Influence of polyacrylamide on the precipitation of gypsum in sodium chloride solutions

• Published in: Environmental earth sciences Vol. 82; no. 23; p. 565
• Main Authors: Kistanova, Natalya S., Chashchukhina, Anna D., Kudryashova, Olga S., Khayrulina, Elena A.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2023; Springer Nature B.V
• Subjects: Biogeosciences; Brines; Calcium; Calcium sulfate; Calcium sulfate dihydrate; Calcium sulphates; Chloride; Chlorine compounds; Crystallization; Crystals; Earth and Environmental Science; Earth science; Earth Sciences; Environmental Science and Engineering; Geochemistry; Geology; Gypsum; Hydrology/Water Resources; Mines; Original Article; Polyacrylamide; Polymers; Porous media; Precipitation; Rocks; Salt; Salts; Sodium; Sodium chloride; Soil contamination; Soil formation; Soil porosity; Soils; Solubility; Sulfates; Synergistic effect; Terrestrial Pollution; Gypsum; Supersaturated solutions; Crystallisation inhibitor; Geochemical barrier; Polyacrylamide
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-023-11260-z

Some natural processes can seal porous rocks, cracks, and joints in soil formations. The precipitation of sparingly soluble calcium salts can either stop the flow of brines into mines or isolate particularly contaminated areas. Gypsum (CaSO 4 ‧2H 2 O), which has a low solubility in water (2.6 g/L at 25 °C), creates a long-lasting insulating layer. Natural mineral formation happens very slowly, and only a small amount of the matter gets through the porous medium of soil and rocks. Supersaturated solutions of sparingly soluble calcium salts with crystallisation inhibitors are used to create artificial geochemical barriers that mimic natural processes. This research looks into the effects of PAM and NaCl on the precipitation of calcium sulphate dihydrate from supersaturated solutions. The efficiency of PAM inhibition was confirmed by studying the processes of spontaneous salt crystallisation from 0.15 mol/L CaSO 4 solutions at 25 °C. The presence of both PAM and NaCl in the solution had a synergistic effect. The induction period of gypsum crystallisation in the presence of NaCl required 33 h at a 500 ppm PAM. XRD results proved that the salt precipitated as CaSO 4 ‧2H 2 O. The morphology of gypsum crystals changed in the presence of a polymer in supersaturated solutions.