Phosphate ores are naturally highly radioactive and their radioac-
tivity originates mainly from 238U and 232Th.
In order to produce phosphoric acid, phosphate ore is processed
either by dry thermal or wet acid methods. The dry thermal
method produces element phosphorus using an electric arc
furnace. The wet chemical phosphoric acid treatment process, or
‘‘wet process’’, is widely used to produce phosphoric acid and
calcium sulphate – mainly in dihydrate form (CaSO4.2H2O) (Eq. (1)).
A general scheme of the processes is shown in Fig. 1.