Highly efficient Cr(vi) removal from water using deep eutectic solvents: a sustainable and comprehensive approach

Area of Science:

• Environmental Chemistry
• Green Chemistry
• Materials Science

Background:

• Hexavalent chromium (Cr(vi)) poses a significant environmental and health risk due to its high toxicity and mobility.
• Conventional Cr(vi) remediation methods often involve harsh chemicals or generate secondary pollutants.
• Developing sustainable and efficient extraction techniques for Cr(vi) is crucial for environmental protection.

Purpose of the Study:

• To develop and evaluate a novel hydrophobic deep eutectic solvent (HDES) for the efficient removal of hexavalent chromium (Cr(vi)).
• To optimize the extraction conditions and investigate the mechanism and thermodynamics of Cr(vi) removal using the developed HDES.
• To assess the environmental friendliness and applicability of the HDES-based method for real wastewater treatment.

Main Methods:

• Synthesis of a hydrophobic deep eutectic solvent (HDES) using acetic acid and tetraoctylammonium bromide.
• Optimization of HDES extraction parameters, including molar ratio and pH range.
• Kinetic and thermodynamic analysis of the Cr(vi) extraction process.
• Validation of the method using real wastewater samples and assessment of environmental impact via AGREE score.

Main Results:

• The optimized HDES demonstrated robust Cr(vi) extraction, achieving over 95% removal across a wide pH range (2-10).
• The extraction process followed pseudo-second-order kinetics, indicating a spontaneous and endothermic nature (ΔH° = 38.21 kJ/mol, ΔG° = -16.88 kJ/mol).
• A high enrichment factor of 87-fold was achieved in real wastewater, with an AGREE score of 0.76 confirming environmental friendliness.

Conclusions:

• The study successfully demonstrates the first application of an acetic acid-based HDES for effective Cr(vi) removal.
• The developed HDES offers a scalable, efficient, and environmentally friendly methodology for Cr(vi) remediation.
• This novel approach provides a promising sustainable solution for tackling hexavalent chromium pollution in industrial wastewater.