This study explores the synergistic effects of microbially induced carbonate precipitation (MICP) combined with graphene-based adsorptive materials, namely graphene (GR) and graphene oxide (GO), for the remediation of lead-contaminated loess. A series of systematic experiments were conducted, including unconfined compressive strength (UCS) testing, toxicity characteristic leaching procedure analysis, zeta potential measurements, scanning electron microscopy (SEM) observation, X-ray fluorescence (XRF) analysis, and microstructural modeling. The results revealed that MICP effectively improved soil strength and immobilized Pb²⁺ through carbonate precipitation and microbial surface adsorption, reducing lead leaching concentrations by up to 39.56%. The addition of GR and GO significantly enhanced the remediation performance by further lowering Pb²⁺ mobility and improving soil mechanical properties. Optimal results were achieved with 1.0% GO content, where UCS increased by approximately 11.7% compared to MICP alone, and lead leaching concentration was reduced by 61.63% relative to untreated soil. Microstructural analysis indicated that the combined remediation process promoted denser soil packing, enhanced calcium carbonate distribution, and facilitated multi-pathway Pb²⁺ immobilization, including precipitation, chemical adsorption, and physical encapsulation. GO exhibited superior performance due to its higher negative surface charge, larger specific surface area, and abundant oxygen-containing functional groups. These findings highlight the potential of integrating MICP with graphene-based materials for the simultaneous stabilization and strengthening of heavy metal-contaminated loess, providing valuable insights for the development of advanced soil remediation technologies.

This study examines the effects and mechanisms of different Enzyme-Induced Carbonate Precipitation (EICP) treatments on loess structure improvement. The study focuses on ordinary EICP and three modified methods using MgCl₂, NH₄Cl, and CaCl₂. A series of unconfined compressive strength (UCS) tests, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and elemental mapping were used to assess both macroscopic performance and microscopic characteristics. The results indicate that ordinary EICP significantly enhances loess particle bonding by promoting calcite precipitation. MgCl₂-modified EICP achieves the highest UCS (820 kPa) due to delayed urea hydrolysis and the formation of aragonite alongside calcite, which results in stronger and more continuous cementation. In contrast, NH₄Cl reduces urease activity and reverses the reaction, which limits carbonate precipitation and weakens structural cohesion. Excessive CaCl₂ leads to a “hijacking mechanism” where hydroxide ions form Ca(OH)₂, restricting carbonate formation and diminishing the overall enhancement. This study highlights the mechanisms behind enhancement, degradation, and diversion in the EICP process. It also provides theoretical support for optimizing loess subgrade reinforcement. However, challenges such as uneven permeability, environmental variability, and long-term durability must be addressed before field-scale applications can be realized, necessitating further research.

The strong adsorption capacity of loess poses a significant limitation to the electrokinetic (EK) remediation process. Modified EK technologies, such as graphene oxide-alginate composite hydrogel (GOCH) electrodes, are increasingly employed for the remediation of heavy metal-contaminated loess. However, the complex interactions among multiple physical fields within these modified systems remain poorly understood. This study utilizes COMSOL Multiphysics version 6.0 to simulate diffusion, electromigration, electroosmotic flow, adsorption, and chemical reactions in loess contaminated with copper (Cu) and lead (Pb). A chemical precipitation and ion transport model, governed by the Nernst–Planck equation, was validated through a comparison of simulation results with experimental data. The investigation examines the effects of electrode placement and size on EK efficiency, revealing that diagonally placed irregular electrodes optimize the electric field, minimize ineffective regions, and enhance ion migration. Larger electrodes enhance current density, whereas smaller electrodes mitigate edge shielding effects. This research offers strategic insights into electrode configuration for improved EK remediation of Cu-Pb-contaminated loess, achieving greater efficiency than traditional systems.