Treatment of Polyacrylamide-Containing Wastewater by Ionizing Radiation: Efficient Reduction of Viscosity and Degradation of Polyacrylamide

Abstract

Polyacrylamide is one of the most widely used polymer to enhance oil recovery in oilfield, leading to generation of a large amount of partially hydrolyzed polyacrylamide (HPAM)-containing wastewater, with high viscosity and emulsification, making the oil droplets and particles in the wastewater stable and difficult to remove. In present work, ionizing radiation was applied to decompose HPAM, thus to reduce the viscosity of HPAM-containing wastewater. During gamma irradiation, at 1.0 kGy the viscosity of HPAM solution declined rapidly, from 5.2-12 mPa to 1.1-1.6 mPa, which was not obviously affected by the initial HPAM concentration and pH, while the value of zeta potential also declined rapidly. The removal efficiency of HPAM was 62-78% at 10 kGy when its concentration was 250-1000 mg/L. The molecular weight of HPAM declined from 12,000 kDa to 320 kDa at 5 kGy. The radiation might destroy hydrogen bonds of intermolecular and intramolecular HPAM molecules preferentially, leading to the destruction of the curling network structure, thus the reduction of viscosity. The attacks on C-N bond, C-C skeleton, amide and carboxyl groups were also occurred, resulting in the formation of intermediate products, such as aliphatic hydrocarbon, ammonium, ketone, etc. In summary, ionizing radiation is a promising alternative to treat HPAM-containing wastewater.

Keywords: Produced wastewater, polyacrylamide, viscosity, Radiation technology