Removal of Organic Impurity in Enzyme for Enhanced Efficacy of Enzyme-Induced Calcite Precipitation in Dust Mitigation Practices

Legacy fly ash, stored in ash ponds and landfills, poses a significant environmental concern due to the dust nuisance caused by its fine particle size, non-cohesive nature, and high susceptibility to atmospheric dispersion. Apart from being ineffective, conventional dust suppression methods, such as water spraying, airborne particle capture, and chemical binders, provide short-lived solutions that are resource- and energy-intensive, lacking long-term sustainability. Enzyme-Induced Calcite Precipitation (EICP) is emerging as a green, durable, and long-term sustainable alternative, which relies on the enzymatic hydrolysis of urea to precipitate calcite minerals. These minerals bind loose, non-cohesive particles together, thereby increasing surface strength while significantly reducing airborne dust particles. However, limited studies have examined the effect of centrifugal purification on plant- derived urease, which influences calcite precipitation and the resulting cementation strength. Urease extracted from plants contains fibers, fatty acids, and other organic impurities that compromise the bonding between the particles of a treated sample. Experimental results indicate that although the cementation solution with unpurified urease yields more calcite precipitation, the associated organic impurities significantly reduce surface strength. In the case of centrifuged-treated urease, the treated samples achieved nearly double the penetration resistance, attributed to enhanced purity. The microstructural attributes confirmed the presence of fibers in samples treated with unpurified urease and illustrated enhanced particle bonding in purified treatments. The pore size distribution characteristics highlight the distinct qualities in terms of pore structure and particle agglomeration between the samples treated with purified and unpurified urease. Overall, the purification process of plant-derived urease was found to be crucial for enhancing EICP performance, thereby improving both the strength and long-term stability of treated fly ash surfaces, thereby mitigating their dust nuisance ability.