Finally, in all experiments the flux values obtained (5 g m2 h1)
were inferior to those described in the literature, such as those
mentioned in work by Molina et al. (2002), who obtained
500 g m2 h1 at a concentration of 15% (wt) under similar operating
conditions. This discrepancy indicates the need for optimization
of the operating conditions. However, the values obtained here are
consistent with the data provided by the membrane supplier. In this
regard, the results are considered to be encouraging because the
parameters show substantial increases in the recovery of ethanol
produced by fermentation using pervaporation compared with
using the standard mixture.
4. Conclusions
The use of the pervaporation process for the recovery of ethanol
from fermentation broth produced from lignocellulosic banana
waste demonstrated a very attractive alternative to classical methods.
When tests were carried out varying operational conditions
with model solutions, it was observed behaviors related to
reported in literature: a higher ethanol concentration in the feed
produces a higher ethanol flux and decrease the separation factor;
an increase of feed flow rate can enhance the permeation rate of
ethanol with the water remaining at almost the same value; water
and ethanol fluxes was increased with the temperature increase;
and the higher effect in flux increase was observed when the vapor
pressure in the permeate stream was close to the ethanol vapor
pressure. One interesting point was that the ethanol flux demonstrated
an increase even with ethanol concentrations less than
5 wt% in the feed (concentration expected in second generation
ethanol), but this increase is even greater at higher concentrations,
as expected. However, water flux increases more than alcohol,
resulting in a separation factor reduction.
It was observed that all of the parameters increased for the pervaporation
of the broth at low flow rates compared with the model