System and method for recycling rare earth and ammonia nitrogen from rare earth wastewater

A method for recycling rare earth from a wastewater from rare earth mining or from rare earth smelting, comprising:

• 1) feeding the wastewater to an oil separator at a flow rate of 1000-3000 liters/hour (L/h), standing, removing oil from the wastewater to form a degreased wastewater, guiding the degreased wastewater to a reaction tank, adjusting pH of the degreased wastewater in the reaction tank to about 3-5, and feeding the degreased wastewater in the reaction tank to a first intermediate water tank by overflowing;
• 2) feeding the degreased wastewater in the first intermediate water tank to a pretreatment system using a first lift pump, treating the degreased wastewater by the pretreatment system to obtain a purified wastewater, and guiding the purified wastewater to a second intermediate water tank;
• 3) feeding the purified wastewater in the second intermediate water tank to at least one rare earth recycling tank filling with a rare earth recycling material at a flow rate of 100-3000 L/h, flowing the purified wastewater through the rare earth recycling material to obtain a low rare earth wastewater and guiding the low rare earth wastewater to a sedimentation tank, wherein after the rare earth recycling material reaches saturated adsorption, the rare earth recycling material is washed with hydrochloric acid to obtain a rare earth slurry;
• 4) adjusting pH of the low rare earth wastewater in the sedimentation tank to about 10-13 using an alkali, standing, guiding the low rare earth wastewater to a third intermediate tank by overflowing, pumping the low rare earth wastewater in the third intermediate water tank to an ammonia degassing device using a third lift pump, converting ammonia nitrogen contained in the low rare earth wastewater in the ammonia degassing device into ammonia to obtain a low nitrogen wastewater, pumping the ammonia to a gas-liquid separator, and detecting a concentration of ammonia nitrogen in the low nitrogen wastewater in the ammonia degassing device, if the concentration of the ammonia nitrogen meets a predetermined standard, discharging the low nitrogen wastewater in the ammonia degassing device via a drain pipe, and if the concentration of the ammonia nitrogen does not meet the predetermined standard, guiding the low nitrogen wastewater to a gas-liquid separation membrane module, and further treating the ammonia nitrogen in the low nitrogen wastewater by controlling the pressure difference between an exterior and an interior of a membrane in the gas-liquid separation membrane module, such that the low nitrogen wastewater travels inside the membrane, and an absorbing solution sulfuric acid travels outside the membrane, and after the step of treating, discharging the low nitrogen wastewater that meets the predetermined standard, and returning the absorbing solution to the reaction tank;
• 5) sucking the ammonia gas to an aqueous ammonia preparation system by a sucking fan to obtain aqueous ammonia.