Viscosity of polymer solution is one of the key factors which, in some case, notably influence its application effect. However, it has been found that the viscosity drops significantly with sulfide ion. To better understand this phenomenon, the rheological behavior, dynamic light scattering (DLS), and 1H NMR analysis were conducted. The results show that sulfide ion significantly reduced the viscosity of HPAM solution and this reduction was further enhanced under low pH and high O2 content and, more specifically, could not be recovered by dialysis. The polymeric network structure of HPAM formed in water was apparently destroyed and the hydrodynamic radius was reduced by sulfide ion. Furthermore, 1H NMR spectra indicated that the chemical environment of some protons in the methyne group connected to amide group in HPAM was modified by sulfide ion. The interaction between sulfide ion and the amide groups in side chain intra-/inter-molecule of HPAM reduces the hydrodynamic radius and destroys the three dimensional network structure and consequently decreases the viscosity of HPAM solution. These results are helpful for investigating the mechanisms of HPAM-sulfide interaction and optimizing the usage of HPAM for enhanced oil recovery in oil reservoirs with sulfide ions produced by sulfate reducing bacteria.
- Amide group
- Sulfide ion