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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

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0 5 10 15 20 25 30 35 40 45 50

Cr(

VI)

in m

g/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

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[Cr(

VI)]

in m

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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

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AB

SO

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TIME (MINUTES)

Cr(VI) STANDARD CURVE