Formation of bromoform in irradiated titanium dioxide suspensions with varying photocatalyst, dissolved organic carbon and bromide concentrations

We report the formation of bromoform in TiO2 suspensions (P25) under simulated solar UV irradiation at different concentrations of photocatalyst (0.5–1.5 g L−1) as well as initial concentrations of bromide ions (1–3 mg L−1) and 2,4-dihydroxybenzoic acid (2–10 mg L−1). The extent of bromoform formation (3–17 μg L−1) was most strongly affected by the amount of photocatalyst present and by the initial bromide concentration, increasing either of which leads to increased bromoform formation. Important interaction effects were observed when simultaneously increasing the concentrations of TiO2 and bromide as well as of bromide and DHBA. The time it takes for bromoform to appear in measurable concentrations in the irradiated TiO2 suspensions was between 10 and 90 min and most strongly depended on the initial concentration of dissolved organic carbon present in the suspensions, along with the amount of photocatalyst, also in interaction with the initial bromide concentration.