Transformation of a Silicate Material for Carbon Negative Magnesia-Based Cement via Electrochemistry

Magnesium silicate hydrate cement (M-S-H) can be formed from magnesium oxide (MgO) and silica phases which offer unique properties compared to traditional calcium-based Portland cement (PC). The present study explores the transformation of a magnesium trisilicate material (Mg₂Si₃O₈) into the precursor phases of M-S-H cement via the electrolysis of water. The investigation examines the change in pH as a consequence of water electrolysis, resulting in the dissolution of the Mg₂Si₃O₈ and formation of Mg(OH)₂ and SiO₂. The material phases collected after dissolution are characterized via SEM, EDX, XRD, IR, ²⁹Si NMR and BET analysis. The results indicate brucite accumulates in large platelet-like structures and analysis of the residual silicate phase present after electrolysis-induced dissolution reveal protons have replaced the Mg²⁺ ions. Amorphous SiO₂ can be recovered from the system through pH adjustment, producing SiO₂ with a high surface area ideal for cement production. As this process is conducted electrochemically, this approach to silicate material transformation represents an avenue toward cement manufacturing devoid of CO₂ emissions. Through carbon-curing, the M-S-H cement can constitute a carbon-negative system. Mg₂Si₃O₈, a synthetic material, serves as a model for extrapolating this processes to earth-abundant silicate minerals enabling their potential use in large-scale sustainable cement manufacturing.