Synergistic effect of hydrophobic modified Welan gum and sodium alcohol ether sulphate in saline solution

Surfactants are often used to change the structure of natural polysaccharide polymers and improve their properties for industrial applications. However, implementing surfactants to boost the Welan gum has yet to be studied. This study prepared the compound system HWG-A by Sodium alcohol ether sulphate (AES) with hydrophobic modified Welan gum (HWG). Compared with HWG, the critical association concentration of HWG-A they have decreased from 3.8 × 103 mg L-1 to 2.8 × 103 mg L-1. The viscosity of 2 × 103 mg L-1 HWG-A remained at 244 mPa s when the salinity was 96,670 mg L-1. The rheological test showed that HWG-A still maintained the characteristics of pseudoplastic fluid under different polysaccharide concentrations, pH and salinity. The viscoelastic test showed that the elasticity of HWG-A was interdependent with the concentration of polysaccharides. When HWG-A was higher than the critical association concentration, the elasticity dominated the whole system. The temperature resistance test showed that the viscosity of HWG-A was still much higher than that of Welan gum and HWG when the salinity was 19,334 mg L-1 at 140 ℃ and lower than the critical association concentration, and the viscosity remained above 350 mPa s. SEM showed that HWG-A presented a regular large network structure when the concentration was lower than its critical association concentration. Otherwise, HWG-A presented a gel shape. Our study promotes the industrial potential of Welan gum in such as Enhanced Oil Recovery (EOR) process. It suggests that the interaction between surfactants and natural polysaccharides is essential in determining the functional properties of the fluid system.