An indigenous tool for the adsorption of rare earth metal ions from the spent magnet e-waste: An eco-friendly chitosan biopolymer nanocomposite hydrogel

Recently, polymer nanocomposite hydrogel (PNC-hydrogel) has attracted the focus and attention of young and dynamic researchers in water remediation and purification due to its cost effectiveness, high processability, modified surface area, and enhanced absorptivity for the elimination of toxic ions of heavy metals and for its tunable properties as well as reusability. Chitosan (Cs), a deacetylated product of chitin, is the most promising and prospective biopolymer for adsorbing toxic heavy metallic ions from wastewater in diluted form. But when it is functionalized with any of its copolymers, its effectiveness and usability capacity are enhanced bythousand times in comparison to the virgin biopolymer, as it is less soluble in acidic aqueous medium. The functionali-zation of the biopolymer is proficient enough to bind the rare earth ions from the wastewater solution, and it is done by grafting the biopolymer with a variety of co-polymers. Herein, SiO2 nanopowder along with chitosan biopolymer based bionanocomposite hydrogel (SCB-hydrogel) has been prepared. This grafted biopolymer-based SCB-hydrogel was investigated by various techniques such as FTIR, XRD, FESEM, TEM, and UV-spectroscopy. The impact of numerous parameters including pH, adsorbate doses, time of contact, concentration of metallic ions, kinetic parameters with proper isotherms, desorptivity, and reusability of the PNC was studied in batch adsorption mode. The adsorption efficiency by the SCB-hydrogel with increasing concentration of lanthanide ions was observed to be 99 % from the waste diluted water followed by the Langmuir adsorption model along with kinetics of pseudo second order. Desorption of the lanthanides was also carried out by using 1 M H2SO4 and HCl solution. The adsorption efficiency of these PNC didn't alter much as with the original in reusability of maximum three times. Keeping in view of cost effectiveness and adsorption efficiency of the SCB-hydrogel we have used it in a maximum of three times availing its uses as well as reusability for a maximum limit of adsorption of the REEs onto its surface.Thus, in conclusion, the PNC can be effectively used as a novel bio-adsorbent for treatment of wastewater containing pollutants along with transition rare earth metal ions (Nd+3, Pr+3).

Automated summary

Recently, polymer nanocomposite hydrogel (PNC-hydrogel) has attracted attention for its cost effectiveness, high processability, modified surface area, and enhanced absorptivity in water remediation. Chitosan-based bionanocomposite hydrogel (SCB-hydrogel) has been prepared and investigated for adsorbing toxic heavy metallic ions from wastewater. The grafted biopolymer-based SCB-hydrogel showed high adsorption efficiency and reusability for lanthanide ions, making it a promising bio-adsorbent for wastewater treatment.