Mechanisms of CaO particle gelation by laser ablation of CaO powder dispersed in alcohol

Abstract

Our earlier study showed that CaO particle gel, with loosened agglomerations of CaO particles, was generated by laser ablation of CaO powder dispersed in ethanol. We also demonstrated that porous CaO, a candidate of a low-cost and non-toxic CO2 absorbent, was obtained by simply drying the gel. For the present study, we conducted further investigation of the gelation mechanism to utilize this phenomenon as a simple and alternative preparation method of porous CaO. First, we observed the relation between the agglomeration tendency, including gelation and non-gelation, and the electrostatic interaction of CaO particles in different alcohols (methanol, ethanol, 1-propanol), because we have assumed electrostatic interaction among CaO particles as the most important factor affecting the gelation. Results showed that the agglomeration tendency of CaO particles increased with the decreasing zeta potential of CaO particles in these alcohols, which is consistent with the assumption. However, no decreased electrostatic repulsion caused by laser ablation was observed, suggesting the presence of another important factor affecting the gelation. As a possible factor, the CaO particle size composition was inferred: the colloid should contain both large particles and small particles. Interestingly, this assumption was validated by the fact that the gel was formed by mixing a raw colloid and a colloid prepared using laser ablation.