Pore Modification in Porous Ceramic Membranes With Sol‐Gel Process and Determination of Gas Permeability and Selectivity

Abstract

Summary: The aim of the study was to investigate the variation in total surface area, porosity, pore size, Knudsen and surface diffusion coefficients, gas permeability and selectivity before and after the application of sol‐gel process to porous ceramic membrane in order to determine the effect of pore modification. In this study, three different sol‐gel process were applied to the ceramic support separately; one was the silica sol‐gel process which was applied to increase porosity, others were silica‐sol dip coating and silica‐sol processing methods which were applied to decrease pore size. As a result of this, total surface area, pore size and porosity of ceramic support and membranes were determined by using BET instrument. In addition to this, Knudsen and surface diffusion coefficients were also calculated. After then, ceramic support and membranes were exposed to gas permeation experiments by using the CO2 gas with different flow rates. Gas permeability and selectivity of those membranes were measured according to the data obtained. Thus, pore surface area, porosity, pore size and Knudsen diffusion coefficient of membrane treated with silica sol‐gel process increased while total surface area was decreasing. Therefore, permeability of ceramic support and membrane treated with silica sol‐gel process increased, and selectivity decreased with increasing the gas flow rate. Also, surface area, porosity, pore size, permeability, selectivity, Knudsen and surface diffusion coefficients of membranes treated with silica‐sol dip coating and silica‐sol processing methods were determined. As a result of this, porosity, pore size, Knudsen and surface diffusion coefficients decreased, total surface area increased in both methods. However, viscous flow and Knudsen flow permeability were detected as a consequence of gas permeability test and Knudsen flow was found to be a dominant transport mechanism in addition to surface diffusive flow owing to the small pore diameter in both methods. It was observed that silica‐sol processing method had lower pore diameter and higher surface diffusion coefficient than silica‐sol dip coating method.

Influence of Water Molar Ratio on Fabrication of Silica Ceramic Membranes via Sol-Gel Dip-Coating Method

“…Polymeric membranes have limitation in some application due to low chemical resistant and cannot work at high temperatures. Hence, inorganic membrane was used as a substitution of the polymeric membrane [3].Inorganic membranes are used in many practical applications such as gas separation, water desalination, treatment of wastewater and ultra-filtration in food industries [4]. Ceramic inorganic membranehad received a great attention as it offers many advantages such as high chemical, thermal, mechanical and physical stability, outstanding separation Nor AmyraZulianeyKahlibet al, 2018 characteristics, long working life and ecologically friendly [5].…”

“…Prepared sol can be deposited onto a substrate in order to form a filmby several methods, for example dip coating. Silica sol-gel dip-coating method can be used whenreduction of pore size of fabricated membrane is desired [4].…”

A study of gas diffusion characteristics on a micro porous composite silica ceramic membrane

“…One major complexity encountered during membrane fabrication is on how to tackle the relationship between getting high flux and high selectivity materials. This can be attributed to the inverse proportionality of flow rate to membrane layer thickness [6] [23]. Some other researchers [23] in their study looked at the relationship between membrane structure and permeation with respect to the material make up of the membrane.…”

“…Inorganic membranes can further be classified as porous or nonporous. While non-porous inorganic membrane is made up of dense separation-film resulting in very good selectivity and minimal permeance, porous type of membrane have lower selectivity and high permeance with pore sizes of up to 10µm [6]. Porous membranes have micro-pores that allow the passage of fluid through its channel while dense or nonporous membranes, allow the flow of fluids to take place through the bulk membrane material itself.…”