원문정보
초록
영어
In recent years, a great deal of concern has been expressed with regard to global climate change and its link to growing atmospheric concentrations of carbon dioxide. Separation of carbon dioxide from a large amount of flue gas by chemical separation is known for many years and considered to be one of the most reliable to capture the CO2. Various studies for improving the capture process have been performed, however, the current applied technology for this separation is still expensive, both in terms of capital cost and operating cost. If an alternative separation system having less energy for CO2 capture and regeneration could be developed, it is very attractive option to install CO2 capture facility. Since recently, emerging ex-vivo applications of carbonic anhydrase for its potential use in CO2 capture technologies are attracting attentions. The objective of the present study was to investigate the feasibility of using enzyme as a biocatalyst for hydration of CO2, as well as its precipitation in the form of calcium carbonate. The bio-catalytic capture of CO2, and its precipitation as CaCO3, over bovine carbonic anhydrase (BCA) and hemocyte for diseased shell (HDS) immobilized on a pore-expanded SBA-15 support was investigated. SBA-15 support was synthesized using TMB as a pore expander, and the resulting porous silica was characterized by XRD, BET, IR and FE-SEM analysis. BCA and HDS were immobilized on support through cross-linked enzyme aggregation. The bio-catalytic activity for hydration of CO2 was calculated for BCA and HDS. The kcat/Km value was 123.8 M-1s-1 for BCA and 119.1 M-1s-1 for HDS. Considering that HDS is a water-soluble, conjugated protein, the kcat/Km value of HDS may be regarded as near to that of BCA. This means that BCA, which is expensive and difficult to extract, can be replaced by the more economical HDS biocatalyst extracted from oysters. CaCO3 was produced by adding Ca2+ ion to the CO2 hydrated solution containing CO32-. The amount of CaCO3 was also measured at different times during the reaction. The initial formation of CaCO3 required about 15 seconds in the CaCO3 precipitation experiment without the biocatalysts. In contrast, when BCA and HDS were added, CaCO3 formation occurred within 5 seconds, on average ,for a 3 times faster reaction rate. The CaCO3 structure was the calcite structure, as indicated by a calcite peak with 2θ=29o. Calcium carbonate is a common and thermodynamically stable mineral found in rocks worldwide. If the widespread transformation of CO2 to CaCO3 is possible, it will represent a stable process for long-term CO2 capture and storage. In addition, the process yields a final product, CaCO3, which can be utilized as road pavement or paper coating materials. The study presented here is only the beginning for the capture and storage of CO2 using enzyme, especially HDS. Additional studies on various conditions which include cloning of enzyme, operating conditions, and scale-up factor are underway.