A novel adsorbent for the determination of the toxic fraction of copper in natural waters

Abstract

A novel adsorbent for the determination of the toxic fraction of copper in natural waters is described. Aluminium hydroxide adsorbed on a sulfonic acid cation-exchange resin quantitatively retains copper(II) ions in the absence of organic ligands such as fulvic, humic and tannic acids. In the presence of these ligands, a smaller fraction of copper is adsorbed and can be related to the toxic fraction. The toxic fraction determined by this method agreed well with results of algal assay with the marine diatom Nitzschia closterium in seawater and the green alga Chlorella pyrenoidosa in a synthetic soft water. The aluminium hydroxide-coated column also quantitatively adsorbs lipid-soluble copper complexes, which can be leached selectively from the column with methanol. The Al:OH ratio on the resin was 1:2 and the conditional stability constants (log K) of the Cu 2+-adsorbent complexes in seawater and synthetic soft water were found to be 9.87 and 11.10, respectively; these values are similar to the equilibrium constatns for the reaction between Cu 2+ and algae. The application of this adsorbent in an in-situ instrument for the continuous, unattended determination of the toxic fraction of copper and some other toxic metals in natural waters is outlined.