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Morphology‐Controlled Preparation of α‐Calcium Sulfate Hemihydrate from Phosphogypsum by Semi‐Liquid Method
Author(s) -
Mi Yang,
Chen Deyu,
He Yulong,
Wang Shuzhou
Publication year - 2018
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.201700162
Subject(s) - phosphogypsum , phosphoric acid , morphology (biology) , microstructure , materials science , hemihydrate , calcium , chemical engineering , molar ratio , nuclear chemistry , chemistry , mineralogy , gypsum , composite material , metallurgy , raw material , organic chemistry , catalysis , biology , engineering , genetics
Abstract Phosphogypsum (PG), a by‐product of phosphoric acid industry, causes environmental issues. In this paper, PG was effectively transformed into alpha‐calcium sulfate hemihydrate (ɑ‐CSH) via a semi‐liquid method. The phase evolution and the effects of different organic acids and pH values on crystal morphology of the α‐CSH were investigated by SEM, XRD and EDS. The properties of the prepared α‐CSH with different aspect ratio were also compared. The results indicate that PG can be successfully transformed into α‐CSH by the semi‐liquid method at 140 °C for 3.0 h. The morphology of the produced α‐CSH is significantly influenced by the concentrations of organic acid and pH value. α‐CSH crystal with well‐morphology is obtained under the condition of 0.1 wt.% maleic acid and pH = 7.0. The obtained α‐CSH with uniform particle size has the aspect ratio of 1.2. The 2 h and 3 d bending/compressive strengths of the hardened paste prepared from the α‐CSH reach 6.4/20.6 MPa and 10.5/43.7 MPa respectively, which are comparable to those of the commercial α‐CSH. Moreover, the lower aspect ratio of ɑ‐CSH results in more compact microstructure and higher mechanical strengths of the hardened paste.