ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

A review of processes for separation and utilization of fluorine from phosphoric acid and phosphate fertilizers

Amol N. Joshi

Department of Chemical Engineering, Institute of Chemical Technology, Mumbai, India

E-mail: che21an.joshi@pg.ictmumbai.edu.in

Received: 25 March 2022  Accepted: 6 June 2022

Abstract:

Phosphoric acid and commercial fertilizers contain a significant quantity of fluoride, which comes from the phosphoric acid mineral, rock phosphate. HF and SiF₄ vapours are two of the most significant emissions from the phosphoric acid industry. The main source of emissions is the reactor where H₂SO₄ combines with phosphate rock. Not only gaseous emissions but also solid emissions in the form of precipitates and insoluble fluoride bearing liquid compounds contribute to the emissions. Besides the solid, liquid and gaseous emissions that are generated from factories during the production of PA, if there is residual fluoride in the PA that is used to make phosphate fertilizers, the concentration of fluoride in the soil is likely to increase both from factory emissions and also from application of phosphate fertilizers downstream. According to recent studies, the fluoride content in a few commercial fertilizers is nearly 1% by weight, which is a concerning figure. Fluoride levels in jowar grains and soil were reported to be 1.4 ppm and 2.6 ppm, respectively, in a few areas in Maharashtra, India, which is again due to the use of fertilizers. Fluoride concentrations as high as 6 ppm have been observed in a few tea samples from the USA and Ireland. As a result, it's critical to separate fluoride from phosphoric acid and use the separated fluoride in the production of industrially important compounds. Many industries avoid fluorine removal because the products obtained post removal have no or very little market value. Hence, efficient fluoride removal and effective utilization technologies are the need of the hour. The paper describes the methods for fluorine separation and its effective utilization.

Keywords: Fertilizers; Fluoride concentration; Fluorine removal; Phosphoric acid

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-022-02323-9

Chemical Papers 76 (10) 6033–6045 (2022)