Weakly basic anion exchangers exhibit a unique selectivity for adsorption of heavy metals such as mercury, copper, lead, zinc, nickel and cadmium. Furthermore, some types of exchangers show a marked preference for chromate over sulphate anions. Application of the respective ion exchange processes may, therefore, offer a promising way to remove traces of hazardous heavy metals very efficiently from the raw water of drinking water supplies. The respective ion exchange processes have been demonstrated both at laboratory and semi-technical scales for the elimination of heavy metal cations (cadmium, mercury, lead, nickel) and of chromate anions from spiked tap water and contaminated groundwaters. In all cases the effluent concentrations of filters could be decreased well below the parametric values of the European Drinking Water Directive.

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