Degradation of tetrabromobisphenol A by ferrate(VI) oxidation: Performance, inorganic and organic products, pathway and toxicity control

Abstract

This study systematically investigated the degradation of tetrabromobisphenol A (TBBPA) by ferrate (VI) oxidation. The reaction kinetics between ferrate (VI) with TBBPA were studied under pseudo-first-order conditions in the pH range 5.5-10.5. Then, a series of batch experiments were carried out to investigate other factors, including the ferrate (VI) dosage, temperature and interfering ions. Additionally, the generation of inorganic products (bromide ion and bromate) was evaluated. The organic intermediates were identified, and possible pathways were proposed. In addition, the toxicity variation was analyzed with marine luminous bacteria (V. fischeri). Degradation of TBBPA by ferrate (VI) oxidation was confirmed to be an effective and environmentally friendly technique. The reaction was fitted with a second-order rate model. With a ferrate (VI) dosage of 25.25 μmol/L, TBBPA concentration of 1.84 μmol/L, an initial pH of 7.0, and a temperature of 25 °C, a 99.06% TBBPA removal was achieved within 30 min. The evaluation of inorganic products showed that the capacity of ferrate (VI) oxidation to yield bromide ions was relatively strong and could prevent the formation of bromate compared to photocatalytic and mechanochemical techniques. Eleven intermediates were identified, and the proposed degradation pathway indicated that TBBPA might undergo debromination, beta scission, substitution, deprotonation and oxidation. The results of toxicity testing showed that ferrate (VI) could effectively control the toxicity of the treated samples, although the toxicity increased in the initial reaction stage due to the accumulation and destruction of more toxic intermediates.

Keywords: Debromination; Ferrate(VI); Kinetics; Pathways; TBBPA; Toxicity.