New Research: Enhancing CO2 sequestration with Wollastonite
This research evaluates the effects of naturally occurring enzymes and specialized human-made compounds on the breakdown of wollastonite to improve the efficiency of carbon sequestration from the atmosphere. In summary, the findings suggest that metal-organic frameworks (MOF) are more effective than naturally occurring enzymes for enhancing carbon sequestration from wollastonite. In case you wanted to know more about MOF’s, here is a summary from the article:
MOFs have also been thoroughly investigated as effective and economic alternatives to natural enzymes . The advantages of using MOFs as catalysts instead of enzymes are several: (i) the cost of MOFs is significant lower because of the easier synthesis and purification process; (ii) their physical/chemical resistance is extremely high in comparison with enzymes, which tend to suffer denaturation; and (iii) the catalytic properties of MOFs can be tuned through an easy variation of substrates or through tailoring synthesis reactions . Their main disadvantage is the lower catalytic effect exerted by the metal clusters in MOFs compared to the active metal sites of enzymes. It should be remarked, however, that the number of metal clusters in a MOF particle can be several orders of magnitude higher than the number of active sites present in an enzyme, so MOFs can achieve an overall comparable catalytic efficiency .
One of the most promising strategies for the safe and permanent disposal of anthropogenic CO2 is its conversion into carbonate minerals via the carbonation of calcium and magnesium silicates. However, the mechanism of such a reaction is not well constrained, and its slow kinetics is a handicap for the implementation of silicate mineral carbonation as an effective method for CO2 capture and storage (CCS). Here, we studied the different steps of wollastonite (CaSiO3) carbonation (silicate dissolution → carbonate precipitation) as a model CCS system for the screening of natural and biomimetic catalysts for this reaction. Tested catalysts included carbonic anhydrase (CA), a natural enzyme that catalyzes the reversible hydration of CO2(aq), and biomimetic metal-organic frameworks (MOFs). Our results show that dissolution is the rate-limiting step for wollastonite carbonation. The overall reaction progresses anisotropically along different [hkl] directions via a pseudomorphic interface-coupled dissolution-precipitation mechanism, leading to partial passivation via secondary surface precipitation of amorphous silica and calcite, which in both cases is anisotropic (i.e., (hkl)-specific). CA accelerates the final carbonate precipitation step but hinders the overall carbonation of wollastonite. Remarkably, one of the tested Zr-based MOFs accelerates the dissolution of the silicate. The use of MOFs for enhanced silicate dissolution alone or in combination with other natural or biomimetic catalysts for accelerated carbonation could represent a potentially effective strategy for enhanced mineral CCS.