The Science behind the Product
The PTH device as in-line Catalyst, used as a water softening method
The Causes of Hardness
Most hardness in water is caused by the presence of dissolved calcium (Ca2+) and magnesium (Mg2+) ions. Other cations, such as Al3+ and Fe3+ can contribute to hardness; however their presence is less critical.
The most common, and troublesome, form of hardness is caused by the presence of calcium bicarbonate (Ca(HCO3)2) which is picked up by rain water passing through lime stone (CaCO3). As rain water falls it dissolves carbon dioxide (CO2) from the air and becomes slightly acidic because carbonic acid (H2CO3) is formed:
In the above equation g=gas, l=liquid and aq=aqueous (i.e. dissolved in water). In the following equation s= solid.
CaCO3 is not very soluble in water. However, when the diluted acid runs through the limestone a reaction occurs that creates calcium bicarbonate, which is readily soluble:
Thus the rainwater has picked up Ca2+ and HCO3– (bicarbonate) ions and become hard. When hard water is heated the previous two reactions are reversed and calcium carbonate, water and carbon dioxide are formed:
Since calcium carbonate is much less soluble in water than calcium bicarbonate it precipitates out of solution as a solid known as scale or lime scale. Because this type of hardness is easily removed (i.e. by simple heating) it is known as temporary hardness. Scale normally appears around heating elements and hot water systems. However, if the water is exceptionally hard scaling may occur in cold water pipes.
Other types of temporary hardness are caused by the presence of Mg2+ ions and the precipitation of magnesium hydroxide (Mg(OH)2) can contribute to scaling problems.
Combinations of Ca2+ and Mg2+ ions with chloride (Cl–), sulphate (SO42-) and nitrate (NO32-) ions are known as permanent hardness. For example in some areas CaSO4 may cause considerable hardness. Permanent hardness cannot be removed by boiling.
The term hardness total hardness is used to describe the combination of calcium and magnesium hardness. However, hardness values are usually quoted in terms of CaCO3 because this is the most common cause of scaling. The standard classifications are given below:
Hardness mg/L as CaCO3
Moderate : 60-120
Hard : 120-180
Very hard: more than 180
Problems Caused By Hardness
- Excessive soap is needed for washing (i.e. soap will not lather). Some modern detergents work less efficiently because anions (also known as surfactants) which are meant to hold dirt particles in suspension, react with Ca2+ and Mg2+ instead.
- Soap based on animal fats can react with Ca2+ and Mg2+ forming a precipitation that can ruin cloths and irritate skin.
- Some foods, particular dried beans and peas, become tough and rubbery when cooked in hard water. Calcium ions cause cross-linking to occur between certain molecules within the beans, the subsequent structure prevents water entering and the bean remains hard. A simple way to counteract this effect is to ad baking soda (sodium bicarbonate (NaHCO3)) to the cooking water.
- Scale can clog pipes and fittings. Also heating elements can become 90% less efficient with a 25mm coating of CaCO3. One millimeter of lime scale cause a staggering rise of 10 % in electricity bills.
Implements that typically suffer as a result of hard water, are:
- Heat exchangers
- Cooling towers
- Geysers (South African colloquial)
- Humid wet walls
- Ice machines
- Coffee machines
- Dentist drills
- High pressure cleaning apparatus’
HOW THE PTH FUNCTIONS
The working principle behind the PTH anti-scaling in-line catalyst is not to remove Ca2+ or CaCO3 but to precipitate CaCO3 in a form that prevents it from making a solid, stubborn scale. After passing through the catalyst the CaCO3 will either stay as very fine particles suspended in the water or to settle out as a flaky, easily dislodged scale. This happens typically when the PTH removes or cleans a toilet cistern, where the built-up scale flakes off from the sides of the cistern and settles on the bottom.
The theory as to how this happens is as follows:
The PTH acts as a catalytic converter.
When water is passed through the PTH device, a small electric and or magnetic field is created which causes a localized increase in pH. This happens via an electro-chemical reaction involving an electron and an O2 molecule producing an OH– ion.
(Positive and negative ions of certain elements can be created depending on the number of electrons in their structure.)
The high pH allows CaCO3crystal nuclei to form in the body of water. These minuscule crystals clump together to form colloids.
A colloid is a homogeneous non-crystalline substance consisting of large molecules or ultramicroscopic particles of one substance dispersed through a second substance. Colloids include gels, sols, and emulsions; the particles do not settle, and cannot be separated out by ordinary filtering or centrifuging like those in a suspension.
Colloids are important in both the natural environment and for manufactured products. A colloid is mixture where at least two types of substances are placed together. The substances, also called particles do not change; each substance retains its own properties. They do not settle out of the mixture and cannot be seen.
As these colloids are carried though the water they will not stick to the pipe surface and any further precipitation that occurs will deposit CaCO3 on the colloids and not the pipe. Thus the CaCO3 is held in a suspension of fine particles and if sedimentation occurs a very loose scale results.
PTH Water Treatment System
The PTH Water Treatment system is basically an in-line water quality enhancer catalyst (a catalyst is an element that can change a chemical reaction without partaking in that reaction). If installed and sized correctly it will have “wetter water”, flora friendly and “cleaner” water as a result.
The working principle of the in-line water catalyst is similar to that of a diesel engine exhaust gasses catalyst that changes the harmful exhaust gasses into less harmful gasses as dictated by European legislation. Both catalysts consist of a noble metals alloy, Platinum and or Palladium and or Rhodium and other noble metals core with a stainless steel housing.
The in-line water catalyst’s core is forged in a specific paten that promotes turbulent water flow to ensure maximum water contact to the core and must be grounded properly to create a weak electric current between the stainless steel housing and the catalyst.
Wetness here is synonymous with “clingingness” – water wets because it clings. Water, of course, is molecularly H 2 O and this compound of hydrogen and oxygen is electrically neutral. However, there are also in water free charged hydroxyls (-OH-, negatively charged) and hydrogen ions (H+ positively charged). These charged particles retain the ability to attract other charged particles (with the opposite charge) just as magnets do. In this way they stick or cling, involving other neutral H 2 O molecules at the same time. If water was made up entirely of neutral particles it would not cling, or wet, because the component elements would ‘prefer’ to stick to each other rather than to make bonds with other substances.
By generating a weak electric current between the outer shell of the catalyst and the catalyst core, the PTH device promotes the availability of free charged hydroxyls – – – negatively charged OH- ions) – and free hydrogen (positively charge ions) and by promoting more free negative and positive ions the water will be wetter with the result that the water will “cling” better to the roots of plants resulting in less water to be used as the plant will be able to use more of the available water. The wetter water will also react quicker and better with the added fertilizers for maximum fertilizer uptake in the plant systems
Water molecules are also ‘electrically neutral’ but are highly polar molecules, that is they have a positive ‘end’ and a negative ‘end,’ though neither ‘end’ carries a full unit of charge. It is this polarity which causes water molecules to ‘stick to’ one another and, given the chance, to other molecules of a polar nature. This is what causes the surface tension of water molecules and further restricts the wetness “clingeness”of water. The turbulent flow that is created by the geometry of the in-line water catalyst core will brake this surface tension to a large extent and the water also becomes wetter.
Cobus Faber, Pr Eng,
Stilbaai, South Africa
Cell (++27) 083 455 2881