Melanin-embedded materials effectively remove hexavalent chromium (Cr^VI) from aqueous solution.

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Toxic heavy metal ions in water pose significant risks to human health.
• Developing effective materials for heavy metal removal is crucial for water purification.
• Melanin is emerging as a promising biomaterial for heavy metal remediation.

Purpose of the Study:

• To synthesize and compare two types of melanin-embedded beads for hexavalent chromium removal.
• To evaluate the sorption abilities of isolated melanin beads (IMB) and commercial melanin beads (CMB).
• To investigate the adsorption kinetics and isotherms of Cr(VI) on these melanin-based materials.

Main Methods:

• Two melanin-embedded beads, IMB (from squid ink) and CMB (from sesame seeds), were synthesized.
• Sorption experiments were conducted to determine optimal conditions (pH, time, ratio, concentration).
• Langmuir and Freundlich models were used to analyze sorption isotherms, and FTIR was employed for surface property analysis.

Main Results:

• Optimized conditions for Cr(VI) sorption were established for both IMB and CMB.
• IMB exhibited a higher maximum sorption capacity (19.60 mg/g) than CMB (6.24 mg/g) based on the Langmuir model.
• Adsorption kinetics followed the Freundlich model for both beads, indicating efficient adsorption. FTIR revealed distinct surface functional groups (-OH, -C=O) in IMB, crucial for Cr(VI) binding.

Conclusions:

• Isolated melanin beads (IMB) demonstrate superior performance in removing hexavalent chromium from aqueous solutions.
• The presence of specific functional groups on IMB enhances its adsorption capacity for Cr(VI).
• IMB holds significant potential as a cost-effective and efficient material for water treatment applications.