Microwave catalyzed carbothermic reduction of zinc oxide and zinc ferrite: effect of microwave energy on the reaction activation energy

摘要

Recently, more attention has been paid to the use of microwave (MW) energy in accelerating chemical reactions. The effect of microwave energy on the reduction of zinc oxide and zinc ferrite was investigated. The results indicated that the temperatures required to initiate zinc oxide and zinc ferrite reduction under MW heating were 550 and 450 degrees C, respectively, while under conventional thermal (CT) heating, were 950 and 850 degrees C, respectively. Apparently, the MW reaction had a negative standard Gibbs free energy (Delta G) at a lower temperature (similar to 400 degrees C) when compared to the CT reaction. Additionally, the activation energy (E-a) substantially decreased from 223.7 and 221.1 kJ mol(-1)under CT heating to 64.8 and 32.9 kJ mol(-1)under MW heating for Zn oxide and zinc ferrite, respectively. The enhancement in zinc reduction under MW energy was due to the rapid and bulk heating phenomena of MWs as well as the interactions occurring between the electromagnetic MW pattern and the molecules of heated materials.