Low-Dosage Viscosity Breakdown and Mechanistic Insights into Cu-MOF-74/PMS Degradation of High-Concentration Polyacrylamide

Abstract

The high viscosity of oilfield produced water caused by high-concentration polyacrylamide (PAM) readily leads to quartz sand filter clogging, necessitating efficient viscosity reduction during the sedimentation stage.This study employed hydrothermally synthesized Cu-MOF-74 to activate peroxymonosulfate (PMS) for efficient PAM degradation and viscosity breakdown. Characterization via SEM, XRD, and XPS confirmed the successful synthesis and stable structure of the catalyst. Under the conditions of a low dosage of 7 mg/L Cu-MOF-74, 0.2 mmol/L PMS, and 20°C, a viscosity reduction rate of 91.59% was achieved after just one hour of reaction. Quenching tests and in-situ EPR revealed that singlet oxygen and hydroxyl radicals were the primary reactive species, followed by sulfate and superoxide radicals. Analyses including UV-Vis, Zeta potential, and COD indicated that the viscosity reduction originated from the cleavage of PAM chains. Py-GC/MS analysis of intermediate products elucidated a stepwise degradation pathway involving main-chain scission, side-chain transformation, and generation of small molecules.