Method for separating iron from pregnant solution leached from automobile exhaust dead catalyst

Abstract

The invention discloses a method for separating iron from a pregnant solution leached from an automobile exhaust dead catalyst. The method comprises the following steps of 1) simultaneously adding caustic soda liquid and the pregnant solution into a reaction kettle by adopting a continuous hydrolysis method, controlling the pH value and temperature of the solution, and filtering after the reaction is completed to obtain a first filter cake; 2) washing the first filter cake with a diluted hydrochloric acid solution, controlling the pH value and temperature, stirring and washing, and filtering to obtain a second filter cake; and 3) dissolving the second filter cake with hydrochloric acid again, controlling the pH value and the temperature, adding sodium nitrite and precious metal nitrite for full complexing, then controlling the pH value again for hydrolysis, and filtering after the reaction is completed to obtain a third filter cake. By means of the method, the iron can be separated thoroughly, iron ions in the pregnant solution with the iron ion concentration being 100 g / L or below can be reduced to 10 mg / L or below through the method, and the requirement for the impurity content of platinum-palladium-rhodium refining is completely met. The precious metal recovery rate is high, the cost is low, the platinum and palladium recovery rates of the process are both 99% or above, and the rhodium recovery rate reaches 95% or above.

Description

technical field [0001] The invention belongs to the section of hydrometallurgy, and in particular relates to a separation method for leaching iron from precious liquid through waste catalyst of automobile tail gas. Background technique [0002] Platinum, palladium and rhodium recovery processes for automobile waste catalysts include fire and wet processes, among which the fire process is widely used because of its strong adaptability, stable recovery rate, and large processing capacity. The iron trapping method is the most commonly used pyrotechnics, which can enrich the platinum, palladium and rhodium in the ferroalloy, while the spent catalyst carrier is removed by slagging. In order to obtain platinum, palladium and rhodium precious liquor with low impurity content, acid leaching is usually used to remove most of the iron in the ferroalloy to obtain platinum, palladium and rhodium concentrate, and then aqua regia leaching is used to obtain precious liquor. Since it is di...

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Problems solved by technology

The reduction method uses hydrazine hydrate or sodium borohydride as a reducing agent, and its disadvantage is that the reduction rate of rhodium is very low under acidic conditions, and 15% to 26% of iron is also reduced; the replacement method uses zinc powder or magnesium powder to replace precious metals. The reason is that the consumption of zinc powder or magnesium powder is large and the cost is high; the precipitation method uses thiourea or sodium sulfide to precipitate platinum group metals.

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