The Application of Submerged Modules for Membrane Distillation

This paper deals with the efficiency of capillary modules without an external housing, which were used as submerged modules in the membrane distillation process. The commercial hydrophobic capillary membranes fabricated for the microfiltration process were applied. Several constructional variants of submerged modules were discussed. The influence of membrane arrangement, packing density, capillary diameter and length on the module performance was determined. The effect of process conditions, i.e., velocity and temperature of the streams, on the permeate flux was also evaluated. The submerged modules were located in the feed tank or in the distillate tank. It was found that much higher values of the permeate flux were obtained when the membranes were immersed in the feed with the distillate flowing inside the capillary membranes. The efficiency of submerged modules was additionally compared with the conventional membrane distillation (MD) capillary modules and a similar performance of both constructions was achieved.

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Effect of flow-rate on ethanol separation in membrane distillation process

Chemical Papers ◽

10.2478/s11696-013-0382-0 ◽

2013 ◽

Vol 67 (9) ◽

Cited By ~ 2

Author(s):

Marek Gryta

Keyword(s):

Flow Rate ◽

Membrane Surface ◽

Positive Influence ◽

Membrane Distillation ◽

Alcohol Concentration ◽

Process Conditions ◽

Capillary Membrane ◽

Enrichment Coefficient ◽

Capillary Membranes ◽

Separation Degree

AbstractThe separation of diluted ethanol solutions and fermentation broths by membrane distillation was investigated. The influence of stream flow-rate on the ethanol flux was studied. An evaluation of the process conditions on the separation degree of ethanol was performed with the application of hydrophobic capillary membranes composed of polypropylene. By removing the alcohol via membrane distillation, it is possible to achieve a higher content of ethanol in the permeate than that in the broth. The enrichment coefficient amounted to 4–6.5, and decreased with an increase of the ethanol concentration in the broth. It was found that the flow-rate affects the value of the enrichment coefficient. A positive influence of carbon dioxide on the ethanol transport through the capillary membrane was observed. The evolution of CO2 bubbles from the broth increases the stream turbulence, probably enhancing the alcohol concentration in the layer adjacent to the membrane surface.

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Resistance of Polypropylene Membrane to Oil Fouling during Membrane Distillation

Membranes ◽

10.3390/membranes11080552 ◽

2021 ◽

Vol 11 (8) ◽

pp. 552

Author(s):

Marek Gryta

Keyword(s):

Membrane Distillation ◽

Water Desalination ◽

Feed Water ◽

Permeate Flux ◽

Feed Composition ◽

Oil Emulsion ◽

Thermally Induced ◽

Polypropylene Membrane ◽

Capillary Membranes ◽

The Impact

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.

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Wettability of polypropylene capillary membranes during the membrane distillation process

Chemical Papers ◽

10.2478/s11696-011-0096-0 ◽

2012 ◽

Vol 66 (2) ◽

Cited By ~ 19

Author(s):

Marek Gryta

Keyword(s):

Electrical Conductivity ◽

Pore Size ◽

Wall Thickness ◽

External Surface ◽

Membrane Distillation ◽

Air Permeability ◽

Lower Wall ◽

Distillation Process ◽

Capillary Membranes

AbstractStudies of membrane wettability in the membrane distillation process were performed with the application of hydrophobic capillary membranes made of polypropylene. Three kinds of Accurel PP membranes (Membrana GmbH, Germany) differing in the diameter of capillaries and pores as well as in the wall thickness were used. It was confirmed that membranes with lower wall thickness and larger pore size provide higher yields of the process. The studies demonstrated that the pores of used membranes located close to the external surface of capillaries are several times larger than those located inside the membrane wall. Based on air permeability measurements it was found that external surface of the membranes with such large pores was completely wetted by water after 50–80 h of membrane distillation. However, the pores located inside the wall with the diameter below 1 μm were not wetted and electrical conductivity of the obtained distillate was maintained at the level of 3–6 μS cm−1.

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Electrospun Nanostructured Membrane Engineering Using Reverse Osmosis Recycled Modules: Membrane Distillation Application

Nanomaterials ◽

10.3390/nano11061601 ◽

2021 ◽

Vol 11 (6) ◽

pp. 1601

Author(s):

Jorge Contreras-Martínez ◽

Carmen García-Payo ◽

Mohamed Khayet

Keyword(s):

