Abstract
The application of the microbially induced carbonate precipitation (MICP) method for remediating heavy metals (i.e., HMs) has recently garnered significant attention. Nevertheless, the inhibition of urease activity by toxic Cd2+, Pb2+, Zn2+, and Cu2+ poses a challenge for MICP-based remediation of HMs contamination. This study: (1) first performed the traditional MICP tests (in which the bacterial solution, urea solution, and HMs were mixed simultaneously), and investigated the toxic effect of HMs on the urease activity and the immobilization efficiency, (2) analyzed the toxicity and immobilization mechanism during the MICP process by combining the simulation and XRD tests, (3) conducted the two-step MICP tests (which initially mixed the bacterial solution and urea solution to promote urea hydrolysis, then added the HMs solutions for HMs precipitation) to improve the immobilization efficiency. The tube experiments and simulations were investigated in the HMs concentration range from 1 to 10 mmol/L. Indicators including ammonium concentration, HMs concentrations, and pH were measured/recorded during the tests. The results show that soluble HMs exhibit a concentration-dependent inhibition of urea hydrolysis during the traditional MICP process, resulting in a decreasing immobilization efficiency. The two-step MICP method can effectively immobilize almost the Cd2+ and Zn2+ when the initial urea hydrolysis period exceeds 1–2 h. In addition, a high immobilization rate of over 90% can be achieved for Cu-contaminated solutions at the optimal first-step reaction time. Compared with the traditional MICP procedure, the effective two-step MICP method exhibits more promising application prospects for the immobilization of soluble HMs in aquatic environments.
Published Version
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
