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Hexavalent chromium reduction by gallic acid.
Christiana Mystrioti1, Stefania Koursari1, Anthimos Xenidis1
1Sch. of Mining and Metallurgical Eng., National Technical University of Athens, 15780, Greece.
Chemosphere
|February 1, 2021
Summary
Gallic acid effectively reduces toxic hexavalent chromium (Cr(VI)) to beneficial trivalent chromium (Cr(III)). This rapid reaction occurs under mild acidic conditions, offering a promising environmental cleanup solution.
Area of Science:
- Environmental Chemistry
- Green Chemistry
- Water Treatment Technologies
Background:
- Hexavalent chromium (Cr(VI)) is a toxic industrial pollutant released into the environment.
- Cr(VI) in wastewater poses significant environmental and health risks due to its toxicity and solubility.
- Trivalent chromium (Cr(III)) is an essential micronutrient, making Cr(VI) reduction a desirable remediation strategy.
Purpose of the Study:
- To investigate the reduction of hexavalent chromium (Cr(VI)) to trivalent chromium (Cr(III)) using gallic acid (GA).
- To evaluate the kinetics of Cr(VI) reduction by GA under varying pH, temperature, and Cr(VI) concentrations.
- To assess the efficiency of GA as a reducing agent for Cr(VI) remediation in contaminated waters.
Main Methods:
- Batch tests were conducted to study the reduction of Cr(VI) by gallic acid.
- The effects of pH (3-6), temperature (25-35 °C), and initial Cr(VI) concentration were systematically examined.
- Reaction kinetics were analyzed to determine the reaction order and rate under different conditions.
Main Results:
- Cr(VI) reduction by GA is a rapid process under mild acidic conditions (pH 3-5).
- The reduction follows a second-order kinetic with respect to Cr(VI) concentration in the pH range of 3-5.
- Complete reduction of 100 μM Cr(VI) was achieved in 20 min at pH 3 and 40 min at pH 4.
- At higher pH (5-6), the reduction mechanism changed, requiring significantly longer reaction times (10-42 hours).
- Slight acceleration of the reaction rate was observed with a temperature increase from 25 °C to 35 °C at pH 6.
Conclusions:
- Gallic acid is an effective natural reducing agent for the detoxification of Cr(VI) in contaminated water.
- Mild acidic conditions (pH 3-5) are optimal for rapid Cr(VI) reduction by gallic acid.
- The study demonstrates a promising, green chemistry approach for environmental remediation of Cr(VI) pollution.
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