Removal of Chromium from Aqueous Solution by Custard Apple (Annona Squamosa) Peel Powder as Adsorbent

Abstract

Chromium has been widely used in various industries like textile, leather, chemical manufacture, metal finishing, paint industry and many other industries. Since hexavalent chromium is a priority toxic, mutagenic and carcinogenic chemical when present in excess, it is very much required to remove chromium from effluents before allowing it to enter any water system or on to land. In the present study, the removal of hexavalent chromium by adsorption on the Custard apple peel powder as adsorbent has been investigated in the batch experiments. The agitation time, the adsorbent size, adsorbent dosage, initial chromium concentration, temperature and the effect of solution pH are studied. The Freundlich model for Cr (VI) adsorption onto Custard apple peel powder is proved to be the best fit followed by Langmuir model and Tempkin model based on high regression coefficient R^2 value. The adsorption behavior is described by a pseudo second order kinetics. The maximum metal uptake is found to be 7.874 mg/g. The morphology on the surface of adsorbents and also the confirmation of chromium binding on adsorbent surface at different stages were obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. The results obtained in this study illustrate that Custard apple peel powder is expected to be an effective and economically viable adsorbent for hexavalent chromium removal from industrial waste water.