Compressed air-assisted solvent extraction (CASX) for metal removal

Area of Science:

• Environmental Science
• Chemical Engineering
• Materials Science

Background:

• Metal contamination in wastewater poses significant environmental and health risks.
• Conventional solvent extraction methods can be slow and inefficient, requiring large solvent volumes.
• Developing novel, efficient, and sustainable metal extraction techniques is crucial.

Purpose of the Study:

• To introduce a novel process, compressed air-assisted solvent extraction (CASX), for generating micro-sized solvent-coated air bubbles (MSAB).
• To evaluate the efficiency of CASX in removing heavy metals from wastewater.
• To assess the physical properties of MSAB for improved solvent recovery.

Main Methods:

• CASX involves pressurizing solvent with compressed air and releasing it into metal-containing wastewater to form MSAB.
• The process leverages the large surface area of MSAB for rapid mass transfer.
• Experiments were conducted using acidic electroplating wastewater (Cr(VI)) and synthetic Cd(II) wastewater.

Main Results:

• CASX completely removed Cr(VI) from electroplating wastewater in under 10 seconds with an aqueous/solvent (A/S) ratio of 115.
• For Cd(II) wastewater, A/S ratios exceeding 714 and 1190 were achieved with different solvent compositions.
• MSAB exhibited distinct physical properties (size, density) facilitating easy solvent separation and recovery from treated effluent.

Conclusions:

• CASX is a highly efficient and rapid method for metal extraction from wastewater.
• The unique properties of MSAB enhance extraction performance and simplify solvent recovery.
• CASX presents a promising sustainable technology for industrial wastewater treatment.