Calcium silicates synthesised from industrial residues with the ability for CO 2 sequestration

Abstract

This work explored several synthesis routes to obtain calcium silicates from different calcium-rich and silica-rich industrial residues. Larnite, wollastonite and calcium silicate chloride were successfully synthesised with moderate heat treatments below standard temperatures. These procedures help to not only conserve natural resources, but also to reduce the energy requirements and CO₂ emissions. In addition, these silicates have been successfully tested as carbon dioxide sequesters, to enhance the viability of CO₂ mineral sequestration technologies using calcium-rich industrial by-products as sequestration agents. Two different carbon sequestration experiments were performed under ambient conditions. Static experiments revealed carbonation efficiencies close to 100% and real-time resolved experiments characterised the dynamic behaviour and ability of these samples to reduce the CO₂ concentration within a mixture of gases. The CO₂ concentration was reduced up to 70%, with a carbon fixation dynamic ratio of 3.2 mg CO₂ per g of sequestration agent and minute. Our results confirm the suitability of the proposed synthesis routes to synthesise different calcium silicates recycling industrial residues, being therefore energetically more efficient and environmentally friendly procedures for the cement industry.