The transformation of CO2 into a precipitated mineral carbonate through an ex situ mineral carbonation route is considered a promising option for carbon capture and storage (CCS) since (i) the captured CO2 can be stored permanently and (ii) industrial wastes (i.e., coal fly ash, steel and stainless-steel slags, and cement and lime kiln dusts) can be recycled and converted into value-added carbonate materials by controlling polymorphs and properties of the mineral carbonates. The final products produced by the ex situ mineral carbonation route can be divided into two categories-low-end high-volume and high-end low-volume mineral carbonates-in terms of their market needs as well as their properties (i.e., purity). Therefore, it is expected that this can partially offset the total cost of the CCS processes. Polymorphs and physicochemical properties of CaCO3 strongly rely on the synthesis variables such as temperature, pH of the solution, reaction time, ion concentration and ratio, stirring, and the concentration of additives. Various efforts to control and fabricate polymorphs of CaCO3 have been made to date. In this review, we present a summary of current knowledge and recent investigations entailing mechanistic studies on the formation of the precipitated CaCO3 and the influences of the synthesis factors on the polymorphs.
This study reports the thermochemical transformation of lignin model compounds using nanoparticle organic hybrid materials (NOHMs). NOHMs have recently been developed as an emerging class of self-suspended nanoparticle solvent systems created by ionically or covalently grafting organic oligomers or polymers (canopy) onto surface-modified inorganic nanoparticles (core). Because NOHMs exhibit negligible vapor pressure with the ability to tailor physicochemical properties, they could be a promising catalytic solvent for the lignin thermochemical conversion process. The thermochemical conversion of lignin model compounds was achieved with the synthesized NOHM at an elevated temperature of 473 K, and the results were compared with the case of the ionic liquid [EMIM][ESO 4 ]. The fractured moieties of the lignin model compounds were qualitatively identified by ATR FT-IR and 2D COSY NMR spectroscopies. The results indicated that the NOHM decomposed the C−O and/or C−C bonds of lignin model chemicals more efficiently than [EMIM][ESO 4 ].
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