Basis for determining the optimal oil-to-water ratio (O/A) for extraction

It’s easy to perform extraction in the laboratory; after running a few sets, it becomes clear

Could you give a detailed example? Is it inferred from the data of extraction isotherms? What is the basis for this inference? Thank you

The determination is based on how much metal you need to extract

For a solution with a certain concentration and flow rate, the higher the ratio, the more metal will be extracted. From an engineering perspective, it is of course better to have as much metal extracted as possible from the organic phase, but this ratio continues to increase. So, which specific comparison is what we need the most? Is the comparison based on experience? Is it still determined through some form of calculation? This is a very crucial issue. Thank you

Are you doing extraction or back-extraction? Extraction is the process of separating metals from a solution, while back-extraction involves recovering the metal of interest from the extractant back into the solution. The ratio of phases and the flow ratio are determined based on the concentration of the extractant, the concentration of the metal in the solution, and the desired concentration of that metal in the back-extraction solution. In experimental settings, control over the ratio of phases is generally the goal, whereas in practical engineering applications, the flow ratio is what matters most. And the flow ratio, in turn, can be adjusted through the design of the extraction tank. There is still a big difference between experiments and engineering. Compared to it, it can be determined based on experience as well as calculated.

Dear expert, I often see you responding to questions and providing answers in posts; thank you. First, let me introduce the background of the project. Our project is related to uranium mining processes, involving extraction followed by precipitation to produce yellow cake. The metal content in the aqueous phase upon entry into the extraction system was 4.27 g/L; the metal content in the organic phase after extraction was 4.13 g/L, while the metal content in the aqueous phase after back-extraction was 5.76 g/L. The flow ratio during the extraction stage is O/A=1.03, while it is O/A=1.4 during the back-extraction stage. In the extraction tank, the specific flow ratios for successive phases are 1.2 and 0.8 respectively. The extractant concentration is 5%. Starting with the extraction stage, if the concentration of the extractant is known, as well as the amount of metal in the aqueous phase that enters the extraction phase and the amount of metal extracted into the organic phase, it is possible to determine the flow ratio for this extraction stage. Based on the description of the project background, the water phase content of 4.27 g/L entering the extraction system can be considered a known value, as determined by preliminary experiments. But how was the metal content of 4.13 g/L in the organic phase obtained? Was it created through experiments? If it is based on experiments, is it derived from experiments on the maximum saturation capacity of the organic phase? Turning to the back-extraction stage, if the concentration of the extractant and the metal concentration in the organic phase entering back-extraction are known, the metal concentration in the aqueous phase after back-extraction can be used to determine the flow ratio during the extraction stage. Based on the description of the project background, the metal concentration in the organic phase entering the back-extraction system, at 4.13 g/L, can be considered a known value; thus, the answer to the previous question should be available. But how can the metal concentration in the aqueous phase after back-extraction, at 5.76 g/L, be determined? As far as I know, the higher the concentration when precipitating yellow cake, the better; why was the value of 5.76 g/L chosen for this project? Or does some other factory have similar data recommending this value? There is another question: what value is appropriate for the flow ratio during the washing stage? For our project, the O/A ratio is 20. I was wondering what your experience suggests? For the washing stage, is it better to use weakly alkaline, weakly acidic water, or just water? There are many issues; sorry for the disturbance. Thank you

First question: Metal concentrations are generally determined through sampling, testing, and analysis in actual experiments or production processes. Second question: The higher the precipitation concentration, the better it might be, but extraction may not necessarily meet this requirement. Because various problems can arise during the extraction process due to excessively high concentrations. As for uranium specifically, I can’t say much because I haven’t conducted that experiment myself. Third question: The washing flow ratio is determined based on the amount of other substances that end up in the organic phase during the extraction process, as well as the concentration of the acid or base used for washing. The acid or base used for washing, in turn, is determined by the metal that needs to be washed and the extractant being used.

Dear expert: Regarding the first question, what I mean is: how was the metal content of 4.13 g/L in the organic phase after extraction determined during the design stage? Is it determined by the metal content in the organic phase based on the extraction isotherm, and then the specific gravity is calculated from that? Regarding the second question, it is understood that there is actually an optimal solution concentration for precipitation during this process; presumably, the design of the project took into account some data from studies or from other factories. I’ll ask the design team about this again ； Is it also possible to determine the metal content in the aqueous phase after back-extraction based on the back-extraction isotherms? I’d like to delve into the third question: what is the flow ratio during the washing stage in general engineering applications? How is it determined whether to use acid or base for washing, based on the type of metal being washed and the type of extractant? Thank you

Has the OP’s brother never operated an extractor? Theoretical calculations and small-scale tests using separatory funnels differ greatly from the actual operation of extraction machines; even under normal operating conditions, the oil-to-water ratio still needs to be adjusted. During the first startup, send the raffinate back to the original liquid tank, then gradually adjust the flow rates of water and oil. Take samples of the raffinate every twenty to thirty minutes for testing, until the metal content reaches an acceptable level. Keep the water flow as high as possible, while ensuring that there is enough oil flow to facilitate extraction; the clarifier should be able to separate oil from water properly. In simple terms, oil should not leak through areas where water is supposed to flow, and water should not leak through areas where oil is supposed to flow. What’s the ratio of the oil to something else?

First question: I mean, during the design phase, how was the metal content of 4.13 g/L in the organic phase after extraction determined? Is it determined by the metal content in the organic phase based on the extraction isotherm, and then the specific gravity is calculated from that? Answer: 4.13 g/L is either a value obtained from experiments or an empirical value. Regarding the second question, it is understood that there is actually an optimal solution concentration for precipitation during this process; presumably, the design of the project took into account some data from studies or from other factories. I’ll ask the design team about this again ； Is it also possible to determine the metal content in the aqueous phase after back-extraction based on the back-extraction isotherms? Answer: Logically speaking, it is better to have a higher concentration of the target metal in the back-extraction solution. But it also needs to be based on the actual situation ； Perhaps 5.76 g/L is also an empirical value or experimental value ； Or consider factors such as the continuity of system operation. I’d like to delve into the third question: what is the flow ratio during the washing stage in general engineering applications? How is it determined whether to use acid or base for washing, based on the type of metal being washed and the type of extractant? Answer: Whether to use acid, base, or water for washing is determined by the properties of the extractant chosen. For example, with TBP, water cannot be used, because water is a back-extraction agent. P204\P507 should be washed with a weak acid.