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Chemical Treatment

Chemical Treatment. Neutralization. “The ocean is the result of a gigantic acid-base titration; acids that have leaked out of the interior of the earth are titrated with bases that have been set free by the weathering of primary rock.”. pH. Acids Taste sour Corrosive

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Chemical Treatment

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  1. Chemical Treatment Neutralization “The ocean is the result of a gigantic acid-base titration; acids that have leaked out of the interior of the earth are titrated with bases that have been set free by the weathering of primary rock.”

  2. pH

  3. Acids Taste sour Corrosive Redden blue vegetable colors Lose all these properties when brought into contact with alkalis Alkalis Give soapy solutions Restore vegetable colors reddened by acids React with acids to give salts Acids and Bases

  4. Acids and Bases continued • Lewis Model • Acid  accepts a pair of electrons • Base  donates a pair of electrons • Brönsted-Lowry Model • Acid  donates one or more protons • Base  accepts one or more protons

  5. Acid Dissociation Constant

  6. Example: Dissociation Constants Calculate the equilibrium pH. • 10-3 mol of HCl are added to 1 L of pure water at 25 oC. • 100 mg of H2SO4 is added to 1 L of pure water at 25 oC. • 10-3 mol of HOCl are added to 1 L of pure water at 25 oC.

  7. Activity – Team Calculate the equilibrium pH. • 10-2 mol of phosphoric acid are added to 1 L of pure water at 25 oC. • 500 mg of perchloric acid is added to 2 L of pure water at 25 0C.

  8. Basicity Constant

  9. Neutralization Measurement of pH only typically inadequate

  10. Acidity • Base neutralizing capacity • Quantitative capacity of a solution to neutralize a strong base to a designated reference point • Sources: • strong mineral acids • weak acids • dissolved carbon dioxide • dissolved metals that complex with hydroxide

  11. Basicity or Alkalinity • Acid neutralizing capacity • Quantitative capacity of a solution to neutralize a strong acid to a designated reference point • Sources: • strong bases • weak bases

  12. Measurement

  13. Example: Titration 500 mL of an acidic solution is titrated with a strong base to increase the pH from 3.9 to 8.3. If 5 mL of a 4-N solution of NaOH is the titrant dosage for the pH change required, calculate the acidity in units of meq/L.

  14. Neutralization Process

  15. Neutralizing Chemicals

  16. Neutralizing Chemicals

  17. Design

  18. Mechanical Mixing

  19. Example: Design A wastewater (100 gpm, 0.38 m3/min ) with 0.1 N H2SO4 is highly acidic and requires neutralization prior to secondary treatment. This flow is to be neutralized to a pH of 7.0 using a limestone bed. Determine the bed depth and limestone requirement given the following pilot test data.

  20. Example continued Bed Depth

  21. Example continued

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