Effects of multi-source plant-derived urease enzyme on the morphology, growth, size, and distribution behavior of calcium carbonate through enzyme-induced carbonate precipitation method: a microfluidic chip experiment

Enzyme-induced carbonate precipitation (EICP) has been extensively studied as an alternative to microbial-induced carbonate precipitation (MICP) in recent years. This study aims to investigate the effects of different plant-derived ureases on the morphology, growth, size, and distribution of calcium carbonate at particle scale within microfluidic chips. The commercial urease (CU), as well as crude sword bean urease (SWU), jack bean meal (JBM), and soybean urease (SOU) were used. The results revealed that crystal morphology and growth are noticeably influenced by organic molecules in different ureases. Relatively low concentrations of organic molecules in SWU and JBM may provide heterogeneous nucleation sites and promote crystal growth, thus achieving the largest individual crystal and total crystal area. For CU, smaller crystal size and total crystal area were observed due to tiny amounts of organic molecules. A high concentration of organic molecules in SOU would limit crystal nucleation and growth, thereby achieving smaller crystal size and total crystal area. In addition, crystals in Test-SWU and Test-JBM present preferential deposition at interparticle contacts with better cementation type than Test-CU and Test-SOU. Acid digestion experiments were also conducted to provide evidence for the hypothesis that organic matter precipitates induced by crude ureases act as heterogeneous nucleation sites. SWU and JBM are recommended as a raw material for EICP to enhance the engineering properties of soil.