Comparison of membrane distillation performance using different feeds

Membrane distillation has been used for desalination of NaCl solutions and concentration of sucrose solutions. The effect of feed concentration on the performance has been studied. For the analysis, a theoretical model whose predictions on water fluxes agree well with the experimental ones has been used. The water flux reduction with the feed concentration increase has been explained in different ways depending on the solute considered.

MD can be used to obtain fresh water from salt solutions as well as concentrate sucrose solutions. MD performance (measured in terms of water flux through the membrane) decreases as the feed concentration increases. But the reason for this decrease is different for both solutions. For NaCl solutions it is due to, above all, water Water flux (10-3 kg/m 2 s) Water flux (10-3 kg/m2 s) Jw JA JB JC Recirculation flow rate (cm /s) Fig. 6. JW, JA, JB and JC ( as calculated in the text) vs. recirculation rate. Feed: 4 molar NaCl solution. Tb1 = 39ºC; Tb2 = 7ºC.