Preparation of α-hemihydrate gypsum from phosphogypsum in glycerol and Na2SO4 mixed solutions under atmospheric pressure

Hydrophobic Modification of the α‐Hemihydrate Phosphogypsum (α‐HH) Surface by Myristic Acid

“…The FT‐IR spectra of α‐HH before and after modification with MA under different preparation conditions are shown in Figures 4 and S2. The FT‐IR spectrum of α‐HH exhibits absorption peaks at 486, 544, 673, 721, 934, and 1113 cm −1 , which correspond to the asymmetric stretching vibrations of SO 4 2− and bending vibration in the CaSO 4 ⋅ 0.5H 2 O powder [20] . The absorption peak corresponding to calcium ions is observed at 1715 cm −1 [8] .…”

“…The peaks at 1298 and 1417–1460 cm −1 correspond to the in‐plane bending vibration of hydroxyl groups. The peaks corresponding to the hydroxyl stretching vibration of crystalline water in the powder appear at 3611 and 3746 cm −1 [20] . The FT‐IR spectrum of MA exhibits an absorption peak at 756 cm −1 arising from −(CH 2 )n− (n>4).…”

“…The hydroxyl stretching vibration results in absorption peaks at 3414, 3734, and 3859 cm À 1 . [20] The FT-IR spectrum of α-HH/MA reveals absorption peaks corresponding to the antisymmetric and symmetric stretching of CÀ H bonds of CH 3 and CH 2 groups at 2858 and 2932 cm À 1 , [21] respectively, and an absorption peak corresponding to the asymmetric stretching vibration of COO À at approximately 1618 cm À 1 . [22] The presence of these groups indicates that MA was chemically adsorbed on the surface of α-HH and that calcium myristate was generated on the surface of the α-HH powder.…”

“…The peaks corresponding to the hydroxyl stretching vibration of crystalline water in the powder appear at 3611 and 3746 cm À 1 . [20] The FT-IR spectrum of MA exhibits an absorption peak at 756 cm À 1 arising from À (CH 2 )nÀ (n > 4). The absorption peaks at 1053, 1375, and 1751 cm À 1 correspond to the CÀ O, À CH 3 , and C=O stretching vibrations in MA, respectively.…”

Facile Preparation of Large‐Sized Columnar α‐HH Crystal via a NaCl Salt Bath Method

“…[4][5][6] Among them, the autoclave-free method would have broad market potential and vital environmental benefits because it avoids a high-pressure environment, reduces energy consumption and requirements for reaction vessels. [7][8][9][10] In this method, DH dehydrates and dissolves in salt solutions with a certain temperature at normal pressure, while HH crystals precipitate due to supersaturation, [11][12][13] which can be described as a dissolutionrecrystallization process for the simultaneous occurrence of DH dissolution and HH crystallization. During this process, the formation of HH crystal is related to temperature, salt solution, time, and the crystal modifier (e.g., inorganic acids).…”