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Table 3 Reaction equations for the soluble particles and their molar Gibbs free energy values (Zhang 2008; Liang 2007).

From: Analysis of Active Ion-Leaching Behavior and the Reaction Mechanism During Alkali Activation of Low-Calcium Fly Ash

Oxides Chemical reaction equations   \( \Delta_{r} G_{m}^{\varTheta } (298.16 \rm {K}) \) (kJ mol−1)
Alkaline oxides \( {\text{CaO}}(s) + {\text{H}}_{ 2} {\text{O}} \to {\text{Ca}}^{{ 2 { + }}} (aq) + 2{\text{OH}}^{ - } (aq)\) (3) − 26.76
\( {\text{Ca}}^{2 + } (aq) + 2{\text{OH}}^{ - } (aq) \to {\text{Ca(OH)}}_{2} (s)\) (4) − 30.00
\( {\text{MgO}}(s) + {\text{H}}_{ 2} {\text{O}} \to {\text{Mg}}^{2 + } (aq) + 2{\text{OH}}^{ - } (aq) \) (5) − 37.79
\( {\text{Mg}}^{2 + } (aq) + 2{\text{OH}}^{ - } (aq) \to {\text{Mg(OH)}}_{2} (s) \) (6) − 76.45
Acid oxides \( {\text{SiO}}_{2} (s) + {\text{H}}_{ 2} {\text{O}} + {\text{OH}}^{ - } (aq) \to {\text{SiO(OH)}}_{3}^{ - } (aq)\) (7) − 26.25
\( {\text{Al}}_{ 2} {\text{O}}_{ 3} (s) + 3{\text{H}}_{ 2} {\text{O}} + 2{\text{OH}}^{ - } (aq) \to 2{\text{Al(OH)}}_{4}^{ - } (aq) \) (8) − 41.86