Biopolymer-assisted enzyme-induced carbonate precipitation for immobilizing Cu ions in aqueous solution and loess

Abstract

Wastewater, discharged in copper (Cu) mining and smelting, usually contains a large amount of Cu 2+ .Immobilizing Cu 2+ in aqueous solution and soils is deemed crucial in preventing its migration into surrounding environments. In recent years, the enzyme-induced carbonate precipitation (EICP) has been widely applied to Cu immobilization. However, the effect of Cu 2+ toxicity denatures and even inactivates the urease. In the present work, the biopolymer-assisted EICP technology was proposed. The inherent mechanism affecting Cu immobilization was explored through a series of test tube experiments and soil column tests. Results indicated that 4 g/L chitosan may not correspond to a higher immobilization e ciency because it depends as well on surrounding pH conditions. The use of Ca 2+ not only prevented the nucleation of the urease with Cu 2+ by the electrostatic repulsion but reduced the potential for Cu 2+ to migrate into nearby environments when malachite and azurite minerals are wrapped by calcite minerals. The species of carbonate precipitation that are recognized in the numerical simulation supported the above claim. On the other hand, UC1 (urease and chitosan colloid) and UC2 (urea and calcium source) grouting reduced the effect of Cu 2+ toxicity by transforming the exchangeable state-Cu into the carbonate combination state-Cu. The side effect, induced by 4 g/L chitosan, promoted the copper-ammonia complex formation in the shallow ground, while the acidic environments in the deep ground prevented Cu 2+ from coordinating with soil minerals. These badly degraded the immobilization e ciency. The Raman spectroscopy and XRD test results tallied with the above results. The ndings shed light on the potential of applying the biopolymer-assisted EICP technology to Cu-contaminated water bodies and sites remediation.

Draft genome analysis for Enterobacter kobei, a promising lead bioremediation bacterium

“…Biopolymer-assisted Enzyme-Induced Carbonate Precipitation (EICP), this technique utilizes enzymes and biopolymers to precipitate carbonates, effectively immobilizing heavy metals and preventing their migration. Xie et al (2023b) highlighted its wide applicability for heavy metal remediation. Electrokinetic technology coupled with a biological permeable reactive barrier, this method uses electrical currents to drive the movement of contaminants towards a reactive barrier composed of biological materials, where heavy metals are removed and immobilized.…”

Numerical analysis of MICP treated sand based on bio-chemo-hydro model

“…The technology can effectively improve the mechanical and hydraulic properties of porous materials such as sands and soils by using the filling and cementing effects of the mineralization product calcium carbonate (Ivanov and Chu, 2008;Soon et al, 2013;Chen et al, 2023). Numerous studies have demonstrated that MICP technology shows potential for application in several research fields, such as soil reinforcement, fissure repair, and bio-inspired heavy metal immobilization (Wang K. et al, 2023;Xie et al, 2023;Xue et al, 2023). Meanwhile, It has a wide range of applications in the field of geotechnical engineering ( Chu et al, 2012;Choi et al, 2016;Jiang and Soga, 2017;Xiao et al, 2019;Wu et al, 2019;Wang and Nackenhorst, 2020;Liu et al, 2023).…”