Recovery of n-butanol from salt containing solutions by pervaporation

The separation of volatile organic compounds (VOCs) from chemical waste streams containing salts is an interesting pervaporation (PV) application for recovery purposes. In this study, the separation of n-butanol (n-BuOH) by PV was investigated, and the influence of temperature, membrane choice, feed concentration, and the presence of sodium chloride (NaCl) was evaluated. Separation factor and partial fluxes were calculated for two hydrophobic commercial membranes (CMX-GF-010-D, CELFA AG, Switzerland and PERTHESE (R) 500-1, Perouse Plastic, France), when permeating pure water, n-BuOH/water, and n-BuOH/NaCl/water mixtures. Further, permeance was calculated for pure water and n-BuOH/water systems at 40 C. Results obtained indicate that an increase in temperature implies higher VOC fluxes and selectivities. The apparent activation energy for the transport of n-BuOH and water through the membranes indicate that n-BuOH flux is more affected by temperature changes than water flux. VOC fluxes through both hydrophobic membranes increase linearly with the driving force. The separation factor of both membranes towards n-BuOH is unchanged by an enhancement in the driving force. It was concluded that the Celfa membrane presents higher fluxes and is less selective towards n-BuOH than the P 500-1 membrane. The calculated overall permeances indicate a faster transport of compounds through Celfa than P 500-1 membrane. Further, the permeance of both membranes towards the transport of water was smaller than of n-BuOH. Celfa and P 500-1 were found not to be permeable to salts. The addition of NaCl caused a minor variation in the activation energy for the n-BuOH transport through the membranes. Further, the addition of salt has a modest effect on the PV properties of n-BuOH/water mixtures through P 500-1 and Celfa membrane.