Green superabsorbent nanocomposite hydrogels for high-efficiency adsorption and photo-degradation/reduction of toxic pollutants from waste water

Abstract

Developing renewable-based biomaterials is an important and sustainable solution to solve environmental and resource problems. Bio-super adsorbent treatment of contaminants is highly effective due to their minimal costs and environmental biocompatibility. Herein, superabsorbent nanocomposite hydrogels have been formed by grafting copolymerization of acrylic acid and acrylamide onto natural polysaccharide (green starch) with incorporation of NPs such as NiFe2O4 NPs and TiO2 NPs into the hydrogel matrix utilizing (MBA) N·N-methylene-bisacrylamide which acts as a cross linker and (APS) ammonium persulphate as an initiator in aqueous medium. Starch-g-poly(acrylic acid-co-acrylamide)/NiFe2O4 (NiFe2O4/SANCH) and starch-g-poly (acrylic acid-co-acrylamide)/TiO2 (TiO2/SANCH) were identified by (TGA) thermal gravimetric analysis, (SEM) scanning electron microscope, (EDX) energy dispersive X-ray, (TEM) transmission electron microscopy, (XRD) X-ray diffraction, and (FTIR) Fourier transform infrared spectroscopy. The adsorption/photodegradation performance of the NiFe2O4/SANCH and TiO2/SANCH were also studied under visible light using Cr(VI) and Congo red dye as template of dyes for a photodegradation target, then comparing the results to the neat starch-g-poly(acrylic acid-co-acrylamide superabsorbent hydrogel (SAH). The effect of irradiation time, pH, and catalyst dose photocatalytic reduction/degradation of Cr(VI) and CR on the prepared hydrogels was evaluated. The results show that, NiFe2O4/SANCH composite has effective photoefficiency towards Cr(VI) and CR than TiO2/SANCH and SAH polymers. The producibility of the reused NiFe2O4/SANCH and TiO2/SANCH composites were also investigated for five cycles with high efficiency. Therefore, these nanocomposite hydrogels possess high photocatalytic degradation/reduction efficiency and can be removed safely by direct filtration from the reaction. With such characteristics, NiFe2O4/SANCH and TiO2/SANCH hydrogels are mostly named green Polymers for usage in the adsorption/photodegradation technique to reduce many contaminants.