Experimental study on treatment of copper ammonia wastewater from printed circuit board by MAP method and folded chlorination process

When waste printed circuit boards are recycled, a large amount of wastewater containing heavy metal ions is usually generated, and generally contains Cu(NH₃)₄²⁺, NH₄⁺, and NH₃·H₂O. These copper ammine complex ions have high stability and are extremely difficult to handle. In this paper, the copper ammonia wastewater generated during the recycling of waste printed circuit boards is taken as the research object. The effective treatment of the wastewater and the recovery of ammonia nitrogen and copper are realized by the combined process of MAP method and broken point chlorination method, which can effectively save economic cost. And the recovery of products can also produce certain economic benefits. The results showed that the optimum conditions for MAP reaction were pH=9.5, the molar ratio of ammonia nitrogen to input phosphorus salt and magnesium salt in wastewater was 4:1:1.1, the removal rate of ammonia nitrogen was 23%, and the removal rate of copper was 2%. Formed a magnesium phosphate precipitate. The optimum pH of the chlorination method was 9.5, the molar ratio of N/Cl was 1:1.6, the ammonia nitrogen treatment effect was 98.8%, and the copper removal rate was 99.8%.