Accelerated Catalytic Fenton Reaction with Traces of Iron: An Fe-Pd-Multicatalysis Approach

摘要

An accelerated catalytic Fenton (ACF) reaction was developed based upon a multicatalysis approach, facilitating efficient contaminant oxidation at trace levels of dissolved iron. Beside the Fe~Ⅱ/H_2O_2 catalyst/oxidant pair for production of OH-radicals, the ACF system contains Pd/H_2 as catalyst/reductant pair for fast reduction of Fe~Ⅲ back to Fe~Ⅱ which accelerates the Fenton cycle and leads to faster contaminant degradation. By this means, the concentration of the dissolved iron catalyst can be reduced to trace levels (1 mg L~(-1)) below common discharge limits, thus eliminating the need for iron sludge removal, which is one of the major drawbacks of conventional Fenton processes. ACF provides fast degradation of the model contaminant methyl tert-butyl ether (MTBE_r C_0 = 0.17 mM) with a half-life of 11 min with 1 mg L~(-1) dissolved iron, 500 mg L~(-1) H_2O_2, 5 mg L~(-1) Pd (as suspended Pd/Al_2O_3 catalyst) and 0.1 MPa H_2, pH 3. The effects of pH, H_2 partial pressure and H_2O_2 concentration on MTBE degradation rates were studied. Results on kinetic deuterium isotope effect and quenching studies are in conformity with OH-radicals as main oxidant. The heterogeneous Pd/Al_2O_3 catalyst was reused within six cycles without significant loss in activity.