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How can you separate alumina from silica in a bauxite ore. |
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Answer» Solution :(i) ALUMINA is separated from silica in a bauxite ore through Baeyer's PROCESS, in which bauazite ore is concentrated by the method of leaching or chemical separation. (ii) Chemical method is employed in case where the ore is to be in a very pureform, e.g., aluminium extraction. Bauxite `(Al_(2)O_(3))`, an ore of aluminium, contains `SiO_(2)` and `Fe_(2)O_(3)` as impurities. When bauxite ore is treated with NaOH, the `Al_(2)O_(3)` goes into solution as sodium meta-ALUMINATE `[Fe_(2)O_(3), SiO_(2), Fe(OH)_(3), etc.]`, which are then filtered off. `Al_(2)O_(3) + 2NAOH rarr underset(underset("(In solution form)")("Sod. meta. aluminate"))(2NaAlO_(2)+ H_(2)O)` (iii) The filtrate (containing sodium meta-aluminate) on dilution, and stirring gives a precipitate of aluminium hydroxide, which is filtered, and ignited to get pure alumina. `NaAlO_(2) + 2H_(2)O rarr underset("Ppt")(Al(OH)_(3)) + NaOH` `2Al(OH)_(3) overset(Delta)rarr underset("Pure")(Al_(2)O_(3)) + 3H_(2)O` |
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