Mass Transfer Study On The Extraction Of Cephalexin By Hollow Fiber Supported Liquid Membrane

Cephalexin is the most widely used cephalosporin antibiotic. The two mainindustrial production methods for Cephalexin are chemical synthesis and enzymaticsynthesis, and the latter offers several advantages owing to its nontoxicity, low energyand solvent consumption as well as environmental friendliness. However, purificationof Cephalexin from this dilute reaction mixture is challenging. Compared totraditional extraction techniques, liquid membrane extraction, as a promising newtechnique, has demonstrated more effective with higher separation efficiency andlower cost, and been widely used.Mass transfer of Cephalexin extraction with hollow fiber supported liquidmembrane has been studied. Experiments used organic membrane solution consistingof Aliquat-336, Isopar L and1-decanol. The aqueous strip solution containingpotassium chloride was dispersed in the organic membrane solution. Aresistance-in-series model was built and solved with the experiment results. Theinfluence of membrane dipping time was also checked and the proper dipping timewas determined.On the basis of experiment, a comprehensive2-D mathematical model for thetransport of Cephalexin has been developed based on Happel’s free surface mode withthe aid of computational fluid dynamics (CFD) simulation. The continuity andmomentum equations were derived and solved using finite element analysis combinedwith adaptive meshing. Effects of process parameters and module parameters on theextraction of Cephalexin were considered in the model, which agreed well with theexperiment data. Simulation results indicated that low Cephalexin concentration in thefeed solution was good for mass transfer. Increase in carrier concentration willenhance the extraction, but the increase is limited. The radial velocity profile in theshell side is approximately parabolic and is not developed in the inlet region ofsolvent. The pressure drop along the membrane contactor could also be neglected,which is one of the important advantages of membrane contactors. Flow rates in thetube and shell side have opposite influence on the extraction efficiency. Membraneparameters, including membrane internal fiber diameter, membrane thickness,porosity, tortuosity and number of fibers, also show different effects respectively. The model built here is suitable for various membrane modules, and the resultscan be a guide to process operation and membrane module design of Cephalexinextraction with hollow fiber supported liquid membrane.