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G.R.A.S.S. – Boyang Li (Henson Group) and Xiangxi (Zoey) Meng (Perry/Schiffman Group)


Tuesday, October 23, 2018 - 11:30am


LGRT 201


Boyang Li – Michael Henson Lab

Modeling of Solid-Liquid Separation Processes in Downstream Pharmaceutical Manufacturing

As a solid recovery step in the purification of APIs (active pharmaceutical ingredients), filtration is an essential liquid-solid separation process in downstream pharmaceutical manufacturing. Many studies are based on cake filtration process, which is a typical unit operation of removing solid particles from a suspension by depositing them on a filter medium that is only permeable to the fluid phase. Some convention models can describe the overall filtration process, but with over-simplified assumptions, their applications are limited. We aim to obtain an in-depth understanding of the various factors affecting the filtration performance. Discrete Element Method (DEM), based on Newton’s equations of motion, is used to model the three-dimensional particle-particle interactions due to various forces. Computational Fluid Dynamics (CFD) is used to study the fluid behavior. As the fluid flow is affected by the suspended particles and the formed porous particle bed, in return the particle dynamics are affected by flow pattern. By two-way coupling of CFD and DEM via an open-source software (CFDEMcoupling, OpenFOAM-LIGGGHTS), both particle-particle and particle-fluid interactions can be captured. This simulation technique can generate detailed information at both microscopic and macroscopic levels, such as cake thickness, spatial cake porosity profile, specific cake resistance, flow rate as a function of time. The validity of this method is tested by comparing the simulated and experimental results under different operating conditions. Controlled numerical experiments are then performed to study the effects of particle properties, liquid properties and operating conditions on filtration performance.

Xiangxi (Zoey) Meng – Sarah Perry/Jessica Schiffman Lab

Shifting the Paradigm of Electrospinning: Forming Fibers from Complex Coacervates

We present the first demonstration of the direct formation of electrospun polyelectrolyte complex (PEC) fibers by investigating an aqueous complex coacervate solution, which is a dense phase from an associative electrostatic phase separation. Electrospun fibers had been well-known for many uses, such as biosensors and wound dressings, but traditional spinning involves organic solvents that can cause biocompatible concerns and limit the uses of fibers to encapsulate small, sensitive molecules as therapeutic agents. In this work, we used a canonical pair of strong polyelectrolytes, poly(styrene sulfonic acid, sodium salt) (PSS) and poly(diallyldimethyl ammonium chloride) (PDADMAC), in potassium bromide (KBr) solution as our model coacervates system to demonstrate the effects of coacervate solution properties, as well as the electrospinning apparatus on the formation of spun PEC fibers. Next, we encapsulated a family of fluorescent dyes (i.e. Brilliant Blue G and Fast Green FCF) in coacervates to achieve for subsequent highly-loaded, functional spun fibers. The effects of dye structures on the phase behavior of coacervates and their subsequent spinnability were studied as a function of dye and salt concentrations. We successfully controlled the formation of spun fibers over a wide range of apparatus and solution properties. Building on my previous studies, I propose to develop a mechanistic understanding of the design rules for spinnable coacervates by correlating the coacervate phase behavior and the subsequent electrospinnability by selecting three coacervate systems with different polymer chemistry and chain lengths. My studies take advantage of the fully aqueous nature of the complex coacervates solution as a new strategy to enable green and robust solid fibers as a next generation materials platform.

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