Nucleation gypsum

A. D. Randolph and D. Etherton, Study of Gypsum Crystal Nucleation and Growth Rates in Simulated Flue Gas Desulfurization Eiquors, EPRI Report CS1885, Electric Power Research Institute, Palo Alto, Calif., 1981. 

At the prevailing pH in the Namibian groundwaters, the predicted solubility of carnotite is low and close to saturation. From one hole in the Tubas deposit, carnotite saturation is close to 0 and predicted to be over saturated around the water-table zone and in the near-surface upper 2m of the gypcrete. Where Eh is positive carnotite is predicted to be nearsaturation. This indicates that carnotite accumulation at or above the regional water-table can occur by upward diffusion of uranyl carbonate species with possible precipitation due to nucleation on clay minerals or gypsum, as evidenced in the Tubas River. 

Etherton studied the growth and nucleation kinetics of gypsum crystallization from simulated stack gas liquor using a one-liter seeded mininucleator with a Mixed Suspension Mixed Product Removal (MSMPR) configuration for the fines created by the retained parent seed. The effect of pH and chemical additives on crystallization kinetics of gypsum was measured. This early fundamental study has been the basis for later CSD studies. 

Measurements were undertaken of the solubility of each phase in acid solutions, of the growth rate of gypsum crystals and the dissolution rate of hemihydrate. The growth rate depends on the square of the supersaturation and on temperature with an activation energy of 64 kJ/mol. The nucleation rate appears to vary linearly with supersaturation. 

Crystallization from supersaturated solutions can occur by two processes, formation of new crystals or nucleation and growth on existing crystals. The internal surfaces of the scrubber can provide nucleation sites, thus resulting in scale formation. For many crystal systems, growth will occur without nucleation if suflBcient seed crystals are provided. Work by other investigators (3) has shown that supersaturated calcium sulfate solutions can be effectively desupersaturated by circulation of 1-5% gypsum seed crystals. 

Cody, R.D. Cody, A.M. (1988) Gypsum nucleation and crystal morphology in analog saline terrestrial environments. Journal of Sedimentary Petrobgy 58, 247-255. 

A well-mixed flow-through system (Figure 2) was widely used by many researchers (e.g. Raines and Dewers, 1997 Prisciandaro et al, 2001 Reznik et al., 2009) to study gypsum nucleation and dissolution kinetics. In such system, the concentration change of the products with time (mol-kg solution -s ) can be expressed as (Reznik et al, 2009) ... 

Gypsum Nucleation Induction Period and the Surface Free Energy... 

As discussed in section 2.3, the surface free energy of a crystal can be obtained by measuring the nucleation induction period at various supersaturation conditions. He et al. (1994a) investigated gypsum nucleation with NaCl concentration vaiying from 0 to 6 mol/kg... 

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