Preparation and characterization of bioadsorbent beads for chromium and zinc ions adsorption

Low-cost chitosan beads were prepared by dropping chitosan solution into an alkaline bath and then were used for Cr(VI) and Zn(II) ions adsorption from aqueous solution. Prepared chitosan beads were characterized by Fourier transform infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) measurements, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The effect of solution-pH, contact time, initial ion concentration, and temperature on both metal ions adsorption was investigated. The kinetics of adsorption suggested a pseudo-second-order model fits better than pseudo-first-order model for both metals. The equilibrium adsorption isotherm of both metals matches well with the Langmuir isotherm model. The maximum adsorption capacity of chitosan beads was 79.56 mg Cr(VI)/g and 109.18 mg Zn(II)/g at initial ion concentration 1,000 mg/L, and temperature 10 °C. Thermodynamic parameters showed that the adsorption of Cr(VI) and Zn(II) ions onto chitosan beads was feasible, spontaneous, and exothermic under the studied conditions. While the chitosan beads enabled a good adsorption application, further lab work and field studies are necessary before using in a practical adsorption process.