Aluminium chlorohydrate is a group of specific aluminium salts having the general formula AlnCl(3n-m)(OH)m. It is used in deodorants and antiperspirants and as a coagulant in water purification.
In water purification, this compound is preferred in some cases because of its high charge, which makes it more effective at destablizing and removing suspended materials than other aluminum salts such as aluminum sulfate, aluminum chloride and various forms of polyaluminum chloride and polyaluminum chlorisulfate, in which the aluminum structure results in a lower net charge than aluminum chlorohydrate. Further, the high degree of neutralization of the HCl results in minimal impact on treated water pH when compared to other aluminum and iron salts.
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Aluminium chlorohydrate is best described as an inorganic polymer and as such is difficult to structurally characterise. However, techniques such as gel permeation chromatography, X-ray crystallography and 27Al-NMR have been used in research by various groups including that of Nazar[1] and Laden[2] to show that the material is based on Al13 units with a Keggin ion structure and that this base unit then undergoes complex transformations to form larger poly-aluminium complexes.
Aluminium chlorohydrate can be commercially manufactured by reacting aluminium with hydrochloric acid. A number of aluminium-containing raw materials can be used, including aluminium metal, alumina trihydrate, aluminium chloride, aluminium sulfate and combinations of these. The products can contain by-product salts, such as sodium/calcium/magnesium chloride or sulfate.[3]
Because of the explosion hazard related to hydrogen produced by the reaction of aluminium metal with hydrochloric acid, the most common industrial practice is to prepare a solution of aluminium chlorohydrate (ACH) by reacting aluminium hydroxide with hydrochloric acid. The ACH product is reacted with aluminium ingots at 100 °C using steam in an open mixing tank. The Al to ACH ratio and the time of reaction allowed determines the polymer form of the PAC n to m ratio.
The variation most commonly used in deodorants and antiperspirants is Al2Cl(OH)5. Aluminium chlorohydrate is one of the most common active ingredients in commercial antiperspirants [4] and is also often used as a flocculant in water treatment stations.
There have been studies that have found an association between exposure to aluminium and long-term use of antiperspirants and Alzheimer's disease, however the studies also have shown that the association is negligible (less than 1%).[5] As of yet, there is no adequate evidence that neurotoxicity of aluminium leads to progressive dementia and Alzheimer's disease.[6]
Heather M. Snyder, PhD, the senior associate director of medical and scientific relations for the Alzheimer's Association, has stated "There was a lot of research that looked at the link between Alzheimer's and aluminum, and there hasn't been any definitive evidence to suggest there is a link".[7]
The International Journal of Fertility and Women's Medicine found no evidence that certain chemicals used in underarm cosmetics increase the risk of breast cancer.[8] Ted S. Gansler, MD, MBA, the director of medical content for the American Cancer Society, stated "There is no convincing evidence that antiperspirant or deodorant use increases cancer risk".[9]
The European Journal of Cancer Prevention stated "underarm shaving with antiperspirant/deodorant use may play a role in breast cancer."[10] The journal Breast Cancer Research proposed a link between breast cancer and the application of cosmetic chemicals in the underarm, including aluminium, with oestrogenic and/or genotoxic properties.[11] Personal care products are potential contributors to the body burden in aluminium and newer evidence has shown that more aluminum is deposited in the outer regions than the inner regions of the breast. But whether differences in the distribution of aluminium are related to higher incidence of tumours in the outer upper region of the breast remains unknown.[12]
Aluminium chlorohydrate is also used as a coagulant in water and waste water treatment process to remove dissolved organic matter and colloidal particles present in suspension.
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