Fe–Al layered double hydroxides in bromate reduction: Synthesis and reactivity

This study presents a rare use of layered double hydroxides of Fe(II) and Al(III) (Fe–Al LDH), as reported for the first time for bromate removal from aqueous solutions. The Fe–Al LDH samples were prepared with Fe/Al molar ratios of 1–4 using a co-precipitation method at pH 7, with subsequent hydrothermal treatment at 120 °C. The Fe–Al LDH (molar ratio of Fe/Al = 1, 2) with a layered structure exhibited nearly complete removal of bromate from initial concentration of 100 μmol/dm3 at a wide pH range of 4.0–10.5 over a 2 h reaction period; the residual bromate concentration in the solution was lower than the detection limit of 0.07 μmol/dm3 (9μg-BrO3-/dm3). During the reaction period, bromide was released into the solution via a reduction process. Reactivity of Fe–Al LDH with a Fe/Al molar ratio of 2 did not decrease the bromate reduction efficiency during 30 days.

BrO3- (100 μmol/dm3) was completely removed on Fe–Al LDH via reduction process releasing Br−, and LDH structure was collapsed due to oxidation of Fe2+ to Fe3+ releasing interlayer Cl−.Figure optionsDownload high-quality image (79 K)Download as PowerPoint slideResearch highlights
► Rare use of Fe–Al LDH as reported first time for bromate removal.
► Initial bromate concentration of 100 μmol/dm3 can be decreased to below 0.078 μmol/dm3 (10μg-BrO3-/dm3) within 1–2 h.
► Presence of chloride, nitrate, sulfate, phosphate and carbonate did not affect bromate removal.
► Reduction of bromate to bromide in solution and oxidation of Fe2+ to Fe3+ in solid were occurring simultaneously, with collapse of LDH structure.