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Hydrophobic Modifications of Membranes with Improved Anti-Wetting Resistance
Published in Kang-Jia Lu, Tai-Shung Chung, Membrane Distillation, 2019
Ceramic membranes are usually made from metal oxides such as alumina, zirconia, silica, titania, or a combination. They usually exhibit high chemical and thermal stability and thus are more appropriate for modification. In addition, their mechanical properties are relatively higher than polymeric membranes and do not easily be deformed during the long-term operation (da Silva Biron et al., 2018). However, ceramic membranes are hydrophilic due to the existence of abundant hydroxyl groups (–OH) which help absorb water into the pores. One must modify these hydroxyl groups via substitution with hydrophobic moieties so that the resultant ceramic membranes become hydrophobic for MD applications (Larbot et al., 2004). The modification methods for ceramic membranes are different from those for polymeric membranes because (1) the former can withstand higher temperatures than the latter and (2) their terminal functional groups are different. Hydrophobic ceramic membranes are usually prepared through surface coating using fluoroalkylsilanes (FAS). Organosilanes are silanes that contain at least one carbon–silicon bond. FAS is one type of organosilanes which also contain CF2–CF2 and CF2–CF3 groups to provide lower surface tension and hydrophobic characteristics (Krajewski et al., 2006). Generally, FAS is grafted on ceramic membrane surfaces via immersion, chemical vapor deposition (CVD), and sol-gel methods.
Microfiltration Membranes: Fabrication and Application
Published in Sundergopal Sridhar, Membrane Technology, 2018
Barun Kumar Nandi, Mehabub Rahaman, Randeep Singh, Mihir Kumar Purkait
Considering the advantages and disadvantages of both ceramic and polymeric membranes, it can be observed that polymeric membranes are more suitable for laboratory use wherein the particular separation performance is the main objective, as compared to life span and cost. However, for industrial scale applications, cost and life span are significant matters in addition to separation efficiency. Most of the polymeric membrane applications have shown an average life span of 12–18 months, extendable up to 36 months by adopting optimal cleaning schemes, as compared to the 10-year life-span for ceramic membranes. Therefore, the ability of ceramic membranes to provide higher flux and applicability to wide range of temperatures and chemical processing conditions make them favorable in comparison to polymeric membranes. Although, ceramic membranes possess separation characteristics similar to polymeric membranes, their higher initial costs restrict their widespread application on a commercial scale.
Applications of Ceramic Membranes
Published in Mihir Kumar Purkait, Randeep Singh, Membrane Technology in Separation Science, 2018
Mihir Kumar Purkait, Randeep Singh
In general, ceramic membranes are composite membranes made up of various inorganic materials such as α-alumina, γ-alumina, zirconia, silica, titania, and kaolin. They are composed of a macroporous support with one or two mesoporous layers and a thin selective microporous top layer [1]. Ceramic membranes are used in various industrial applications. Nowadays, efforts are made to replace polymeric membranes from the industrial applications with ceramic membranes. Compared to polymeric membranes, ceramic membranes possess superior chemical, thermal, and mechanical stability. The only drawback of ceramic membranes is their initial cost. There is a need to develop techniques for the production of ceramic membranes on a large scale and also to increase their packing density, which are the two areas where ceramic membranes remain behind the polymeric membranes. Advancements in ceramic membranes are making them the membranes of choice for various industrial applications. The cost of operation and maintenance is far lower as compared to polymeric membranes. The costs of pre- and posttreatments, membrane replacement and lifetime, energy consumption, and cleaning operations all show that the ceramic membranes are on par with the polymeric membranes.
Effect of MgO on the microstructure and properties of mullite membranes made by phase-inversion tape casting
Published in Journal of Asian Ceramic Societies, 2021
Rafael Kenji Nishihora, Ellen Rudolph, Mara Gabriela Novy Quadri, Dachamir Hotza, Kurosch Rezwan, Michaela Wilhelm
The use of ceramic membranes has attracted much attention in separation technologies because of their superior chemical, thermal and mechanical stability compared to organic membranes [1]. Thus, ceramic membranes present extended lifespan even under extreme fouling and cleaning conditions, which would easily damage their organic counterparts [2]. There are numerous methods to prepare ceramic membranes such as slip casting, tape casting, extrusion, sol-gel, freeze casting, phase-inversion, etc. [3,4]. For instance, tape casting is a standard technique to prepare thin flat ceramic tapes [5,6]. This technique starts from homogeneous ceramic slurries, which are cast onto a substrate resulting in thin ”green tapes” after drying; and a consolidated ceramic tape after heat treatment [7]. In addition, phase inversion is one of the most popular techniques for the preparation of porous membranes, in which a polymer is dissolved in a suitable solvent and then formed into the desired shape in this process (thin film, tube, hollow fiber). The addition of a precipitant or nonsolvent (such as water) to this polymer solution causes the homogeneous phase to separate into a solid polymer (polymeric matrix) and a liquid solvent layer (porous network) [8,9].
Synthesis, characterization of cellulose acetate membrane and application for the treatment of oily wastewater
Published in Environmental Technology, 2020
Recently, membrane technology is being used for oil water separation, especially water-soluble oil emulsion [11]. The mechanism involved in membrane technology is macromolecular solute separation, which allows the passage of solvents through the membrane retaining the larger molecules [12]. Literature survey [13] indicates that polymeric membranes, ceramic membranes and carbon membranes can be used effectively for the treatment of oil-in-water emulsion. The use of ceramic membranes always includes high cost and complex fabrication methods. Carbon membranes possess advantages such as excellent chemical stability, thermal and mechanical resistance and use of cheap precursors. Even though, carbon membranes are quite restricted because their pore dimensions are suitable only for gas permeation.
Performance of a new ceramic microfiltration membrane based on kaolin in textile industry wastewater treatment
Published in Chemical Engineering Communications, 2019
Priyanka Saini, Vijaya Kumar Bulasara, Akepati S. Reddy
In comparison with organic membranes, ceramic membranes have several benefits such as ease of cleaning and regeneration, high mechanical strength, thermal stability, corrosion resistance and less degree of fouling (Hofs et al., 2011; Kaur et al., 2016a). Also, ceramic membranes can be applied in large scale treatment as polymeric membranes proved inadequate for industrial applications due to their short life span (Jedidi et al., 2011; Singh and Bulasara, 2015). Therefore, several researchers are focusing on the development of low cost ceramic membranes from cheaper and abundant natural materials such as clay and waste substances such as fly ash (Jedidi et al., 2011; Fang et al., 2011; Rawat and Bulasara, 2018). Lee and Cho (2004) showed that a tight-UF range ceramic membrane behaves in a way similar to that of a nanofiltration (NF) range polymeric membrane. The authors also concluded that an equivalent ceramic membrane exhibits good retention of organics and higher permeability in terms of natural organic matter removal. Presently, ceramic membranes are successfully implemented in desalination processes, chemical, metal, textile, food, and beverage industries (Barredo-Damas et al., 2010; Barredo-Damas et al., 2012). However, a major limitation of membrane processes is flux decline due to membrane fouling (Fersi et al., 2009). Membrane fouling can be overcome by using feed specific pretreatment process prior to membrane treatment (Marcucci et al., 2003).