Extraction of calcium from red gypsum for calcium ...
The extraction efficiency of calcium and iron from red gypsum was measured using 2 M H 2 SO 4, HCl, and HNO 3 at solution temperatures of 30 °C, 50 °C, and 70 °C. Different reaction times ranging from 5 min to 120 min were also investigated in order to maximize the extraction efficiency.