The invention relates to a method for recycling used lead-acid batteries in a full circulation mode. According to the technical scheme, a band sawing
machine for
cutting the used lead-acid batteries is used for sawing and
cutting a used lead-acid battery into an upper cover, a groove body, an
electrode set and acid liquid, and the upper cover, the groove body, the
electrode set and the acid liquid are respectively processed to obtain lead-
antimony alloy, plastic, lead plaster, lead-
calcium alloy and dilute sulphuric acid. Then, the lead plaster is added into a reaction tank,
amidogen-contained substances are added to the lead plaster, stirring is conducted, desulfurization is conducted after carbon-contained substances are added,
solid-liquid separation is conducted, and therefore desulfurated lead plaster and filter liquid are obtained. Then, the filter liquid is evaporated and crystallized to obtain
ammonium sulfate, and liquid evaporated in the
evaporation and
crystallization process is cooled to the
room temperature and recycled. The washed desulfurated lead plaster is dried, and the dried desulfurated lead plaster is roasted at the temperature larger than 400 DEG C and smaller than or equal to 500 DEG C or at the temperature larger than 500 DEG C and smaller than or equal to 650 DEG C to obtain lead tetroxide or
lead oxide. The method has the advantages of being simple in process, low in recycling cost, high in recycling rate, high in product purity and
environmentally friendly.