Biosorbents have demonstrated considerable potential for the remediation of metals in aqueous environments. An aqueous extract of Enteromorpha intestinalis L. (EiE) and its extract-coated silver nanoparticles have been prepared and employed for the removal of iron. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV-visible spectroscopy, transmission electron microscopy (TEM), gas chromatography-mass spectroscopy (GC-MS), and zeta potential were employed to characterize the prepared biosorbents. The adsorption properties of the biosorbents were investigated in batch experiments, with a range of factors taken into account, including pH, contact time, initial ion concentrations, biosorbent dosage, and temperature. A minimum-run resolution IV design (MRR-IV) was developed with the objective of optimizing the removal efficiency. The mechanisms of adsorption were investigated using both the Langmuir and Freundlich isotherms. Kinetic studies were conducted using the pseudo-first-order and pseudo-second-order models. A variety of active constituents, including organic acids, lipids, alcohols, and terpenes, were identified through the use of GC-MS, with the findings supported by FTIR spectra. Transmission electron microscopy (TEM) revealed that the nanoparticle size ranged from 5 to 44 nm, while X-ray diffraction (XRD) demonstrated a high degree of crystallinity. A screening study employing the MRR-IV methodology, facilitated by the Design-Experiment, Ver 13., indicates that three factors exert a considerable influence on the biosorption process. The study demonstrated that the biosorption mechanism is pH-dependent, with an optimal pH of 5. The adsorption performance was found to follow Freundlich isothermal models and pseudo-first-order kinetics.