The waste liquor containing AlCl_3 along with free hydrochloric acid (HCl),chlorides of copper and iron in small quantities, is a major effluent from dye manufacturing units & Ethylbenzene manufacturing units. This effluent can be treated to produce gelatinous Aluminium hydroxide of high quality suitable for pharmaceutical grade. As per the process discussed here effluent is first treated with Ammoninium hydroxide to convert the salts of copper and iron in proper form so that they can be removed from the main streams and can be recovered subsequently. The new mechanism is postulated and accordingly the compound Nitro trialuminium hydroxide is assumed to be formed. The precipitates are separated by filtration. The subsequent treatment is by sodium hydroxide to produce sodium salt of Nitro trialuminium hydroxide. On heating the solution of this salt sodium aluminate solution is formed, which while isolating itself from other compounds also helps in settling the impurities. Supernatant solution of sodium aluminate is seperated and treated with dilute hydrochloric acid to obtain finally the white gelatinous precipitates of Aluminium hydroxide.The blue colored solution containing complex copper tetramine ion, obtained during first filtration, is given metallic treatment to make the solution colorless and is evaporated to obtain ammonium chloride.
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