Reverse Osmosis ◽

Polyvinylidene Fluoride ◽

Membrane Distillation ◽

Permeate Flux ◽

Electrospinning Technique ◽

Salt Rejection ◽

Rejection Factor ◽

Nanofibrous Membranes ◽

Membrane Engineering ◽

Desalination Plants

As a consequence of the increase in reverse osmosis (RO) desalination plants, the number of discarded RO modules for 2020 was estimated to be 14.8 million annually. Currently, these discarded modules are disposed of in nearby landfills generating high volumes of waste. In order to extend their useful life, in this research study, we propose recycling and reusing the internal components of the discarded RO modules, membranes and spacers, in membrane engineering for membrane distillation (MD) technology. After passive cleaning with a sodium hypochlorite aqueous solution, these recycled components were reused as support for polyvinylidene fluoride nanofibrous membranes prepared by electrospinning technique. The prepared membranes were characterized by different techniques and, finally, tested in desalination of high saline solutions (brines) by direct contact membrane distillation (DCMD). The effect of the electrospinning time, which is the same as the thickness of the nanofibrous layer, was studied in order to optimize the permeate flux together with the salt rejection factor and to obtain robust membranes with stable DCMD desalination performance. When the recycled RO membrane or the permeate spacer were used as supports with 60 min electrospinning time, good permeate fluxes were achieved, 43.2 and 18.1 kg m−2 h−1, respectively; with very high salt rejection factors, greater than 99.99%. These results are reasonably competitive compared to other supported and unsupported MD nanofibrous membranes. In contrast, when using the feed spacer as support, inhomogeneous structures were observed on the electrospun nanofibrous layer due to the special characteristics of this spacer resulting in low salt rejection factors and mechanical properties of the electrospun nanofibrous membrane.

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Membrane Distillation Process

Membranes ◽

10.3390/membranes11020144 ◽

2021 ◽

Vol 11 (2) ◽

pp. 144

Author(s):

Alessandra Criscuoli

Keyword(s):

Water Stress ◽

New Technologies ◽

Membrane Distillation ◽

Distillation Process

The water stress that we have been experiencing in the last few years is driving the development of new technologies for the purification and recovery of water [...]

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Experimental Investigation on Floating Solar-Driven Membrane Distillation Desalination Modules

Membranes ◽

10.3390/membranes11050304 ◽

2021 ◽

Vol 11 (5) ◽

pp. 304

Author(s):

Qingxiu Miao ◽

Yaoling Zhang ◽

Shuo Cong ◽

Fei Guo

Keyword(s):

Power Source ◽

Membrane Distillation ◽

Small Scale ◽

Sea Waves ◽

Permeate Flux ◽

Practical Application ◽

Rejection Ratio ◽

Cold Source ◽

Mild Temperature ◽

Feed Temperature

Membrane distillation (MD) processes need a relatively mild temperature gradient as the driving force for desalination. In the field, it is reasonable to utilize solar energy as the heat source for the feed, and seawater as the infinite cold source for condensation. Solar-driven MD provides a route for the practical application of seawater desalination at a small scale. In this work, we focus on floating MD modules with a solar heating bag as the power source, and perform proof-of-principle experiments on the MD performance under various conditioning parameters, including feed flow rate, feed temperature, salinity, air gap, and sea waves. The results indicate that floating solar-driven MD modules are feasible in terms of permeate flux and salt rejection ratio, and the upward evaporation MD configuration leads to a better performance in terms of permeate flux. The simulation and experiments also show that the natural sea waves disturb the heating bag and the MD module floating on the surface of seawater, and effectively enhance the feed circulation and transport in the system.

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Organic Fouling Impact in a Direct Contact Membrane Distillation System Treating Wastewater: Experimental Observations and Modeling Approach

Membranes ◽

10.3390/membranes11070493 ◽

2021 ◽

Vol 11 (7) ◽

pp. 493

Author(s):

Amine Charfi ◽

Fida Tibi ◽

Jeonghwan Kim ◽

Jin Hur ◽

Jinwoo Cho

Keyword(s):

Particle Size ◽

Membrane Fouling ◽

Direct Contact ◽

Feed Solution ◽

Membrane Distillation ◽

Mixed Solution ◽

Permeate Flux ◽

Direct Contact Membrane Distillation ◽

Organic Fouling ◽

Specific Cake Resistance

This study aims to investigate the effect of operational conditions on organic fouling occurring in a direct contact membrane distillation (DCMD) system used to treat wastewater. A mixed solution of sodium alginate (SA) and bovine serum albumin (BSA) was used as a feed solution to simulate polysaccharides and proteins, respectively, assumed as the main organic foulants. The permeate flux was observed at two feed temperatures 35 and 50 °C, as well as three feed solution pH 4, 6, and 8. Higher permeate flux was observed for higher feed temperature, which allows higher vapor pressure. At higher pH, a smaller particle size was detected with lower permeate flux. A mathematical model based on mass balance was developed to simulate permeate flux with time by assuming (i) the cake formation controlled by attachment and detachment of foulant materials and (ii) the increase in specific cake resistance, the function of the cake porosity, as the main mechanisms controlling membrane fouling to investigate the fouling mechanism responsible of permeate flux decline. The model fitted well with the experimental data with R2 superior to 0.9. High specific cake resistance fostered by small particle size would be responsible for the low permeate flux observed at pH 8.

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