Abstract:

The agitation tank and Keltics static mixer were used to remove arsenic (As) from industrial phosphoric acid by using phosphorus pentasulfide (P₂S₅). The single factor experiments, orthogonal experiment and response suface methodology were conducted to acquire the optimal process conditions. The results showed that the removal efficiencies of both of the two reactors were higher than 98.8% and the content of As were less than 0.5 mg·kg^-1 in the purified phosphoric acid, which met the national standard of China GB 1886.15-2015 for food grade phosphoric acid. As the agitation tank was the reactor, the optimum process conditions were that the actual dosage of dearsenifying agent was 4 times of the theoretical dosage, reaction temperature was 65℃, reaction time was 70 min and the stirring speed was 300 r·min^-1. As the Keltics static mixer was the reactor, the optimum process conditions were that the actual dosage of dearsenifying agent was 4 times of the theoretical dosage and the phosphoric acid flow was 0.66 m³·s^-1. Under this condition, the disposal phosphoric flow was increased greatly, and the reaction time was only 2.4 s and the amount of phosphoric acid treated per unit of time is 372 times that of the stirred reactor. As Keltics static mixer is used to remove arsenic (As) from industrial phosphoric acid, there are many advantages, such as the shorter technological process, the simpler construction, the continuant operation, etc., which is hopefully to realize the process intensification of dearsenifying As from phosphoric.