Zinc Ions In The Wet Zinc Smelting Slag Flotation Recovery Of Silver

Flotation recovery silver from smelting slag of zinc hydrometallurgy is an important way to produce silver now. A hydrometallurgical zinc refinery in Gansu has done that for a long time, but the production index is not good, the recovery waves between45%～65%. The indexes of silver deteriorate when zinc ion concentration in the pulp rises, the massive existence of zinc ions have serious influence on silver flotation. In this paper the influence of zinc ion on flotation recovery silver from smelting slag of zinc hydrometallurgy is studied.The study sample is an intermediate product of zinc smelting system comes from a hydrometallurgical zinc refinery in Gansu. The process mineralogy research of the sample showed silver grade of the slag waved from310to340g/t (the data was got by using inverse analysis lots of experiment results), most of the silver was in the form of silver sulfide (about60%), in addition, there were a number of AgO,AgSO4,AgCl in leaching slag. Besides some oxidized silver sulfide on surface and some indissoluble wrapped silver were difficult to floating, most of the silver could be reclaimed. The energy spectrum and electron microscope analysis of the zinc slag indicated that the independent silver mineral was rare, sphalerite was the main carrier of silver mineral. In addition, the slag also contained Cu0.36%, Fe16.36%, Pb4.72%, Zn15.52%.In flotation experiments, the sample released many zinc ions during mixing, they had great influence on silver flotation. The research showed that when the pulp pH in3.6, used the reagent regime:combination of collector system(butyl xanthate and D amine black medicine), new pH adjustment agent Z-1#and special foaming agent YT-1#, through the closed-circuit process of one rough-three concentrating-two scavenger, the influence of zinc ions could be avoided, silver concentrate were obtained with silver grade of6900g/t,recovery of66.7%, but the tailing contained silver116g/t.Experiments on argentite, elemental silver and pure silver sphalerite mineral showed that they all had good flotability in pH3.0to9.0, zinc ion concentration increased in the pulp greatly inhibited the silver mineral floating, their recovery reduced with the increase of zinc ion concentration.Research on hydrolysis balance of zinc ion shows zinc ions could precipitate well only when pH in8.0～10.0.Thereby most zinc existences as ionic form while most silver flotation process in pH3.0～7.0. The corrosion electrochemical of the silver mineral and the corrosion electrochemical Evans chart of silver mineral-collector system indicates that the massive existence of zinc ions would reduce the corrosion current of silver mineral surface and silver mineral-collector system, at the same time, made it move to negative potential, inhibiting the silver mineral float to some extent. Therefore, it has serious influence on silver minerals flotation when there are many zinc ions in the pulp.