Membrane recovery method: recovery of waste acid and metal salt in pickling waste liquid

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(1) Diffusion dialysis membrane method

Diffusion dialysis is a process in which the solute in the solution is transferred from the high concentration side to the low concentration side by using a semi-permeable membrane or a selective permeable ion exchange membrane.

This process does not consume electricity and has low operating costs, but there are few cases in engineering applications of this method, mainly because of the long treatment process route, large equipment, limited processing capacity, and the concentration of recovered acid is affected by the equilibrium concentration, and the concentration of recovered acid obtained is less than 1.77mol/L, which cannot be directly used for pickling production.

(2) electrodialysis method

Since the driving force of the diffusion method is only the concentration difference, the researchers pass direct current into the solution, and under the action of the applied electric field, the negative and cation move to the negative and cation membrane respectively and enter the other side through the membrane, so that the waste liquid is deacidified to recover the acid, which is called the electrodialysis method.

The electrodialysis method is driven by electric field force, and the dialysis rate is faster than diffusion dialysis, and the concentration of recovered acid is higher. At the same time, the electrodialysis method does not produce excess waste water residue in the treatment process, can reduce the amount of other chemical agents, is an efficient recovery of waste acid and metal salt in pickling waste liquid method.

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