A new method of alkalinity remediation for Cd-contaminated groundwater by PAAS-modified MgCO < sub > 3 < /sub > /Mg(OH) < sub > 2 < /sub > colloid

Chemosphere. 2024 Apr 30:142200. doi: 10.1016/j.chemosphere.2024.142200. Online ahead of print.ABSTRACTMg(OH)2 dissolves slowly and can provide a long-term source of alkalinity, thus a promising alternative reagent for the in situ remediation of heavy metal polluted groundwater. Unfortunately, it exhibits a relatively poor stabilization effect on heavy metal Cd due to the higher solubility of the resulting stabilized product, Cd(OH)2. To overcome this limitation, we investigated the use of MgCO3/Mg(OH)2 colloid modified by sodium polyacrylate (PAAS) to remove Cd from groundwater. Through ultrasonic dispersion, the molecular chains of PAAS are broken, causing a transformation from flocculation to surface modification, resulting in the production of a stable colloid. The colloidal particles of MgCO3/Mg(OH)2 have a smaller size and a negatively charged surface, which significantly enhances their migration ability in aquifers. The combination of MgCO3 and Mg(OH)2 provides a complementary effect, where MgCO3 effectively precipitates Cd in the aquifer while Mg(OH)2 maintains the required pH level for stabilization. The optimal compounding ratio of MgCO3 to Mg(OH)2 for achieving the best stabilization effect on Cd is found to be 1:1. Column experiments demonstrate that the injection of MgCO3/Mg(OH)2 colloid substantially enhances Cd stability, reducing the exchangeable fraction of Cd in aquifer media from 88.61% to a range of 22.50-34.38%. Based on these results, the MgCO3/Mg(OH)2 c...

Source: Chemosphere - May 2, 2024 Category: Chemistry Authors: Bowen Li Meiling Tang Peng Wang Shibin Liu Meng Yao Jun Dong Source Type: research