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