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Equilibrium partition of polycyclic aromatic hydrocarbons in a cloud-point extraction process
Jing-Liang Li1, Bing-Hung Chen
1Department of Chemical and Environmental Engineering, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore. bhchen@alumni.rice.edu
Journal of Colloid and Interface Science
|August 12, 2003
Summary
Cloud-point extraction (CPE) effectively isolates polycyclic aromatic hydrocarbons (PAHs) from water using Tergitol 15-S-7 and sodium sulfate. This method enhances PAH preconcentration by optimizing salt and surfactant concentrations for improved hydrophobic partitioning.
Area of Science:
- Environmental Chemistry
- Analytical Chemistry
- Separation Science
Background:
- Polycyclic Aromatic Hydrocarbons (PAHs) are persistent organic pollutants requiring efficient extraction methods.
- Cloud-point extraction (CPE) offers a greener alternative for separating hydrophobic compounds from aqueous matrices.
- Nonionic surfactants like Tergitol 15-S-7 are suitable for micellar-enhanced extraction processes.
Purpose of the Study:
- To investigate the efficacy of cloud-point extraction (CPE) for selected polycyclic aromatic hydrocarbons (PAHs).
- To optimize CPE conditions using Tergitol 15-S-7 and sodium sulfate for enhanced PAH preconcentration.
- To elucidate the partitioning mechanisms of PAHs in the surfactant-rich phase.
Main Methods:
- Cloud-point extraction (CPE) utilizing the nonionic surfactant Tergitol 15-S-7.
- Addition of sodium sulfate (Na(2)SO(4)) to reduce the cloud-point temperature and facilitate extraction at ambient conditions (approx. 22°C).
- Analysis of preconcentration factors and equilibrium partition coefficients (K(p)) for model PAHs.
Main Results:
- CPE achieved high preconcentration factors (up to 40) for PAHs at 1 wt% surfactant and 0.6 M Na(2)SO(4).
- Equilibrium partition coefficients (K(p)) were largely independent of surfactant concentration (up to 3 wt%).
- PAH partitioning into the surfactant phase correlated strongly with hydrophobic affinity (K(ow)) and molar volume (V(x)), indicating hydrophobic interactions govern the process.
- Increased sodium sulfate concentration enhanced PAH partitioning into the surfactant-rich phase.
Conclusions:
- Cloud-point extraction with Tergitol 15-S-7 and sodium sulfate is an effective method for preconcentrating PAHs from aqueous solutions.
- The extraction efficiency is significantly influenced by salt concentration and hydrophobic interactions between PAHs and surfactant aggregates.
- This optimized CPE method provides a promising approach for the analysis of PAHs in environmental samples.