Kinetics of oxidation of ethylenediaminetetraccetic acid (EDTA) by chromium(VI) in the presence of perchloric acid

摘要

the kinetics o the oxidation of EDTA by Cr(VI0 in the presence of perchloric acid has been followed by visible spectrophotometry at 350 nm.The effects of the total [Cr(VI))],[EDTA] and [HClO_4] on the rate are determined.The reacton is first-order each in [Cr(VI)] and [EDTA] whereas the rate-[H~+] profile suggests complicated kinetic features.Addition of Mn(II) has a larg eaccelerating influence.These observations permit to propose detailed mechanism for the oxidation of EDTA by Cr(VI) in the presence and adsence of Mn(II).The Catalytic effect of Mn(II) has been ascribed to a one-step,three-electorn proces sin which a termolecular complex is formed between the oxidant,Mn(II) and EDTA.The oxdiation has the rate expresssion:-d[Cr~VI]_T/dt=k_1K_an[H~+]_2K_1[Cr~VI]_T[EDTA]_T/(1/[jH~+]+K_a3+K_1+K_a3[H~+])