The defluorination of the wet-process phosphoric acid with the use of mechanochemically modified activated carbon

Grishin Ilia Sergeevich¹, Smirnov Nikolai Nikolaevich¹, Kochetkov Sergei Pavlovich²

¹ Federal state budget educational institution of higher education «Ivanovo State University of Chemistry and Technology», Ivanovo, Russia

² Kolomna Institute of Moscow Polytechnic University, Kolomna, Russia

Abstract:

The paper is devoted to the search for more effective adsorbents for the defluorination of wet-process phosphoric acid, as well as methods for their synthesis. It was established that mechanochemical modification of activated carbon allows more complete removal of fluoride from the acid. Modification was carried out in a roller-ring vibrating mill. The original and modified samples were analyzed using such methods as scanning electron microscopy, low-temperature nitrogen adsorption/desorption, and potentiometric titration. It was revealed that the mechanical effect on activated carbon for 5 minutes leads to an increase in the specific surface by 11.6%, the concentration of carboxyl and phenol groups by 59.6 and 12.8%, respectively. This led to an increase in the efficiency of phosphoric acid defluorination. When using a modified sample, fluorine content decreased from 2.06 to 1.73 wt. %. The positive effect of mechanical action is due to the active oxidation of activated carbon, that is, an increase in the concentration of functional groups containing a hydroxyl fragment that is replaced by fluorine during the purification process.

Keywords:

Wet-process phosphoric acid, activated carbon, purification, mechanochemical modification, fluorine.