Enhanced Cr(VI) stabilization in soil by chitosan/bentonite composites

Area of Science:

• Environmental Science
• Soil Science
• Materials Science

Background:

• Chromium contamination in soil poses significant environmental and health risks.
• Immobilization of heavy metals in soil is crucial for remediation.
• Chitosan/bentonite composites offer a promising material for soil passivation.

Purpose of the Study:

• To synthesize chitosan/bentonite composites (CSBT) for chromium immobilization in soil.
• To investigate the influence of CSBT on different chromium forms in soil.
• To evaluate the effectiveness and kinetics of CSBT in reducing chromium bioavailability.

Main Methods:

• Batch experiments were conducted to assess CSBT's impact on soil chromium.
• Analysis of various chromium fractions (exchangeable, oxidizable, reducible, residual) was performed.
• Soil pH and passivation effect over time were monitored.

Main Results:

• CSBT significantly reduced exchangeable and oxidizable chromium forms.
• The residual form of chromium increased substantially, indicating enhanced immobilization.
• Optimal CSBT dosage (0.2 g·kg⁻¹) led to notable reductions in labile chromium fractions.
• Passivation effects stabilized within 28 days, showing long-term efficacy.
• CSBT demonstrated minimal impact on soil pH.

Conclusions:

• CSBT is an effective material for immobilizing chromium in soil.
• The functional groups of CSBT facilitate the conversion of available chromium to a stable residual state.
• CSBT reduces chromium bioavailability, offering a viable soil remediation strategy.