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Water And Soil


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Water And Soil

  1. 2. Precipitations <ul><li>The removal of </li></ul><ul><li>heavy metal ions , </li></ul><ul><li>phosphates and </li></ul><ul><li>nitrates from water </li></ul>
  2. 3. <ul><li>Higher concentrations of heavy metal ion, phosphates and nitrates are removed from water by precipitations. </li></ul><ul><li>We can use H 2 S or SOLUBLE SULFIDES </li></ul><ul><li>For example.. </li></ul>
  3. 4. Using soluble sulfides <ul><li>Hg (aq) 2+ + S (aq) 2- -> HgS (s) </li></ul><ul><li>Heavy metal precipitation = 2 liquids adding together, giving a solid. </li></ul>
  4. 5. Using hydroxides <ul><li>Heavy ions can also be removed from water sewages and soil by using hydroxides. </li></ul><ul><li>Cu (aq) 2+ + 2OH (aq) - -> Cu(OH) 2 (s) </li></ul><ul><li> Copper hydroxide </li></ul>
  5. 6. CEC <ul><li>Stands for… CATION EXCHANGE CAPACITY = the amount of positively charger cations that a soil can hold </li></ul><ul><li>Soil organic matter and clay particles in soil have a negative change and therefore will attract and bond to positive ions. </li></ul><ul><li>They are classified as… </li></ul><ul><li>Basic ions </li></ul><ul><li>Acidic ions </li></ul>
  6. 7. Basic ions <ul><li>This includes… </li></ul><ul><li>Calcium, Ca 2+ </li></ul><ul><li>Magnesium, Mg 2+ </li></ul><ul><li>Sodium, Na 2+ </li></ul><ul><li>Potassium, K + </li></ul>
  7. 8. Acidic ions <ul><li>This includes… </li></ul><ul><li>Hydrogen ions, H + </li></ul><ul><li>Aluminum ions, Al 3+ </li></ul>
  8. 9. K sp <ul><li>Solubility product K sp is the measure of solubility. </li></ul><ul><li>For example, </li></ul><ul><li>Lead can be precipitated out using.. SULFIDE IONS. </li></ul><ul><li>Pb (aq) 2+ + S (aq) 2- = PbS (s) </li></ul><ul><li>General equation will be… </li></ul><ul><li>K sp = [Pb (aq) 2+ ] [S (aq) 2- ] </li></ul><ul><li>Note that Ksp is the temperature dependent. </li></ul><ul><li>The concentration of the solid does not appear as it is a constant. </li></ul>
  9. 10. <ul><li>The precipitation depends on Ksp. </li></ul><ul><li>Precipitate will form if the product of the ions (looking at the general equation) exceeds the numerical value of Ksp at that temperature. </li></ul>
  10. 11. <ul><li>The larger the CEC the more cations the soil can hold. </li></ul><ul><li>Basic ions are EXCHANGED for H + ions on the root hairs and this is how plants get their ions. </li></ul><ul><li>More acidic the soil is (which means more H + ), the higher the % of acidic cations, the lower the pH </li></ul><ul><li>For example </li></ul><ul><li>Aluminum is an acidic cation. This is harmful to plants which shows the pH to plants are very important. </li></ul>
  11. 12. Neutralizing the soil! <ul><li>To neutralize the soil, we can add LIME. </li></ul><ul><li>This increases the concentration of basic cations held by clay and soil </li></ul><ul><li>SOM can also be added. </li></ul><ul><li>This binds with organic and inorganic compounds which helps remove pesticides , heavy metal ions and other pollutants ! </li></ul>