Physically-crosslinked polyvinyl alcohol composite hydrogels containing clays, carbonaceous materials and magnetic nanoparticles as fillers

Polyvinyl alcohol (PVA)/ Bentonite, acid-modified Bentonite, magnetic nanoparticles and mesoporous carbonaceous composite hydrogels were synthesized via an eco-friendly freeze-thawing technique, which is a simple and non-toxic crosslinking methodology. After thorough characterisation using X-Ray Diffraction (XRD), Scanning Electron microscopy (SEM), Dynamic Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and swelling assessment. Furthermore, the prepared materials were tested in order to explore their cadmium adsorption potential, a heavy metal usually found as a pollutant in water bodies. The data obtained showed that PVA has no affinity for cadmium ions but the incorporation of the different fillers makes the materials develop important adsorbent characteristics. Under the selected working conditions, and for a contact time of 1440 min, the maximum amount of cadmium ions adsorbed was 50.9 mg/g, 33.9 mg/g, 42.6 mg/g and 30.5 mg/g for composites containing bentonite; acid-modified bentonite; magnetic nanoparticles and carbonaceous materials, respectively. For all cases the higher the filler amounts the higher the adsorption efficiency.