Activity of metal chromate and phosphate supported on ion-exchange resins toward hydrogen peroxide decomposition

Abstract

The mixed resins, Dowex MR-3 and MR-12, in the H+/Cl− form, and the cation resin, Dowex-50W, in the H+ form, were used as a support for some metal chromate and phosphate salts. Similarly, anionic resin, Amberlite IRA-400, in the Cl− form, was used as a support for some metal chromate salts. The activity of these metal salt-supported on four different resins toward hydrogen peroxide decomposition was investigated. The decomposition of H2O2, with these catalysts, was found to follow first-order kinetics with respect to [H2O2]. Factors that affected the rate of reaction, such as mesh size of the support, amount of supported salt, and the electrostatic interactions, were investigated. With Ag(I)-chromate supported on mixed resin MR-3 in the Ag+/NO3− form, the rate of reaction was greater than that with the mixed resin MR-12 in the same form. Moreover, the rate with Ag(I) chromate supported on the anion resin IRA-400 in the R-NO3− form was greater than mixed resins. Also, the rate with Fe(III) chromate supported on Amberlite IRA-400 in the R-CrO42− form was greater than other counter-anionic forms as well as Dowex-50W resin in the metal ion form. However, Fe(III)-chromate supported on cation resin R-Fe3+ showed greater activity than other cationic forms. On the other hand, the rate with MR-3 resin in the Na+/PO43− form was greater than that in the presence of supported Fe(III) phosphate. However, the rate of reaction increased when Fe(III) was replaced by Ba(II). Iron(III) phosphate supported on Dowex-50W resin in the Na+ form showed greater activity compared to MR-3 resin in the Na+/PO43− form. In the case of Fe(III) phosphate supported on mixed resin MR-12, the rate was much greater than that with unsupported resin. However, when Ba(II) phosphate was incorporated instead of Fe(III) phosphate, the rate of reaction increased considerably. The activity of Fe(III) chromate is greater than that of Fe(III) phosphate supported on the same cation resin. Activation parameters were evaluated and a probable reaction mechanism was proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 667–675, 2000