Radiolytic oxidation and degradation of 2,4-dichlorophenol in aqueous solutions

• Published in: Environmental science and pollution research international Vol. 26; no. 17; pp. 17055 - 17065
• Main Authors: Albarrán, Guadalupe, Mendoza, Edith
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.06.2019; Springer Nature B.V
• Subjects: 2,4-Dichlorophenol; Aeration; Aquatic Pollution; Aqueous solutions; Aromatic compounds; Atmospheric Protection/Air Quality Control/Air Pollution; Biological Oxygen Demand Analysis; Chemical attack; Chemical oxygen demand; Chemical reduction; Chlorophenols - analysis; Chlorophenols - radiation effects; Degradation; Dependence; Earth and Environmental Science; Ecotoxicology; Electron density; Environment; Environmental Chemistry; Environmental Health; Environmental science; Gamma Rays; Irradiation; Kinetics; Nitrous oxide; Organic chemistry; Oxidation; Oxidation-Reduction; Oxygen; Radiation; Radiation effects; Reaction kinetics; Research Article; Solutions; Waste Water Technology; Water Management; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - radiation effects; Water Pollution Control; Water Purification - methods; Radiolytic oxidation; 2,4-Dichlorophenol; Radiation-induce degradation; Chemical oxygen demand; Radiolytical yield; Hydroxyl radical
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-019-04845-4

Radiolytic oxidation of 2,4-dichlorophenol (2,4-DClP) in aqueous solutions demonstrated that ·OH predominantly adds to the unsubstituted positions of the aromatic ring and that elimination of chloride at the 4 position is important because the –OH group enhances the electron density at this position, which is favorable for the electrophilic reactions. The total yield obtained was 0.540 μmol/J. Radiation-induced degradation of 2,4-DClP was conducted in oxygen-free aqueous solutions (0.1, 0.25, 0.50, and 0.7 mmol/dm 3 ), saturated with N 2 O, and aerated and under irradiation at low and high doses. The results demonstrate that the largest degradation occurred in oxygen-free solutions due to oxidation (·OH) and reduction reactions (H· and e aq − ) and attack of the e aq − at the ipso position of –Cl, producing HCl. The degradation was affected to a large extent by the concentration and to a lesser extent by the presence or absence of oxygen in which the 2,4-DClP solution was irradiated. At concentrations less than 1 mmol/dm 3 , 2,4-DClP was degraded in the solution at an absorbed dose level of 1 kGy. At higher doses, the product concentrations increased to up to 30% of the dose required for the total degradation of 2,4-DClP; then, they decreased. A graph plotting the logarithm of the relative concentration as a function of the dose shows a linear correlation, which indicates that the radiolytic degradation followed pseudo-first-order reaction kinetics. The oxidation was followed by the chemical oxygen demand (COD). COD decreases when the solute concentration increases. This fact has a dependence on the presence or absence of oxygen too.