Influence of crystal modifier on the preparation of α-hemihydrate gypsum from phosphogypsum. (15th February 2017)

• Record Type: Journal Article
• Authors: Duan, Zhengyang; Li, Jianxi; Li, Tianguo; Zheng, Shurui; Han, Weiming; Geng, Qingyu; Guo, Huibin
• Is Part Of: Construction & building materials. Volume 133(2017)
• Page Start: 323
• Page End: 329
• Publication Date: 2017-02-15
• Subjects: Crystal modifier -- α-Hemihydrate gypsum -- Phosphogypsum -- Semi-dry method; Building materials -- Periodicals; 624.18
• DOI: 10.1016/j.conbuildmat.2016.12.060
• Languages: English
• ISSNs: 0950-0618

Abstract

Highlights: Original phosphogypsum was utilized for the preparation of α-CaSO4 ·0.5H2 O. Semi-dry method process was adopted for the preparation of α-CaSO4 ·0.5H2 O. Low cost, high value-added and met the requirements of Chinese standard of α-CaSO4 ·0.5H2 O were prepared. Abstract: Crystal modifier is an important factor in preparation of α-hemihydrate gypsum (α-CaSO4 ·0.5H2 O) from phosphogypsum (PG). Here, α-CaSO4 ·0.5H2 O was prepared from PG using a semi-dry method. SEM, XRD, XPS were used to explore the effects of one or more crystal modifiers on crystal growth and mechanical properties after hydration and hardening of α-CaSO4 ·0.5H2 O. The results showed that addition of RCOO − can delay the hydration process of α-CaSO4 ·0.5H2 O and improve productivity. Al 3+ can be adsorbed selectively on the gypsum crystal surface, inhibiting the crystal growth along axis c, which could alter the speed in all directions and turn the crystal into a short hexahedron pole. But when RCOO − and Al 3+ were composited, a superposition effect occurred, resulting in production of a crystal with a smaller length to diameter ratio and more perfect crystal form. When RCOO − and Al 3+ were both added in 0.06% level, the flexural and compressive strength of the hardened α-CaSO4 ·0.5H2 O could reach to 6.7 and 25.65 MPa, respectively.