Synthesis, characterization, and adsorption capacity of sodium alginate poly grafted (fumaric acid-co-polyacrylic acid)/graphene oxide hydrogel as adsorbent for Cr (VI) and Pb (II) removal

This study involves the preparation of sodium alginate poly grafted (fumaric acid-polyacrylic acid)/graphene oxide, SA-g-p(FA-AA)/GO hydrogel to explore its potential as a promising adsorbent for water treatment mainly chromium (VI) and lead (II) removal. Prepared adsorbent was characterized by FTIR, TGA, XRD, FESEM, and TEM techniques for exploring the chemical structure, thermal stability, crystallography, surface area and morphology, as well as pore size and distribution of SA-g-p(FA-AA)/GO, respectively. The average size of the prepared nanoparticles was observed to be 78.48 nm. The TEM images exhibit a predominantly spherical shape and heterogeneous. Effect of different physiochemical parameters such as pH, temperature, adsorbent dosage, and contact time was explored for maximum metal adsorption. The results of the study revealed that the maximum adsorption capacity of SA-g-p(FA-AA)/GO (0.045 mg g⁻¹ for Cr (VI) and 22.371 mg g⁻¹ for Pb (II)) was achieved under optimized conditions, i.e., adsorbent dose of 0.05 g at 25 °C for pH of 2, 4.5 when contact time of 5 and 100 min was used for Cr(VI) and Pb(II), respectively. Data fits best to the pseudo-second-order kinetic equation revealing the multilayer adsorption of Cr (VI) and Pb (II) ions on the heterogeneous adsorbent surface. Thermodynamically, the process of Cr (VI) and Pb (II) adsorption was non-spontaneous, exothermic and feasible revealing the potential of the prepared adsorbent to be used as an efficient adsorbent for metal removal.