Kinetic study of photodegradation of water soluble polymers

The kinetic models of the photo-oxidative degradation of water-soluble polymers, as the main component of water-soluble composite films in aqueous solutions, by ultraviolet radiation and hydrogen peroxide (UV/H2O2) are developed. The rate expressions of the photochemical degradation of soluble polymers are developed based on the mass balance of the main chemical species in water. Continuous-distribution kinetics is applied for the kinetic modeling of the photo-oxidative degradation of polymers in aqueous solutions based on the population balance equations (PBEs). It is assumed that the random chain scission is the mechanism of the chain cleavage. The PBEs are solved by the moment operation which transforms the integro-differential equations into ordinary differential equations that could be readily solved to obtain the rate coefficients of the polymer photodegradation. The model predictions for the number average molecular weight and the number of chain scissions per molecules are in good agreement with the experimental data obtained from the open literature for the photodegradation of poly(ethylene glycol) by the UV/H2O2 process in aqueous solution. The results confirmed the random chain scission assumption. The sequential quadratic programming was used as an optimization technique to find the kinetic parameters that could be used for scaling-up purposes.