络合萃取3-氯苯酚的平衡研究

Studies on Reactive Extraction of 3-chlorophenol

3-氯苯酚(3-Chlorophenol,3-CP)是一种重要的化工原料,但也是一种毒性较大的环境污染物.本文使用最常用的萃取剂——磷酸三丁酯(TBP)为络合剂,四氯化碳为稀释剂,详细探讨了磷酸三丁酯萃取3-氯苯酚的平衡时间、络合剂种类和浓度、体系的pH、溶质浓度等因素对萃取效果的影响;还比较了四氯化碳、磺化煤油对萃取分配比(D)的影响;同时使用红外光谱定性分析了其络合萃取过程,并建立了萃取模型.实验发现:在常温下,振荡频率为(200±10)rpm,振荡2h,即可达到萃取平衡.与三烷基胺和2-乙基己基膦酸单2-乙基己基酯相比,TBP是萃取3-氯苯酚最好的萃取剂;且萃取分配比随萃取剂浓度的增大而增大.体系的pH是影响萃取效率的关键因素,在pH3~4.5范围内其萃取效果最好.四氯化碳作为稀释剂比磺化煤油好.分配比随溶质3-氯苯酚浓度的减小而增大,这也正是络合萃取的优势.红外光谱分析表明,TBP萃取3-氯苯酚是氢键作用机理,体系的pH不影响萃取机制.根据实验结果和萃取机理,建立了萃取模型,其表观络合萃取反应平衡常数为316.8L·mol-1.本研究结果不仅为萃取理论的发展提供了数据,同时也为3-氯苯酚的提纯及工程处理含酚废水、乃至酸性有机废水的治理提供了参考依据.

3-Chlorophenol(3-CP)is an important raw chemical material.However,it is also an environmental pollutant with high toxicity.In this work,the extraction conditions and the extraction mechanism of 3-chlorophenol using tributylphosphate(TBP)as extractant and tetrachloromethane as diluent were discussed.The factors that affect the extraction efficiency,such as extraction time,the type and the concentration of extractant,the aqueous pH and the concentration of 3-CP were investigated in detail.The reactive extraction process was analyzed qualitatively based on infrared spectroscopy results.It is found that the extraction equilibrium would reach in 2 h under the room temperature and 200±10 rpm of oscillation frequency.Comparing with trialkylamine and 2-ethylhexylphosphoric acid mono-2-ethylhexyl ester,TBP shows the best extraction efficiency for the extraction of 3-chlorophenol.Moreover,the extraction distribution is increased with the increase of the concentration of TBP.pH is the key factor that affects the extraction efficiency and the best pH value is in the range of 3-4.5.The extraction efficiency with tetrachloromethane as diluent is better than that with sulfonated kerosene.The extraction distribution ratio increases with the decrease of 3-CP concentration,which is exactly the advantage of reactive extraction.Infrared spectroscopy analysis indicates that the extraction of 3-chlorophenol with TBP belongs to hydrogen bonding mechanism,and the pH shows no effects on the extraction mechanism.According to the experiment and extraction mechanism,the extraction model was proposed,in which the reaction constant for the reactive extraction was calculated to be ca.316.8 L·mol-1.The results would not only supply useful data for the development of extraction theory,but also provide reference for the purification of 3-CP,the treatment of phenolic wastewater,and even the treatment of acidic organic wastewaters.