Mihaela NICULESCU, Aura Dana Ionita, Laurentiu Filipescu<br>Chromium Adsorption on Neutralized Red Mud

Mihaela NICULESCU, Aura Dana Ionita, Laurentiu Filipescu
Chromium Adsorption on Neutralized Red Mud

Abstract:

Red mud, the well known byproduct of Bayer process applied in alumina refineries, was extensively investigated as neutralizer and adsorbent of heavy metals from waste waters. Both red mud ion exchange capacity and ionic species adsorption specificity largely depend on its preliminary processing and chemical treatments applied to convert the raw material into useful product [1-3]. This paper reports the results of researches concerning the particularities of the adsorption process of trivalent chromium from tannery waste waters. Red mud samples were collected from the SC Alum SA Tulcea, Romania disposal pond. The preliminary treatment consists in neutralization with the following reactants: sulphuric acid (mass concentration 20%), magnesium chloride 1M, and a mixture magnesium chloride 1M and calcium chloride 1M. All the treatments have promoted the formation of new ion exchanging amorphous or crystalline phases on red mud particle surface. Adsorption studies were carried out by batch technique which yields equilibrium data, enables ion exchange capacity estimation and provides information about the residual chromium concentration in the treated effluent. The experimental data have shown the ion exchange capacity may be raised up to 60 - 62 mg/g of red mud and the concentration of chromium in the treated waters ranges between 0.03 to 0.4 mg/L. Also, it was demonstrated that above ion exchange mechanism for entrapping chromium is valid only if available chromium in waste water in contact with a given quantity of red mud is less than total chromium amount required to reach the upper limits of ion exchange capacity. Additional amounts of chromium may be physically adsorbed as chromium hydroxide gel on red mud particle surface at higher pH values, but these amounts could not be predicted when the chromium concentration in treated effluent has to be hold under some secured limits. Keywords: chromium tannery, red mud, adsorption capacity, leaching chromium

Issue: 2010, Volume 61, Issue 2

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This article is published under the Creative Commons Attribution 4.0 International License

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