Journal
JOURNAL OF WATER PROCESS ENGINEERING
Volume 1, Issue -, Pages 54-63Publisher
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jwpe.2014.03.005
Keywords
Aluminium hydroxide; Gibbsite; Metasilicate; Hydroxyaluminosilicate; Zeta potential; Total surface charge
Funding
- Academy of Finland [134278]
- Academy of Finland (AKA) [134278, 134278] Funding Source: Academy of Finland (AKA)
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Interactions of aluminium (1 mM) and silicon (0.1-2 mM) in aqueous solutions were studied at a low ionic strength medium representing fresh water and water treatment process environments, attempting to quantify elemental relationships of the formed precipitates as well as their surface charge properties with a novel combination of analytical techniques. FESEM analyses showed that the Al:Si ratio in the obtained precipitates was clearly affected by the Al:Si ratio in the initial aqueous solution. According to XRD, the precipitates originated from the 1 mM Al and the 1 mM Al + 0.1 mM Si solutions were gibbsite, while for the initial Al:Si ratios equalling to 1:0.5 or higher, only amorphous material was precipitated. Zeta potential decreased as a function of the initial silicon content, and reached negative values at pH 6.2 with the initial concentrations of 1 mM Al + 2 mM Si. In contrast, for the total surface charge, a maximum value was found between pH 4.5 and 5, and it clearly decreased with the amount of silicon present. To conclude, the dissolved silicon had a significant effect on the formation of charged aluminium species. This may have considerable environmental and health effects. A reaction mechanism for the formation of hydroxyaluminosilicates from silicic acid and aluminium hydroxide was proposed. (C) 2014 Elsevier Ltd. All rights reserved.
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