Micelle-Mediated Extraction of Heavy Metals from Environmental Samples: An Environmental Green Chemistry Laboratory Experiment

Summary

Analysis of trace metals and organic substances often rely on the use of organic solvent-based extractions. In this laboratory exercise, students will use analytical chemistry to determine heavy metals from water samples using a greener, micelle-mediated extraction procedure called a cloud-point extraction. Water samples are treated with a chelating agent, ammonium pyrrolidinedithiocarbamate, and the nonionic surfactant Triton X-114. After acidifying the solution, samples are heated to promote micelle formation and heavy metals are removed with the surfactant-rich phase. Samples are heated to remove remaining water and then prepared for atomic absorption spectroscopy operating in the flame mode. Developed for an undergraduate analytical chemistry laboratory this exercise focuses on the fundamental concepts of micelle formation, phase separation and cloud-point extraction methodology. The greener, micelle mediated preconcentration technique replaces high volume, more hazardous organic solvent extraction methods.

Supplemental materials are provided on the J. Chem. Educ. website and include instructor notes.

Summary prepared May 2005 by Julie A. Haack, Department of Chemistry at the University of Oregon.

Category Descriptors

Chemistry Concepts

• Phases/Phase Transitions
• Solutions/Solvents

Laboratory Techniques

• Atomic Spectroscopy
• Extraction

Green Chemistry Principles

• Avoid Chemical Derivatives
• Minimize the Potential for Accidents
• Prevent Waste
• Use Safer Solvents/Reaction Conditions

Chemistry Subdiscipline

• Analytical Chemistry
• Environmental Chemistry

Target Audience

• Colleges/Universities

Source

• Journal Articles