Bio-based CaCO3 production enhanced by arginine as a carbon-nitrogen source: Intensified carbonation and weakened nitrification

The early hydration of cementitious materials can be improved by using concrete slurry waste (CSW) to form bio-based CaCO 3. The yield of CO 3 2− produced by carbon and nitrogen metabolism was investigated. Compared with septic liquid, glucose and sodium acetate, the highest conversion rate of arginine was 3.98. Arginine maintains a pH of 9, which facilitates the sequestration of CO 2 in water. In contrast, the nitrogen metabolism of NaNO 3 is weak, and the pH of urea was reduced to 3.9 after nitrification. Compared with other nitrogen utilization, arginine addition is beneficial to the synthesis and secretion of tryptophan-like proteins rather than nitrification. Arginine mainly results in less humification and encourages dissolved organic matter (DOM) degradation, shown by humification index (HIX) dropping by 0.02 and freshness index (FrI) by 0.11. Arginine also decreases Nitrospira populations and reduces nitrite oxidoreductase subunits A and B (NxrAB) abundance by 0.9‰, limiting NO 2 − to NO 3 − conversion. . In conclusion, the production of bio-based CaCO 3 can be regulated by arginine, with field applications depending on the protein content in carbon and nitrogen sources to maintain a pH close to 9 and delay the biological nitrification process. • Arginine served as a carbon source to achieve a carbonate conversion of 3.98, yielding bio-based calcium carbonate. • Arginine, as a nitrogen source, is suitable for pH adjustment to 9 and CO 2 capture. • Arginine mainly contributes to less humification and prone to DOM degradation. • Arginine reduced the population of Nitrospira and the abundance of NxrAB involved in nitrification decreased by 0.9‰.