Selective Removal of Copper(II) from Aqueous Solutions Using Fine-Grained Activated Carbon Functionalized with Amine

Abstract

To develop an effective transition-metal-ion adsorbent material, functionalization of amine (−NH2) onto fine-grained activated carbon (AC) was performed via the electrophilic aromatic substitution of nitro (−NO2) groups onto the aromatic backbone of the AC, followed by reduction of −NO2 to −NH2. Fourier transform infrared, Brunauer−Emmett−Teller surface area analysis, gravimetric method, and batch metal ion adsorption experiments were performed in parallel on unmodified AC and amine-functionalized AC (NH2-AC). The competitive adsorption of transition-metal ions (Cd2+, Cu2+, Ni2+, and Pb2+) was measured in batch experiments at pH 2.0−5.8. Metal ions favored the NH2-AC over the unmodified AC. Based on the distribution coefficients (Kd), the NH2-AC had an affinity for metal ions in decreasing order of Cu2+ ≫ Pb2+ > Ni2+ > Cd2+. On the NH2-AC, the copper adsorption equilibrium was reached within 1 min with a saturation loading capacity of 0.86 mmol of Cu/g, 2.5 times greater than that on the unmodified AC. The Langmuir and Redlich−Peterson isotherm models were used successfully to characterize the Cu2+ adsorption isotherms. Having Kd values up to 100 000, the NH2-AC is a useful adsorbent material for removing Cu2+ from aqueous wastes.