Preparation of a salt-thickening polymer by the quaternization of welan gum

Welan gum (WG) is widely used in food, petrochemical, and other industries owing to its excellent thixotropy and water solubility. However, WG is susceptible to high temperatures as well as inorganic cations, resulting in a decrease in its viscosity. Nowadays, modifications and optimization of WG have further expanded its applications. In this work, a cationic welan gum (CWG) biopolymer was developed from WG by introducing quaternary ammonium groups. FTIR results confirmed the partial incorporation of cations into the WG chains. Moreover, the degree of substitution calculated based on the elemental analysis and molecular weight results correlated positively with the viscosity. Furthermore, the rheological properties, viscoelasticity, temperature resistance, and salt resistance of WG and CWG solutions were investigated and compared with those of polyacrylamide. It was observed that the viscosity of CWG was increased by 45-120% compared to that of WG. In high-temperature and high-salt environments, the viscosity of CWG increased by 2-5 times compared to that of WG and 4-14 times compared to that of HPAM. Thus, CWG showed superior temperature and salt resistance, especially in high-salinity solutions. This indicates that CWG is a ideal candidate for tertiary oil recovery in high-temperature and high-salt conditions.