Lithium ceramics as an alternative for the CO₂ capture. Analysis of different physicochemical factors controlling this process

Carbon dioxide (CO₂) amounts have been raised in the atmosphere dramatically, mainly due to the combustion of different carbonaceous materials. Then, the so-called greenhouse effect has been increased, as well. Several proposals have been established trying to solve this problem, where a possible key means, for reducing the greenhouse effect, is to capture and concentrate CO₂. In that sense, a considerable variety of materials have been tested as CO₂ captors, some alkaline ceramics among them.Different lithium ceramics have been proposed for the CO₂ capture through an absorption process. The CO₂ capture mechanism is divided in two steps: 1) Initially, CO₂ reacts on the particle surface. This superficial reaction involves the formation of an external shell composed of lithium carbonate and a residual ceramic (which depends of the initial ceramic). 2) Then, in order to continue the CO₂ absorption by the ceramic, bulk diffusion processes must be activated and then the CO₂ absorption is controlled by diffusion processes.Finally, it must be mentioned that CO₂ absorption process on lithium ceramics not only depends on the intrinsic factors mentioned above. CO₂ absorption depends on other external factors as well, such as the flow gas where the solid-gas interface may presentdifferent regimes; the gas composition, where the CO₂ concentration vary or where CO₂ competes with the other gases for the superficial ceramic active sites and the effect produced by the H₂O vapor presence, among others. Therefore, the aim of the present chapter is to describe and summarize how each of these factors, intrinsic or not, affect the CO₂ absorption process on the lithium ceramics.