Effect of extractant p204 concentration on extraction

Generally, when the p204 concentration exceeds 25%, there is not much difference.

-- Anything will break down after being used for a long time. The method of improvement depends on the specific situation. --

-- Didn’t understand what you meant? --

Reply to 4# FILTRATION-MAN: During the extraction of indium, when the concentration of p204 is above 25%, the extraction capacity does not change significantly.

It has been used for a long time. Then all kinds of problems will arise.

-- Could you explain the reason? --

Reply to 7# FILTRATION-MAN: This is a conclusion drawn from theory and experiments.

-- Which theory? Is the experiment representative? --

Reply to 9# FILTRATION-MAN: Of course it’s representative. As for the theory, you should take a look at the book on indium metallurgy; it’s difficult to upload the formulas!

-- I have no idea where to find the book for now. Let me guess this theory first; if I’m wrong, please feel free to correct me. Generally, for these rare metals, from an industrial perspective, sulfuric acid or hydrochloric acid media are often used. The extractant is often D2EHPA (P204) or N503. If indium is extracted using P204 in a sulfuric acid medium, I guess the equilibrium equation should be: In(3+) + 3P204 + 3H+; for P204, acid is generated during the extraction process. Unfortunately, P204 is an organic acid extractant that has high requirements regarding pH. Similarly, the selectivity of P204 is also poor; these two factors determine that the pH range for the extraction stage is very narrow. In practice, I assume that everyone uses a set of fixed equipment and processes for operations. The concentration of the slurry is likely to be similar for everyone; if it differs too much, it becomes difficult to operate. In this case, if the concentration of the extractant is too high, too much acid is produced, the pH cannot be controlled, and it becomes difficult to continue the reaction. Furthermore, regarding the concentration of the extractant, there is an optimal and economical operating concentration; if the concentration is too high, the density becomes too great, operational efficiency declines, and entrainment becomes severe. At the same time, the concentration of P204 might be too high, which could also have an impact on saponification. Theoretically, for any extractant, the higher its concentration, the higher the extraction efficiency should be. However, in practice, for various reasons, the difference is quite large. --