Effect of monovalent/divalent ions and SiO2-based nanocomposite dosage on thermochemical stability of HPAM polymeric solutions

Abstract

This study evaluated the effect of monovalent and divalent ions and the dosage of a SiO₂-based nanocomposite on the thermochemical stability of HPAM polymeric solution. Chelating amine–functionalized NPs (AFNPs) were used to enhance the thermochemical stability of HPAM based on capturing monovalent/divalent ions after seven days at 70°C. Different polymer solutions prepared with calcium chloride dihydrate (CaCl₂·2H₂O) at 2000 mg/L and sodium chloride (NaCl) at 10000 mg/L, and two different dosages of HPAM (1000 and 2000 mg/L) were assessed in the presence and absence of AFNPs at dosages of 200, 500 and 1000 mg/L. The nanocomposite was characterized by N₂ adsorption, Fourier-transformed infrared spectrophotometry (FTIR), thermogravimetric analysis (TGA), dynamic Light Scattering (DLS), and Zeta potential (ZP). Stability tests over time confirmed the positive effect of nanocomposite on increasing the thermochemical stability of polymer solutions. Results revealed that adding 0, 200, and 500 mg/L of nanocomposite to the polymeric solution at 1000 mg/L of HPAM, 10000 mg/L of NaCl, and 2000 mg/L of CaCl₂·2H₂O led to the viscosity reductions of 73.5%, 18%, and less than 1% after 7 days (70°C), respectively. Nanocomposite at 200 mg/L reduces the polymer degradation in the presence of the two salts evaluated separately, i.e., 20% for 10000 mg/L of NaCl and 15% for 2000 mg/L of CaCl₂·2H₂O. The adsorption tests on AFNPs and SiO₂ NPs concluded that AFNPs had higher adsorption of cations in comparison to SiO₂ NPs and that greater adsorption of cations is related to a reduction in polymer degradation.