Continuous biosorption of Cd(II) ions from aqueous solutions by sesame waste: thermodynamics and fixed-bed column studies

Abstract

The present study explored the ability of sesame waste biomass in removing Cd(II) from aqueous solutions in a fixed-bed column. The biosorbent was characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscope (SEM). There were hydroxyl group, carboxyl group, etc. on the surface of the adsorbent from FTIR. A continuous study was carried out to evaluate the effects of flow rate, initial Cd(II) concentration, and bed height on breakthrough curves. The maximum uptake of Cd(II) in a fixed-bed adsorption column was 22.88 mg g⁻¹ and the initial Cd(II) concentration, bed height, flow rate, and pH were 60 mg L⁻¹, 2 cm, 2.5 mL min⁻¹, and 5.5, respectively. Bohart–Adams, Thomas, and Yoon–Nelson models were applied to the data to predict breakthrough curves and find the characteristic parameters. Unique characteristic features of the mentioned models, such as adsorption capacity (Thomas model) and time required, for 50% breakthrough (Yoon–Nelson model) were achieved too.

Keywords:

• Sesame waste
• Biosorption
• Cadmium ion
• Fixed-bed
• Modeling
• Thermodynamic