Preparation of Anhydrous Calcium Sulfate Whiskers from Phosphogypsum in H₂O-H₂SO₄ Autoclave-Free Hydrothermal System

Abstract

The anhydrous calcium sulfate (AH) whiskers were prepared in H 2 O-H 2 SO 4 autoclave-free hydrothermal system by using phosphogypsum (PG) as raw materials. The in uences of solid/solution ratio, reaction time, H 2 SO 4 concentration and maleic acid on crystal growth were detected.The whiskers with smooth surface and high aspect ratio were obtained in a 20 mass% H 2 SO 4 solution for hydrothermal 1 h with 1:60 ratio of solid/solution. The aspect ratio decreased but the amount of whiskers increased in sample by increasing the addition amount of maleic acid.The whiskers were not obtained in 30 mass% H 2 SO 4 solution for hydrothermal 1, 2 and 3 h, respectively, with 1:60 ratio of solid/solution, and the whiskers were also not obtained by adding maleic acid in the solution.

Recycling phosphogypsum in road construction materials and associated environmental considerations: A review

“…Despite their high strength and good toughness, wear resistance, and temperature resistance, the applications of calcium sulphate whiskers (CSWs) are limited other than serving as the reinforcing and toughening agents for materials such as rubber. High-quality anhydrous CSWs were produced in an autoclave-free hydrothermal system prepared with a 20 wt% H 2 SO 4 solution, a 1 to 5 wt% maleic acid, and a PG to solution ratio of 1:60 ( Tan et al., 2017 ). CSWs can be used in highway engineering, such as asphalt modification, to improve the performance of modified asphalt, thus greatly increasing the utilisation of PG and CSWs and promoting solid waste reuse.…”

Experimental Investigation of Eco-Friendly Anhydrous Calcium Sulfate Whisker and Waste Cooking Oil Compound Modified Asphalt Mixture

“…Large volumes of phosphogypsum waste are dumped into the environment, polluting the soil and water and endangering human health. To minimize pollution and promote sustainable development, phosphogypsum waste could be utilized to synthesize anhydrous calcium sulfate whiskers (ACSW) [ 18 , 19 , 20 ], which are inorganic needle-like fibrous submicron materials. These materials offer high-temperature resistance, high toughness, chemical corrosion resistance, and high-cost performance [ 18 , 21 ].…”

Study of Semi-Dry High Target Solidification/Stabilization of Harmful Impurities in Phosphogypsum by Modification

“…In recent years, many environmentalists have attached great importance to the resource treatment of PG and have been eager to solve this problem. The current studies on resource utilization of PG are primarily focused on the following aspects: preparation of sulfuric acid and cement [14], construction materials [15], improvement of soil [16], and synthesis of high-strength gypsum [17], CaCO 4 [18], calcium sulfate whiskers [19], agricultural fertilizers [20][21][22], soil conditioners and so on [23][24][25][26]. Especially, much of the work revealed the great opportunities related to the use of PG in different applications.…”