A Novel Debromination of Tetrabromobisphenol A (TBBPA) by Hydrothermal Treatment with Reactive Minerals

Abstract

Tetrabromobisphenol A (TBBPA) is widely used as a flame retardant and relatively persistent in the environment. There has been increasing interest in the developing alternative approach for its degradation and debromination. In this study, we explored the debromination of TBBPA by alkaline hydrothermal treatment with reactive minerals, namely iron powder, layered double hydroxide (LDH) and gibbsite. The effects of hydrothermal temperatures and time, the initial TBBPA concentrations, and additive amounts of reactive minerals on debromination were investigated. As a comparison, the conventional hydrothermal treatment with no additive as the control group was included. The UV-vis absorption spectra of TBBPA before and after debromination were studied as well. The results showed that increasing temperature was helpful for the improvement of debromination. It significantly increased by 223.5, 54.3 and 78.1% with increasing temperature from 140 to 160 °C for the control, iron power and LDH groups, respectively. When the hydrothermal time was shorter than a critical value, the debromination rate increased with time rising. A maximum rate of 79.9% was achieved for iron powder group after reaction for 8 h. The preferred initial TBBPA concentration was determined as 60 ppm for all groups. The optimum amounts of reactive minerals were not consistent and determined as 0.08 g for iron powder, 0.32 g for LDH and 0.16 g for gibbsite, respectively. The maximum absorption bands of TBBPA increased as the pH was raised. They were located at 209 and 308 nm for neutral TBBPA and increased to 211 and 311 nm for TBBPA-Na2CO3. New absorption bands in the wavelength region of 225-275 and 300-350 nm were observed, when TBBPA was subjected to hydrothermal treatment. Keywords: Brominated flame retardants (BFRs); tetrabromobisphenol A (TBBPA); debromination; hydrothermal treatment; UV-vis absorption spectra