Free radical induced degradation of high molecular weight partial hydrolysis polyacrylamide (HPAM) in a ferrous iron containing system

High molecular weight partial hydrolysis polyacrylamide (HPAM) is widely used in the oil recovery, and however, these high molecular weight HPAM will experience a rapid degradation when Fe 2+ was existed in the system. Some studies have implied it was a radical assisted decomposition process. However, no direct evidence had been provided in the reported works. Here, we investigated the effect of different metal ions, and the addition of (2,2,6,6-tetramethylpiperidinooxy) TEMPO to know the polymer degradations of the system. Further, by conducting electron paramagnetic resonance (EPR) on the Fe 2+ /HPAM system, we firstly provide a solid proof of the radical assist degradation process for the HPAM in the presence of Fe 2+ and oxygen. The mechanism has also been provided based on the observations. Graphical abstract The degradation mechanism is first revealed by EPR measurements for a Fe 2+ containing HPAM solution. A solid proof of the radical assists degradation process for the HPAM in the presence of Fe 2+ and oxygen.