The invention discloses a method for producing food-grade
disodium hydrogen phosphate by using wet-process dilute
phosphoric acid. The method comprises the steps as follows: (1) membrane
filtration: placing wet-process dilute
phosphoric acid in an acid-resistant container, and filtering the wet-process dilute
phosphoric acid by membrane
filtration equipment to obtain purified wet-process dilute phosphoric acid; (2)
neutralization reaction and simultaneous defluorination and desulfurization: placing the dilute phosphoric acid in an acid-resistant container, adding a defluorination and desulfurization agent and a
potassium hydroxide solution, and carrying out stirring to obtain a
neutralization solution; (3) oxidative
arsenic removal, slightly alkaline heavy
metal removal and membrane
filtration: carrying out stirring, adding an
oxidizing agent, adjusting the pH value to slight
alkalinity, and carrying out heating, cooling and membrane filtration to obtain alkaline heavy
metal removal and oxidative
arsenic removal solution; (4)
pH regulation and concentration: adjusting the pH of the slightly alkaline heavy
metal removal and oxidative
arsenic removal solution to obtain a
disodium hydrogen phosphate concentrated solution; (5) cooling
crystallization: transferring the
disodium hydrogen phosphate concentrated solution in equipment, decreasing the temperature, and continuing
crystallization; and (6)
crystallization and
drying. The method is easy to implement, simple and convenient to operate, low in cost and high in purity, arsenic and heavy metal ions are fully removed, the
solubility property is good and
mechanization can be realized.