Precipitations

The removal of

heavy metal ions,

phosphates and

nitrates from water

Higher concentrations of heavy metal ion, phosphates and nitrates are removed from water by precipitations.

We can use H2S or SOLUBLE SULFIDES

For example..

Using soluble sulfides

Hg (aq) 2+ + S(aq) 2- -> HgS (s)

Heavy metal precipitation = 2 liquids adding together, giving a solid.

Using hydroxides Heavy ions can also be removed from water

sewages and soil by using hydroxides.

Cu (aq) 2+ + 2OH(aq) - -> Cu(OH)2 (s)

Copper hydroxide

CECStands for… CATION EXCHANGE CAPACITY =

the amount of positively charger cations that a soil can hold

Soil organic matter and clay particles in soil have a negative change and therefore will attract and bond to positive ions.

They are classified as…1.Basic ions2.Acidic ions

Basic ions

This includes…

Calcium, Ca2+

Magnesium, Mg2+

Sodium, Na2+

Potassium, K+

Acidic ions

This includes…

Hydrogen ions, H+ Aluminum ions, Al3+

Ksp

Solubility product Ksp is the measure of solubility.

For example,

Lead can be precipitated out using.. SULFIDE IONS.

Pb(aq)2+ + S(aq)

2- = PbS(s)

General equation will be…

Ksp = [Pb(aq)2+] [S(aq)

2-]

Note that Ksp is the temperature dependent.The concentration of the solid does not appear as it is a constant.

The precipitation depends on Ksp.Precipitate will form if the product of the ions

(looking at the general equation) exceeds the numerical value of Ksp at that temperature.

The larger the CEC the more cations the soil can hold.

Basic ions are EXCHANGED for H+ ions on the root hairs and this is how plants get their ions.

More acidic the soil is (which means more H+), the higher the % of acidic cations, the lower the pH

For example

Aluminum is an acidic cation. This is harmful to plants which shows the pH to plants are very important.

Neutralizing the soil!

To neutralize the soil, we can add LIME.This increases the concentration of basic

cations held by clay and soil

SOM can also be added.This binds with organic and inorganic

compounds which helps remove pesticides, heavy metal ions and other pollutants!