As an important and industrial raw material, the use of palladium is of great significance, palladium nitrate waste contains trace amounts of palladium, is one of the important methods of palladium, liquid-liquid extraction is an effective method of purifying palladium, which uses the principle of material distribution between two immiscible liquids, through the addition of extractants, so that palladium is transferred from one phase to another phase to achieve the purpose of purification and separation.
For liquid-liquid extraction, we choose dibutyl phosphoric acid (DBP) as the extractant, first of all, we need to pretreat the palladium nitrate waste, remove the suspended particulate impurities in the waste liquid by filtration, determine the palladium content and other chemical components in the filtrate, calculate the amount of extractant that needs to be added according to the measurement results, and then add the acid and alkali solution to adjust the pH value of the liquid phase, which is generally adjusted to the strong acidic conditions of 2-3.
An equal volume of the extractant dibutyl phosphoric acid (DBP) was added to the pretreated palladium nitrate solution and placed in a stirring tank for mixing. Usually we generally stir at 300rpm, stir for 1-2 hours, maintain the temperature at 25 °C, palladium ions migrate from the aqueous phase to the organic phase of DBP extractant, and after static stratification, the organic phase containing palladium and the aqueous phase of palladium removal are separated by a separating funnel.
Then the palladium-containing organic phase needs to be treated, rinsed with dilute sulfuric acid solution to remove the corrosive salt impurities mixed in the extraction process, and then the organic phase is concentrated at a temperature of 60 °C to increase the mass concentration of relative palladium, and then the pH is adjusted to weak alkalinity with sodium hydroxide solution to return the palladium to the aqueous phase.
The adjusted basic palladium solution is filtered and placed in the electrolytic cell, and electrolytically deposited at the cathode under the action of anodized lead and cathode carbon to obtain crude palladium products. Electrolysis conditions can be optimized to increase yield and purity.
The crude palladium obtained by electrolysis can be smelted and refined to remove impurities, improve purity, and finally obtain high-purity palladium products.
In the refining process, each step of the process must strictly control various parameters, such as temperature, stirring speed, pH value, current density, etc., to ensure that palladium can be efficiently and selectively separated and refined from complex matrices. Liquid-liquid extraction method is an effective method for refining palladium, which has the characteristics of simple operation, high extraction efficiency and environmental friendliness, and has been applied in industry and has a good application prospect.