%0 Journal Article
%T Radiolytic degradation of 4-hydroxybenzoate in aerated and deoxygenated aqueous solutions.
%A Albarrán G
%A Mendoza E
%J Water Sci Technol
%V 89
%N 12
%D 2024 Jun
%M 39150419
%F 2.43
%R 10.2166/wst.2024.167
%X The radiolytic degradation of 4-hydroxybenzoate (4-HBA-) in aerated, oxygen-free and N2O-saturated aqueous solutions at concentrations of 0.10 and 0.25 mmol/dm3 were gamma irradiated at different doses in a source of Co-60. The results show that ·OH adds predominantly to the 3 position of the aromatic ring, and elimination of the acid group leads to the degradation of 4-HBA-. With an N2O-saturated 0.10 mmol/dm3 4-HBA- solution, total degradation occurred at 1.6 kGy, and with a 0.25 mmol/dm3 solution, total degradation occurred at 3.5 kGy. In the aerated and oxygen-free 0.25 mmol/dm3 4-HBA- solutions, the behavior was similar, degradation occurring at a dose of 13.1 kGy. At the concentration of 0.10 mmol/dm3, total degradation occurred at 7.0 kGy, with small amounts of radiolytic products and byproducts. We propose a mechanism for the degradation of 4-HBA- caused by water radicals produced in the three environments, leading to formation of the identified stable products. Oxidation was followed by chemical oxygen demand (COD), which decreased as the 4-HBA- concentration increased. The kinetics showed a pseudo-first-order behavior. The rate constant of degradation was similar for the solutions with and without oxygen.