Process and Dynamic Characteristics of Vanadium Leaching Respectively in Ultrasonic and Mechanical Field

The effects of mechanical stirring intensity,ultrasonic current intensity and leaching time on acid consumption and leaching ratio for vanadium leaching process respectively in ultrasonic and mechanical field were investigated.The results show that with increase of stirring intensity,the acid consumption curve in ultrasonic field reveals well stability with a higher vanadium leaching rate.The stability of acid consumption and leaching ratio of vanadium are enhanced with increase of ultrasonic current intensity.In both of ultrasonic and mechanical field,leaching ratio of vanadium sharply increases in first 30 min then gently raises with increase of leaching time,resulting in vanadium leaching rate of more than 97% in ultrasonic field but 94% in mechanical field.The rate controlling steps of two reaction stages were comparatively analyzed using rate control equations of external diffusion,chemical reaction and internal diffusion,respectively.It is indicated that the rate in the first stage is controlled by external diffusion,with 0.020 7 min^-1 of rate constant and 1-3（1-η）^2/3+2（1-η） =0.020 7 t of rate equation for leaching in ultrasonic field while 0.018 9 min-1 of rate constant and 1-3（1-η）^2/3+2（1-η） = 0.018 9 t of rate equation for leaching in mechanical field.The rate in the second stage is of chemical reaction control.The rate constant and rate equation for leaching are separately determined as 0.005 3 min^-1 and 1-[（1-η）/（1-0.937 1） ]^1/3= 0.005 3（t-30） in ultrasonic field,but respectively 0.003 8 min^-1 and 1-[（1-η）/（1-0.919 1） ]^1/3= 0.003 8（t-30） in mechanical field.