The potential of nonliving Sargassum hemiphyllum as a biosorbent for nickel(II) removal—isotherm, kinetics, and thermodynamics analysis

Abstract

The ability of non‐living Sargassum hemiphyllum to remove nickel(II) from aqueous solutions was investigated. The optimum adsorption condition was occurred at a pH range from 4 to 8, a biomass of 0.5 g L−1, and an initial nickel(II) concentration of 250 mg L−1 with a contact time of 20 min. The Langmuir, Freundlich, and Dubinin‐Radushkevich isotherm models were used to fit the adsorption isotherms. The fitting results were more in line with the Langmuir model (R2 = 0.9915), and the maximum adsorption capacity obtained by Langmuir model was 42.95 mg g−1 at 308 K, respectively. The biosorption kinetics were analyzed using the pseudo‐first‐order, pseudo‐second‐order and intraparticle diffusion, and it was determined that they followed pseudo‐second‐order kinetics (R2 = 0.9996) at 308 K. The enthalpy (ΔH°) and entropy (ΔS°) change of adsorption was 3.95 kJ mol−1 and 20.28 J mol−1 K−1, respectively, which indicated that the adsorption was spontaneous and endothermic. The biosorbents were also characterized by Fourier infrared spectroscopy (FT‐IR), Scanning electron microscopy and Energy disperse spectroscopy (SEM‐EDS), and X‐ray photoelectron spectroscopy (XPS). The characterization analysis demonstrated that the functional groups such as hydroxyl, carboxyl, amino, and methyl on the algal surface involved in the adsorption for nickel(II). Our results suggested that the nonliving S. hemiphyllum could be used as an effective biosorbent for the removal of nickel(II) from wastewater. © 2018 American Institute of Chemical Engineers Environ Prog, 38: S250–S259, 2019