Toxicity evaluation of phenol by-products resulted from degradation of phenol by Fe (III)-doped TiO2/UV process

The objective of this study was the evaluation of phenol toxicity and by-products resulted from its degradation by Fe (III)-doped TiO2/UV process. 10 mg/L of phenol solution was manipulated for degradation by Fe (III)-doped TiO2 (synthesized by sol-gel method) under UV ray. By-products detected using GC-MS. In order to toxicity assessment of phenol by-products, the effluent was used in bioassay tests performed using Daphnia magna at 24, 48, 72, and 96 h exposure and 50% lethal concentration (LC50) was determined using probit analysis in SPSS ver. 16.0 software. Results indicated that after 210 min, phenol concentration was decreased to 1.022 mg/L. Detected by-products consisted of catechol, resorcinol, hydroquinone, glycerol, glutaric acid, oxalic acid, 1,2,3-benzenetriol, phenol, acetic acid, and E-2-butenedioicacid. According to the obtained values of LC(50)s, the effluent toxicity was 6-9-fold higher than that of initial phenol solution at all of the exposure times. Results of the present study confirmed that the by-products of phenol oxidation by Fe(III)-doped TiO2/UV may introduce more toxic effects on Daphnia magna and this phenomenon should be considered in the future applications.