A synthetic urease-mimetic catalyst for wind erosion control via carbonate precipitation

Wind erosion in arid and semi-arid regions poses a significant global environmental challenge, threatening infrastructure and human health. Conventional enzymatic-induced carbonate precipitation (EICP) for soil stabilization, while effective, relies on the natural urease enzyme extracted from plants or microorganisms, thereby being limited by extraction methods, purification levels, and the availability of biological sources, as well as the natural enzyme's environmental sensitivity. This study introduces a novel approach utilizing synthetic urease-mimetic catalysts to induce calcite precipitation for dust suppression. Two Schiff base complexes, derived from glycine and salicylaldehyde with central metal ions of copper(II) and zinc(II), were synthesized and evaluated as catalysts for urea hydrolysis. The zinc-based complex was selected as the superior catalyst based on higher calcite precipitation yield and lower cost. Through response surface methodology (RSM) and wind tunnel testing on erodible siliceous sand, the optimal application parameters were determined to be a solution containing 8 g/L urea, 13 g/L CaCl₂, and 1 g/L Zn-complex applied at a rate of 1.65 L/m². This treatment effectively reduced wind erosion to negligible levels (mass loss per original mass of the sample ~ 1%). Supplementary tests, including successive wet-dry cycles, surface strength measurement, and SEM analysis, confirmed the formation of a durable calcite crust that bonds soil particles, increasing surface strength to over 150 kPa. The stabilized soil exhibited excellent resistance to simulated environmental stressors, including heat (50 °C) and long-term aging (one year), with only a minimal increase in erosion (mass loss percent of 1.5%). This research demonstrates that Schiff base complexes, particularly the zinc variant, are highly effective and durable catalysts for soil stabilization via chemical carbonate precipitation, offering a promising alternative to biological enzyme-based methods.