A water ionizer (also known as an alkaline ionizer) is an home appliance which claims to raise the pH of drinking water by using electrolysis to separate the incoming water stream into acidic and alkaline components. Proponents claim that consumption of the alkaline stream results in a variety of health benefits, making it similar to the alternative health practice of alkaline diets. Such claims are not accepted in chemistry, physiology, and evidence-based medicine.
Contents
The machines originally became popular in Japan and other Far Eastern countries before becoming available in the U.S. and Europe.
Operation
Despite being described as 'water ionizers' the machines are designed to work as water electrolyzers. This is an electrochemical process in which water is split to form hydrogen and oxygen by an electric current. The overall chemical reaction is shown below:
2 H2O(l) → 2 H2(g) + O2(g)During this process, the water near the anode is acidic while the water near the cathode is alkaline.
2 H2O + 2e– → H2 + 2 OH– (at the cathode) 2 H2O → 4e− + O2 + 4 H+ (at the anode)Water ionizers work by simply siphoning off the water near the cathode. Water siphoned off the cathode side contains increased levels of hydroxide (OH−) and would be expected to have a higher pH (i.e. be more alkaline), whereas water siphoned off near the anode would have increased levels of H+ making it acidic. The acidic water is claimed to be useful for household disinfecting.
The effectiveness of the process is debatable because electrolysis requires significant amounts of time and power; hence, the amount of hydroxide that could be generated in a fast moving stream of water such as a running tap would be minimal at best. Additionally, the process of reversing the reaction requires much less energy, so if the area between the alkaline and acidic water is at least semi-permeable, the water will undergo another reaction that just leaves neutral water. The second reaction is shown below:
H+ + HO− → 2 H2OSimilar machines have been used to produce electrolyzed water which is chemically much different because it also contains sodium hypochlorite, the main ingredient in bleach, and may therefore be used as a disinfectant.
Health claims
Water ionizers are often marketed on the basis of health claims which are normally focused on their putative ability to make water more alkaline. A wide variety of benefits have been claimed, including the ability to slow ageing, prevent disease, offer protection from nuclear fallout, give the body more energy, and offset the effects of acidic foods.
There is no empirical evidence to support these claims, nor the claims that drinking ionized water will have a noticeable effect on the body. Drinking ionized water or alkaline water does not alter the body's pH due to acid-base homeostasis.