In-situ synthesis of goethite-modified-Albizia lebbeck for sequestration of Zn2+ and Pb2+ from aqueous environments: Equilibrium, isotherm, and thermodynamic studies

Herein, we incoporated goethite on Albizia lebbeck pod via the in-situ coprecipitation method for an enhanced adsorption of Zn 2+ and Pb 2+ from aqueous environments. The microstructure, crystallinity, chemical state, textural properties, surface chemistry, and thermal stability of the unmodified (UNALB) and modified Albizia lebbeck (GMALB) materials were examine using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) The FTIR spectra and BET measurement of GMALB demonstrated the presence of additional functional groups including Fe-OH, and Fe-O with enhanced BET surface area of 28.762 m²/g, confirming that the modification was accomplished successfully. The incorporation of goethite enhanced the surface potential of the UNALB, offering more adsorption sites for Zn²⁺ and Pb²⁺ removal. The adsorption data of Zn²⁺ and Pb²⁺ by UNALB and GMALB were better explained by the Langmuir isotherm and pseudo-second-order kinetic models, suggesting that the adsorption process is predominance of chemisorption on homogeneous surfaces. The maximum adsorption capacities of UNALB and GMALB were 10.24 and 66.99 mg/g for Zn 2+ and 16.07 and 83.33 mg/g, outperforming that of numerous adsorbents previously reported. The adsorption thermodynamic examination revealed that the adsorption reaction was spontaneous and exothermic in character. These results underscore the potential of an effective and sustainable goethite-modified Albizia lebbeck for an heavy metals removal from an aqueous environment. • Goethite was used to modify biowaste Albizia lebbeck to produce green nanoporous GMALP. • GMALP exhibited enhanced BET surface area (28.762 m 2 /g) and pore volume (0.079 cm 3 /g). • The Langmuir isotherm predicts the monolayer coverage of 83.33 mg/g for Pb 2+ by GMALP. • Zn 2+ and Pb 2+ sorption data fitted well into Langmuir isotherm model. • Sorption of Zn 2+ and Pb 2+ occurred predominantly by chemisorption.