Removal of Cr(VI) from wastewater by adsorption on iron nanoparticles

Abstract

Due to rapid industrialisation, the presence of heavy metals in water and wastewater is a matter of environmental concern. Though some of the metals are essential for our system but if present beyond their threshold limit value (TLV), they are harmful and their treatment prior to disposal becomes inevitable. The present communication has been addressed to the removal of Cr(VI) from aqueous solutions by nanoparticles of iron. Nanoparticles of iron were prepared by sol-gel method. The characterisation of the nanoparticles was carried out by XRD and TEM analysis. Batch experiments were adopted for the adsorption of Cr(VI) from its solutions. The effect of different important parameters such as contact time and initial concentration, pH, adsorbent dose, and temperature on removal of chromium was studied. The removal of chromium increased from 88. 5% to 99.05% by decreasing its initial concentration from 15 to 5 mg L −1 at optimum conditions. Removal of Cr(VI) was found to be highly pH dependent and a maximum removal (100%) was obtained at pH 2.0. The process of removal was governed by first and pseudo-second-order kinetic equations and their rate constants were determined. The process of removal was also governed by intraparticle diffusion. Values of the thermodynamic parameters viz. G • , H • , and S • at different temperatures were determined. The data generated in this study can be used to design treatment plants for chromium rich industrial effluents. Adsorption results indicate that nanoiron particles can be effective for the removal of chromium from aqueous solutions.A cause de l'industrialisation rapide, la présence de métaux lourds dans l'eau et dans les eaux usées est une question environnementale d'une importance cruciale. Même si certains métaux sont essentiels au bon fonctionnement de notre organisme, s'ils y sont présents dans une concentration supérieureà la valeur limite d'exposition (VLE), ils deviennent nocifs et leur traitement avantélimination devient inévitable. La présente communication traite de l'enlèvement du Cr(VI) présent dans les solutions aqueuses au moyen de nanoparticules de fer. Les nanoparticules de fer ontété obtenues au moyen du procédé sol-gel. La caractérisation des nanoparticules aété effectuée au moyen d'une analyse diffractométrique et d'une analyse par MET. On a effectué des essaisà renouvellement périodique pour mesurer l'adsorption de Cr(VI) dans les solutions où on en trouvait. L'effet de différents paramètres importants comme le temps de contact et la concentration initiale, le pH, la dose d'agent adsorbant ainsi que la température au moment de l'enlèvement du chrome ontétéétudiés. La proportion de chromeéliminée est passée de 88,5%à 99,05% en diminuant sa concentration initiale de 15à 5 mg/l, en conditions optimales. Il aétéétabli que l'élimination du Cr(VI) estétroitement liée au pH et l'élimination optimale (100%)été obtenueà un pH de 2,0. Le processus d'élimination aété régi par deséquations cinétiques du premier et du deuxième ordre et les constantes cinétiques ontété ...

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