A water ionizer is an appliance that filters and ionizes water.

How It Works

The Electrolysis device electrolyses the water. This takes place in the electrolysis chamber, which is divided into two compartments by a diaphragm or membrane. One side has positive electrodes (anode) and the other has negative electrodes (cathode). It produces two flows one with a high ORP (at the anode) and the other with a low ORP (at the cathode), it also re-arranges the minerals in the water, according to their electrical charge.

Originally when experiments in Japan began to indicate potential health benefits of reduced water, the original explanations went to the notion of alkalinity, because it was the most obvious property of the cathodic outflow. This theory was advanced among others by Dr. Hidemitsu Hayashi, a cardiologist at Kiowa Hospital. Later, research began to focus on the potential antioxidant properties of the water (Prof. Sanetake Sirahata, of Kyushu University), in collaboration with Dr. Hayashi and others (see also Hydrogen Rich Water Saves Mankind by H. Hayashi M.D. & M. Kawamura M.D., October 1999, Tokyo).

Simultaneously, what happens with the mineral load of the water, is as follows: when the filtered water enters the electrolysis chamber, the negative electrodes attract the positive alkaline minerals to their compartment; while the positive electrodes attract the negative acid minerals to theirs. So one side has only alkaline minerals and the other only acid, at which point alkaline water flows out from the Ionizer’s top outlet, and acid water from the bottom.

In the past it was thought that the alkaline water contains the minerals essential to our health – calcium, magnesium, sodium, potassium and silicon. It was thought that the health benefits flowed from the fact that this water was therefore highly beneficial in neutralizing body acids. Modern understanding focuses however on the antioxidant potential of the reduced water.

Acid water on the other hand can be used in place of hydrogen peroxide and vinegar, e.g. for washing vegetables. It has a shortage of electrons giving it the ability to oxidize and sterilize. It also seems to contain hypochlorous acid, resulting from the oxidation of the chlorine present in the source water, and thus is equally effective for sterilization as water to which a certain proportion of Clorox has been added.

You can use a simple pH test kit to assess the alkalinity or acidity of the water. Most Ionizers include this. You can also test alkaline water's oxidation reduction potential, with an ORP meter.

Criticisms

A common manufacturer's claim is that in non-ionized water, water molecules form tightly bound clusters, and that ionizing water breaks up those clusters. Manufacturers claim that ionized water is more readily absorbed by the body than ordinary water, and that minerals in ionized water are more readily available to the body. There is an element of truth to the first part; water molecules are held together by hydrogen bonding, and (especially in the presence of cations) can form clusters .Critics argue that water ionizers have no permanent effect on water. Water spontaneously self-ionizes to 10^-14 M under normal conditions. If the concentration of these ions is increased (hydroxide and hydronium), then they will react with each other to restore the original concentration. The reaction is very rapid (strong acids and strong bases completely react with each other in seconds, so hydronium hydroxide (or ionized water) should have a half life measured in fractions of a second (or, at best, a few seconds). If the water is removed from normal conditions (e.g. heated) the concentrations may be increased slightly, but not very much, and are reversed when the water is returned to standard conditions. Therefore, water ionizers cannot increase the concentrations of these ions for a significant time, without the addition of oppositely-charged ions, to produce an electrostatically neutral solution.

The above criticism is based on a misunderstanding of the process of ionization. because electrolysis facilitates a split of molecules into separate HO and OH- (Hydroxyl) streams, the 'instantaneous reversion' mentioned above is not correct. reversion to H2) can be easily measured using an Oxidatioon Reduction Meter (ORP) and this demonstrates a slow reversion as Hydroxyl Ions begin to reassociate with atmospheric H2O

A link is often made between consumption of non-ionized water and a medical condition known as chronic cellular dehydration. Another claim is that ionized water is an antioxidant.

Support from Medical Doctors about Safety

The most serious research in the field is from Prof. Sirahata of Japan of Kyushu University (c.f. Electrolyzed-reduced water scavenges active oxygen species, and protects DNA against oxydative damage, in Biochemical and Biophysical Research Communications (BBRC) 237/4.1997). Shirahata's research demonstrates that redox potential of the water does have a value as an antioxidant.

Electrolysis of water

Electrolysis of water is an electrolytic process which decomposes water into oxygen and hydrogen gas due to the flow of electric current. A DC voltage source, such as a battery, is commonly used to induce the flow of electrical current. The voltage of the battery creates a current in the water that is equal to the voltage of the battery divided by the resistance of the water, as per Ohm's law. For water to conduct a substantial electric current, an electrolyte is required to reduce resistance. An electrolysis cell can consist of an electrode or parallel plate design. The former utilizes two or more electrodes, (usually an inert metal such as platinum), submerged in water with electrolyte. The latter utilizes two or more plates, also usually an inert metal, with water situated between them, also with an electrolyte added.

The electric current disassociates water molecules into hydroxide (OH⁻) and hydrogen (H⁺) ions.

