The Application of Polypropylene Membranes for Membrane Distillation
Marek Gryta*
Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Poland
Submission: July 24, 2018; Published: August 01, 2018
*Corresponding author: Marek Gryta, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Poland; Email: marek.gryta@zut.eu.pl
How to cite this article: Marek Gryta. The Application of Polypropylene Membranes for Membrane Distillation. Academ J Polym Sci. 2018; 1(3): 555565. DOI: 10.19080/AJOP.2018.01.555565
Abstract
Microporous hydrophobic membranes are applied in membrane distillation. During a long-term of module exploitation, a part of the pores is filled by water, and the membrane wetting causes that the industrial implementation of this process is hindered. Several investigators achieved promising results using the polypropylene membranes formed via TIPS method for various applications of membrane distillation.
Keywords:Membrane distillation; Polypropylene membrane; Hydrophobic membrane
Abbrevations: MD: Membrane Distillation; PTFE: Polytetrafluoroethylene; PP: Polypropylene PE: Polyethylene; TIPS: Thermally Induced Phase Separation
Introduction
Membrane distillation (MD) is an evaporation process of water through non-wetted porous membranes. In this process the salts and other non-volatile compounds present in the feed water are retained and the quality of produced distillate is close to distilled water [1-4]. The results of studies presented in the literature indicate that the MD process is not only an effective method for water desalination [1-3, 5], but also can be applied for wastewater treatment, especially when the salts concentration is high [3,6,7].
A huge amount of energy is required for water evaporation; thus, a good thermal efficiency is important for industrial implementation of the MD process [7,8]. The capillary MD modules allowed to obtain the thermal efficiency at a level of 70-80% [9]. Moreover, as MD can be operated with low-grade heat, the coupling of MD with waste energy makes the MD process very attractive [8,10].
The porous hydrophobic membranes are assembled in the membrane modules and the membrane wetting is the major problem of MD process [1-3]. The membrane wettability may be accelerated by scaling and fouling [2,3]. The possibility of NaCl solutions concentration in the MD process up to the saturation state has been already demonstrated many times for different types of the hydrophobic membranes [3,10,11]. However, during the separation of actual brines, which contain besides NaCl also hardly soluble salts, a serious problem is scaling (precipitation e.g. CaCO3 and CaSO4) [2,12,13]. Therefore, the high salt concentrations in the feed water (scaling) may restrict e.g. the fresh water production from brines [2,3,12]. For this reason, the number of works presenting the preparation of MD membranes with enhanced resistance to wetting has significantly grown [7,11,14-16]. However, the performance and durability of these membranes is most often tested over a period of below 10-50h, hence, the MD process has been used so far on the pilot scale for desalination with utilization of the traditional membranes made of polytetrafluoroethylene (PTFE), polypropylene (PP) and polyethylene (PE) [1,5,9,17].
A promising method to mitigate fouling and scaling intensity is the application of low feed temperature [12], however, a large membrane area should be used in order to achieve a high efficiency of the installation [18]. Thus, the realization of industrial implementation requires the membranes as cheap as possible, namely, manufactured by a simple method from inexpensive raw materials [11,19]. Such conditions are fulfilled by the capillary membranes produced from polypropylene by a TIPS method [3,20]. The TIPS process parameters and the diluents type and its concentration in the initial polymer/diluents system affected considerably the phase separation behaviors and the final membrane microstructure for PP membranes [21,22]. The PP membranes manufactured in the industrial installation were presented in Figure 1. The small increase (from 30 to 35wt%) of PP concentration in the casting solution caused significant changes in the pores structures. This showed while such a different membrane morphology is obtaining during the PP membranes preparation via TIPS method [20-22]. For this reason, only a few kinds of membranes produced from PP are appropriate for the MD process (e.g. Accurel PP [2,9,16,23]).
The promising results were achieved using PP membranes for various applications of MD process [2,9,24]. A disadvantage of the PP membranes is a formation of the hydrophilic groups on their surface during MD [22]; as a result, the membrane surface was wetted after 40-50h of MD process operation [2]. However, in spite of a rapid wetting of the surface, the pores were not wetted over the entire membrane cross-section during long-term MD studies, which confirmed that the capillary PP membranes exhibit the excellent resistance to wetting over a period of 2-4 years of MD module exploitation [9,25].
Conclusion
The polypropylene membranes formed via TIPS method can be applied for MD process. However, the membrane morphology is strongly affected by the TIPS conditions. Therefore, not all hydrophobic PP membranes produced for microfiltration process are appropriate for MD. The good results were obtained applying the Accrual PP membranes for MD process.
In the pilot scale studies of seawater desalination, an intensive scaling caused the need to replace the membrane modules after several months of operation [21]. Although the scaling can be limited by lowering the feed temperature below 50 ͦC, but the operational efficiency will be several times lower [12]. In this case it is necessary to increase the membrane area in the installation, hence, the application of cheap membranes such as the proposed capillary PP membranes allows to reduce the production costs.
