Silicate removal in aluminum hydroxide co-precipitation process

Chiharu Tokoro*, Shinya Suzuki, Daisuke Haraguchi, Sayaka Izawa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


The removal mechanisms of silicate using an aluminum hydroxide co-precipitation process was investigated and compared with an adsorption process, in order to establish an effective and validated method for silicate removal from wastewater. Adsorption isotherms, XRD and FT-IR analyses showed that silicate uptake occurred by adsorption to boehmite for initial Si/Al molar ratios smaller than two, but by precipitation of poorly crystalline kaolinite for the ratios larger than two, in both co-precipitation and adsorption processes. Silicate was removed by two steps: (i) an initial rapid uptake in a few seconds; and (ii) a slow uptake over several hours in both processes. The uptake rate in the first step was higher in the co-precipitation process than in adsorption process, presumably due to increased silicate adsorption to boehmite and rapid precipitation of kaolinite. These results suggest that silicate removal using aluminum salts could be effectively achieved if the pH adjustment and aluminum concentration are strictly controlled.

Original languageEnglish
Pages (from-to)1084-1096
Number of pages13
Issue number2
Publication statusPublished - 2014


  • Adsorption
  • Aluminum hydroxide
  • Boehmite
  • Co-precipitation
  • Kaolinite
  • Sorption density

ASJC Scopus subject areas

  • Materials Science(all)


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