In the electrolytic cell, at the cathode (negatively charged electrode), hydrogen ions accept electrons in a reduction reaction that forms hydrogen gas:

Cathode (reduction): 2H₂O(l) + 2e⁻ → H₂(g) + 2OH⁻(aq)

At the anode (positively charged electrode), hydroxide ions undergo an oxidation reaction and give up electrons to the anode to complete the circuit and form oxygen gas:

Anode (oxidation): 2H₂O(l) → O₂(g) + 4H⁺(aq) + 4e⁻

hence decomposing water into oxygen and hydrogen;

Overall reaction: 2H₂O(l) → 2H₂(g) + O₂(g)

The number of hydrogen molecules produced is therefore twice the amount of oxygen molecules. Assuming equal temperature and pressure for both gases, the hydrogen gas has twice the quantity of moles as oxygen.

Spontaneity of the process

Decomposition of water into hydrogen and oxygen at standard temperature and pressure is not favorable in thermodynamical terms, as half of the reaction's standard potential are negative values...

... On the other hand, Gibbs free energy for the process at standard conditions is a higher positive value, about . Those considerations makes the process "impossible" to occur without adding electrolytes in the solution.

Electrolyte selection

Main article: Electrolyte

As pure water conducts electricity very poorly, a water-soluble electrolyte must be added to establish substantial conductivity. The electrolyte dissolves and disassociates into cations and anions (positive and negative ions) that carry the current. Electrolytes are normally acids, bases, or salts.

Care must be taken in choosing an electrolyte, since an anion from the electrolyte is in competition with the hydroxide ions to give up an electron. An electrolyte anion with less standard electrode potential than hydroxide will be oxidized instead of the hydroxide, and no oxygen gas will be produced. A cation with a greater standard electrode potential than a hydrogen ion will be reduced in its stead, and no hydrogen gas will be produced.

The following cations have lower electrode potential than H⁺ and are therefore suitable for use as electrolyte cations: Li⁺, Rb⁺, K⁺, Cs⁺, Ba²⁺, Sr²⁺, Ca²⁺, Na⁺, and Mg²⁺. Sodium and lithium are frequently used, as they form inexpensive, soluble salts.

If an acid is used as the electrolyte, the cation is H⁺, and there is no competitor for the H⁺ created by disassociating water.

The most commonly used anion is SO₄^2-, as it is very difficult to oxidize.

Standard potential for oxidation of this ion to the peroxydisulfate ion is −0.22 volts.

Frequently used electrolytes:

Strong acids such as Sulphuric acid (H₂SO₄), and strong bases such as Potassium Hydroxide (KOH), and Sodium Hydroxide (NaOH) are frequently used as electrolytes.

Techniques

Fundamental Application

Two leads, running from the terminals of a battery, are placed in a cup of water with a quantity of electrolyte added to establish conductivity. Hydrogen and Oxygen gases will stream from the oppositely charged electrode. Oxygen will collect at the anode and hydrogen will collect at the cathode.

Hofmann voltameter

Main article: Hofmann voltameter

The Hofmann voltameter is often used as a small-scale electrolytic cell. It consists of three joined upright cylinders. The inner cylinder is open at the top to allow the addition of water and the electrolyte. A platinum electrode is placed at the bottom of each of the two side cylinders, connected to the positive and negative terminals of a source of electricity. When current is run through the hofmann voltameter, gaseous oxygen forms at the anode and gaseous hydrogen at the cathode. Each gas displaces water and collects at the top of the two outer tubes, where it can be drawn off with a stopcock.

Industrial electrolysis

Many industrial electrolysis cells are very similar to Hofmann voltameters, with complex platinum plates or honeycombs as electrodes. Hydrogen gas is usually created and collected on site for use in other chemical processes, although in case of refineries it then makes more sense to produce it from natural gas. It can also be produced as a by-product, for example in brine electrolysis. Electrolysis could be used in a hydrogen economy to produce hydrogen from e.g. solar power.

Electrolysis in nature

Plants electrolyze water in the process of photosynthesis utilizing a naturally occurring catalyst.

2 H₂O + 2 NADP+ + 2 ADP + 2 Pi + light → 2 NADPH + 2 H+ + 2 ATP + O₂

High-temperature electrolysis

Main article: High-temperature electrolysis

High-temperature electrolysis (also HTE or steam electrolysis) is a method currently being investigated for water electrolysis with a heat engine. High temperature electrolysis is more efficient than traditional room-temperature electrolysis because some of the energy is supplied as heat, which is cheaper than electricity, and because the electrolysis reaction is more efficient at higher temperatures.

Applications

About four percent of hydrogen gas produced worldwide is created by electrolysis, and normally used onsite. Hydrogen is used for the creation of ammonia for fertilizer via the Haber process, and converting heavy petroleum sources to lighter fractions via hydrocracking. There is some speculation about future development of hydrogen as an energy carrier, although the rapid evolution of electric battery technology makes overall efficiency a major consideration. Hydrogen fuel injection is also a potentially viable application. ^{[citation needed]}

Efficiency

The energy efficiency of water electrolysis varies widely. Some report 50–70%, while others report 80–94%.These values refer only to the efficiency of converting electrical energy into hydrogen's chemical energy. The energy lost in generating the electricity is not included. For instance, when considering a power plant that converts the heat of nuclear reactions into hydrogen via electrolysis, the total efficiency may be closer to 25–45%.