References
- Winter D, Koschikowski J, Gross F, Maucher D, Düver D, et al. (2017) Comparative analysis of full-scale membrane distillation contactors - methods and modules. J Membr Sci 524: 758-771.
- Gryta M (2017) The application of polypropylene membranes for production of fresh water from brines by membrane distillation. Chem Pap 71(4): 775-784.
- Wang P, Chung TS (2015) Recent advances in membrane distillation processes: Membrane development, configuration design and application exploring. J Membr Sci 474: 39-56.
- Khalifa A, Ahmad H, Antar M, Laoui T, Khayet M (2017) Experimental and theoretical investigations on water desalination using direct contact membrane distillation. Desalination 404: 22-34
- Guillén-Burrieza E, Blanco J, Zaragoza G, Alarcón DC, Palenzuela P, et al. (2011) Experimental analysis of an air gap membrane distillation solar desalination pilot system. J Membr Sci 379(1-2): 386-396.
- Lu D, Liu Q, Zhao Y, Liu H, Ma J (2018) Treatment and energy utilization of oily water via integrated ultrafiltration forward osmosis–membrane distillation (UF-FO-MD) system. J Membr Sci 548: 275-287.
- Edwie F, Teoh MM, Chung TS (2012) Effects of additives on duallayer hydrophobic–hydrophilic PVDF hollow fiber membranes for membrane distillation and continuous performance. Chem Eng Sci 68(1): 567-578.
- Jantaporn W, Ali A, Aimar P (2017) Specific energy requirement of direct contact membrane distillation. Chem Eng Res Des 128: 15-26.
- Gryta M (2017) Investigations of a membrane distillation pilot plant with a capillary module. Desalination and Water Treat. 64: 279-286.
- González D, Amigo J, Suárez F (2017) Membrane distillation: Perspectives for sustainable and improved desalination. Renew. Sustain. Energy Rev 80: 238-259.
- Eykens L, De Sitter K, Dotremont C, Pinoy L, Van der Bruggen B (2017) Membrane synthesis for membrane distillation: A review. Sep Purif Technol 182: 36-51.
- Duong HC, Gray S, Duke M, Cath TY, Nghiem LD (2015) Scaling control during membrane distillation of coal seam gas reverse osmosis brine. J Membr Sci 493: 673-682.
- McGaughey Al, Gustafson RD, Childress AE (2017) Effect of long-term operation on membrane surface characteristics and performance in membrane distillation. J Membr Sci 543: 143-150.
- Rezaeia M, Warsinger DM, Lienhard V JH, Samhaber WM (2017) Wetting prevention in membrane distillation through superhydrophobicity and recharging an air layer on the membrane surface. J Membr Sci 530: 42-52.
- Hamzah N, Leo CP (2017) Membrane distillation of saline with phenolic compound using superhydrophobic PVDF membrane incorporated with TiO2 nanoparticles: Separation, fouling and selfcleaning evaluation. Desalination 418: 79-88.
- Hou D, Ding Ch, Li K, Lin D, Wang D, et al. (2018) A novel duallayer composite membrane with underwater-superoleophobic/ hydrophobic asymmetric wettability for robust oil-fouling resistance in membrane distillation desalination. Desalination 428: 240-249.
- Duong HC, Chivas AR, Nelemans B, Duke D, Gray S, et al. (2015) Treatment of RO brine from CSG produced water by spiral-wound air gap membrane distillation - A pilot study. Desalination 366: 121-129.
- Tavakkoli S, Lokare OR, Vidic RD, Khanna V (2017) A techno-economic assessment of membrane distillation for treatment of Marcellus shale produced water. Desalination 416: 24-34.
- Rezaei M, Warsinger DM, Lienhard V JH, Duke MC, Matsuura T, et al. (2018) Wetting phenomena in membrane distillation: Mechanisms, reversal, and prevention. Wat Res 139: 329-352.
- Wang YJ, Zhao ZP, Xi ZY, Yan SY (2018) Microporous polypropylene membrane prepared via TIPS using environment-friendly binary diluents and its VMD performance. J Membr Sci 548: 332-344.
- Lin YK, Chen G, Yang J, Wang XL (2009) Formation of isotactic polypropylene membranes with bicontinuous structure and good strength via thermally induced phase separation method. Desalination 236(1-3): 8-15.
- Zhang X, Zhang D, Liu T (2012) Influence of nucleating agent on properties of isotactic polypropylene. Energy Procedia 17: 1829-1835.
- Schneider K, Hölz W, Wollbeck R, Ripperger S (1988) Membranes and modules for transmembrane distillation. J Memb Sci 39(1): 25-42.
- Tang N, Feng Ch, Han H, Hua X, Zhang L, et al. (2016) High permeation flux polypropylene/ethylene vinyl acetate co-blending membranes via thermally induced phase separation for vacuum membrane distillation desalination. Desalination 394: 44-55.
- Gryta M (2018) The long-term studies of osmotic membranes distillation. Chem Pap 72(1): 99-107.