Adsorption of Hydrolysed Polyacrylamide onto Calcium Carbonate

Carbonate rock strengthening using chemical techniques is a strategy to prevent excessive fines migration during oil and gas production. We provide herein a study of the adsorption of three types of hydrolysed polyacrylamide (HPAM) of different molecular weight (F3330S, 11-13 MDa; F3530 S, 15-17 MDa; F3630S, 18-20 MDa) onto calcium carbonate (CaCO₃) particles via spectrophotometry using a Shimadzu UV-2600 spectrometer. The results are compared to different adsorption isotherms and kinetic models. The Langmuir isotherm shows the highest correlation coefficient (R² > 0.97) with equilibrium parameters (R) ranging between 0 and 1 for all three HPAMs, suggesting a favorable monolayer adsorption of HPAM onto CaCO₃. The adsorption follows pseudo-second order kinetics, indicating that the interaction of HPAM with CaCO₃ is largely dependent on the adsorbate concentration. An adsorption plot reveals that the amount of HPAM adsorbed onto CaCO₃ at equilibrium increases with higher polymer molecular weight; the equilibrium adsorbed values for F3330S, F3530S and F3630S are approximately 0.24 mg/m², 0.31 mg/m², and 0.43 mg/m², respectively. Zeta potential analysis shows that CaCO₃ has a zeta potential of +12.32 mV, which transitions into negative values upon introducing HPAM. The point of zero charge (PZC) is observed at HPAM dosage between 10 to 30 ppm, in which the pH here lies between 9-10.