Experimental modeling and optimization for the reduction of hexavalent chromium in aqueous solutions using ascorbic...

Area of Science:

• Environmental Chemistry
• Water Treatment Technologies
• Inorganic Chemistry

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks due to its toxicity.
• Effective and efficient methods for Cr(VI) remediation in diverse aqueous matrices are crucial for environmental protection.

Purpose of the Study:

• To investigate the efficacy of ascorbic acid in reducing toxic Cr(VI) to less toxic Cr(III) across different water qualities.
• To optimize ascorbic acid dosage for achieving high-percentage Cr(VI) removal using statistical experimental design and response surface methodology (RSM).

Main Methods:

• Statistical experimental design and Response Surface Methodology (RSM) were employed to model Cr(VI) reduction.
• Key parameters investigated included initial Cr(VI) concentration, humic acid concentration, and ascorbic acid dosage.
• Optimized ascorbic acid dosages were predicted, validated experimentally, and reaction kinetics were analyzed.

Main Results:

• Ascorbic acid demonstrated high efficiency in reducing Cr(VI) across deionized, synthetic soft, synthetic hard, and real tap water.
• Optimized conditions achieved >99.5% Cr(VI) reduction, with >99.9% removal observed even at 100 mg/L initial Cr(VI) using 500 mg/L ascorbic acid and 20 mg/L humic acid.
• The reaction kinetics supported rapid reduction, achieving >99.9% Cr(VI) removal within 20 minutes.

Conclusions:

• Ascorbic acid is a highly effective reductant for Cr(VI) in various aqueous environments, including those with humic substances.
• The study provides a validated model for optimizing ascorbic acid dosage for efficient Cr(VI) water treatment.
• This research offers fundamental knowledge for developing environmentally sound endpoints for Cr(VI) remediation in contaminated water.