Treatment method for waste phosphoric acid in electrode foil production

Abstract

The invention discloses a treatment method for waste phosphoric acid in electrode foil production. DP1 process waste phosphoric acid contains 4% phosphoric acid and 4% aluminum dihydrogen phosphate. The treatment method includes: conducting nanofiltration membrane separation of partial free phosphoric acid, performing multistage washing, carrying out filtration with a combined membrane of reverse osmosis membrane and nanofiltration membrane, further washing the remaining 2m<3> of a mixed solution of phosphoric acid and aluminum dihydrogen phosphate by countercurrent washing so as to obtain 2m<3> of a mixed solution containing 2% phosphoric acid and 20% aluminum dihydrogen phosphate finally, thus maximumly recovering free phosphoric acid. Relying on the rapidly developing ion membrane technology of the 21st century, the treatment method for waste phosphoric acid in electrode foil production provided by the invention utilizes the nanofiltration membrane and anionic membrane to realize recovery of 4% free acid by the nanofiltration membrane firstly, then utilizes the anionic membrane to regenerate aluminum dihydrogen phosphate into free acid, also generates a aluminum hydroxide product at the same time, realizes recovery of capacitive products of ultrapure water, phosphoric acid and aluminum hydroxide, and fundamentally achieves "0 emission".

Description

technical field [0001] The invention relates to the technical field of waste phosphoric acid treatment methods, in particular to a waste phosphoric acid treatment method for producing electrode foils. Background technique [0002] In the production process of electrode foil (aluminum foil), there will be a process called phosphoric acid electrochemical corrosion, hereinafter referred to as "DP1 process". In the case of direct current, it is uniformly electrochemically corroded, in which the elemental aluminum of the anode will become Enter the liquid system, in the case of PH=1.2, the chemical formula Aluminum dihydrogen phosphate exists. When the content of aluminum ions reaches a certain level, the acidity in it cannot meet the electrochemical corrosion liquid environment of aluminum foil, and it will be discharged from the DP1 process system in front of the waste liquid and become waste acid (a kind of waste acid containing 4% phosphoric acid, 4% aluminum dihydrogen p...

AI Technical Summary

Problems solved by technology

[0005] ①When the pH of the waste liquid neutralized with lime is 7, some calcium dihydrogen phosphate is formed, which cannot form slag to settle down. Therefore, the pH value of the external drainage is qualified, but the total phosphorus requirement of the national discharge standard is not up to the standard

[0006] ② Waste of resources. In the aluminum foil production process, 8% capacitive grade phosphoric acid is used to electrochemically corrode aluminum foil, and the corroded aluminum becomes soluble aluminum dihydrogen phosphate. The waste liquid contains 4% phosphoric acid and 4% The purity of aluminum dihydrogen phosphate is relatively high, and they all have high value of chemical raw materials. If lime is used for neutralization treatment, 4% phosphoric acid and 4% aluminum ions cannot be recovered, and social resources are greatly wasted, and the slag after neutralization Subsequent pollution hazards of landfill environment are great

[0007] ③The treatment cost is high, and lime is used for treatment. It takes 70 kg of lime to process each ton of waste phosphoric acid solution, and produces 300 kg of slag with a water content of 30%.

Images