Electronic Grade Phosphoric Acid Refining and Purification-Ion Exchange

Phosphoric acid is an inorganic acid that serves as an important basic chemical raw material and is widely used in fields such as agriculture, chemical industry, metallurgy, national defense, food, medicine, and electronics industry.

The ultimate use of phosphoric acid depends on its purity, among which high-purity electronic grade phosphoric acid has very strict requirements for insoluble solid particles and metal ion impurities. For example, the impurity content of metal ions and halogens usually needs to be controlled below 10 ppb (i.e. 1 × 10-9), so electronic grade phosphoric acid chemical products are less affected by impurities during use, and can maintain excellent electrical properties such as insulation voltage resistance, corrosion resistance, and uniform resistance. It can be widely used in the microelectronics industry.

Electronic grade phosphoric acid, as one of the key basic chemical raw materials in the production process of large-scale integrated circuits (ICs), is mainly used for wet cleaning and wet etching of electronic components.

At present, the processing and preparation technology of electronic grade phosphoric acid is mainly divided into two categories: thermal method and wet method. Among them, thermal method preparation is to burn phosphate ore through a heat treatment process to produce high-purity yellow phosphorus, and then oxidize and hydrate to produce phosphoric acid; Wet method preparation uses inorganic acid to treat phosphate rock to prepare phosphoric acid, and then uses purification and purification methods to control the impurity content of each component in the phosphoric acid and produce electronic grade phosphoric acid that meets the standards.

Due to the high energy input required for thermal preparation, the cost is expensive. Currently, wet process production of phosphoric acid still dominates in China.

However, phosphoric acid prepared by wet method often contains various impurity ions, such as arsenic, iron, calcium, magnesium, lithium, potassium, sodium, sulfate ions, nitrate ions, which can greatly reduce the quality of the product during the etching process of the circuit board. This requires additional separation, purification, and refining processes for wet process phosphoric acid.

Ion exchange method, as a separation and purification technique, achieves chemical adsorption process through the complexation reaction between chemical ions. The purification of phosphoric acid by ion exchange method mainly utilizes the combination of acid ions in strong acids with impurity ions in phosphoric acid solution, such as Ca2+, Fe3+, Al3+, Mn2+, to generate insoluble or insoluble precipitates in water.

The ion exchange method has many advantages, including ease of operation, environmental friendliness, high selectivity, and is widely applicable for the purification of phosphoric acid and aqueous media.