Kinetics of iron precipitation at elevated temperatures from Fe(III)-H2SO4-(NH4)(2)SO4 system

Abstract

In the present work a systematic study has been reported on the precipitation of iron from Fe(III)-H2SO4-(NH4)(2)SO4 system at elevated temperatures 150-250 degrees C. The effects of various parameters such as time, acid, ammonium sulphate and jarosite seed concentrations on precipitation of iron have been discussed Since all the reagents are charged to the autoclave initially, the iron precipitation starts during heating itself. The kinetic equations are proposed for precipitation of iron during i) Non-isothermal phase (np) and ii) Isothermal phase (ip) as shown below: rate, mol L-1 min(-1) = r(np) - (k(1) + k(2)[Seed](i)(0.087)) f(1)(x) where f(1)(x) = [Fe(III)](i)(2.466) [H2SO4](i)(-3.34) [(NH4)(2)SO4](i)(0.364) 10(-4191.48/T) rate, L mole(-1) min(-1) = r(2 ip) = (k(1)' - k(2)'[Seed](i)(-0.085))f(2)(x) where f(2)(x) = [Fe(III)](i)(-0.434) [H2SO4](i)(-0.527) [(NH4)(2)SO4](i)(0.335) 10(-3292.98/T) The activation energies for the non-isothermal and isothermal phases are found to be 80.25 and 63.05 kJ mole(-1) respectively.