Rheological Properties and Composition of Products of Phosphogypsum Conversion with Sodium Carbonate.

The study presents results on the dependence of changes in the rheological characteristics (density and viscosity) of the products of phosphogypsum conversion with sodium carbonate on various factors, including temperature, concentration, sodium carbonate rate, stirring duration, and the temperature of the components mixture. Density was determined using the pycnometric method, and viscosity was measured with a VPJ-2 capillary viscometer. An increase in the concentration of sodium carbonate from 5 to 30%, maintaining it at a constant 105% of the stoichiometric rate, leads to an increase in the density and viscosity of the suspension from 1.0813 to 1.3922 g/cm3 and from 0.78 to 3.30 cP at 20°C, and from 1.0514 to 1.3091 g/cm3 and from 0.31 to 1.86 cP at 80°C, respectively. It was shown that increasing the stirring time from 15 to 120 minutes resulted in an average increase in the density and viscosity of the suspension by 1.02 to 1.08 times and 2.20 to 3.07 times, respectively, at 20°C and 80°C. The study revealed that the temperature of the mixture of phosphogypsum and sodium carbonate in the range of 20-90°C significantly increases the density and viscosity from 1.1922 to 1.2381 g/cm3 and from 1.35 to 2.75 cP, respectively, and from 1.1650 to 1.2033 g/cm3 and from 0.50 to 1.77 cP. With a 30-min conversion of phosphogypsum at varying rates (100–110%) and concentrations (10-30%) of sodium carbonate, the degree of phosphogypsum conversion increased from 84.09 to 97.07%. The optimal degree of phosphogypsum conversion (93.94%) was achieved at a sodium carbonate rate of 105% and a concentration of 20%. Experimental data on the rheological properties of the suspension obtained at various rates and concentrations of sodium carbonate showed the possibility of describing these properties using a linear and logarithmic function, with high correlation coefficient values (R2 = 0.95–0.99). The results provide an assessment of the feasibility of easily pumping the suspension in existing industrial equipment. [ABSTRACT FROM AUTHOR]