Jarosite法における鉄の沈殿反応速度

Abstract

Measurements of elimination rate of iron have been carried out by addition of K2 SO4, Na2SO4, or (NH4) 2SO4 to the leaching solution of zinc ferrite residue producted in hydrometallurgical zinc process.A small amount of precipitation was producted in the leaching solution without any addition of alkali sulfate only by the treatment of pH conditioning and heating. This precipitation was found to be amorphous S-Fe0.OH, and filtration property was poor.The elimination of iron was improved with formation of jarosite by addition of alkali sulfate. The elimination rate of iron increased with elevating temperature. Potassium jarosite have the best effect upon the elimination of iron among the three kinds of jarosite. Good crystallinity of each jarosite was observed with scanning electron microscope. Good filtration property of jarosite seems to be due to the good crystallinity.The precipitation reaction of iron in jarosite method was indicated to follow the following rate equation of 2 order reaction._??_k2; rate constant, t; time, a; Fe2 (SO4) 3 concentration, b; M2 SO4 concentration, x; formation amount of jarosite. Activation energy of the reaction for each jarosite was calculated as follows, Potassium jarosite; 5.43 kcal/mol 22.73 kJ/mop Sodium jarosite; 8.394 kcal/mol 34.96 kJ/mop Ammonium jarosite; 16.675 kcal/mol (69.81 kJ/mol)From the aspect of the kinetics, addition of K2SO4 is favorable to the elimination reaction of iron.