Sol-Gel Derived Adsorbents with Enzymatic and Complexonate Functions for Complex Water Remediation

Area of Science:

• Materials Science
• Environmental Chemistry
• Nanotechnology

Background:

• Enzymatic reagents grafted on nanocarriers are effective for removing organic pollutants in water purification.
• Enzymes, such as urease, are susceptible to deactivation by heavy metal cations like Cu(II) and Cd(II).
• Protecting immobilized enzymes from heavy metal inactivation is crucial for developing stable and efficient water treatment adsorbents.

Purpose of the Study:

• To develop novel magnetic nanocomposite sorbents for water purification applications.
• To prevent the inactivation of immobilized urease by Cu(II) and Cd(II) ions.
• To evaluate the adsorption capacity and stability of the developed nanoadsorbents for heavy metal ions and urea decomposition.

Main Methods:

• Sol-gel technology was used to synthesize Fe₃O₄/SiO₂-NH₂-DTPA magnetic nanoparticles.
• Complexonate (diethylene triamine pentaacetic acid - DTPA) functions were introduced to protect immobilized urease.
• Nanomaterials were characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM).
• Adsorption capacities for Cu(II) and Cd(II) ions were determined, and adsorption mechanisms were evaluated using the Langmuir model.
• Immobilized urease was crosslinked with glutaraldehyde to enhance its stability and reusability.

Main Results:

• The Fe₃O₄/SiO₂-NH₂-DTPA nanoadsorbents exhibited high adsorption capacities for Cu(II) (1.1 mmol/g) and Cd(II) (1.7 mmol/g) ions.
• The Langmuir model accurately described the adsorption behavior for both cations within a specific concentration range.
• Crosslinking significantly improved the stability and reusability of immobilized urease, maintaining activity over at least 18 cycles.
• The presence of DTPA groups protected urease activity from Cu²⁺ ions at concentrations as low as 1 µmol/L.
• Efficient urea decomposition was achieved, reducing concentration from 20 mmol/L to 2 mmol/L in multiple cycles.

Conclusions:

• The developed magnetic Fe₃O₄/SiO₂-NH₂-DTPA-Urease nanocomposite sorbents show high potential for water purification.
• These sorbents effectively decompose urea even in the presence of heavy metal ions, overcoming enzyme inactivation issues.
• The DTPA functionalization and enzyme crosslinking provide a robust strategy for creating stable enzymatic adsorbents for environmental remediation.