Electrophilic Aromatic Substitutions of Amine and Sulfonate onto Fine-Grained Activated Carbon for Aqueous-Phase Metal Ion Removal

ABSTRACT

Two new materials for adsorption of metal ions from aqueous media have been developed. The organic functional groups amine (−NH₂) and sulfonate (−SO₃H) were successfully attached to a commercially available fine-grained activated carbon (AC) via electrophilic aromatic substitutions. The surface properties of the materials were investigated using FTIR spectroscopy, XPS, BET surface area analysis, gravimetric methods, and elemental analysis. The NH₂-AC and SO₃H-AC each had a functional group density of 3 mmol/g. Batch metal ion adsorption experiments were conducted to determine metal binding properties of the adsorbent materials. Based on the distribution coefficients (K_d) of metal ions tested, the unmodified AC and sulfonated-AC both had an affinity for metal ions in decreasing order of Nd > Lu ≈ La > Pb > Cu > Ni ≈ Cd > Mn ≈ Ca, while the amine-AC had an affinity for metal ions in the order of Cu ≫ Nd ≈ Lu ≈ La > Pb > Ni > Cd > Mn ≈ Ca. With maximum K_d values of 130,000 for amine-AC and 25,000 for sulfonated-AC, compared to a K_d of 2,000 for unmodified AC, the modified activated carbons have a strong potential for use in removing heavy metal ions and lanthanide ions from aqueous wastes.

Key Words::

• Metal separation
• Nanoporous sorbent
• Chemically modified carbon