Nanofiltration and reverse osmosis membranes for purification and concentration of a 2,3-butanediol producing gas fermentation broth

Data collection method:

The membranes used in all dead-end filtration experiments were either purchased from Sterlitech (USA) or fabricated according to (Section 4.3.2). 2,3-Butanediol (98 %), Ethanol (≥ 99 %) and Acetic Acid (≥ 99 %) were purchased from Sigma Aldrich (UK). Ammonium Acetate (97 %) was purchased from Alfa Aesar (UK). Dead end filtrations were carried out in a Sterlitech HP4750 stirred cell made of stainless steel with an active membrane area of 14.6 cm2. A magnetic stirrer just above the membrane surface was used for mixing of the feed and minimizing concentration polarization. The dead end cell was placed in a water bath on a heater-stirrer for stirring speed and temperature control. Pressure was applied using compressed nitrogen and measured with a pressure gauge. Weight of permeate was recorded using a Sartorius LC3201D-00MS balance with a data logging program developed in Labview. Flat sheet membrane discs of 47 mm diameter were either cut out from larger flat sheets with a scalpel or used as received as pre-cut discs. NF and RO membranes were conditioned by permeating DI water under pressure before use for ~ 2 hrs, until constant flux was achieved. Polysulfone ultrafiltration membranes were conditioned at 60 ºC for 90 min with DI water. After conditioning, membranes were stored in DI water. The concentration of organic solutes in feeds, permeates and retentates were analysed by HPLC using an Agilent Technologies 1200 series instrument. A Phenomenex organic acids column (7.8 x 300 mm) was used at 60 °C with 5 mM H2SO4 as mobile phase and a flow rate of 0.7 mLmin-1. Solutes were detected with an RI detector and concentrations interpreted through the peak area using external calibration. Fermentation samples were prefiltered with a 0.22 μm syringe filter (Millipore, UK) before analysis to remove any suspended particles. pH measurements of solutions were conducted on a Denver Instruments 250 pH meter. The pH meter was calibrated to solutions of pH 4, 7 and 10 before use. Conductivity measurements were carried out on a Thermo Scientific Orion Versa Star conductivity meter.

Methodology link: