title: Extraction of alumina and sodium oxide from red mud by a mild hydro-chemical process.
abstract: A mild hydro-chemical process to extract Al(2)O(3) in red mud to produce sodium aluminate hydrate was investigated, and the optimum conditions of Al(2)O(3) extraction were verified by experiments as leaching in 45% NaOH solution with CaO-to-red mud mass ratio of 0.25 and liquid-to-solid ratio of 0.9, under 0.8 MPa at 200 degrees C for 3.5h. Subsequent process of extracting Na(2)O from the residue of Al(2)O(3) extraction was carried out in 7% NaOH solution with liquid-to-solid ratio of 3.8 under 0.9 MPa at 170 degrees C for 2h. Overall, 87.8% of Al(2)O(3) and 96.4% of Na(2)O were extracted from red mud. The final residues with less than 1% Na(2)O could be utilized as feedstock in construction materials. The chemical reactions taking place in both Al(2)O(3) and Na(2)O extractions from red mud are proposed.
authors.affiliation: National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology, Beijing 100190, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhong
authors.forename: Yifei
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000537:Aluminum Oxide / Q000302:isolation & purification*; D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D003252:Construction Materials; D010087:Oxides / Q000302:isolation & purification*; D017670:Sodium Compounds / Q000302:isolation & purification*
chemical_list: D000538:Aluminum Silicates; D010087:Oxides; D017670:Sodium Compounds; C096707:sodium oxide; D000537:Aluminum Oxide; D000077215:Clay