US 11,807,542 B2
Method for preparing urea ammonium nitrate solution from waste nitric acid after stripping tin from circuit board
Wei-Hong Wang, Shenzhen (CN); Jian-Gang Wu, Shenzhen (CN); Chao-Lin Mao, Shenzhen (CN); Chun-Hua Liao, Shenzhen (CN); Chang-Ming Chen, Shenzhen (CN); Kuan-Wei Huang, Shenzhen (CN); and Xue-Qiang Huang, Shenzhen (CN)
Assigned to SHENZHEN ENVIRONMENTAL TECHNOLOGY GROUP CO. LTD., Shenzhen (CN)
Appl. No. 17/048,050
Filed by SHENZHEN ENVIRONMENTAL TECHNOLOGY GROUP CO. LTD., Shenzhen (CN)
PCT Filed Jun. 6, 2019, PCT No. PCT/CN2019/090435
§ 371(c)(1), (2) Date Oct. 15, 2020,
PCT Pub. No. WO2019/233488, PCT Pub. Date Dec. 12, 2019.
Claims priority of application No. 201810575331.6 (CN), filed on Jun. 6, 2018.
Prior Publication US 2021/0163305 A1, Jun. 3, 2021
Int. Cl. C01C 1/00 (2006.01); C01C 1/18 (2006.01); C02F 1/00 (2023.01); C02F 1/04 (2023.01); C02F 1/66 (2023.01); C05C 1/00 (2006.01); C05C 9/00 (2006.01); C02F 101/16 (2006.01); C02F 101/20 (2006.01); C02F 101/22 (2006.01); C02F 101/30 (2006.01)
CPC C01C 1/185 (2013.01) [C02F 1/001 (2013.01); C02F 1/04 (2013.01); C02F 1/66 (2013.01); C05C 1/00 (2013.01); C05C 9/00 (2013.01); C02F 2101/163 (2013.01); C02F 2101/203 (2013.01); C02F 2101/22 (2013.01); C02F 2101/30 (2013.01); C02F 2301/08 (2013.01)] 10 Claims
 
1. A method for preparing urea ammonium nitrate solution from waste nitric acid after stripping tin from circuit board, the method comprising:
mixing the waste nitric acid after stripping tin with ammonia water, causing the waste nitric acid after stripping tin and the ammonia water to undergo a neutralizing and precipitating reaction through acid-base neutralization, a pH value of the neutralizing and precipitating reaction being between 4 and 5, a temperature of the neutralizing and precipitating reaction being between 50 degrees Celsius and 90 degrees Celsius, filtering a reaction solution of the waste nitric acid after stripping tin and the ammonia water, thereby obtaining a tin-containing filter mud and a primary filtrate;
adding iron powders into to the primary filtrate to initiate a copper-iron replacement reaction, the iron powders being reduced iron powders, thereby recovering a portion of copper ions in the primary filtrate to copper powders, filtering the primary filtrate, thereby obtaining iron-containing coarse copper powders and a secondary filtrate;
adding hydrogen peroxide to the secondary filtrate, which undergoes a redox reaction with ferrous ions and organic impurities in the secondary filtrate, and adjusting a pH value of the secondary filtrate to be between 5.5 and 6 by ammonia water, filtering the secondary filtrate, thereby obtaining an iron-containing sludge and a tertiary filtrate;
adding a heavy metal capturing agent to the tertiary filtrate, thereby causing remaining heavy metal ions in the tertiary filtrate to undergo a complex reaction to form heavy metal precipitates, the heavy metal ions comprising at least one of tin ions, mercury ions, cadmium ions, arsenic ions, lead ions, chromium ions, and nickel ions and further comprising another portion of copper ions, separating the heavy metal precipitates and filtering the tertiary filtrate, thereby obtaining a heavy metal sludge and an ammonium nitrate solution;
measuring a concentration of the ammonium nitrate solution, adding urea and liquid fertilizer corrosion inhibitor to the ammonium nitrate solution to obtain a urea/ammonium nitrate dilute solution, evaporating and concentrating the urea/ammonium nitrate dilute solution, the evaporating being at a temperature between 36 degrees Celsius and 100 degrees Celsius, and terminating the evaporating and the concentrating when a specific gravity of a concentrated liquid is between 1.28 and 1.32, thereby obtaining the urea ammonium nitrate solution, which comprises a total nitrogen content of 28% to 32%.