Towards enhanced oil recovery: Effects of ionic valency and pH on the adsorption of hydrolyzed polyacrylamide at model surfaces using QCM-D

Adding polymers to the injection water in water-flooding oil recovery increases viscosity and thereby enhances factor. However, beneficial effects are often counteracted by adsorption of polymer ambient mineral surface. In here, we used Quartz Crystal Microbalance with Dissipation (QCM-D) measurements study frequently hydrolyzed polyacrylamide (HPAM), a weak polyelectrolyte, silica alumina model surfaces representing sandstone reservoirs. At pH 6 8 concentrations from 1 mM 100 NaCl CaCl 2 , find that negatively charged HPAM molecules generally adsorb more strongly positively surfaces. For surfaces, presence Ca 2+ ions, which form strong complexes carboxyl groups on polymer, as evidenced titration measurements, adsorption. This effect is attributed formation -mediated ion bridges substrate. Kinetic suggest two-step process consisting primary onto surface followed – most cases slower secondary process, involves rearrangements previously adsorbed molecules, including polymer-on-polymer