The feasibility studies for radical-induced decomposition and demetalationof metalloporphyrins by ultrasonication

A feasibility study of the decomposition and demetalation of metalloporphyr ins by ultrasonic irradiation process in the presence of radical-induced re actions is presented in this paper. Two representative model compounds, NiT PP and VOTPP, were investigated in this ultrasonic process on the laborator y scale. The extent of the decomposition was determined by UV-vis, while th e metal analysis was measured by ICP/MS. In the initial investigation, the decomposition of metalloporphyrins, which were dissolved in different solve nt-water mixtures, was performed under the ultrasonication process. Among t hese solvents, the chlorinated-type solvents (e.g., chloroform and dichloro methane) achieved a higher efficiency because they generated more oxidizing species under sonication at 20 kHz frequency. Other additives such as surf actant and hydrogen peroxide, which affect the decomposition efficiency, we re also investigated. Under optimal condition, the decomposition efficiency reached about 90% in 1 h for both model compounds. An oxidative intermedia te existed for both metalloporphyrins under ultrasonication. The decomposit ion reaction rates of these two compounds followed pseudo-first-order in re actant concentration and were inhibited by initial feed concentration. The dependence of the rate Constants on the different initial concentrations co uld be determined by the Langmuir-Hinshelwood equation.