Abstract
Nowadays heavy metals are among the higher environmental priority pollutants, therefore, the identification of new, effective, reusable and easy-to-handle adsorbent materials able to remove metal ions from water is highly desired. To this aim, in this work for the first time, sulfonated pentablock copolymer (s-PBC, Nexar™) membranes and s-PBC/graphene oxide (GO) nanocomposite membranes were investigated for the removal of heavy metals from water. Membranes were prepared by drop casting and their chemical, structural and morphological properties were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, dynamic mechanical analysis (DMA) and small-angle X-ray scattering (SAXS). The adsorption abilities and adsorption kinetics of both the polymer and the s-PBC/GO nanocomposite were investigated for the removal of different heavy metal ions (Ni2+, Co2+, Cr3+ and Pb2+) from aqueous solutions containing the corresponding metal salts at different concentrations. The investigated s-PBC membrane shows a good efficiency, due to the presence of sulfonic groups that play a fundamental role in the adsorption process of metal ions. Its performance is further enhanced by embedding a very low amount of GO in the polymer allowing an increase by at least three times of the adsorption efficiencies of the polymer itself. This can be ascribed to the higher porosity, higher roughness and higher lamellar distances introduced by GO in the s-PBC membrane, as evidenced by the SEM and SAXS analysis. Both the polymeric materials showed the best performance in removing Pb2+ ions.
Highlights
Over the few years, within the high rate of population growth, the demand for fresh water is expected to increase, but its quality is seriously limited by anthropogenic activities: around two million tons of waste are produced by humans and disposed every day in water courses
Fourier transform infrared (FT-IR) analysis of the polymer and the nanocomposite was performed in order to verify if the preparation of this membrane in a different solvent (DMF) with respect to the commercial product could affect its chemical structure
FT-IR spectrum of graphene oxide is reported in Figure S1 as a comparison
Summary
Over the few years, within the high rate of population growth, the demand for fresh water is expected to increase, but its quality is seriously limited by anthropogenic activities: around two million tons of waste are produced by humans and disposed every day in water courses. The mass use of cosmetic, cleaning and pharmaceutical products increases the level and variety of water pollutants, which are not removed by conventional wastewater treatment. These contaminants are removed by coagulation followed by an advanced treatment process, such as membrane filtration, ion exchange/adsorption and ozonation/biodegradation. Metals and metalloids play significant roles at trace levels in living organisms, at higher concentration levels these are toxic and/or carcinogenic. If it exceeds its critical level, Ni is carcinogen like Cr, but it might cause gastrointestinal distress, pulmonary fibrosis and skin dermatitis [5]. Blood disorders and damage to the nervous system have a high occurrence in Pb toxicity
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