甲苯组成的络合萃取剂对硼酸没有物理萃取能力,只有化学萃取能力,即通过异辛醇与硼酸发生酯化反应,生成硼酸异辛酯,硼酸异辛酯溶于有机相,来完成硼酸的萃取;而且萃合物只包括硼酸单异辛酯和硼酸二异辛酯,且相比越大,卤水中镁离子浓度越高,萃合物中硼酸二异辛酯所占的比例越大。应用热力学基本原理,从基本电解质溶液理论出发,建立了强酸性高镁低硼条件下异辛醇络合萃取硼酸的液-液平衡模型,回归了交互作用参数。应用此模型模拟了四级和八级错流萃取过程,以及八级逆流萃取过程,模型计算结果与实验值偏差不大于5%,验证了模型了可靠性。在机理研究的基础上,开发了从强酸性高镁低硼卤水中络合萃取硼酸的工艺流程,模拟结果表明此工艺可以将卤水中硼含量降低到30 mg·L-1(以B2O3计)以下,使卤水达到生产高品质氧化镁材料的要求,同时回收了硼酸,实现了卤水资源的综合利用。更多还原

【Abstract】 The boric acid complexation extraction from strong acid brine with high concentration of magnesium and low concentration of boron was studied by using isooctyl alcohol as complexing agent and toluene as dilution agent. A liquid-liquid equilibrium model of boric acid complexation extraction was established and the complexation extraction process was developed for low concentration of boric acid extraction.The effects of concentration of complexing agent isooctyl alcohol and different dilution agents (kerosene, toluene and methyl-phenol) on extraction efficiency, coefficient of distribution and phase splitting time were investigated. The best extraction result was achieved with toluene as dilution agent and the concentration of complexing agent isooctyl alcohol of 0.5 (v/v). Under the conditions of 0.5 (v/v) isooctyl alcohols and extraction phase ratio O/A=1:1 (organic phase: aqueous phase), the effects of pH value of brine and magnesium ion concentration on extraction phase equilibrium were also studied. The boric acid complexation extraction is promoted as the pH<3 and the concentration of magnesian ion is more than 3.3 mol·L-1, while the partition coefficient of boric acid is larger in two phases. The regeneration of extractent with water was also investigated and the regeneration conditions of six-stage countercurrent regeneration were determined while A/O = 0.7:1 (aqueous phase: organic phase).The mechanism of boric acid complexation extraction was studied by the combination of IR and slope ratio method. The components of the complexation were qualitatively analyzed by using IR, and then the composition of the complexation was calculated with slope ratio method. The research results were concluded as the followings: (1) The complexation agent that was composed of isooctyl alcohols and toluene has the chemical extraction ability on the boric acid, but does not have the physical extraction ability. The extraction of boric acid was accomplished by the formation of isooctyl borate through esterification reaction of isooctyl alcohols and boric acid, because the isooctyl borate can be dissolved into the organic phase. (2) The complex compound only includes mono-isooctyl borate and di-isooctyl borate. The biger phase ratio and concentration of the magnesium ion, the biger percentage di-isooctyl borate in the complexation.According to the thermodynamic fundamental and the electrolyte solution theory, a liquid-liquid equilibrium model was established for the boric acid complexation extraction with isooctyl alcohol under the conditions of high concentration of magnesium and low concentration of boron, and the interaction parameters of the model were calculated through regression. The four-stage and eight-stage cross extraction process, as well as the eight-stage countercurrent extraction were simulated by the model. The data deviation between the experiment and the model calculation is less than 5%, which proves the validity of the model.A complexation extraction process of boric acid from the strong-acid magnesium ion brine was developed on the basis of above investigation. The simulation of the process demonstrated that the boric acid concentration of extracted brine can reduce to less than 30 mg·L-1 (based on B2O3). This extraction process makes the brine good material for producing high purity magnesium oxide and recovers boric acid, which realizes the comprehensive utilization of the brine.更多还原