Selective removal of copper(II) from aqueous solutions using fine-grained activated carbon functionalized with amine

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 (K-d), the NH2-AC had an affinity for metal ions in decreasing order of Cu2+ much greater than 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.