Development status and research progress of wet phosphoric acid extraction technology

As an important chemical raw material, phosphoric acid occupies an extremely important position in the chemical industry. The application of phosphoric acid is mainly determined by the purity of phosphoric acid, low purity phosphoric acid can be used in industrial and agricultural neighborhoods, while high purity phosphoric acid can be used in pharmaceutical, food, electronics and other industries. In recent years, with the increasing demand for batteries and semiconductors, the purity of phosphoric acid has put forward higher requirements. There are two main manufacturing methods of phosphoric acid, among them, thermal phosphoric acid consumes large energy and environmentally unfriendly, which does not meet the needs of China's development of green chemistry. Wet phosphoric acid has low energy consumption and bulk and complex product impurities, which is more suitable for treating low-grade phosphate rock in China. Compared with chemical precipitation, crystallization, electrodialysis, ion exchange resin and other purification technologies, the extraction method has the advantages of green environment, simple operation and large production capacity, and is a phosphoric acid purification method with great development prospects. This article summarizes in detail the research status of various extraction methods in recent years. The basic principles and development trends of solvent extraction, aqueous two-phase extraction, reverse micelles extraction, ultrasonic-assisted extraction and supercritical fluid extraction were emphatically introduced , and the solvent extraction method and various extractants were emphatically sorted out. The research of single extractants such as TBP, MIBK, and NOA mainly focuses on exploring the optimal extraction conditions (O/A phase ratio, temperature, and air pressure), but a single extractant can usually only extract a single impurity and cannot meet the extraction of multiple impurities, so the composite extractant has significant advantages in phosphoric acid purification. At present, researches highlight composite extractants are mainly on the proportion of extractants（usually the volume ratio） and the optimal conditions for extraction. In addition to composite extractants, the new extractants can also solve the problem of low extraction efficiency of a single extractant. Finally, the future development trend of extraction technology of phosphoric acid is proposed: 1) development of green composite extractants, new extractants, new materials combined with extractants that can achieve efficient separation of impurities from phosphoric acid, 2) increase the research on the application of aqueous two-phase extraction and reverse micelles extraction in ion extraction, and explore new aqueous phase systems, 3) use ultrasonic technology to accelerate the extraction process, and study how supercritical fluids can improve the solubility and extraction efficiency of ions. Reduce costs and explore specific application areas.