Chromium Remediation: Removal of Hexavalent Chromium from the Environment
Chromium Remediation:Removal of Hexavalent Chromium
from the Environment
What is Chromium?Hexavalent Chromium Cr (VI) Trivalent Chromium Cr (III)
K2Cr2O7
CrO3
CrCl3
Cr2(SO4)3
The Good The Bad The Ugly
Chromium in the Environment1. 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
Where Does Chromium Come From
Fate of Chromium in Environment
ChromiumRemediation
Batch Reactor
BiochemicalNanotechnology Precipitation
Filtration
Ion exchange
Chromium Filtration Devices
Biological Treatment
Batch Reactor
Precipitation
1.Organic Reagents
2.Back Titration
3.Colorimetric Analysis: UV-Vis
Analysis of Chromium
Organic Analysis of Chromium
Dipehenylcarbazide
Sulfamic acid, Iodide, Dichromate reaction6I-(aq) + Cr2O7
2-
(aq)
+ 14H+
(aq) → 3I2(aq) + 2Cr3+
(aq) + 7H2O (l)
Dichromate
Diluted Chromium Sample
Sulfamic Acidand Potassium Iodide
Titration Analysis
Formation of Triiodide
I-(aq) + I2(aq) → I3-(aq)
triiodide
Black-blue complex
I3-(aq) + Starch → Black-Blue
ComplexStarch Indicator
Iodine Oxidation-Reduction
Titration with thiosulfate
I3-(aq) + 2 S2O3
2-
(aq)
→ 3 I-(aq) + S4O62-
(aq)
thiosulfate tetrathionate
After Titration
Back Titration
Colorimetric Analysis of Chromium
0 200 400 600 800 1000 12000
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
f(x) = 9.22285714285714E-05 x − 0.0016R² = 0.985807379375591
Colorimetric Analysis Chromium Standard Curve
Concentration (microgram/L)
Abs
orba
nce
Purified Chromium Solutions
Filtration Filtration Precipitation E.Coli Batch
Before
DPA: 139,000,000 ppb
Titration: 10 g/L
UV-VIS: >1000 μg/L
27,800,000
10 g/L
139,000,000 ppb
10 g/L
>1000 μg/L
139,000,000 ppb
10 g/L
>1000 μg/L
100 ppb
<5 mg/L
>1000 μg/L
After
DPA: 780,000 ppb
Titration: 5 g/L
UV-VIS: >1000 μg/L
37,700 ppb
0.60 g/L
13 ppb
0 g/L
Not Measured
25,000 ppb
0.6 g/L
Not Measured
56 ppb*
<5 mg/L
>1000 μg/L
*10 minutes
Analysis of Chromium
Summary of Results
AcknowledgementsCal Poly Pomona
Dr. Monica PalomoDr. Ali SharbatLucas TownsendKahao Lim
SHINE
Dr. Graciela MatrajitBrian RucciKristine Schroeder
Pasadena City College
Dr. Veronica JaramilloRafik NazarpoorPhu Nguyen