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 (R-2 > 0.97) with equilibrium parameters (R-L) 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/m(2), 0.31 mg/m(2), and 0.43 mg/m(2), 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.

Automated summary

This study investigates the adsorption of three types of hydrolysed polyacrylamide (HPAM) with different molecular weights onto calcium carbonate particles. The results show that all three HPAMs can adsorb favorably onto the surface of calcium carbonate, with higher adsorption observed for higher molecular weight polymers. Additionally, the study reveals that the surface charge of calcium carbonate changes upon introducing HPAM within a certain dosage range.