Upload
diuton
View
556
Download
3
Tags:
Embed Size (px)
Citation preview
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!