Mihaela Niculescu, Aura Dana Ionita, Laurentiu Filipescu<br>Alkaly Earth Metal Salts as Neutralizers of Red <br>Mud from Alumina Refining

Mihaela Niculescu, Aura Dana Ionita, Laurentiu Filipescu
Alkaly Earth Metal Salts as Neutralizers of Red
Mud from Alumina Refining

Abstract:

Red mud disposal embodies the most critical issue in any alumina refinery. Reasons like caustic nature, huge discardable quantities and unusual rheological properties are demanding neutralization of the red mud with simple and non-expensive available chemicals to allow its future reuse or at least for its safe disposal. This paper purpose was to investigate the neutralization of the red mud alkalinity with concentrated neutralizers in order to increase the rates of stabilized solid crystallization on the red mud particles surface, as well as to promote the crystallization of hydroxide and hydrotalcite phases, which are mainly responsible for heavy metals entrapment in their crystalline structure. It was found that the end down limit of neutralization with sulphuric acid in order to prepare adsorbent materials or simply to prepare red mud for disposal as non-hazardous material is the pH 8.5 - 9.0, when the entire sodicity is removed from red mud and aluminium silicate ion exchanging phases are insignificantly altered, preserving their both ion exchange and acid neutralizing capacities. Alkali metal earth salt as neutralizers act similarly with sea water, releasing the sodicity into liquid phase and conveying the entire alkalinity into the mixture of new born solid phases like hydrocalumite, hydrotalcite carbonate and hydrotalcite sulphate. Adequate neutralization process parameters (aluminate content, reactant concentrations, neutralization rates, temperature, etc.) improve the performances of neutralized red mud as adsorbent and frame its properties to some quality reproducible standards. Also, it was found the fresh red mud rich sodium aluminate is highly recomended to be selected and processed for working out good adsoption properties; if the neutralization process is practiced to yield a non hazardous material to be safely disposed, then the wheathered red mud is recomended to be selected for convenient neutralization process. Keywords: red mud disposal, hydrocalumite, hydrotalcite, heavy metals entrapping

Issue: 2009, Volume 60, Issue 11

Pages:

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

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