Synthesis, characterisation, and utilisation of copper nanoflower for biocementation for ground improvement applications

Microbially-induced calcium carbonate precipitation (MICP) has recently emerged as a sustainable ground improvement method. Nevertheless, the technique’s applicability in soils with narrow pore throats has been queried. To overcome these challenges, the use of enzymes (including bacterially produced enzymes) was proposed for these soils. However, the use of free enzymes entails many challenges linked predominantly to the limited enzyme supply, the poor stability of the enzyme once released into the soil, and the poor reusability of the enzyme. This paper studies the use of nano enzymes with a high biocementation efficacy for carbonic anhydrase (CA) enzyme delivery as one possible way to overcome potentially these challenges. CA enzyme was used because it has the potential to be an environmentally sustainable biocementation pathway due to its ability to sequester CO2 for biocement production. The paper presents the synthesis, characterisation, and utilisation of CA-enwrapped copper phosphate-based inorganic hybrid nanoflowers for innovative delivery and enzyme stabilisation due to the enhanced thermal and enzyme activity efficiency and due to their reusability, if recovered at the end of the treatment. The results from this study show that the bovine carbonic anhydrase enzyme enhanced the CO2 hydration reaction, resulting in a bioprecipitation reaction and the production of calcium carbonate and increased strength of treated soil with 500kPa for free CA and approximately 1000kPa for the hybrid CA-Cu. The material analysis confirmed calcite as the primary precipitate formed, which would act as a bonding agent between soil particles for ground improvement applications.