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† 500-1, Perouse Plastie, 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 408C. 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.

Separation of organic compounds from aqueous solutions holds importance for its potential of preventing water pollution and recovering valuable materials. PV of n -BuOH through Celfa and P 500-1 membranes was conducted at different n -BuOH concentrations and temperatures in binary systems. In addition, the effect of salt content was analyzed. Results indicate that the membranes used are effective for the recovery of n -BuOH, even when an electrolyte is present. Fluxes through the membranes and the separation factor increased with temperature, with n -BuOH flux more influenced by changes in temperature than water flux. An increase in PV driving force implies increase in n -BuOH flux through the membranes. Selectivity values that P 500-1 and Celfa exhibit toward n -BuOH remained constant. Celfa and P 500-1 membranes are found not to be permeable towards NaCl. The presence of electrolyte caused a minor change in the temperature effect on n -BuOH fluxes through the membranes. Permeate flux and separation factor were independent of the existence of NaCl. Comparing the performance of both membranes, it can be concluded that Water flux, 66.41 kg m(2 s(1 9 1.12 through Celfa and 21.60 kg m(2 s(1 9 1.27 through P 500-1, were independent of the presence of salt. Celfa membrane presents higher fluxes but is less selective towards n -BuOH than P 500-1. The calculated overall permeances indicate a faster transport of compounds through Celfa than / Celfa membrane P 500-1 membrane Fig. 6. Effect of the presence of salt on the separation factor that Celfa and P 500-1 membranes exhibit towards n -BuOH when permeating n -BuOH/NaCl/water, mixtures at 313.15 K (408C) and a feed composition 0.2 wt.% n -BuOH.