Adsorption of heavy metals from wastewater graphic industry using clinoptilolite zeolite as adsorbent

Abstract

Most paints used for printing in the graphic industry contain traces of heavy metals that are dissolved and carried in the effluent, and the risk posed by these contaminants in the environment is associated with toxicity and bioaccumulation in living beings. The aim of this study was to evaluate the use of natural clinoptilolite zeolite (CL) as adsorbent for removal of heavy metals in wastewater from the graphic industry. Adsorption experiments were performed with the CL zeolite for copper(II), chromium(III) and iron(III) so as to determine equilibrium constants and kinetic models. Kinetic assays performed for each metal resulted in removal up to 95.4% iron, 96.0% copper and 85.1% chromium, at 25.0°C and pH 4.0. The zeolite selectivity followed the order Fe>Cr>Cu and the adsorption mechanism followed pseudo-first order kinetic model for copper and chromium and pseudo-second order for iron. The Langmuir model provided the best fit of adsorption isotherms for chromium and copper while Freundlich model was the best for iron. Toxicity and genotoxicity assays in Allium cepa showed the efficiency of the use of CL zeolite as an adsorbent for treating printing industry effluent, showing no toxic and genotoxic potential, contrary to untreated effluent which showed a decrease in germination and increase in total cells with alterations (toxic and genotoxic effect).