(533c) Production of Carbonates from Industrial Waste Via Carbon Mineralization Towards a Circular Economy

Carbon mineralization is a process to fix CO₂ into solid carbonates for permanent storage. This process has been proposed as an efficient approach to achieving the goal of net-zero greenhouse gas emissions. From a thermodynamic perspective, mineralization occurs spontaneously, however, the kinetics are very slow and can be accelerated through engineering. Industrial wastes (e.g. demolition & construction materials, coal fly ash, steel slags, etc.), which contain a high concentration of alkaline earth metals (i.e. calcium) can be used as sources to produce calcium carbonates instead of landfilling them.

Herein, we present studies focusing on the utilization of alkaline industrial wastes to produce different polymorphs of calcium carbonates for different industrial applications. We propose a multiple-stage process to treat the feedstock to obtain high purity carbonates. First wastes are dissolved in an acidic solution to extract out Ca, and followed by an impurities removal (Fe, Al and partial Si) via pH swing process, and finally a crystallization reaction is occurred by bubbling CO₂. We also investigated the effects of various parameters on different metals extraction, such as pH values, temperatures, acid dosing speed, slurry densities, etc. We are optimizing the process by applying life cycle assessment and techno economic assessment to evaluate it from environmental and economic perspectives. Salt electrolysis is used to produce acid and base to offset chemical costs and the recycled salty solution will be the parent solution for this process. Finally, we scaled up this process to a 30 L reaction with mild and simple reaction conditions. These produced carbonates and solid residues can be used as supplementary cementitious materials or fillers to achieve a circular economy.