Valorization of a natural biomaterial, onion skin, for the sorption ofhexavalent chromium.

International audienceImplementation of biosorption at an industrial scale needs the use of easily available and low-cost adsorbents. Agricultural residues, such as onion skin, fit these two requirements. The purpose of this work was to examine the relevance of onion skin, cold-treated with sulfuric acid, for the treatment of hexavalent chromium. The results showed that a time-contact allowed to achieve equil. Langmuir, Freundlich and Sips models were used to describe isotherm equil. The Sips model involving three parameters appeared the most relevant to describe exptl. data and led to the maximal adsorption capacity (17.43 mg/g). Variations of chromium fixation rate were examd. regarding some operational conditions, like the initial concn., the mass and the granulometry. The results showed that an almost total chromium removal was recorded within one hour. Both exptl. and modeling approaches were considered to examine biosorption mechanism. Pseudo-first and pseudo-second order models, as well as intra-particle and extra-particle diffusion models, were considered to det. the predominant steps. The results of both approaches converged toward a negligible effect of diffusional limitations; surface reactions controlled biosorption. [on SciFinder(R)