Effective degradation of hydrolyzed polyacryamide (HPAM) in a simultaneous combination of acoustic cavitation and microbubbles ozonation: Process optimization and degradation mechanism

Abstract

Managing environmental contamination with hydrolyzed polyacryamide (HPAM) is essential due to its persist long with slow biodegradability influence on the environment. In this study, the simultaneous combination of acoustic cavitation and microbubbles ozonation (US/O3) was applied to generate additional highly reactive hydroxyl radicals (·OH) and thus to enhance the degradation of HPAM. Compared with the two separated degradation process methods, the coupled method exerts a synergistic effect on the decomposition of HPAM, with an enhancement factor of 1.50. Effects of aeration pattern, ultrasound irradiation, operating temperature, initial HPAM concentration, and valance state of cations on the removal of HPAM were investigated intensively. An increase in valance state of cations contributes to HPAM removal. The maximum HPAM degradation, chemical oxygen demand (CODcr) removal and viscosity reduction of the HPAM wastewater were 97.35%, 89.01% and 93.25%, respectively. The degradation of HPAM conformed to the first-order reaction kinetic model. Removal of HPAM followed hydroxyl radical mechanism. The degradation mechanism of HPAM was also discussed with the change of FTIR and UV–Visible spectra of HPAM in investigated processes. The main reaction intermediates, such as heptanoic anhydride, oleamide, myristamide, acetic acid, acetamide, and propanamide, are identified and a possible degradation pathway is proposed during the US/O3 process. The process was proved to be a suitable technique for dealing with HPAM-containing wastewater.