Inhibitory effect of novel green polymer (Aspartic-citric acid) on the process of nucleation during gypsum scale formation

Abstract

The presence of metal salts in the process fluid in industries leads to scale deposition over the heating or cooling surfaces and causes an significant increase in the overall process and product cost of the product. This further reduces the efficacy of the equipment and the quality of the product is compromised. Hence, in order to avoid this various conventional additives containing nitrogen, phosphorous and sulphur are used as antiscaling agents due to their superior scale inhibition properties. However, excessive use of these antiscalants has created an imbalance in the ecosystem. Hence, there is a necessity to look for more reliable compounds that are as equally efficient as the conventional ones and are eco-friendly, biodegradable and cost effective. In the present study, homo and hetero polymers of aspartic acid and citric acid have been synthesized using condensation method and their antiscaling properties against gypsum deposition is been evaluated. Characterization of the synthesized polymers and deposited scale was performed by FTIR, GPC, SEM and XRD. The polymer showing the highest efficiency in the preliminary screening test was further evaluated to study its effect on the process of nucleation and crystal growth. The synthesized polymers were found to be efficient in inhibiting the scale deposition process at additive concentration as low as 3 ppm. The presence of additive (PAS-co-CA2) increased the induction time, surface free energy of formation, critical nuclei size and number of molecules per critical nuclei. Hence, rate of nucleation was reduced. Molecular weight and functional groups were the crucial factors in determining the scale inhibition properties of the polymer. The process of crystal formation and deposition was significantly retarded in presence of the additive with a change in the crystal morphology of the deposited crystals.