Comprehensive recovery method for zinc, copper and cadmium in copper-cadmium slag

The invention discloses a comprehensive recovery method for zinc, copper and cadmium in copper-cadmium slag, which comprises the following steps: firstly, chromium slag is subjected to oxidation alkaline leaching and solid-liquid separation, then the copper-cadmium slag is added into acidified leachate, zinc in the slag is oxidized by dichromate to generate zinc sulfate, cadmium and copper do not react with dichromate and are enriched in a slag phase, copper-cadmium-rich slag is formed, solid-liquid separation is carried out, and the copper-cadmium-rich slag is obtained; ammonia water is added into the acid leaching solution, the pH of the solution is adjusted, chromium is made to generate chromium hydroxide precipitates, zinc is made to generate [Zn (NH3) 4] (OH) 2, solid-liquid separation is carried out, and a slag phase is subjected to oxidation acid leaching, so that Cr (III) is converted into Cr (VI), and the Cr (VI) is recycled; sulfuric acid is added into a liquid phase to adjust the pH value of the so