Worked with different particle size of coffee as an antioxidant to find which size creates a reaction at a faster rate in the reduction of Chromium IV to Chromium III.

1. The Particle Size Effect on the Hexavalent
Chromium Reduction in the Presence of Coffee
Regis Estevez & Lawrencia Cobbinah | Professor Chulsung Kim | Guttman Community College | City University of New York
Objectives
• Investigate the potential application of commercial coffee for the
remediation of Cr(VI)-contaminated wastewater.
• Study the effects of mass and particle size of the commercial coffee on
Cr(VI) reduction rate.
Abstract
The reaction between artificially prepared Cr(VI)-contaminated wastewater and
commercial coffee was observed as a function of reaction time. Furthermore, the
particle size effect of the applied coffee on Cr(VI) reduction was studied. The Well
designed batch experiments were performed under room temperature and the
amount of Cr(VI) in the solution was determined using the diphenylcarbazide
colorimetric method with an Aquamate 8000 UV-Vis modified spectrophotometer
at a 540 nm wavelength. The results indicate that the hexavalent chromium can be
reduced effectively by commercial coffee. When the ratio of mass in gram to the
volume of 50 mg/L Cr (VI) solution in L is 62.5, no Cr (VI) was not observed
within 25 minutes. In addition, the particle size of the applied coffee is an
important factor controlling the Cr (VI) reduction. According to the research
findings, commercial coffee is a potential alternative eco-friendly electron donors
that detoxifies hexavalent chromium contaminated resources.
Materials and Methods
Color developmental
solutions were
prepared by adding
1mL of both
Phosphate Buffer and
DCP solution into test
tubes.
Step 1
One gram of
grounded, sieved
coffee is added into
the beaker containing
40 ml of simulated 50
mg/L of Cr (IV)
contaminated water.
Step 2
At every 5 minutes,
appropriate amount of
samples were taken
followed by filtration.
The filtrate was kept
in a clean test tube.
Transfer 0.1mL of the
filtrate to the color
developmental
solution.
Step 3
After 7 min of color
developmental
period, the amount
of Cr(VI) was
determined using a
spectrophotometer.
Step 4
Results and Conclusions
• The modified Cr(VI) determination method showed strong relationship between
Cr(VI) concentration and absorbance.
• Commercial coffee—a strong antioxidant–significantly reduced hexavalent chromium
in the simulated Cr(VI)-contaminated water.
• The smaller the particle size of commercial coffee is, the faster the Cr(VI) reduction
as a function of time is.
• When the particle size is smaller than 150um, then the effect of particle size on the
Cr(VI) reduction rate disappeared.
• More coffee was applied, Cr(VI) reduction rate increased.
Works Cited
• Jacobs, J. & Test, S. (2004). Overview of Chromium(VI) in the environment:
Background and history. Retrieved from http://www.engr.uconn.edu.
• Liddell, A. (2015). Coffee polyphenols. Retrieved from http://www.livestrong.com
• All chemicals used for this research were ACS or higher grade.
• 1,000 mg/L of Cr(VI) stock solution was prepared using potassium dichromate
(K2Cr2O7).
• A fresh 50 mg/L Cr(VI) solution was prepared every week.
• Commercial Coffee was obtained from a local shop.
• Sieves #100 (150um) and #150 (75um) were used to separate coffee particles.
• Fisherbrand Filter paper P8 (Particle Retention: 20–25µm) was used to filter solid
coffee particles.
• Modified diphenylcarbazide method was adopted for the determination of Cr(VI) in
solutions using an Aquamate 8000 UV-Vis modified spectrophotometer
Chromium is primarily found in two oxidation states: trivalent chromium [Cr (III)]
and hexavalent chromium [Cr (VI)]. Trivalent Chromium is a stable insoluble
form and has an essential role balancing blood sugar in the human body.
Hexavalent Chromium is unstable, “considered a carcinogen and a surface water
and groundwater contaminant” (Jacobs & Test, 2004). Due to these two
distinguishing toxicity and solubility properties of Cr(VI) and Cr(III), reduction of
Cr(VI) to Cr(III) has been applied as a remediation technology for Cr(VI)-
contaminated water. Various reducing agents, such as iron compounds, small
organic compounds, hydrogen sulfide gas, and microorganisms, have been studied
and applied to remediate Cr(VI)-contaminated water. “Coffee contains a type of
polyphenol called chlorogenic acids… a compound that has potent antioxidant
activity” (Liddell, 2015). The polyphenols liberated from the coffee are potential
electron donors to reduce Cr(VI) in the Cr(VI)-contaminated water This research
studied the potential application of coffee for the remediation of Cr(VI)-
contaminated water.
Introduction
0
10
20
30
40
50
60
0 5 10 15 20 25 30 35 40 45 50
Cr(VI)inmg/L
TIME (MINUTES)
MASS EFFECTS ON Cr(VI) REDUCTION
Cr(VI) solution: 40 mL OF 50 mg/L CR(VI)
1 gram of coffee 2g coffee 2.5g coffee
0
10
20
30
40
50
0 5 10 15 20 25 30 35 40
[Cr(VI)]inmg/L
REACTION TIME (MINUTES)
THE PARTICLE SIZE EFFECT ON Cr(VI) REDUCTION
> 150 macro meter 150 macro meter < x > 75 macro meter 75 macro meter
y = 0.0351x + 0.2627
R² = 0.99566
0.00
0.50
1.00
1.50
2.00
2.50
0 10 20 30 40 50 60
ABSORBANCE
TIME (MINUTES)
Cr(VI) STANDARD CURVE