4. 1. Cr (VI) detected in 3342/5477
wells tested
2. Los Angeles [Cr6+] > 10 μg/L
3. 2104 CA to limit Cr6+ to 10 ppb
4. Hinkley, CA had Cr6+ levels
of 31.8 ppb
22. Cal Poly Pomona
Dr. Monica Palomo
Dr. Ali Sharbat
Lucas Townsend
Kahao Lim
SHINE
Dr. Graciela Matrajit
Brian Rucci
Kristine Schroeder
Pasadena City College
Dr. Veronica Jaramillo
Rafik Nazarpoor
Phu Nguyen
Hinweis der Redaktion
Methods: 1) Packets of walnut shells, corncob, saw dust (mix of various types of wood), woodshavings and activated charcoal powder were made using coffee filter paper and placed into a container Above media known to adsorb chromium 2) Chromium solution was diluted by a factor of 10^6 in order to use UV vis throughout entire sample range (the UV Vis test kit used only measured accurate values 300ppb and below),
it was then added to reactor for single batch
3) Samples of the solution were collected every 5 minutes for an hour
4) Samples were analyzed using UV Vis and titration
Methods: 1) Packets of walnut shells, corncob, saw dust (mix of various types of wood), woodshavings and activated charcoal powder were made using coffee filter paper and placed into a container Above media known to adsorb chromium 2) Chromium solution was diluted by a factor of 10^6 in order to use UV vis throughout entire sample range (the UV Vis test kit used only measured accurate values 300ppb and below),
it was then added to reactor for single batch
3) Samples of the solution were collected every 5 minutes for an hour
4) Samples were analyzed using UV Vis and titration
Method is use only for low concentration of Cr -- 1.0 ppm or 0.1 mg/L or less
must dilute sample before using test
machine measures the absorbance of green light and gives reading in ppb
Only measures Cr(VI); if want to measure Cr(III) in sample, must convert to Cr(VI) first.
1,5-Diphenylcarbazide reacts with Cr(VI) ions under acidic condition to create a pink solution
Diphenylcarbazide is oxidized to Diphenylcarbazone, while Cr(VI) is reduced to Cr (III)
the intensity of color is dependent on the concentration of Cr
Source:
google book
formula
Describe what Titration is
Redox reaction
Dichromate reacts with iodide in acidic solution to form elemental iodine
Solution becomes more yellow after reaction
sulfamicacid, KI, Dichromate: https://answers.yahoo.com/question/index?qid=20080815061454AAF0vsr
Also see “Production and Use” section of : http://www.britannica.com/science/iodine
Compared to clock experiment reaction
The iodine from the previous reaction reacts with excess iodide ions to form triiodide
2 drops of starch indicator is added to the mixture
A black-blue complex is formed from triiodide and the starch indicator
https://en.wikipedia.org/wiki/Starch_indicator
https://en.wikipedia.org/wiki/Iodine_test
A thiosulfate solution is added drop by drop
The thiosulfate reacts with the triiodide in the black-blue complex to form the iodide ion
There is no more triiode to create the black-blue complex, making the mixture clear
The amount of Chromium is figured in relation to the amount of triiode, which is figured out by the known amount of thiosulfate added.
http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch19/oxred_2.php
