Preparation of sorbents containing ettringite phase from concrete sludge and their performance in removing borate and fluoride ions from waste water

Yusuke Tsunashima, Atsushi Iizuka, Junichiro Akimoto, Teruhisa Hongo, Akihiro Yamasaki

    Research output: Contribution to journalArticlepeer-review

    26 Citations (Scopus)

    Abstract

    Concrete sludge is an industrial waste slurry containing hydrated cement, aggregates and water. Solid sorbents containing ettringite, Ca6Al2(SO4)3(OH)12·26H2O, were prepared from concrete sludge by adding various amounts of aluminum sulfate to enhance ettringite formation. Anion exchange performance of the sorbents was examined using model waste waters containing boron or fluoride ions. The removal behavior depended on the calcium/aluminum ratio and the heat treatment temperature after drying. For the same Ca/Al ratio, improved removal performance was observed for sorbents treated at higher temperatures. The highest removal capacity was found when the sorbent was prepared with a molar ratio of Ca/Al of 3.2 and heat treatment at 175°C. The final concentrations of boron and fluoride were 6.3mg-B/L, and less than 4mg-F/L for initial concentrations of 100mg-B/L and 300mg-F/L. Treatment of the sorbents at higher temperature dehydrated the ettringite phase to form metaettringite phase. The sorbents prepared in the present study can be used in a boron and fluoride removal process that meets the effluent standard in Japan.

    Original languageEnglish
    Pages (from-to)338-343
    Number of pages6
    JournalChemical Engineering Journal
    Volume200-202
    DOIs
    Publication statusPublished - 2012 Aug 15

    Keywords

    • Boron removal
    • Concrete sludge
    • Ettringite
    • Fluoride removal
    • Waste water treatment

    ASJC Scopus subject areas

    • Chemical Engineering(all)
    • Chemistry(all)
    • Industrial and Manufacturing Engineering
    • Environmental Chemistry

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