Ultrasound process-enhanced removal of the toxic disinfection by-product bromate from water by aluminum: A comparative study

As bromate removal and reduction can be also achieved using metals, aluminum (Al) appears as the most promising one for reduction of bromate because Al is abundant element and exhibits a high reduction power. Reactions between bromate and Al shall be even enhanced through ultrasound (US) process because US can facilitate mass transfer on liquid/solid interfaces and clean surfaces via generating microscale turbulence to facilitate reactions. Therefore, the aim of this study is for the first time to investigate the effect of US on bromate removal by Al metal. Specifically, Al particle would be treated by HCl to afford HCl-treated Al (HCTAL), which is capable of removing bromate and even reducing it to bromide. Such a mechanism is also validated by density function theory calculation through determining adsorption energy as −152.8 kJ/mole, and oxygen atoms of bromate would be extracted and reacted with Al atoms, releasing bromide ion. US not only facilitated bromate removal by further increasing removal capacity under the acidic condition but also suppressed the inhibitive effect from basicity at relatively high pH. The spent HCTAL could still remove bromate and convert it to bromide after regeneration. These features indicate that US considerably enhances bromate removal by Al. Practitioner points: Bromate removed by Al is elucidated by DFT calculation with E_absorption = −152.8 kJ/mole. Oxygen atoms of bromate are extracted and reacted with Al atoms, releasing bromide ion. A higher power of ultrasound would substantially enhance bromate removal efficiency. Ultrasound also suppresses the inhibitive effect from basicity at relatively high pH. With ultrasound, the interference of co-existing anions on bromate removal is lessened.