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Effect of pH on the aluminum salts hydrolysis during coagulation process: Formation and decomposition of polymeric aluminum species

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Abstract.
Effect of pH on the aluminum chloride hydrolysis at low concentration was investigated in detail by
electrospray ionization (ESI) mass spectrometry. In particular, formation and decomposition processes of
polymeric aluminum species were discussed. When coagulant AlCl3 was diluted to normal coagulant
dose (1.5×10−4 mol/L), hydrolysis occurred immediately. Monomeric and dimeric aluminum species
were the main products at pH 4.0. With pH increasing, hydrolysis and polymerization processes
were accelerated. Monomeric and dimeric aluminum species hydrolyzed and polymerized into small
polymeric aluminum species (Al3–Al5 species) at pH 4.8. Through aggregation and self-assembly, the
small polymeric aluminum species polymerized into median polymeric species (Al6–Al10 species) at
pH 5.0. In the same way, small and median polymeric aluminum species further aggregated into large
polymeric species (Al11–Al21 species). When pH was up to 5.8, metastable median and large polymers
species decomposed into small aluminum species, then further disaggregated into dimeric species. With
pH increased to 6.4, majority of aluminum species formed to Al(OH)3 amorphous flocs. Accordingly,
coagulant hydrolysis mechanism from polymerization toward decomposition was proposed. Furthermore,
formation and decomposition of polymeric aluminum species in AlCl3 solution followed the “Core-links”
model, while those of Keggin-Al13 species in polyaluminum solution was based on the “Cage-like” model.

Keywords:
Aluminum hydrolysis
ESI MS
Polymeric aluminum species
Coagulant

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Informasi Detail

Judul Seri

Journal of Colloid and Interface Science

No. Panggil

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Penerbit

London : Elsevier Inc.., 2009

Deskripsi Fisik

Journal of Colloid and Interface Science 330 (2009) 105–112

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

Versi lain/terkait

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