Serafin Stiefel

7 Sep 2012

Practical Experience

07/2009-02/2011 - 3M Germany, Neuss, Germany

Trainee program.

04/2008-10/2008 - Internship at Boehringer-Ingelheim,

Biberach. Division Engineering & Technology


02/2011 - Graduate Student, Institute for Chemical Process

Engineering (Prof.Matthias Wessling), RWTH Aachen University

Project focus: Electrochemical Membrane Reactors

10/2002-05/2009 - Rheinisch Westfälische Technische Hochschule Aachen University

Diploma in Mechanical Engineering, Majoring: Biochemical Process


01/2007-05/2007 - Diploma Thesis, Institute for Chemical Process Engineering, RWTH Aachen University

Title: “Modelling and Optimisation of a Membrane-based Reactive Extraction for the Separation of Organic Acids and Bases”

04/2007-04/2008 - Graduate research assistant for the Institute for Chemical Engineering, RWTH Aachen University

PDF of presentation


Acid-Base Reactions Enhancing Membrane Separation: Model Development and Implementation

Membranes are an efficient means of extracting organic acids from an aqueous solution. Separation performance can be increased by utilizing the acid-base behavior of the target molecules. In this work, a composite membrane separates the feed stream and the stripping fluid and is preferably permeable for non-polar molecules. The organic acids (e.g. phenol) permeate through the active layer of the membrane and deprotonate in the alkaline stripping fluid present in the porous membrane support, leading to a higher concentration of the respective conjugated base (e.g. phenolate). The consequence of the reaction is an increased concentration gradient of phenol across the membrane and thus improved mass transport. In addition, the charged bases in the stripping fluid are retained by the non-polar membrane.

An additional phenomen raises the complexity of the simulation: a convective water flux across the membrane can occur. The exact nature of how the water crosses the membrane has yet to be evaluated, but it is assumed that the osmotic pressure across the membrane is the main driving force. The influence of the water flux on the separation performance is highly complex, as it affects the transport of target molecules but might also hinder the influx of hydroxide-ions into the support structure and so lead to an undesired shift in the acid-base equilibrium in the support.

To improve understanding of the non-linear behavior of the governing system parameters and to investigate the character of the convective water flux across the membrane, the objective of this work is to develop a model covering mass transport coupled to the acid-base equilibrium reaction inside a composite membrane with Comsol Multiphysics.