Synthesis of Anion-Exchange Materials from Concrete Sludge and Evaluation of Their Ability to Remove Harmful Anions (Borate, Fluoride, and Chromate)

Abstract

Concrete sludge is an industrial waste slurry containing hydrated cement, aggregates, and water. In the current study, anion-exchange materials: ettringite, metaettringite, and Ca-Al layered double hydroxide were synthesized from concrete sludge, and tested to see if they could remove harmful anions (borate, fluoride, and chromate) from solutions. Metaettringite showed high borate and fluoride removal ability, reducing initial concentrations of 100 mg B/L and 300 mg F/L to 6.3 mg B/L and 14.5 mg F/L. The Ca-Al layered double hydroxide showed high fluoride and chromate removal ability, reducing initial concentrations of 300 mg F/L and 180 mg Cr/L to 14.5 mg F/L and 0.4 mg Cr/L.