Ionized Water Definition
"Ionized water" is a recently coined phrase used for the commercial selling of "water ionizers." Within this market, it can be synonymous with alkaline water. However, "ionized water" is a term not generally used in the physical sciences. Though pure water is de-ionized, or ion-free, naturally occurring water already contains ions, and it can be slightly acidic or alkaline. Ions are introduced into water when dissolved from minerals in the environment and can also occur from water's self-ionizing ability. Water cannot be "ionized" by process: its pH can be neutralized to be less basic or acidic, or ions can be removed to make the water de-ionized.
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Understanding the ion
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Ions are atoms or molecules with a positive or negative electrical charge. The numbers of electrons within the atom/molecule are not equal to the total number of protons, thus giving it a net positive or negative charge. Ions commonly found in water include cations from sodium, calcium, iron, copper and anions from chloride and bromide. Cations are ions with a positive charge, anions are negative. A water molecule by itself has no charge. A single water molecule (H20) is made up of two hydrogen ions and one oxygen ion. The hydrogen ions each have a charge of +1 while the oxygen ion has a charge of -2. Two hydrogen ions plus one oxygen ion, therefore, combine to have a net charge of zero, or neutral.
A polar compound
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Water is a polar compound, in which one side of the molecule has a slightly different charge than the other. In the water molecule, the hydrogen ions arrange themselves on one side while the bigger oxygen atom "leans" to another side. Thus, one side of the water molecule has a slightly positive charge while the other, slightly negative. As a result, when ionic compounds (salts) enter water, they dissociate into their base ions. The anion moves to the positively charged side of a water molecule, while the cation is attracted to the partially negative oxygen.
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Source of ions in water
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Ionic compounds are picked up and dissociated as water flows over various surfaces, dissolving minerals from the source. When water is piped from wells or lakes for drinking use, it picks up ions from the ground as well as a few from the pipes and structures it moves through. In addition, ions like fluoride may be artificially added to water supplies. Thus, materials can ionize and become incorporated into the water. Discharge into water supplies can change the conductivity of water, depending on its makeup. If water flows over granite bedrock, the relatively inert materials will not ionize, thereby making the water less conductive.
Water and pH
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Though ions naturally occur in water, their charges must be balanced for the water to be considered pure. Pure water is neutral, with a pH of 7. De-ionized water is defined as pure water. It does not contain organic dissolved solids, cations or anions. It is commonly used in lab settings. The abundance of calcium and magnesium cations in groundwater make it slightly more alkaline. Alkaline water has a higher pH and tends to make water "hard." More acidic water is "softer" but more corrosive on pipes. EPA secondary standards for drinking water require a pH of between 6.5 to 8.5. Low pH in water can be attributed to excess acid rain, iron, nitrates and sulfates. Filtering the water through a neutralizer, like calcite chips, is a common method of reducing acidity.
Self-ionizing ability of water
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Two molecules of water can interact to create a hydronium ion (H3O+) and a hydroxide ion (OH'). Water molecules "self-ionize" to transition from a neutral state to a lower energy, ionized state. This process occurs spontaneously, though the ion concentration is very low: about one pair of ions exist for every 560 million water molecules. De-ionized water technically contains these ions produced from self-ionization, though their concentration is too small to make a substantial effect. Because it can self-ionize, pure water can act as either an acid or base.
Water electrolysis
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"Water ionizers" claim to work via the electrolysis of water. "Ionized water" is claimed to produce alkaline and acidic water counterparts. However, the electrolysis of water does not produce "ionized water," but rather oxygen and hydrogen gas. It requires excessive energy, is extremely costly, and is rarely used in industrial applications. Hydrogen gas can be produced from fossil fuels at lower cost.
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Comments
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waterchem
Jun 29, 2009
hydrated in solution. The hydration of these metal cations is an important point as it can control the pH (pH=-LOG(H), master variable of fresh water), which in turn controls metal solubility. Cations can bond to water, water acts and competes as a ligand (latin- ligare, to bond). The number of water molecules bonding to a cation is determined by the cations coordination number (the ratio of ionic radii cation/anion). This complexation of metals and water essentially forms Lewis acids, which can donate protons (H+) to solution. The amount of protons donated to solution in turn is determined by the bond strength of metals to oxygen (in general high charge cations, polyvalent cations, have a stronger bond to oxygen and hence the bond of oxygen-hydrogen is weakened). Therefore, by weathering bedrock and releasing elements such as Al, Fe, Cd, Zn etc., the composition and pH of water is d... -
waterchem
Jun 29, 2009
determined. It is also worth noting that a charge balance (cationic charge=anionic charge) does not equate to a neutral pH. A charge balance is important when determining whether the water quality data you have in front of you is complete and accurate.
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waterchem
Jun 29, 2009
"If water flows over granite bedrock, the relatively inert materials will not ionize, thereby making the water less conductive." It is worth noting that the minerals that constitute a rock of granitic composition are not "inert". Minerals by definition have a net charge of 0, however, this does not preclude chemical and redox (oxidation-reduction, loss and gain of electrons respectively) reactions from occurring to these rocks. In fact, the chemical weathering of rocks such as granite is an important control of the chemical composition of natural waters. For instance, ferrous iron (Fe 2+) is contained in the mineral biotite. In surface and some ground waters this iron can oxidize to Fe (3+) and reduce the coulombic forces within biotite leading to the eventual decomposition of the mineral. These elements (solutes) can then be transferred to water (solvent) and will become hydrated i...
