Abstract
We investigated the adsorption of lead (Pb2+) and nickel (Ni2+) ions by electrospun membranes of polyacrylonitrile (PAN) nanofiber activated with NaHCO3 (PANmod). Analysis by Fourier-transform infrared spectrometry (FTIR), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDX) validated the functionalization of PAN nanofibers with NaHCO3, and the successful agglomeration of Pb2+ and Ni2+ onto PANmod. After a rapid uptake of the heavy metal ions (15 min), the equilibrium contact time was attained (60 min) following a linear increase of both adsorption capacity and removal efficiency. PANmod showed a better affinity for Ni2+ than Pb2+. The adsorption on PANmod was best described by the pseudo-second-order kinetic model for both studied models, supporting chemisorption. By varying the solution pH from 2.0 to 9.0, we found that the adsorption capacity followed an increasing trend, reaching a maximum at the pH of 7.0. Despite increasing adsorption capacities, the removal efficiency of both heavy metal ions exhibited a decreasing trend with increase in initial concentrations. The amount of PANmod directly affects the removal efficiency, with 0.7 and 0.2 g being the optimum dose for maximum uptake of Pb2+ and Ni2+, respectively. The Langmuir model fitted well the Pb2+ adsorption data suggesting monolayer adsorption, and the Freundlich model perfectly fitted the Ni2+ adsorption data, indicating heterogeneous adsorption. The estimated values of the mean free energy of adsorption in the D–R isotherm indicated a physical adsorption of both heavy metal ions into the surface of the PANmod.
Highlights
Rapid industrial development and urbanization introduced large amount of waste effluents into various environmental compartments [1]
Its chemical groups and surface morphology were examined by Fourier-transform infrared spectrometry (FTIR) (Vertex 70 Bruker, Karlsruhe, Germany), field emission scanning electron microscopy (FESEM) (JSM-7600 JEOL, Tokyo, Japan) and energy dispersive X-ray spectroscopy (EDX) (Inca software installed inside FE-SEM)
We studied the successful adsorption of the heavy metal ions Pb2+ and Ni2+ on an electrospun membrane of PAN nanofiber activated with NaHCO3 (PANmod)
Summary
Rapid industrial development and urbanization introduced large amount of waste effluents into various environmental compartments [1]. Those effluents contain large amounts of toxic metals/metalloids, drastically polluting the ecosystem. Elevated levels of the non-biodegradable Ni2+ and Pb2+ ions in freshwater sources pose a significant threat to animal and human health, because they accumulate in living tissues through the food chain [4]. Exposure to metals/metalloids may induce severe deterioration in human health including memory loss, cardiovascular disease, abdominal pain, weakness, chronic bronchitis and cancer of the lung [5]. In pursuance of a pollution-free ecosystem, these toxic metals/metalloids should be eliminated from industrial wastewater before it is discharged into freshwater resources
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