Influence of inorganic fillers on the degradation of polypropylene membranes during membrane distillation

During water desalination by membrane distillation (MD) both process of wetting of hydrophobic polymeric membranes and their gradual degradation have been observed. The mechanical properties of polymer can be improved by the addition of fillers. The effect of introduction of inorganic fillers (mainly talc) on the properties of polypropylene membranes obtained by a thermally induced phase separation process has been investigated. Three types of capillary membranes manufactured in the industrial installation were used. A polypropylene homopolymer (Moplen HP 420 M) was applied for membranes production. Performance of the obtained polypropylene membranes was determined in the long-term studies of MD, using NaCl solutions (1-200 g/L) as a feed. The membrane resistance to thermal degradation was additionally evaluated using boiling brine enriched in HCO3- ions. The concentrated salt solutions slightly accelerated the membrane wetting and the electrical conductivity of distillate increased to a level of 200-500 mu S/cm after 850 h of MD process. However, the retention coefficient over 99% was achieved in each case. It was confirmed that the addition of inorganic fillers significantly improved the mechanical properties of membranes and decreased the thermal degradation of polypropylene.

Automated summary

The study investigated the effects of introducing inorganic fillers on the properties of polypropylene membranes in membrane distillation, showing improved mechanical properties and reduced thermal degradation. Performance of the membranes during MD process was evaluated using concentrated salt solutions, demonstrating slightly accelerated membrane wetting and increased distillate electrical conductivity while maintaining a high retention coefficient.