Sodium-alginate/poly (acrylamide co-acrylic acid) semi-interpenetrating hydrogels for removal of heavy metals from aqueous solutions

Abstract Water contamination by heavy metals is a serious ecological problem due to their toxicity to humans, animals and plants. The synthesis of new low-cost adsorbents used in the treatment of polluted water is therefore generating growing interest. In this work, the synthesis of semi-interpenetrating network (SIPN) hydrogels by in-situ free radical polymerization was carried out. Materials based on poly(acrylamide-co- acrylic acid) and different ratios of sodium alginate (Alg-Na) have been prepared to examine their potential use in wastewater treatment. The swelling capabilities of these materials were evaluated observing a general trend of low swelling in acidic pH solutions and more significant swelling in solutions with a pH above 5. The structure and morphology of the hydrogels were investigated using X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The adsorption capacity of the hydrogels for metal ions Pb 2+ , Cd 2+ , and Cr 3+ was studied in aqueous media containing different concentrations of these ions (25–100 ppm). The results showed that the hydrogels have great potential for heavy metal removal from aqueous solutions concluding also that the addition of Alg-Na enhances the metal uptake.