Abstract: The vacuum aluminothermic reduction process can produce magnesium metal and the reducing residue contains rich 12CaO·7Al2O3. The reducing residue can be solved by a mixture solution of sodium hydroxide and sodium carbonate. The filter residue is rich boron stuff and the filtrate is a solution of sodium aluminate which can be decomposed by CO2 to obtain aluminum hydroxide. In present work the effects of leaching temperature， time， NaOH concentration and Na2CO3 concentration on the leaching rate of alumina were investigated systematically and the performances of aluminum hydroxide obtained were detected with the reduction residue as raw materials. The results showed that the alumina leaching rate from the residue was above 85.21% at the conditions of NaOH concentration 12g/L， Na2CO3 concentration 210g/L， leaching temperature 95℃， leaching time 120min and liquidsolid ratio 6. The whiteness of the aluminum hydroxide obtained was over 98. The chemical formulation of the product is αAl(OH)3. The SEM results showed that the grain size was less than 1μm.

Key words: szaibelyite, reduction residue, leaching, carbonation precipitation, highwhiteness aluminum hydroxide