https://doi.org/10.1016/j.cej.2022.135394
“A standard sol–gel process proposed by Santos et al. was used to synthesize a CaO adsorbent [34]. A predetermined amounts of calcium nitrate tetrahydrate (Ca(NO3)2·4H2O) and citric acid monohydrate (C6H8O7·H2O) acting as chelation agent, were added to the deionized water at room temperature (water and citric acid to metal ion molar ratios were 40:1 and 1:1, respectively). The mixture was continuously stirred at 80 °C to form a translucent pale-yellow sol with good dispersion. After drying the prepared sol overnight at 130 °C, the translucent pale-yellow sol turned into low-density foam. The obtained foam was then calcined in a muffle furnace at 850 °C for 2 h at a heating rate of 2 °C min−1. This synthesized sample was designated as sol–gel CaO. A detailed investigation into the CaO adsorbent, including extensive characterisation and the carbonation mechanism can be found in our previous publication [35].”