Biosorption investigation of Cu(II) ions from aqueous solutions using sericin–alginate particles: Kinetic, equilibrium, and thermodynamic

In this study, sericin–alginate particles are produced for use as a biosorbent to remove Cu(II) ions from an aqueous solution in a batch biosorption system. Sericin is a protein present in silkworm cocoons and is considered a byproduct of the silk industry. Its use in the production of biosorbents has emerged as an environmentally friendly alternative. Sericin–alginate particles are characterized using N 2 physical adsorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy, and point of zero charge. Additionally, they are evaluated via kinetic, isothermal, and thermodynamic biosorption tests. Kinetic modeling is performed using Lagergren pseudo-first-order, pseudo-second-order, Weber–Morris intraparticle diffusion, homogeneous solid diffusion, and external liquid-film diffusion models. For equilibrium modeling, the Langmuir, Freundlich, and Temkin isotherm models are applied. The Cu(II) ions biosorption is spontaneous and exothermic, as biosorption capacity decreases with temperature: 87.27 mg g -1 (20 °C), 82.54 mg g -1 (40 °C), and 76.18 mg g -1 (60 °C). Based on kinetic modeling, it is verified that internal mass transfer limits the biosorption rate. The Langmuir isotherm model shows a better fit for the biosorption equilibrium, indicating that biosorption occurs in the monolayer. Tests to evaluate the reusability of sericin–alginate particles are performed. It is discovered that even after five adsorption–desorption cycles, the biosorbent shows excellent biosorption capacity. The obtained results and a comparison of the biosorption capacity of different biomaterials demonstrate the high potential of the sericin–alginate particles as a biosorbent for Cu(II) ions. • Sericin-alginate particles are efficient for removing Cu(II) ions by biosorption. • Kinetic, isothermal, and thermodynamic tests were performed in this study. • The biosorbent had a maximum adsorption capacity of 87.27 mg g -1 for Cu(II) ions. • The particles presented a high adsorption potential compared to other biosorbent. • There was almost no change in adsorption capacity after five cycles of reuse.