Water desalination using membrane distillation with acidic stabilization of scaling layer thickness

Membrane scaling during water desalination by membrane distillation has been studied. A tap water was applied as a feed and diluted HCl solutions were used for periodical cleaning of module. The membrane morphology and the composition of deposits were determined using scanning electron microscopy coupled with energy dispersion spectrometry. The CaCO3 deposit covered not only the membrane surfaces but was also formed in the pores' interior. During the membrane rinsing an HCl solution dissolved the deposit inside the pores, which is synonymous with flooding of these pores by liquid. Due to the membrane wetting, a significant flux decline was observed. It was confirmed that the rate of membrane wettability might be limited by shorting a period between the cleaning operations. In this work the membranes were cleaned every 1-5 h, and as a result, the penetration of deposit into the pores was restricted up to the depth of 30 μm during 200 h of MD process. A periodical rinsing of membranes by HCl solutions did not have a negative influence on the membrane performance, and the MD module efficiency was stabilized during this period.