Oxidative removal of aqueous cyanide by manganese(IV)-containing oxides

Abstract

Manganese(IV)-containing oxides are effective catalysts for oxidation of water-soluble cyanide over a wide pH range (0.5-12) and temperature (15.degree.-250.degree. C.). Oxygen is the preferred oxidizing agent at partial pressures between about 0.2 and 5 atmospheres (2.9-75 psi, 20-517 kPa). Electrolytically deposited MnO.sub.2 is one preferred form of the catalyst. Another preferred manganese(IV)-containing oxide is the group of cation-stabilized manganese(IV)-containing oxides illustrated by cryptomelane. Yet another preferred form of manganese(IV)-containing oxide is a group of crystalline manganese phosphate compositions having an extended network and an empirical composition on an anhydrous basis expressed by an empirical formula of: (A.sup.a+).sub.v (Mn.sup.b+)(M.sup.c+).sub.x P.sub.y O.sub.z where A is a templating agent selected from the group consisting of alkali metals, alkaline earth metals, hydronium ion, ammonium ion, organoammonium ions, and mixtures thereof, "a" represents a weighted average valence of A and varies from 1.0 to 2.0, "v" is the mole ratio of A to Mn and varies from about 0.1 to about 5, "b" is the average valence of Mn and has a value of greater than 3 to about 4, M is a metal selected from the group consisting of Al, Fe.sup.3+, Ca, Sn.sup.4+, Ti, Sb.sup.5+, and mixtures thereof, "x" is the mole ratio of M to Mn and varies from 0 to about 3.0, "c" is the weighted average valence of M and varies from about 1.0 to about 5.0, "y" is the mole ratio of P to Mn and varies from about 0.10 to about 5.0 and "z" is the mole ratio of O to Mn and has a value determined by the equation z=1/2(a.times.v+b+x.times.c+5.times.y).

Dependencies are inferred from the claim text.