Feasibility of zinc recovery from hot-filtrate cake (waste) as practical approach to resolve of environmental problems in zinc industry

Cake from hot-filtrate of zinc production industries containing about 16-24% of zinc and harmful metals such as cobalt, which it releases to environment caused to the harmful effects. These pollutions are one of the main concerns of this industry so the goal of present work is cobalt impurity cementation method and reuse of zinc recovery.

The work is containing three steps leaching of hot-filtrate cake, optimization of affective parameters on process using Response Surface Methodology (RSM) and removal of cobalt impurity. Using RSM necessary experiments was designed and finally optimum conditions were determined.

Using Design of Expert (DOE) software parameters such as temperature, zinc powder amount, contact time and additive concentration of antimony trioxide were evaluated. Based on the obtained results, the most impressive are belonged to zinc powder amount, temperature, time and additive concentration, respectively. Optimum conditions for cobalt removal containing temperature of 84 C°, concentration of 12.74 g L-1 for zinc powder, contact time of 118 min and concentration of 22.28 mg L-1 were obtained. At these conditions, cobalt impurity amount is reached to the allowed limit for electrolysis process and can be recovery of zinc from obtained solution.

 Using cementation method about 75% of zinc in cake was recovery and cobalt impurity was removed and finally, obtained zinc solution was conducted to the zinc production route. Furthermore, addition of dissolving environmental problems from cake, recovery of zinc and cobalt from the point of economical was important.