Copper removal using bio-inspired polydopamine coated natural zeolites

Area of Science:

• Environmental Science
• Materials Science
• Chemistry

Background:

• Copper (Cu(II)) contamination in aqueous solutions poses environmental and health risks.
• Natural zeolites offer a low-cost base for adsorbents, but their capacity for heavy metal removal can be limited.
• Bio-inspired polydopamine (PDA) is a versatile coating material with strong chelating properties.

Purpose of the Study:

• To investigate the efficacy of natural clinoptilolite-rich zeolite modified with polydopamine (PDA) as an adsorbent for copper cations (Cu(II)).
• To characterize the PDA-modified zeolite and evaluate the adsorption performance under various conditions.
• To assess the recyclability of the modified adsorbent for sustainable copper removal.

Main Methods:

• Synthesis of PDA-modified zeolite powders.
• Characterization using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA).
• Adsorption studies involving atomic absorption spectroscopy (AAS) and neutron activation analysis (NAA) to determine the effects of pH, treatment time, contact time, and initial Cu(II) concentration.
• Adsorption isotherm and kinetic modeling (Langmuir and pseudo-second-order).

Main Results:

• Successful grafting of PDA onto the zeolite surface was confirmed by spectroscopic and thermal analyses.
• The maximum adsorption capacity for Cu(II) significantly increased from 14.93 mg/g for pristine zeolite to 28.58 mg/g for PDA-modified zeolite, a 91.4% enhancement.
• Adsorption followed Langmuir isotherm and pseudo-second-order kinetics, indicating chemisorption.
• The modified adsorbent demonstrated recyclability, with over 50% copper removal achievable using mild acid or base solutions.

Conclusions:

• Polydopamine-modified natural zeolite is a highly effective adsorbent for removing copper ions from aqueous solutions.
• The enhanced adsorption capacity is attributed to the chelating properties of PDA on the zeolite surface.
• The material shows promise for practical applications in wastewater treatment due to its high efficiency and recyclability.