| 摘要 |
<p>A method (Fig. 1a) for improving the brightness level of aluminum hydroxide removed from a caustic solution comprises contacting the solution with an adsorbent comprising a calcined compound having the formula: AwBx(OH)yCz.nH2O wherein A represents a divalent metal cation selected from the group consisting of: Mg<2><+>, Ni<2><+>, Fe<2><+>, Ca<2><+> and Zn<2><+>; B represents a trivalent metal cation selected from the group consisting of: Al<3><+>, Fe<3><+> and Cu<3><+>; C represents a mono- to tetravalent anion selected from the group consisting of: OH<->, Cl<->, Br<->, NO3<->, CH3COO<->, C2O4<2><->, CO3<2><->, SO4<2><->, PO4<3><->, Fe(CN)6<3><-> and Fe(CN)6<4><->; and w, x, y, z and n satisfy the following: 0 < z </= x </= 4</= w </= 1/2 y and 12 >/= n >/= 1/2 (w-x); and filtering the solution before and/or after said contacting. A preferred adsorbent comprises calcined hydrotalcite. An improved aluminum hydroxide product having a whiteness level of 85% or higher based on a 100% TiO2 reference standard, having been removed from a caustic solution and decolorized by the foregoing method, is obtained. <IMAGE></p> |
