Simultaneous uptake of ammonium and phosphate ions by compounds prepared from paper sludge ash

Kiyoshi Okada, Yosuke Ono, Yoshikazu Kameshima, Akira Nakajima, Kenneth J.D. MacKenzie

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27 Citations (Scopus)


Al-containing CaO-SiO2-H2O phases were prepared by hydrothermal treatment of mixtures of paper sludge ash (PSA) with various silica and calcia sources and their properties were determined with particular reference to the simultaneous uptake of ammonium and phosphate ions, which are implicated in the eutrophication of lakes and ponds. After examination of various silica and calcia sources, Ca(OH)2 and SiO2 sol were selected as the most appropriate starting materials. Dry milling was found to be superior to wet milling in avoiding contamination from the milling media during mixing. Nine samples with three different Ca/Si ratios and Al2O3 contents were prepared with various mass ratios of Ca(OH)2, PSA and SiO2. The chemical compositions of the hydrothermal products of these mixtures moved towards the tieline of CaSiO3-PSA, with respect to the starting compositions. The major phase formed in all samples was poorly crystalline C-S-H(I), with hydroxysodalite also formed in the Al-containing mixtures. All the products showed a capacity for the simultaneous uptake of ammonium and phosphate ions. The saturated sorption capacities calculated from the Langmuir equation ranged from 0.9 to 2.4 mmol/g for the ammonium ion and from 3.3 to 5.2 mmol/g for the phosphate ion. Since the sorption capacities for both ions increased with increasing Ca contents of the product, substitution of Ca2+ for NH4+ and the formation of calcium phosphate phases such as apatite and brushite by precipitation are thought to be the main sorption mechanisms.

Original languageEnglish
Pages (from-to)622-629
Number of pages8
JournalJournal of Hazardous Materials
Issue number3
Publication statusPublished - Mar 22 2007
Externally publishedYes


  • Ammonium ion
  • CaO-SiO-HO phase
  • Eutrophication
  • Paper sludge ash
  • Phosphate ion
  • Simultaneous uptake

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution
  • Health, Toxicology and Mutagenesis


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