(216d) Pilot Plant Scale up in Liquid Membrane Permeation with Supported Liquid Membranes (SLM)

Liquid Membrane Permeation is considered as an efficient membrane based separation technology. It can be applied to a wide range of separation tasks including removal of several heavy metal ions from industrial wastewater, extraction of pharmaceuticals or food additives such as lactic acid. Advantages of SLM over comparable processes like solvent extraction are low consumption of organic solvent and extractant and the permanent maximum driving force. Extraction and reextraction proceed in one step.

Goal of the current research project is to establish a SLM based continuous process for the recycling of heavy metal ions from aqueous solutions in industrial scale. In a first step two liquid membrane permeation units of different scales were constructed and commissioned. The construction principle is similar to a filter press arrangement. As support layer microporous polyethylene membranes were used. All experiments were carried out using the EFCE test system for reactive extraction Zn2+|DEHPA|H+. Subject of investigation was the determination of mass transfer coefficients and the comparison of model predicted transfer rates with the experimental results for test facilities of different size.

Based on the experimental data obtained from mass transfer experiments in a bench scale unit and a CFD simulation of the flow pattern in the aqueous phases, a pilot plant scale unit was constructed. The mass transfer area was increased by a factor of 70. Expectedly mass transfer is controlled by diffusion of species through the membrane. From bench scale experiments a mass transfer coefficient (Diffusion coefficient/membrane thickness) of k = 10-6 m/s was determined. Scale up was based on modeling a plug flow reactor. Validation of the pilot scale module confirmed the model.