Green triiron tetraoxide@Algae (Fe ₃O ₄@Algae) nanoparticles for highly efficient removal of lead (Pb ²⁺), cadmium (Cd ²⁺), and aluminum (Al ³⁺) from contaminated water: an isothermal, kinetic, and thermodynamic study

Developing and producing a versatile adsorbent for effective wastewater treatment remains a significant obstacle to wastewater processing. As the objective is to eliminate various metal ions (lead, cadmium, and aluminum) from wastewater, we therefore strategically designed and synthesized new iron oxide nanoparticles (Fe ₃O ₄ NPs) based on the green algae called triiron tetraoxide@algae nanoparticles (Fe ₃O ₄@Algae NPs) that grow in the same contaminated water using a facile one-pot green synthetic method. Investigations were conducted into the adsorption circumstances, including pH, starting concentration, adsorbent dosage, and adsorption time. More importantly, great absorption of lead, cadmium, and aluminum was achieved, with 97.5%, 81.3%, and 75.13%, respectively. The best conditions were 60 min, 0.1 g of nanoparticles, at 25 °C, and 150 mL of water containing 30 mg/L of Pb, Cd, and Al, with pH 6 for Cd and Pb and pH 5 for Al. To analyze the kinetics and equilibrium adsorption data and to evaluate the interaction between the metal ions and the adsorbent, a variety of kinetic and isotherm models were employed. The Langmuir isotherm and a pseudo-second-order were the best ways to look at the adsorption isotherm and kinetics data for how the Fe ₃O ₄@algae removes metal ions. Furthermore, thermodynamic studies showed that the adsorption process was an exothermic, favorable, and spontaneous reaction. For the elimination of Al(III), Pb(II), and Cd(II), the Fe ₃O ₄@algae experimental adsorption capacity was 33.8 mg/g, 56.70 mg/g, and 36.58 mg/g, respectively. The composite of Fe ₃O ₄@algae nanoparticles was characterized using several analytical techniques including scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and UV–vis spectroscopy. In addition, the material exhibited notable durability and recyclability, with the metal removal effectiveness remaining at a high level even after undergoing five successive adsorption cycles. This study paves the way to the use of green nanotechnology for eco-friendly, cheap, and rapid techniques that can be used in the purification of wastewater.