GAS DESULFURIZATION WITH FERRIC CHELATES OF EDTA AND HEDTA - NEW MODEL FOR THE OXIDATIVE ABSORPTION OF HYDROGEN-SULFIDE

The experimental data of Wubs and Beenackers (AIChE J. 1994, 40 (3), 4 33-444) on the oxidative absorption of H2S into aqueous solutions of f erric chelates of ethylenediaminetetraacetic acid (EDTA) and hydroxyet hylethylenediaminetriacetic acid (HEDTA) were reinterpreted using a ne w penetration model for mass transfer parallel to chemical reaction. D ifferent from the discussion by Wubs and Beenackers (1994), which was based on general, approximate models for the reactive absorption of ga ses into liquids, it now appears that the diffusivity of ferric chelat es of EDTA and HEDTA are in good agreement with the values determined from the reactive absorption of molecular oxygen into aqueous solution s of ferrous EDTA and HEDTA (Wubs and Beenackers, Ind. Eng. Chem. Res. 1993, 32, 2580-2594). Also, it now appears that the data from Wubs and Beenackers (1994) are compatible with ferric chelate complex equilibr ium constants, reported elsewhere (for instance, Martell and Smith, Cr itical Stability Constants, 1982). Reinterpretation of the absorption data from Wubs and Beenackers (1994) resulted in the following kinetic rate constants (T = 293 K, C-Fe(III) = 78 mol/m(3) and 2 less than or equal to pH less than or equal to 9): EDTA, monohydroxylated complex, 250 less than or equal to k(1,1) less than or equal to 300 m(3)/(mol s); HEDTA, monohydroxylated complex, 1.4 less than or equal to k(1,1) less than or equal to 1.6 m(3)/(mol s); HEDTA, dihydroxylated complex, 550 less than or equal to k(1,1) less than or equal to 650 m(3)/(mol s); for the reaction rate expressed by -R-H2S = k(1,1)C(H2S)C(Fe(III)) .