Bromide removal and recovery with layered double hydroxides as an adsorbent

Grignard regents have been applied extensively in chemical industry, especially in pharmacy. A mass of bromide-containing wastewater was produced after reaction, and ozonation of these organic contaminants can produce bromate and other brominated pollutants. The US Environmental Protection Agency （EPA） has established a maximum contaminant level of 10 μg/L for bromate in finished water. Therefore, it is necessary and significant to remove the DBP （disinfection by-products） precursor - bromide. On the other hand, since the bromine is a valuable element, recovery of it from wastewater is significant. Bromide removal is important to control DBP （disinfection by-products） contaminant and an ion exchange process is one of several treatment processes for this purpose. Layered double hydroxides （LDHs） are useful as adsorbents for bromide removal because of theft ion exchange properties. In this study, the adsorption properties of LDHs for bromide and the method of regeneration of this material were examined. It has been found that the LDHs with Mg/Al molar ratio of 2 represented the highest capacity to remove bromide ion from aqueous solution at pH 6.0. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation. Bromide adsorbed on the LDHs was effectively desorbed at 30% Na2CO3 solution and the LDHs were regenerated at the same time. The regenerated LDHs could be reused repeatedly for the bromide removal. Bromide in the exhausted desorption solution was recovered as bromine by oxidation using Cl2.

Bromide removal and recovery with layered double hydroxides as an adsorbent