Permeation properties of polymeric membranes for biohydrogen purification

Abstract

Palm Oil Mill Effluent (POME), generated from the oil extraction process, possesses high Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). POME can be treated in an efficient bioreactor under controlled conditions to produce high value biohydrogen mixture containing CO2. The H2 existence in the valuable gas mixture (in a reasonable quantity) could be used as a clean energy source for renewable energy i.e., in hydrogen fuel cell. CO2 presence in fuel cell causes CO2 poisoning and affects its performance. Therefore, the purification of H2 from CO2 produced from POME fermentation is desirable to ensure that an appropriate purity of H2 is achieved. This work focused on the performance of gas membrane separation technology; by specifically using two different polymeric membranes, namely polysulfone (PSF) and polydimethylsiloxane (PDMS). Based on the results obtained, the selectivity for H2/CO2 was achieved using PSF membranes; with the values obtained of 1.54–3.32 at a pressure of 1–8 bar. This result shows that PSF membranes have better performance for H2 purification than PDMS membranes. This is supported by the analysis of the membranes after the test, which includes Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. PSF membranes showed no changes on their FTIR spectra after permeation, while PDMS membranes, of 75 and 200 μm thicknesses, recorded higher transmittance of their spectra after permeation. The flexibility of the PDMS membranes is evidence of more permeance of the hydrogen mixture that leads to less selectivity of H2/CO2. Meanwhile, SEM and AFM analyses proved the morphology effects; which include changes of pore size distribution cross-section, membrane thickness and surface roughness, after permeation of the applied pressure from 1 to 8 bar, which was possibly due to the compaction effect.