Synthesis of silica ceramic membrane via sol-gel dip-coating method for removal of carbon dioxide (CO2) from biogas

Abstract

Biogas energy conversion is a new technique that has been developed for effective and proper utilization of renewable energy. The carbon dioxide (CO2) has to be removed in order to increase the energy conversion. The silica ceramic membranes were fabricated via sol-gel dip-coating method. The silica sol was prepared using mixture of water, tetraethyl orthosilicate (TEOS), ethanol and nictric acid. Various process method are used such as amount of acid, water:TEOS molar ratio, number of dipping and calcination temperature. The ceramic substrate was dipped into the prepared silica sol. After the dipping step, the samples were dried for 24 hours at room temperature and then heat treated via calcination process. For XRD analysis, all fabricated silica ceramic membranes shows the existence of silica. The FTIR analysis showed the major peaks for all fabricated membranes occurs in the same area of absorption band, with the range of 1070 to 1080 cm-1, are corresponds to the existence of Si-O-Si bond. After silica particles was deposited onto the substrates, the surface of the membranes shows the appearance of fine particle aggregates, which is proved to be the agglomeration of silica particles via FESEM analysis. The pore size of the raw ceramic substrate is around 0.5 to 0.6 µm. The pore size of fabricated silica ceramic membranes was reduced to around 4 to 25 nm, which analyzed using TEM and BET analysis. Weight and thickness of fabricated silica ceramic membranes were increasing with increasing of the value of water:TEOS molar ratio, amount of acid, and numbers of dipping. However, when silica ceramic membranes were heat treated at the different calcination temperature, the weight and thickness were decreased as the temperature increased. From the permeability test, the silica ceramic membrane able to permeate only a small amount of CO2, which is around 1%. In summary, silica ceramic membranes are successfully fabricated and pore size of the membranes has been reduced. Besides, the fabricated silica ceramic membranes demonstrate the potential in the removal of CO2 from the biogas despite having a small permeation percentage.