Compared to other desalination technologies, membrane distillation (MD) possesses several advantages, including the tolerance to high salinity, the capability to leverage low-grade heat sources, and the low capital expenditure.
However, MD faces the problems of membrane wetting and fouling when desalinating wastewater and seawater with complex compositions. Membrane wetting is a prominent challenge to MD because it allows direct permeation of the salty feed across membrane pores, resulting in salt passage and process failure. The inherent hydrophobicity of conventional MD membranes increases the fouling propensity of organic foulants (e.g., proteins and oil). This blocks the membrane pores, which leads to a lower water productivity. Oil-induced fouling is particularly relevant to MD because MD has been extensively explored and shown promising to desalinate the produced water from hypersaline shale oil/gas streams.
This technology relates to a novel NF/MD membrane to combat the issue of surfactant-induced wetting in MD. A dense top layer, which mimics the selective layer of NF membranes, is constructed on top of a polyvinylidene fluoride (PVDF) MD membrane.
The technology owner is currently seeking interested commercial entities to license the technology and develop it into a product.
This technology relates to the addition of a hydrophilic layer as well as an anti-fouling and anti-wetting layer onto a polyvinylidene fluoride (PVDF) membrane. The vapour flux data have confirmed that the hydrophilic layer does not add extra resistance to water vapour transport. The said membrane exhibits excellent resistance toward both surfactant-induced wetting and oil-induced fouling in direct contact MD (DCMD) experiments.
This membrane has enhanced hydrophilicity and oil-fouling resistance, leading to higher productivity.
Fouling Resistance of Membranes
An oil-containing saline solution was employed as the feed to test the fouling resistance of the three membranes.
After 4 hours of direct contact MD operation with an oil-in-water emulsion (1 g/L oil, 0.03 g/L SDS, and 0.6 M NaCl)
Hydrophilicity of Membranes
The global membrane separation technology market size was estimated at USD 17.9 billion in 2019 and is expected to register a CAGR of 11.7 % from 2020 to 2027.