Effects of raw water conditions on solution-state aluminum speciation during coagulant dilution

• Published in: Water research (Oxford) Vol. 37; no. 14; pp. 3341 - 3350
• Main Authors: Exall, Kirsten N., vanLoon, Gary W.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-08-2003; Elsevier Science
• Subjects: 27Al NMR; Alum; Alum Compounds - chemistry; Aluminum - chemistry; Applied sciences; Colloids; Drinking water and swimming-pool water. Desalination; Exact sciences and technology; Magnetic Resonance Spectroscopy; Organic Chemicals; Organic matter; Pollution; Prehydrolyzed coagulants; Sulfate; Temperature; Water Purification; Water treatment and pollution; Prehydrolyzed coagulants; Temperature; Organic matter; Sulfate; Alum; 27Al NMR; Polyelectrolyte; Drinking water treatment; Suspended particle; Flocculation reagent; Flocculation; Speciation; Aluminium sulfate
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/S0043-1354(03)00229-X

The speciation of aluminum in solutions of alum and various prehydrolyzed, aluminum-based water treatment coagulants was investigated by
27Al NMR at 5°C and 25°C. Alum solutions were seen to contain only mononuclear species including an AlSO
4
+ complex, while the prehydrolyzed coagulant solutions contained polynuclear aluminum species, as well. The relative proportions of both polynuclear species and AlSO
4
+ complex decreased in cold water. The presence of organic matter had little effect on the speciation of aluminum in diluted alum, but markedly reduced the relative proportion of the tridecamer species in the prehydrolyzed coagulant solutions. The relationship between Al speciation in the coagulants and organic matter removal during jar tests was considered, and the possible role of sulfate in both the formation of the tridecamer species and the effect of organic matter on coagulation efficiency was discussed.