Investigation of CaCO₃ precipitation kinetics using environment-friendly inhibitors based on amide, carboxylic and sulfonic groups in ASTM D1141 standard solution

Calcium carbonate (CaCO3) is the most frequently occurring scaling in process equipment including cooling water systems. In this work, the kinetics of CaCO3 precipitation (CCP) was investigated using chemical method in the absence and presence of green inhibitors including polyacrylic acid homopolymer (PAA), poly maleic acid homopolymer (PMA), polyacrylic acid: 2-acrylamido-2- methylpropane sulfonic acid copolymer (AA/AMPS) and polyacrylic acid:2-acrylamido-2-methylpropane sulfonic acid: t-butyl acrylamide terpolymer (AA/AMPS/TBAA). The effects of the solution composition, temperature, pH, and type of inhibitor agent on the inhibition efficiency were examined. Results showed that increasing immersion time, in a solution without inhibitor, decreased the concentration of Ca2+ and solution pH. However, the inhibitor increased the inhibition efficiency up to 96 h. Also, the effect of temperature was examined on the precipitation kinetic, and it was found that the rate of scaling formation increases with the increase in temperature from 25 to 55 degrees C. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) illustrated that morphology of CCP changed and calcite and aragonite scaling occurred at 55 degrees C under the influence of amide, carboxylic and sulfonic groups of the inhibitors. Moreover, the kinetics scaling in the presence of PMA was investigated by the electrochemical method and was compared with the chemical methods. The results of the chemical method in the current work are more reasonable than the electrochemical method. The study provides new insights into the mineral scaling kinetics by identifying the known parameters dependence of CaCO3 scale formation processes.