Selective solvent filters for non-aqueous phase liquid separation from water

Area of Science:

• Environmental Science
• Materials Science
• Chemical Engineering

Background:

• Contaminated aquifers pose risks to downstream receptors due to non-aqueous phase liquids (NAPL).
• Effective containment and remediation strategies are crucial for protecting groundwater resources.

Purpose of the Study:

• To develop injectable filters capable of containing NAPL within contaminated aquifers.
• To assess the filter's permeability to water and impermeability to non-polar solvents.
• To evaluate the separation efficiency of different emulsifiers for NAPL remediation.

Main Methods:

• Injectable filters were fabricated using aqueous solutions of chitosan, hydroxyethylcellulose, and quaternized hydroxyethylcellulose in sand columns.
• Polymer sorption was verified using quartz-crystal microbalance with dissipation monitoring.
• Solvent separation was analyzed using fluorescence and gas chromatography mass spectrometry; surface properties were assessed via contact angle measurements.

Main Results:

• Filters demonstrated permeability to water and impermeability to non-polar solvents like hexane and toluene, with low ppm solvent concentrations in eluted water.
• Surface analysis indicated oleophobicity for non-polar solvents (contact angle >90°).
• Polar solvents like tetrachloroethylene (TCE) were not separated, showing greater surface affinity than non-polar solvents.
• Emulsion separation varied, with partial success using humic acids and zein particles, but not classical surfactants.

Conclusions:

• Injectable filters show potential for NAPL containment in aquifers, protecting water resources.
• The filters exhibit selective separation based on solvent polarity, retaining non-polar solvents while allowing water passage.
• Further research is needed to optimize emulsifier use for efficient NAPL extraction and remediation.