The study of performance of polyethylene chlorinetrifluoroethylene membranes used for brine desalination by membrane distillation

In this work the possibility of production of fresh water from brines by membrane distillation process was discussed. Water desalination by membrane distillation is restricted by scaling and membrane wettability. The intensity of these phenomena was affected by membrane material. The presented studies were performed with the capillary hydrophobic membranes made from polyethylene chlorinetrifluoroethylene (ECTFE). For comparison, the membranes from polyvinylidene fluoride (PVDF), often used in studies of membrane distillation, were also applied. The both types of used membranes are commercial, and are manufactured for microfiltration. The membranes morphology and composition of deposits were determined using scanning electron microscopy coupled with energy dispersion spectrometry. The membranes resistance on wetting was confirmed during a long-term exploitation of the modules. The formation of scaling layer on the membrane surfaces was observed. The formed deposit covered not only the membrane surfaces but was also found in the pores interior and partial membrane wettability was observed. Due to these phenomena the permeate flux was gradually decreased, although a flux decline was faster for PVDF membranes. The FTIR analysis indicated that the membranes made from ECTFE are more chemical resistance than that from PVDF.