Removal of Heavy Metals from Water: An Environmentally Significant Atomic Absorption Spectrometry Experiment

A laboratory experiment that combines the environmentally significant topic of wastewater treatment with atomic absorption spectrometry (AAS) is described. In the first portion of the laboratory project, students perform treatment studies on simulated wastewater samples that contain heavy metal contaminants common to the effluent of the metal finishing industry. Following pretreatment reduction of Cr(VI) to Cr(III), sparingly soluble metal hydroxides are produced by pH adjustment and removed by filtration with the aid of a polyacrylamide flocculant. In the second portion of the experiment, AAS is used to determine metal concentrations in treated and untreated water samples, thus enabling the students to determine the effectiveness of the treatment process. Details of how this experiment integrates topics such as the pH-dependent solubility of metal hydroxides, complex equilibria, matrix interference, and polymers in the context of an environmentally important analysis are presented.