Abstract: There is disclosed a method for improving the brightness level of aluminum hydroxide removed from a caustic solution. The method comprises:(a) pre-filtering the solution to remove contaminants therefrom; and (b) contacting the filtered solution with an adsorbent consisting essentially of a calcined compound having the formula: A.sub.w B.sub.x (OH).sub.y C.sub.z.nH.sub.2 O wherein A represents a divalent metal cation selected from the group consisting of: Mg.sup.2+, Ni.sup.2+, Fe.sup.2+, Ca.sub.2+ and Zn.sup.2+ ; B represents a trivalent metal cation selected from the group consisting of: Al.sup.3+, Fe.sup.3+ and Cu.sup.3+ ; C represents a mono- to tetravalent anion selected from the group consisting of: OH.sup.-, Cl.sup.-, Br.sup.-, NO.sub.3.sup.- CH.sub.3 COO.sup.-, C.sub.2 O.sub.4.sup.2-, CO.sub.3.sup.2-, SO.sub.4.sup.2-, PO.sub.4.sup.3-, Fe(CN).sub.6.sup.3- and Fe(CN).sub.6.sup.4- ; and w, x, y, z and n satisfy the following: 0<z.ltoreq.x.ltoreq.4.ltoreq.w.ltoreq. 1/2 y and 12.gtoreq.n.gtoreq.

Abstract: A method for production of aluminum by carbothermic reduction of Al.sub.2 O.sub.3 in a stack-type reactor. A charge of Al.sub.2 O.sub.3 and C is inserted into an upper reaction zone of the reactor and reacted at an elevated temperature to form CO and a first liquid comprising Al.sub.2 O.sub.3 and Al.sub.4 C.sub.3. The first liquid is transferred to a lower reaction zone beneath the upper reaction zone and heated to form CO and a second liquid of Al and C. A portion of the second liquid is removed, and liquid Al is extracted therefrom. In a preferred method, Al.sub.2 O.sub.3 and C in the upper zone are heated by partial combustion of the C, and the lower zone is heated electrically. Gaseous Al and Al.sub.2 O formed in the lower zone are reclaimed in the upper zone. Gaseous CO produced in both zones heats the Al.sub.2 O.sub.3 and C in the upper zone. Excess CO is removed from the upper zone and used for generation of electricity or chemical process use. Liquid Al.sub.4 C.sub.