Method for deeply purifying calcium sulfate dihydrate from coarse-particle ardealite

The invention discloses a method for deeply purifying calcium sulfate dihydrate by using coarse-particle phosphogypsum, which comprises the following steps: screening phosphogypsum particles, collecting coarse-particle phosphogypsum, adding water, and fully stirring; adding nano TiO2 under high-frequency vibration, irradiating the slurry by adopting an ultraviolet light source to generate a photocatalytic oxidation reaction, keeping high-frequency vibration, and stirring the slurry to sufficiently disperse the phosphogypsum particles again; repeating for three times; carrying out solid-liquid separation on the slurry to obtain filtrate and filter residues; placing the filtrate in a low-temperature environment, and cooling and crystallizing calcium sulfate dissolved in the filtrate; filtering the obtained liquid with crystals to obtain a crystal substance; and placing the obtained filter residue and the obtained crystal substance in a microwave field for irradiation to obtain a dried material which is purified