Optimization Analysis of Silver Extraction from Waste Monolithic Ceramic Capacitor Using Persulfate-Ammonia System

Monolithic ceramic capacitors (MLCCs) contain a high level of silver. This paper describes a method to recover silver from the waste MLCCs. First, the effects of persulfate species, reaction time, temperature, persulfate concentration, ammonia, and alkali on silver leaching were investigated. Second, the effects of hydrazine hydrate, reaction time, formaldehyde, and temperature on silver reduction were also investigated. The results showed that potassium persulfate was the best leaching agent among the three kinds of persulfate, with its maximum silver leaching yield of 90.8%. The reduction rate of hydrazine hydrate was better than formaldehyde. The optimal reduction rate of hydrazine hydrate to silver was 99.8%. The mechanism analysis indicated that molecular oxygen generated from the reactions of persulfate ion with hydroxide ion, ammonium ion, and water could facilitate the oxidation of silver and further develop silver ammonia ligand ion that could accelerate the silver leaching yield.