Envr 403 introduction to environmental chemistry
Download
1 / 37

ENVR 403 Introduction to Environmental Chemistry - PowerPoint PPT Presentation


  • 115 Views
  • Uploaded on

ENVR 403 Introduction to Environmental Chemistry. Philip C. Singer Department of Environmental Sciences and Engineering [email protected] 919-966-3865 April 2010. Topics. 1. Chemistry of Natural Waters 2. Purification of Water. 1. Chemistry of Natural Waters. Redox Equilibria

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' ENVR 403 Introduction to Environmental Chemistry' - tyronica-ramirez


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Envr 403 introduction to environmental chemistry

ENVR 403Introduction to Environmental Chemistry

Philip C. Singer

Department of Environmental Sciences and Engineering

[email protected]

919-966-3865

April 2010


Topics

Topics

1. Chemistry of Natural Waters

2. Purification of Water


1 chemistry of natural waters

1. Chemistry of Natural Waters

Redox Equilibria

-speciation

-dissolved oxygen resources

Acid-Base Equilibria

-speciation

-the carbonate system and alkalinity

Solubility Equilibria

-metal solubility

-aqueous lead (Pb) solubility


Ph and pe as master variables
pH and pE as Master Variables

H2CO3 = HCO3- + H+ Ka1

pH = pKa1 + Log [HCO3-]/[H2CO3]

NO3- + 10H+ + 8e- = NH4+ + 3H2O Kred

pE = -1/8 (pKred) + 1/8 (Log [NO3-] [H+]10/[NH4+])

pEo = -1/n (Log Kred)

pE = pEo + 1/n Log [Ox]/[Red])

Analogous to Nernst Equation

EH = EoH + 2.3 RT/nF (Log [Ox]/[Red])






Electroneutrality equation charge balance for natural waters

Electroneutrality Equation (Charge Balance) for Natural waters

Major Cations: Na+, K+, Ca2+, Mg2+

Major Anions: Cl-, SO42- , NO3-, HCO3-, CO32-

Charge Balance

[Na+]+ [K +] + 2[Ca2+] + 2[Mg2+]+ [H +] = [Cl- ]+ 2[SO42-]+ [NO3-] + [HCO3-] + 2[CO32-]+ [OH-]

Cb-Ca = Acid neutralizing Capacity = Alkalinity =

[HCO3-] + 2[CO32-]+ [OH-] – [H +]


What is the pH of pure rainwater? waters

Pure rainwater contains only dissolved CO2 in equilibrium with the atmosphere.

H2CO3 = KH PCO2 ~ 10-5M

What is the pH of a 10-5M solution of H2CO3?

Cb-Ca = Alkalinity = 0

[H+] = [HCO3-] + 2[CO32-] + [OH-] = K1[H+]C/D + 2 K1K2C/D

where D = [H+] 2 + K1 [H+] + K1K2

Answer: pH 5.65


If a body of water has a pH of 7.5 and an alkalinity of 2x10 waters-3 equivalents/L, what is the equilibrium pH of the water if 10-3 eq./L of acid is added to the water?

Use initial pH and given alkalinity to find total carbonate concentration C

C = (Alkalinity + [H+] - [OH-]) /((K1[H+]/D) + 2K1K2/D) = 2.12x10-3 M

Added acid consumes alkalinity

New alkalinity = 2x10-3 – 10-3 = 10-3 eq/L

Find new pH from alkalinity expression

Alkalinity = [HCO3-] + 2[CO32-]+ [OH-] – [H +]

10-3 = ((K1[H+]/D) + 2K1K2/D) 2.12 x10-3 + [OH-] – [H +]

Find pH = 6.35



Solubility of caco 3 s
Solubility of CaCO waters3(s)

  • Kso = [Ca2+][CO32-]

  • [Ca2+] = Kso/[CO32-] = Kso/α2[TOTCO3]

  • Solubility of Ca increases with decreasing pH


Lead in drinking water
Lead in Drinking Water waters

Pb(II) Pb(IV)

OCl-

Cl-

Particulate

CO32-, PO43-

CO32-, PO43-, Cl-

Pb2+

Pb 2+

Pb(IV)O2, Pb3(CO3)2OH2, PbCO3, Pb5(PO4)3OH

Lead Pipe Pb(0)

  • Lead pipe (Pb0) develops scales of corrosion products.

  • The products formed (oxides, carbonates, and phosphates) depend on the water chemistry.

  • Changes in distribution system water chemistry can destabilize corrosion products.

  • Optimization of water chemistry can mitigate lead release to solution.


Solubility of potential lead containing phases
Solubility of Potential Lead-containing Phases waters

Hydrocerussite

(Pb3(CO3)2(OH)2)

with 50 mg/L DIC

Hydroxylpyromorphite

(Pb5(PO4)3OH)

with 1 mg/L P

Plattnerite (PbO2)

-2

-3

Litharge (PbO)

-4

(M)

-5

diss

-6

Log[Pb]

15 ug/L Pb

-7

-8

-9

4

5

6

7

8

9

10

11

pH



Operation of falcon waterfree cartridge
Operation of Falcon Waterfree cartridge waters

Urine in

Source: Falcon Waterfree


Falcon—6 months waters

Fed Ex Global Health Building (highuse)


Chemical composition of urine udert et al 2003
Chemical Composition of Urine waters(Udert et al. 2003)


Underlying chemical theory hydrolysis of urea
Underlying Chemical Theory: waters Hydrolysis of Urea

  • NH2(CO)NH2+2H2O2NH4++CO3-2

  • Urease is urea-hydrolyzing enzyme

  • Urease decomposes urea into ammonium and carbonate, causing the pH to increase

  • Increase in pH and addition of ammonium and carbonate leads to over-saturation with respect to several different minerals, including struvite (MgNH4PO4) and calcium hydroxyapatite Ca5(PO4)3(OH)2.



O waters

P

Mg

Ca

SEM Results for RDU Terminal A Composition Similar to Struvite, MgNH4PO4 (s)


ad