Remove Hardness of Water (Temporary)

Calcium ions and bicarbonate ions in water make water seem hard at first. This happens when these ions are dissolved: Calcium and Magnesium cations are formed, and Calcium and Magnesium anions are formed. It is because of the metal cations that make the water hard. There are ways to get rid of hardness, like boiling or adding lime (calcium hydroxide). The bicarbonate needs to be heated to a specific temperature to make carbonate. This causes calcium carbonate to come out of the solution, making the water softer when it cools. The original insoluble carbonate is changed into something that can mix with other things. Let us learn more about how to remove the hardness of water (temporary). 

Remove the temporary hardness from the water

1) Boiling (physical method)

In this case, boiling breaks down calcium and magnesium hydrogen into their (carbonates) and water and CO2 gas, becoming their carbonates. Carbonates are formed when calcium and magnesium ions are removed from the water and then deposited as solids at the bottom of the boiler.

Ca(HCO3)2(aq) → CaCO3(s) + CO2(g) + H2O(l)

2) Add calcium hydroxide (lime water)

There are soluble magnesium or calcium hydrogen carbonates that can be mixed with water. Calcium hydroxide reacts with them to make magnesium or calcium carbonates that aren’t soluble.

Ca(HCO3)2(aq) + Ca(OH)2(aq) → 2CaCO3(s) + 2H2O(l)

3) Remove the calcium or magnesium ions from the water by adding washing soda to it:

C𝑎(𝐻𝐶𝑂3)2 (𝑎𝑞) + 𝑁𝑎2𝐶𝑂3 (𝑎𝑞) → 2𝑁𝑎𝐻𝐶𝑂3 (𝑎𝑞) + 𝐶𝑎𝐶𝑂3 (𝑠)

4) Ammonia water is added

There is a change in the hydrogen carbonates that can be dissolved into carbonates that the water can’t break down. Magnesium and calcium ions are out of the water with this method.

2NH4OH(aq) + Mg(HCO3 )2(aq) → MgCO3(s) + (NH4 )2CO3(aq) + H2O(l)

The chemistry of how to remove hardness:

When calcium and magnesium are taken out of water in the form of calcium carbonate and magnesium hydroxide, it causes the water to become less acidic. CO2 concentration and pH play a significant role in how these two solids come together. When hydroxides are added, and the pH is raised to above 10, they can help eliminate carbonate hardness. 

Bicarbonate ions can be changed into carbonate ions when the pH of the water is more than 10. There is a lot more carbonate in the air than calcium carbonate forms. There is still a lot of calcium in the water that can’t be removed by changing the pH. This is called noncarbonate hardness. 

So, you must add soda ash (sodium carbonate) outside of the body to precipitate the calcium still there. Magnesium is removed because magnesium hydroxide forms when magnesium and water mix. Lime is added to the lime-soda ash process to raise the pH level.

5) To get the carbonate ion, sodium carbonate is put in.

H2CO3 + Ca(OH)2 → CaCO3 + 2H2O

Inference:

• When CO2 carbonic acid and lime are mixed, Eq.(1) is the process of neutralising them. This equation doesn’t change the hardness of the water, so there is no net change from it. Many carbonic acids will also need to be neutralised with a lot of lime, which will need to be in the form of CaCO3. Stochastic ratios can also help you.
• Eq.(2) shows how you can remove calcium carbonate hardness from water. It also shows that every molecule of calcium bicarbonate can form two carbonate ions by raising the pH of the water. These stoichiometric ratios also show that for every mg/L of calcium bicarbonate, 1 mg/L of lime in the form of CaCO3 will be needed to get rid of it.
• Calcium and noncarbonate hardness is removed from Eq. (3), which means less hardness is in it. CaCO3 will have to be used for every mg/L of calcium noncarbonate hardness to remove it from the water.
• It’s the same as Eq. 4, which says:  To get rid of each mg/L of magnesium bicarbonate hardness in the water, you’ll need two mg/L of lime in the form of CaCO3 or lime.
• Eq. (5) shows how much magnesium noncarbonate hardness is lost when you cut it. To get rid of magnesium noncarbonate hardness, you need one mg/L of lime, or CaCO3, for every mg/L that the hardness is in the water. There is an exchange: A magnesium ion is taken out, and a calcium ion is added for each magnesium one that is taken out. This means that the hardness level didn’t change, which is true.

Conclusion

For the water to be hard, it has to have a lot of multivalent cations in it. They are called “multivalent” cations because they have more than one charge. Then, they are made up of metal complexes with more than one charge, +1. Most of the time, the cations have +2. The cations in hard water are mostly Ca2+ and Mg2+. These ions enter a water source by breaking down minerals in an aquifer. Calcium-rich minerals like calcite and gypsum are prevalent. There is a common magnesium mineral called dolomite that is found worldwide (which also contains calcium). There aren’t many ions in rainwater or water that have been distilled, so they are soft.

There are dissolved bicarbonate minerals in water that make it hard, making it “temporarily hard” (calcium bicarbonate and magnesium bicarbonate). It is because of the metal cations that make the water hard. The hardness caused by sulphate and chloride compounds, on the other hand, lasts for a long time and can’t be removed by boiling water. This article covered how to remove the hardness of water (temporary).