De-watering, disposal and utilization of red mud: state ... - Redmud.org
De-watering, disposal and utilization of red mud: state ... - Redmud.org
De-watering, disposal and utilization of red mud: state ... - Redmud.org
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7.5. Radiation<br />
Fig 7. Rehabilitation <strong>of</strong> a dry <strong>mud</strong> stacking <strong>disposal</strong> site<br />
There are sharp differences among different <strong>red</strong> <strong>mud</strong> as far as concentration <strong>of</strong> various<br />
radioactive elements is concerned. The extent <strong>of</strong> usage varies with applications, ~ 14% in<br />
bricks, no restriction in floor tiles <strong>and</strong> ro<strong>of</strong> tiles, 61% in ceramics for exterior applications in<br />
the case <strong>of</strong> a Greek bauxite residue, using the activity index method [44]. Radioactivity<br />
should always be checked for each bauxite residue when its <strong>utilization</strong> is targeted.<br />
8. Uses <strong>of</strong> <strong>red</strong> <strong>mud</strong>/bauxite residue/bauxite tailings<br />
Technically successful research <strong>and</strong> development activities have been carried out aiming at<br />
the <strong>utilization</strong> <strong>of</strong> <strong>red</strong> <strong>mud</strong>. The applications which have been in use either in pilot or<br />
commercial scale are shortly reviewed here:<br />
– for amendment <strong>of</strong> acidic soils, for immobilization <strong>of</strong> heavy metals [45] <strong>and</strong>/or for<br />
retaining <strong>of</strong> certain nutrients, such as phosphorus in agriculture [46]<br />
– for making crude <strong>and</strong> fine ceramics, such as tiles, floor tiles, [47,48]<br />
– for making bricks [49,50],<br />
– in road contruction, first <strong>of</strong> all the coarse fraction [51]<br />
– as a component in making cement, OPC [52-55] <strong>and</strong> special cements [56], cement mortar<br />
[57]<br />
– an an additive in ferrous metallurgy [58-60]<br />
– as a filler in rubber [61] <strong>and</strong> plastic industry<br />
– as pigment in production <strong>of</strong> paints [62]<br />
– as a material used for trapping carbon dioxide [63,64] <strong>and</strong>/or sulfur dioxide [65] from flue<br />
gases<br />
– as a feedstock for manufacturing adsorbents <strong>and</strong> catalysts [66]<br />
– as a feedstock for making water <strong>and</strong> sewage treatment agents [67]<br />
8. Emerging technologies/solutions<br />
8.1. Hyper-Baric Filtration (Hi-Bar Filtration, Continuous Pressure Filtration)<br />
Hyper Baric Filter with possible steam enhancement is an option to obtain bauxite tailings<br />
cake with about 75-77% solids content (moisture content 23-25%). The cake is crumbly in<br />
nature <strong>and</strong> can be h<strong>and</strong>led easily. This feature is important if the bauxite residue is utilized<br />
instead <strong>of</strong> being disposed <strong>of</strong>. Pilot scale <strong>and</strong> field trials have been carried out in Bauxilum,<br />
Venezuela [68,69] <strong>and</strong> in Aluminium Oxid Stade GmbH, Germany [70]. It should be pointed<br />
10