Process for Treating Fluorine-Containing Wastewater in the Phosphate Fertilizer Industry

The production process of phosphate fertilizer mainly involves the decomposition of phosphate ore by sulfuric acid. Although the production process and conditions are different, high concentration fluorine-containing wastewater is generated during the production process, and some are accompanied by high chemical oxygen demand (COD), which is extremely difficult to treat. Despite the rapid development of new technologies and treatment materials in the domestic environmental protection industry in recent years, there has been relatively little attention paid to fluorides, especially in terms of research on treatment methods for fluorine-containing wastewater. As a result, there is limited room for selecting treatment solutions for this type of wastewater.

According to the GB15580-95 standard, the mass concentration of fluoride ions should be less than 10mg/L. There are various methods for treating fluorine-containing wastewater, such as precipitation, freezing, resin ion exchange, activated carbon defluorination, electrodialysis, etc. Due to treatment costs and other reasons, the currently widely used methods are lime milk precipitation, flocculant precipitation, and inorganic salt addition. In industry, calcium hydroxide solution (lime lotion) is usually added to form calcium fluoride with fluoride ion and then precipitate and separate. This process can effectively reduce the concentration of fluoride ion to about 20ppm. In order to achieve a lower fluoride concentration (<10ppm), it is necessary to deeply treat the wastewater after calcium pretreatment. The Haipu special adsorption method can ensure stable effluent of<10ppm.

The defluorination treatment process developed by Jiangsu Haipu Functional Materials Co., Ltd. selectively adsorbs and enriches fluoride ions in wastewater or waste acid into adsorption materials, thereby achieving the goal of separating fluoride ions. The fluoride content in the adsorbed water is greatly reduced, meeting the relevant requirements of subsequent steps.

Haipu high-performance adsorbent has the following advantages:

1. Wide applicability and good practicality

This method can be applied to wastewater concentrations ranging from a few to several hundred ppm, and the adsorption is not affected by the inorganic salts contained in the solution. It can also be applied in non-aqueous systems.

2. High adsorption efficiency, easy desorption and regeneration

For fluorine-containing wastewater, after adsorption, it can generally meet or approach the discharge standards, with a material adsorption rate of over 95%, without producing secondary pollutants, and can significantly reduce the fluoride content. Common acid-base or organic solvents are used for desorption, and the desorption rate can generally reach over 92%.

3. Stable performance and long service life

The material has high resistance to oxidation, acid and alkali, and organic solvents, and can be used for a long time below 150 ℃. Under normal circumstances, the annual material loss rate is less than 5%.

4. Beneficial for comprehensive utilization and turning waste into treasure

The raw material intermediates or products present in wastewater generally have higher prices. The adoption of this method can largely recycle and use, which will generate considerable economic benefits. Usually, the recycling value is equivalent to the daily operating expenses, and some have surplus

5. Easy to operate and low energy consumption

Using this technology, the process is simple, no special equipment is required, the technology is easy to master, and the consumption of thermal and electrical energy is relatively low during operation.

Haipu Handling Case

The main products of a phosphate fertilizer enterprise in Guangdong include 800000 tons of phosphoric acid, 1.2 million tons of sulfuric acid, 1.6 million tons of ammonium phosphate, etc. During production, 300t/d of phosphorus containing and fluorine-containing wastewater is generated. The enterprise originally used the traditional two-stage lime defluorination method, but in production and operation, it cannot meet the defluorination requirements of high fluoride wastewater. In response to this, methods such as first level lime milk method, first level lime excess method, polyaluminum (iron) defluorination method, and CaCl2 addition were used separately, but none of them met the discharge requirements for fluoride in the wastewater. In the exploration, Haipu adopted a combination of first-order lime excess method and special adsorption technology. After using this method, the fluoride in the wastewater can be reduced from over 2000ppm to 3-10ppm, and the phosphorus can be reduced from over 1000ppm to within 300ppm.

After being treated by the Haipu adsorption process, the fluoride content in the wastewater is reduced to below 10ppm, thus meeting the requirements of enterprise management.