Sodium Alginate/Cellulose Nanofiber/Polyacrylamide Composite Hydrogel Microspheres for Efficient Removal of Heavy Metal from Water

Graphical Sodium alginate/cellulose nanofiber/polyacrylamide (SA/CNF/PAM) composite hydrogel microspheres are prepared by grafting PAM onto porous SA/CNF microspheres. These microspheres demonstrate exceptional adsorption capacity for heavy metal ions, outstanding salt tolerance, and reusability, providing a highly effective and sustainable solution for wastewater treatment. Water contamination derived from heavy metal ions has caused serious harm to water ecosystem and human health. Hence, it is crucial to exploit a material that can effectively remove heavy metal ions from wastewater to solve this problem. Herein, sodium alginate/cellulose nanofiber/polyacrylamide (SA/CNF/PAM) composite hydrogel microspheres for heavy-metal adsorption were prepared by grafting PAM onto the porous SA/CNF hydrogel microspheres, which was produced by integrating sodium alginate with cellulose nanofibers utilizing microfluidic method. The adsorption performances of the original SA/CNF microspheres were enhanced with the introduction of PAM. Various factors influencing adsorption processes, including pH, temperature, co-existing ion, salinity, etc. were systematically explored. The results showed the adsorption course for Pb 2+ was the most consistent with the Langmuir isotherm and pseudo-second-order kinetic models, forecasting a predominantly chemical adsorption mechanism. At 20 °C, the adsorption capacity of Pb 2 ⁺ using the Langmuir model was up to an unprecedented 676.97 mg/g. In summary, an extremely utility adsorption technology derived from hydrogel adsorbents has been gestated, offering an effective solution for the removal of heavy metal ions from real-world wastewater.