Application of cold plasma technology for the simultaneous degradation and viscosity removal of polyacrylamide and its copolymers from contaminated wastewater.

Polyacrylamide and its copolymers are routinely employed for polymer flooding, generating an emulsifying and highly viscous wastewater that warrants enhanced treatment due to its recalcitrant nature. Herein, a falling-film dielectric barrier discharge (DBD) plasma reactor was used to examine the simultaneous viscosity removal and degradation of polyacrylamide (PAM), hydrolyzed, and cationic polyacrylamide (HPAM and CPAM) wastewater. The reactor conditions (pH: 6.3, airflow rate: 3 L/min, power: 200 W, recirculation flow rate: 150 mL/min, treatment time: 20 min) led to about 45% degradation and an approximately 48% viscosity removal ratio for the polymers. The recirculation and atomizing of the solution at the nozzle ensured a uniform mixture exploiting the falling-film effect of the reactor. The indispensable role of the radicals in the plasma treatment process was confirmed by scavenger tests, with hydroxyl and superoxide radicals influencing the polymer degradation process. The degradation of the polymers and viscosity removal increased 2 folds following the 1st order kinetics when the initial pH was adjusted to 3. The degradation and viscosity removal ratios for PAM, HPAM, and CPAM were 94.33%, 92.54%, and 90.66%, respectively, and 98.58%, 97.01%, and 97.01%, respectively, with an energy yield of 14.114, 13.813 and 13.513 g/kW∙h for PAM, HPAM, and CPAM, respectively. The results will be a requisite reference for implementing the DBD technology in wastewater treatment.