Degradation of Polypropylene Membranes Applied in Membrane Distillation Crystallizer

Abstract

Abstract:The studies on the resistance to degradation of capillary polypropylene membranes assembled in a membrane crystallizer were performed. The supersaturation state of salt was achieved by evaporation of water from the NaCl saturated solutions using membrane distillation process. A high feed temperature (363 K) was used in order to enhance the degradation effects and to shorten the test times. Salt crystallization was carried out by the application of batch or fluidized bed crystallizer. A significant membrane scaling was observed regardless of the method of realized crystallization. The SEM-EDS, DSC, and FTIR methods were used for investigations of polypropylene degradation. The salt crystallization onto the membrane surface accelerated polypropylene degradation. Due to a polymer degradation, the presence of carbonyl groups on the membranes' surface was identified. Besides the changes in the chemical structure a significant mechanical damage of the membranes, mainly caused by the internal scaling, was also found. As a result, the membranes were severely damaged after 150 h of process operation. A high level of salt rejection was maintained despite damage to the external membrane surface.

Slippery for scaling resistance in membrane distillation: A novel porous micropillared superhydrophobic surface

“…MVR and ED not only require high energy but also suffer from corrosion. Membrane distillation (MD) has attracted wide attention for desalinating highly concentrated brine with concentrations up to crystallization (Ji, Curcio et al 2010, Nghiem, Hildinger et al 2011, Edwie and Chung 2013, Chen, Lu et al 2014, Hickenbottom and Cath 2014, Naidu, Jeong et al 2014, Bouchrit, Boubakri et al 2015, Chen, Wang et al 2015, Eykens, Hitsov et al 2016, Gryta 2016, Shin and Sohn 2016, Bouchrit, Boubakri et al 2017, Chen, Tian et al 2017, Chen, Zheng et al 2017, Duong, Hai et al 2017, Junghyun, Heejung et al 2017, Choi, Naidu et al 2018 2018, Kim, Kim et al 2018, Naidu, Zhong et al 2018.…”

“…Single NaCl crystals of 40 µm were also reported in a membrane distillation-crystallization (MDC) process, where about 9 to16% of the total crystals were on the membrane surface and the piping (Nariyoshi, Pantoja et al 2016). Scaling often occurred when the feed reached saturation (Bouchrit, Boubakri et al 2015, Gryta 2016, Bouchrit, Boubakri et al 2017). Injection of air (Choi, Choi et al 2017) and increase of the feed flow velocity (Naidu, Jeong et al 2014, Choi, Choi et al 2017) can mitigate scaling.…”

Environmentally Friendly Photothermal Membranes for Halite Recovery from Reverse Osmosis Brine via Solar-Driven Membrane Crystallization

“…However, heterogeneous crystallization leads to a significant deposition of crystallized salts on membrane surfaces (Figure 9), which impedes vapor transport and results in detrimental effects. These effects include a decrease in hydrophobicity, posing a risk of membrane wetting [70] as well as the deterioration of the chemical and mechanical stability [71]. These aspects impose the need for further studies to avoid this phenomenon, focusing on process optimization [72].…”

Keramische Membranen in der Membrandestillation

“…Die Aufbereitung aggressiver Lösungen kann aber den Einsatz besonders stabiler Membransysteme notwendig machen. Beispielsweise können Kristalle in hochkonzentrierten Lösungen zu einer schnellen und permanenten Degeneration von Polymermembranen führen , . Keramische Membranen sind durch extreme mechanische, chemische und thermische Beständigkeit gekennzeichnet und damit gut für einen Einsatz in aggressiven Medien geeignet.…”