Reactivity of granite scraps in the synthesis of green hydrogen and sequestration of carbon dioxide processes via mechanochemical activation

As definitely emerged from the last IPCC report, the mechanism of the greenhouse effect, crucial for the sustainability of the planet, is closely associated to the presence of carbon dioxide (CO2), one of the main greenhouse gases. The ever-increasing CO2 emission, mainly related to the widespread use of fossil fuels, is contributing to the global temperature increase, with dramatic environmental effects. Nowadays, several scientific and technological research activities in this field are carried out, and, among them, the CCUS scheme, which is focused on the CO2 Capture, Utilization and Storage, represent the most appealing way for mitigation and valorize carbon dioxide1,2. Within this context, the carbon dioxide-based weathering process, in which a gas-solid reaction is involved, leads to the formation of carbonate phases together with the evolution of green hydrogen and light hydrocarbons3–6. According to the most recent results, the kinetic of this process, can be dramatically enhanced when olivine powders are mechanically milled under water and carbon dioxide5,6. Starting from this evidence, the aim of this work is to investigate the reactivities of granite scraps subjected to mechanical processing, analyzing the structural transformation and gas evolution under different experimental conditions (i.e. pH, milling parameters). The experiments were carried out in a Spex stainless-steel jar opportunely modified for introducing reactive gases. Structural properties and gas composition were evaluated by X-ray diffraction and gas chromatography, respectively. Preliminary results confirms that generation of hydrogen and methane gases can be improved by tuning the pH of the systems analyzed.