Water is a crucial part of our lives. It is enriched with minerals that are important for our good health. Permanent Hardness of water is not only a theory but also a real-life problem we deal with every day in our lives. Knowledge of this concept helps the students relate the chemistry concepts to real-life problems and is also important for many exams like JEE and NEET. While temporary hardness is easy to eliminate by boiling, permanent hardness is not, so we have to use some chemical methods in this case. In this article, we will discuss in detail the methods of removing the permanent hardness of water, along with a few topics related to it.
What is Hardness of Water?
The Hardness of water is a measure of the total concentration of soluble minerals such as calcium and magnesium ions including their bicarbonates, sulfates, and chlorides. The hardness of water is also caused by the presence of iron, aluminum, and manganese ions. The geographical location is also responsible for the richness of minerals. The hardness of water is determined by the milligrams per liter (mg/L) and is reported in parts-per-million (ppm) units.
- Water can be classified into two parts – soft water and hard water. Hard water does not lather with soap and detergents due to the minerals, while soft water, such as rainwater, lathers with soap and detergents.
- Hard water is safe to drink when taken in minimal amounts and helps protect against rectal cancer, pancreatic cancer, gastric problems, etc., but using it in large amounts may cause several health issues, such as dry skin, hair problems, etc.
- Hard water is not suitable for laundry, as it does not lather with soap and detergents.
- Temporary hardness can be removed by boiling, but permanent hardness requires some chemical treatments including Calgon’s method, ion exchange, using washing soda, etc.
Permanent Hardness of Water
Permanent hardness of water is caused due to the presence of sulfates and chlorides of calcium and magnesium such as CaCl2 , MgCl2 , CaSO4 , MgSO4 in water. When we boil the water to eliminate these sulfates and chlorides we can see a white coating on the utensils due to these salts or compounds steadiness. Since boiling can not remove permanent hardness, we have to use some chemical methods for it.
How to Remove Permanent Hardness of Water?
Permanent hardness of water occurs because of the presence of CaCl2, MgCl2, CaSO4, MgSO4 compounds. To permanently remove the hardness of water we will use certain chemical methods. These methods are discussed below:
By Using of Washing Soda
In this method we add washing soda i.e., Na2CO3 ·10H2O to hard water. The washing soda converts soluble chlorides and sulfates of calcium and magnesium into insoluble salts. The reactions are:
CaCl2 + Na2CO3 → CaCO3 + 2NaCl
MgCl2 + Na2CO3 → MgCO3 + 2NaCl
CaSO4 + Na2CO3 → CaCO3 + Na2SO4
MgSO4 + Na2CO3 → MgCO3 + Na2SO4
These CaCO3 and MgCO3 can be removed from the water by filtration. After filtration we get Ca+2 and Mg+2 ions free water which is the soft water.
Calgon’s Method
In this method we add Calgon i.e., Sodium Hexametaphosphate (Na6P6O18) to water. In this reaction, Ca+2 and Mg+2 ions of hard water displace two Na+ ions of Calgon, resulting in the removal of calcium and magnesium minerals from water and addition of sodium ion from Calgon into the water. After this reaction the water becomes soft. The chemical reactions are:
Na6P6O18 → 2Na+ + Na4P6O18 2-
Mg2+ + Na4P6O18 2- → Mg Na4P6O18
Gan’s Permutit Method
In this method we use Zeolite or Sodium Aluminum Ortho Silicate i.e., Na2Al2Si2O8 ·KH2O to remove hardness from water permanently. The reaction is:
Na2Al2Si2O8·KH2O + Ca+2 → 2Na+2 + CaAl2Si2O8·KH2O
Ion-Exchange Resins Method
To remove permanent hardness of water we also use ion-exchange method. In this method we add synthetic ion-exchange resins (RNa+) or Zeolite i.e., Sodium Aluminum Silicate to the water, which is insoluble in water. In this reaction the ion-exchange process occurs between it and the Ca2+ or Mg2+ ions of the hard water. By this process the water becomes free from Ca+2 and Mg+2 ions and no longer remains hard.
How to Detect Hardness of Water?
We can detect hardness of water at home using simple methods mentioned below:
Soap Test
- Take a clean plastic bottle and fill it halfway with the water sample.
- Add a few drops of liquid soap or detergent to the bottle and shake vigorously.
- If the water forms a lot of suds that last for a while, it is likely soft water. If the water forms scum or the suds quickly disappear, it is likely hard water.
Boiling Test
- Fill a clean pot with the water sample and bring it to a rolling boil.
- Allow the water to boil for several minutes, then turn off the heat and let it cool.
- Check the bottom of the pot for any white or cloudy deposits. If present, these indicate the presence of dissolved minerals and suggest hard water.
Commercial Test Kits
- There are various water hardness test kits available for purchase at hardware stores or online.
- These kits typically contain test strips or tablets that react with the minerals in the water to produce a color change.
- Follow the instructions provided with the kit to perform the test and interpret the results.
Conclusion
Water is naturally enriched with minerals that are essential for our good health. Hardness of water are of two types – temporary and permanent. Temporary hardness is easy to deal with but permanent hardness isn’t. It is because of the chlorides and sulfates of magnesium and calcium minerals. Hard water is not useful for industries, for laundry works, and also not in our daily life. So, to get rid of permanent hardness of water we use several methods such as Calgon’s method, ion-exchange method, Gan’s permutit method etc. This knowledge of removing hardness and softening water becomes a practical knowledge, as it helps in improving water quality for household uses.
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FAQs on Methods to Remove Permanent Hardness of Water
What are the types of hardness of water?
Hardness of water can be divided into two types-
- Temporary hardness of water
- Permanent hardness of water
What is the permanent hardness of water?
Permanent hardness of water is caused because of the presence of soluble chlorides and sulfates of magnesium and calcium in water.
what are the units of permanent hardness of water?
The units of permanent hardness of water are parts-per-million or ppm and milligrams per liter or mg/L and degree french.
How to remove permanent hardness of water?
Permanent hardness of water can not be removed by boiling method because of the steadiness of sulfates and chlorides of calcium and magnesium. In this case we can remove this hardness by applying Calgon’s method, Gan’s permutit method, ion-exchange method and by using washing soda.
Which salt makes water permanently hard?
CaCl2 , MgCl2 , CaSO4 , MgSO4 are the salts responsible for the permanent hardness of water.
Why is water hardness is important for health?
Though hard water is harmful for our skin and hair, but presence of calcium and magnesium in hard water, in a right combination, helps in treating constipation, often gastric problems. It is also helpful in the treatment of rectal cancer, pancreatic cancer etc. Hence it is important for our health as well.
What is the pH of hard water?
The hard water is alkaline that means its pH level is higher, above 8.5 .
What are the ppm of hard and soft water?
Water is considered soft if total hardness is less than 75 ppm, hard when total hardness is in between 150 to 300 ppm. and very hard when hardness is above 300 ppm.