# Urea-Mediated Biomineralization and Adsorption of Heavy-Metal Ions in Solution by the Urease-Producing Bacteria C7-12

## TL;DR

A urea-producing bacteria strain, C7-12, effectively removes heavy metals from solution through biomineralization and adsorption, offering potential for bioremediation.

## Contribution

The study identifies a new Serratia marcescens strain with high heavy-metal removal efficiency via urea-mediated biomineralization and adsorption.

## Key findings

- Serratia marcescens C7-12 achieved an 85% removal rate of cadmium in solution.
- The bacteria form CdCO3 through biomineralization and adsorb heavy metals via functional groups.
- The strain removes multiple heavy metals (Cd, Pb, Zn, Cu) with varying efficiencies.

## Abstract

Urease-producing bacteria (UPB) have great potential for the bioremediation of heavy-metal pollution through biomineralization and adsorption. In this study, a strain of UPB, C7-12, was isolated from heavy-metal-contaminated soil in a lead–zinc mining area and identified as Serratia marcescens. The heavy-metal removal ability, influencing factors, and precipitation mode of this UPB strain in solution were investigated. The cadmium (Cd) removal rate in a Cd (1 mg/L) solution from C7-12 reached 85%, and pH was the main influencing factor. With urea mediation, S. marcescens C7-12 biomineralizes the Cd2+ in solution to form CdCO3 and removes it through extracellular precipitation and surface adsorption. Furthermore, the removal rates of Cd2+, Pb2+, Zn2+ and Cu2+ in solution by S. marcescens C7-12 were 33–65%, 28–32%, 22–49%, and 38–44%, respectively. The precipitation mode involves coprecipitation of multiple heavy metals to form a mineral. These heavy metals are adsorbed on the surface of bacteria through the participation of carboxyl, amino, and phosphate functional groups and extracellular polymeric substances. Therefore, S. marcescens C7-12 has strong biomineralization and adsorption capacity for heavy-metal ions in solution, which can provide potential resources for the bioremediation of heavy-metal-contaminated soil and water.