Method for leaching and recycling metals in waste printed circuit boards in steps by using ionic liquid

The invention discloses a method for leaching and recycling metals in waste printed circuit boards in steps by using an ionic liquid. The method comprises the following steps: adding the waste printed circuit boards which are used as the raw materials, and adding an ionic liquid and an oxidant aqueous solution according to a solid-liquid mass volume ratio of (1 to 5)-(1 to 20) to leach for 1-3 hours; filtering after finishing leaching, electrolyzing and reducing copper and zinc in a filtrate; dissolving filtration residues by using ammonia water, reducing the filtrate by using hydrazine hydrate after filtering to prepare crude silver, adding a sodium hydroxide solution into the filtration residues, dissolving, filtering, electrolyzing and reducing tin in the filtrate; dissolving nickel in filtration residues by using hydrochloric acid, concentrating, crystallizing and recycling nickel chloride; and finally dissolving gold in the filtration residues by using nitromurlatic acid and reducing the gold in the filtrate. The method for leaching and recycling metals in the waste printed circuit boards in steps by using the ionic liquid is simple in process and low in cost; the metal in the circuit boards can be leached in steps; the difficulty for reducing the subsequent metal is reduced; the consumption of a large quantity of strong acids can be avoided; and the operation environment is improved.