Microwave-assisted dissolution of pyrite in acidic ferric sulfate solutions

The use of microwaves in synthetic chemistry has gained greatly in importance in the past 10 years. An observed accelerating effect of microwaves on reactions rates has been explained either by a specific microwave effect or by a superheating phenomenon. This paper considers the dissolution of pyrite mineral in acidic ferric sulfate solutions in the absence and presence of microwaves. For this purpose, a computer-controlled microwave experimental apparatus was designed in our laboratory. The experiments show that the reaction rate between pyrite and acidic ferric sulfate solution is chemically controlled and that the reaction order with respect to each Fe3+ and H2SO4 is equal to 0.5 for both classical and microwave heating; thus, the reaction mechanism is not affected by microwave irradiation. At the same time, the activation energies calculated as 33.43 and 18.72 kJ/mol in the classical and microwave systems, respectively, reveal the net effect of microwave on the activation energy.