Resistance of Polypropylene Membrane to Oil Fouling during Membrane Distillation

Abstract

The influence of oil emulsion presence in the water on the course of water desalination by membrane distillation was studied. The feed water was contaminated by oil collected from the bilge water. The impact of feed composition on the wetting resistance of hydrophobic polypropylene membranes was evaluated during long-term studies. Two types of the capillary membranes fabricated by thermally induced phase separation method were tested. It has been found that these membranes were non-wetted during the separation of NaCl solutions over a period of 500 h of modules exploitation. The addition of oil (5–100 mg/L) to the feed caused a progressive decline of the permeate flux up to 30%; however, the applied hydrophobic membranes retained their non-wettability for the consecutive 2400 h of the process operation. It was indicated that several compounds containing the carbonyl group were formed on the membranes surface during the process. These hydrophilic compounds facilitated the water adsorption on the surface of polypropylene which restricted the oil deposition on the membranes used.

Membrane Distillation Crystallizer Applied for Separation of NaCl Solutions Contaminated with Oil

“…The brines contaminated up to 100 mg/L of oil separated by the MD process conducted for several thousand hours showed a good wetting resistance of capillary PP membranes [ 11 , 33 ]. However, some unfavorable changes were noticed after several hundred hours of MD, when the concentration of NaCl in the feed was 300 g/L [ 11 ].…”

“…In the present study, the Accurel PP V8/2 polypropylene capillary membranes manufactured by Membrana GmbH (Wuppertal, Germany) were tested. These membranes are fabricated by thermally induced phase separation (TIPS) and exhibited a partial oleophobic performance [ 33 ]. The capillaries inner diameter and the wall thickness were equal to 5.5 mm and 1.5 mm, respectively.…”

“…The desalinated water can also contain petroleum pollutants, which accelerate the wetting of membranes at high salt concentrations in the MDC installation [ 19 ]. A previous work has shown that the presence of small amounts of oil (up to 100 mg/L) forming an emulsion with micrometer droplets does not wet the PP membranes [ 11 , 33 ]. The hydrophilic groups, such as carboxyl groups, are formed on the polymer surface during the MD process, which gives the PP membrane some oleophobic properties [ 33 ].…”

“…A previous work has shown that the presence of small amounts of oil (up to 100 mg/L) forming an emulsion with micrometer droplets does not wet the PP membranes [ 11 , 33 ]. The hydrophilic groups, such as carboxyl groups, are formed on the polymer surface during the MD process, which gives the PP membrane some oleophobic properties [ 33 ]. Strongly hydrophobic membranes do not possess such properties, hence a much higher wetting of PTFE membranes was noted with a lower oil content in the treated feed [ 19 ].…”

Wettability Studies of Capillary PTFE Membranes Applied for Membrane Distillation

“…Usually, in such cases, the oil concentration is much lower than that noted in produced water, and contamination occurs in the form of an emulsion containing oil droplets with a diameter below 50 µm [ 13 , 31 ]. The previously performed investigation [ 32 ] demonstrated that polypropylene (PP) membranes show wetting resistance by such solutions. With regard to PTFE membranes, in [ 8 ], it was observed that the wetting resistance increased with decreasing oil concentrations in the feed from 1000 to 100 mg/L.…”