Applicability of fine industrial metallic iron-rich waste powders for hydrothermal production of hydrogen gas: The influence of non-ferrous contaminants

Hydrothermal Production of H2 and Magnetite From Steel Slags: A Geo-Inspired Approach Based on Olivine Serpentinization

“…Another approach would consist in using a low-value ferrous starting material to achieve water splitting without considering further reduction steps. The steel industry does produce such potential starting materials (waste, byproducts, mine tailing), the H 2 -production capacity of which has already been investigated in a few experimental studies (Azad et al, 2008;Matsuura and Tsukihashi, 2012;Malvoisin et al, 2013;Michiels et al, 2015Michiels et al, , 2018Shatokha et al, 2016;Crouzet et al, 2017b;Kularatne et al, 2018 for olivine-bearing mine tailings of nickel extraction). The steam-iron process can be categorized as a thermochemical water-splitting method which uses iron as reducing agent.…”

“…There is so far no comprehensive experimental dataset on the effect of impurities on the formation of magnetite and H 2 from FeO-bearing slags. Michiels et al (2015Michiels et al ( , 2018 studied the hydrothermal oxidation of Fe • contained in industrial wastes with the aim of producing H 2 . Although iron is not divalent in their Fe-rich starting-materials, the oxidation route also involves iron oxidation, water splitting and magnetite precipitation.…”

“…Although iron is not divalent in their Fe-rich starting-materials, the oxidation route also involves iron oxidation, water splitting and magnetite precipitation. Michiels et al (2015) showed that the addition of carbon dioxide under basic pH, which dissolves as CO 2− 3 , promotes the oxidation of iron metal into magnetite at 160 • C. Furthermore, Michiels et al (2018) studied the effect on H 2 yield of a wide range of metal and oxide impurities as typically encountered in products of the steel industry. The authors identified reaction inhibitors that basically slow down the H 2 production.…”

“…Probably more relevant to our concern, Michiels et al (2018) identified Ni as a catalyst of the H 2 production reaction. Based on previous studies, Michiels et al (2018) proposed that Ni catalyzes the water-splitting reaction, which is thus implicitly considered as the rate-limiting step. Magnetite production flux at 160 • C increases from 4 to above 40 g Fe3O4 .L −1 .h −1 when Ni is added FIGURE 5 | Arrhenius plot of H 2 production reaction from BOF slag and pure FeO.…”

“…in optimized proportions (Michiels et al, 2018). Liu et al (2016) studied the effect of HCl and Pd on the kinetics of hydrothermal H 2 (and magnetite) production from Fe • powder at 120 • C. They showed the positive effect of adding acid due to an enhanced Fe • dissolution rate.…”