Removal of lead from groundwater using carbide-derived carbon

In the current work, the use of carbide-derived carbon (CDC) as a novel adsorbent to remove lead (Pb2+ ions) from water is presented for the first time. The effect of different adsorption factors, including CDC dose, adsorption contact time, and lead concentration, was studied. The CDC adsorbent was characterized by using advanced characterization techniques such as scanning electron microscopy (SEM), energy-dispersive spectrometer (EDS), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area analyzer and zeta potential measurement. It was observed that CDC showed a BET surface area of 1597.15 m2/g and showed a point-of-zero charge (PZC) at pH 6. The batch adsorption experiments showed that CDC has a high removal efficiency of 98.9% for Pb2+ ions at CDC dose of 6.25 mg/L. It was shown that adsorption kinetic is very fast and 98% of lead removal was reached just in five minutes adsorption time. The adsorption data were fitted to the Langmuir, Freundlich, Temkin, and Sips isotherms, which showed that the adsorption process follows the Langmuir isotherm with a regression value of 0.9302. The adsorption of Pb2+ ions onto CDC showed a maximum adsorption capacity of 89.16 mg/g. Moreover, the experimental adsorption data were fitted to pseudo-first order, pseudo-second order, the Elovich model, intraparticle diffusion, and liquid film diffusion, kinetic models and the experimental adsorption results were consistent with the pseudo-second order model, with a regression value of 0.9999. The thermodynamic study indicated that the adsorption is spontaneous at temperatures of 25, 35, and 45 ℃. The ionic strength experiment showed that increasing the ionic strength of the solution causes a decrease in adsorption capacity due to decreasing electrostatic interactions between negatively charged CDC surface and lead ions; however, a removal efficiency > 99% was achieved even at 0.1 M NaCl feed solution. Moreover, the mechanisms of adsorption of lead towards CDC were discussed. The treatment of real groundwater spiked with 500 µg/L of lead showed a complete removal of lead at CDC dose of 1 g/L. The study showed the possibility of efficient regeneration of lead-saturated adsorbent for further reuse. These findings support the potential application of CDC for lead removal from water.