Superior Adsorption Property of a Novel Green Biosorbent Yttrium/Alginate Gel Beads for Dyes from Aqueous Solution

A novel biosorbent yttrium/sodium alginate (Y/SA) hydrogel was prepared by the crosslinking of sodium alginate (SA) and yttrium (Y) ions and characterized by Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS), X-ray Diffraction (XRD), Fourier Transform-Infrared (FTIR), UV visible diffuse reflectance spectroscopy (UV–Vis DRS) and Thermogravimetric Analysis (TGA), respectively. The important parameters affecting the adsorption of Congo Red (CR) and Weak Acid Brilliant Blue RAW (WABB RAW) onto Y/SA were investigated systematically, respectively. The results show that Y/SA gel beads have super-strong adsorption performance for CR and WABB RAW dyes in a wide pH range of 2.0–10.0. The equilibrium data fitted by Langmuir and Freundlich models were found to completely follow Langmuir model where the obtained maximum adsorption capacities of 1567 and 1087 mg/g for CR and WABB RAW were very close to the experimental adsorption capacities, respectively, showing the adsorption of monomolecular layer. The adsorption kinetic data of two dyes by Y/SA fully accorded with the pseudo-second-order rate equation and adsorption processes were mainly controlled by intraparticle diffusion. The results of thermodynamic study indicate the feasible, spontaneous and exothermic nature of adsorption reaction. The further study revealed that electrostatic adsorption, hydrogen bonding and ion exchange reaction were the predominant adsorption for dye removal from aqueous solution by Y/SA gel beads. As a highly efficient, green and conducive to solid–liquid separation biosorbent, Y/SA hydrogel has great potential-application prospects for the purification of high-concentration dyestuff effluent.