Intensified depolymerization of aqueous polyacrylamide solution using combined processes based on hydrodynamic cavitation, ozone, ultraviolet light and hydrogen peroxide

Abstract

The present work deals with intensification of depolymerization of polyacrylamide (PAM) solution using hydrodynamic cavitation (HC) reactors based on a combination with hydrogen peroxide (H2O2), ozone (O3) and ultraviolet (UV) irradiation. Effect of inlet pressure in hydrodynamic cavitation reactor and power dissipation in the case of UV irradiation on the extent of viscosity reduction has been investigated. The combined approaches such as HC+UV, HC+O3, HC+H2O2, UV+H2O2 and UV+O3 have been subsequently investigated and found to be more efficient as compared to individual approaches. For the approach based on HC+UV+H2O2, the extent of viscosity reduction under the optimized conditions of HC (3 bar inlet pressure)+UV (8 W power)+H2O2 (0.2% loading) was 97.27% in 180 min whereas individual operations of HC (3 bar inlet pressure) and UV (8 W power) resulted in about 35.38% and 40.83% intrinsic viscosity reduction in 180 min respectively. In the case of HC (3 bar inlet pressure)+UV (8 W power)+ozone (400 mg/h flow rate) approach, the extent of viscosity reduction was 89.06% whereas individual processes of only ozone (400 mg/h flow rate), ozone (400 mg/h flow rate)+HC (3 bar inlet pressure) and ozone (400 mg/h flow rate)+UV (8 W power) resulted in lower extent of viscosity reduction as 50.34%, 60.65% and 75.31% respectively. The chemical structure of the treated PAM by all approaches was also characterized using FTIR (Fourier transform infrared) spectra and it was established that no significant chemical structure changes were obtained during the treatment. Overall, it can be said that the combination of HC+UV+H2O2 is an efficient approach for the depolymerization of PAM solution.

Polyacrylamide degradation and its implications in environmental systems

“…122 The ozone molecule is extremely unstable in the presence of UV, releasing oxygen and forming hydrogen peroxide after reaction with water. 123 Ozone degrades PAM via free radical induced chain scission as described previously. 123 Ozonation at a concentration of 3.0 mg/L (w/v) leads to an 80% reduction in the MW of PAM within 15 min at pH 3.…”

“…123 Ozone degrades PAM via free radical induced chain scission as described previously. 123 Ozonation at a concentration of 3.0 mg/L (w/v) leads to an 80% reduction in the MW of PAM within 15 min at pH 3. Suziki et al 117 also demonstrated that acrylamide monomer could be almost completely degraded after 30 min of exposure to ozone at pH 6.…”

Microwave‐assisted degradation of chitosan with hydrogen peroxide treatment using Box‐Behnken design for enhanced antibacterial activity

“…The biological activities of chitosan, including anticancer, antimicrobial and scavenging reactive oxygen species, were influenced by the degree of deacetylation (DDA) and MM of chitosan (Czechwska-Biskup et al, 2012;Pastor et al, 2013). To improve its solubility and biological properties, several methods including chemical (oxidative and acidic degradation) (Tsao et al, 2011;Prajapat & Gogate, 2016a), physical (irradiation treatment) (Yue et al, 2009;Fiamingo et al, 2016;Prajapat & Gogate, 2016b) and enzymatic treatment (Mengibar et al, 2011) were employed to prepare low MM of chitosan with high DDA without altering its chemical structure. The physical methods used alone had many drawbacks such as an expensive apparatus, irregular degradation rate and long reaction time.…”

Investigation of a polyelectrolyte degradation with viscometry

“…In addition, cavitation results in sonophysical effects such as shear forces, velocity gradients, microstreaming, micro-jets and shock waves. [17][18][19] The first effect of applying US to polymer solutions (sonication) is polymer degradation (polymer-chain scission). Solvodynamic forces resulting from the cavitation cause the polymer chain to become divided and the molecular weight to decrease.…”