## 3 Discussion
The process was modeled numerically by [PERSON] et al. [81], indicating that at high temperatures (\(>\)315 \({}^{\circ}\)C), the rates of serpentinization reactions are fast, and their reaction is represented by Equation (8) which follows:  
\[\Delta G^{\circ}=-RT\ln(K) \tag{1}\]0  
[PERSON] et al. [82] mention that the dissolution of (Mg\({}_{1-x}\)Fe\({}_{x}\))\({}_{2}\)SiO\({}_{4}\) is faster in acidic solutions than in alkaline ones. The acidic solution of (Mg\({}_{1-x}\)Fe\({}_{x}\))\({}_{2}\)SiO\({}_{4}\) can be written as (Mg,Fe)\({}_{2}\)SiO\({}_{4}\) + 4H\({}^{+}\)\(\geq\) 2(Mg\({}^{2+}\),Fe\({}^{2+}\)) + H\({}_{4}\)SiO\({}_{4}\). As (Mg\({}_{1-x}\),Fe\({}_{x}\))\({}_{2}\)SiO\({}_{4}\) dissolves and Si is produced, protons that are consumed cause the pH to increase. [PERSON] et al. [83] also indicate that the dissolution rate of (Mg\({}_{1-x}\)Fe\({}_{x}\))\({}_{2}\)SiO\({}_{4}\) is fast relative to other silicates. In the experiments carried out with (Mg\({}_{1-x}\)Fe\({}_{x}\))\({}_{2}\)SiO\({}_{4}\) with CO\({}_{2}\)/H\({}_{2}\)O, they conclude that olivine only reacted with H\({}_{2}\)O to produce Mg\({}_{3}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\), (Mg,Fe)(OH)\({}_{2}\)), and Fe\({}_{3}\)O\({}_{4}\). The latest research is aimed at estimating the influence of the amount of H\({}_{2}\) on the serpentinization process in a temperature range of 50 to 320 \({}^{\circ}\)C through numerical modeling [84]. Silica has been investigated in depth by [PERSON] et al. [68, 85, 86], who studied the oxidation kinetics of chemically vapor deposited (CVD) silicon carbide (SiC) in the temperature range of 1200-1400 \({}^{\circ}\)C [85] and 1000-1400 \({}^{\circ}\)C [86] in H\({}_{2}\)O/O\({}_{2}\) gas mixtures. They observed that the silica scales formed in SiC can be volatilized simultaneously, forming silicon hydroxide (SiO(OH)\({}_{2}\)) or silicon oxyhydroxoxide (Si(OH)\({}_{4}\)) at atmospheric pressures (0.1 MPa). The formation of volatile hydroxides depends, in some cases, on the partial pressures of water vapor and oxygen, and for processes at 0.1 MPa and temperatures below 1300 \({}^{\circ}\)C the volatility of silica can be attributed to the reaction SiO\({}_{2}\) + 2H\({}_{2}\)O \(\rightarrow\) Si(OH)\({}_{4}\). At higher temperatures and at lower partial pressures of water steam and oxygen, the reaction SiO\({}_{2}\) + H\({}_{2}\)O \(\rightarrow\) SiO(OH)\({}_{2}\) is more likely [68]. [PERSON] et al. [87] studied the adsorption of water on the surface of a single crystal of MnO at low water steam pressures (1.33 \(\times\) 10\({}^{-6}\)-1.33 \(\times\) 10\({}^{-2}\) Pa), in which the reaction with H\({}_{2}\)O molecules results in the formation of hydroxyl groups on the surface (MnO + H\({}_{2}\)O \(\rightarrow\) Mn(OH)\({}_{2}\)). Another thermodynamic and experimental study of thermochemical cycles (three steps) to produce H\({}_{2}\) involving hydroxides (NaOH and KOH) and MnO among others, has concluded that the reaction of hydroxides with MnO is stable, but they did not produce H\({}_{2}\) at 750 \({}^{\circ}\)C, even in strong oxidizing media [88]. Finally, [PERSON] et al. [89] indicate that the Mn-oxide cycle is the most studied, but unfortunately the H\({}_{2}\)O cleavage reactions with MnO are not thermodynamically favorable and the H\({}_{2}\) produced is negligible. Zn is a metal that when placed in contact with water releases H\({}_{2}\) and produces ZnO. Among the research found, [PERSON] et al. [90] carried out the direct decomposition of H\({}_{2}\)O in a temperature range of 2000-2500 \({}^{\circ}\)C and proposed the exothermic reaction of water vapor, 2 Zn + 2H\({}_{2}\)O \(\rightarrow\) 2 ZnO + 2H\({}_{2}\). [PERSON] [91] considered the production of H\({}_{2}\) from H\({}_{2}\)O dissociation through a thermochemical solar cycle (two steps) with ZnO/Zn. In the second step (exothermic, non-solar), they propose the hydrolysis of Zn at 427 \({}^{\circ}\)C to form H\({}_{2}\) and ZnO through the reaction Zn + H\({}_{2}\)O \(\rightarrow\) ZnO + H\({}_{2}\).