CO2 sequestration by CA-mediated CaCO3 precipitation using calcium source in recycled concrete aggregates

Please check whether enrolling in this project is possible by directly contacting the responsible supervisor(s) indicated below as soon as possible. Note that although we announce many topics, we won't be able to offer all of them simultaneously due to limited lab capacity.

The emission of CO₂ has increased rapidly in the last decades which has pushed the global environment out of safe boundaries. The utilization of recycled concrete aggregate (RCA) derived from substantial volumes of global construction waste represents an environmentally and economically advantageous solution. RCA is an eco-friendly calcium source that can be used for CO₂ sequestration. Ca²⁺ can be extracted from RCA in solutions and CO₂ can be sequestrated in the Ca²⁺ rich solution by CaCO₃ precipitation. The produced CaCO₃ solids can be further used for different purposes, such as supplementary cementitious materials in concrete.

Carbonic anhydrase (CA) is a group of enzymes that could be a promising candidate to accelerate CO₂ sequestration by acting as a catalyzer for CO₂ hydration to H⁺ and HCO₃^-. and CA can increase the reaction rate by about 10⁷ times compared to the process without CA. Larger amounts of CO₂ may thus be sequestered via CaCO₃ precipitation in a shorter period. The CaCO₃ precipitation process is controlled by various factors. The precipitation rate was found to increase with an increase in Ca²⁺ concentration, but excessively high concentrations could also have a negative effect, and lower Ca²⁺ concentrations were beneficial to form vaterite, while higher Ca²⁺ concentrations were beneficial to form calcite.

In this project, we aim to understand the effect of CA on CaCO₃ precipitation using the calcium source from RCA. In addition, parameter studies such as Ca²⁺ concentrations, the presence of other ions from RCA, solution pH, CO₂ concentrations, and temperature, are interesting to study to fully understand the CaCO₃ precipitation processes in RCA leaching solutions.

The student is expected to carry out experiments in the lab, which involve working with RCA samples. The student will get an opportunity to work with characterization techniques such as thermogravimetric analysis (TGA), BET surface area analysis, and selected microstructural investigations.