Characterization of Two Bulgarian Herbs for Use as Biosorbents for Copper(II)

Abstract

Two biomaterials based on the abundant Bulgarian medicinal plants Mentha spicata L. (denoted as MS) and Ruta graveolens L. (denoted as RG) were investigated as environmentally friendly biosorbents for Cu(II) removal from aqueous solutions. Grain size distribution, slurry pH, texture parameters, thermal behavior and mineralogical composition of MS and RG were determined. Instrumental methods such as scanning electron microscopy (SEM), X-ray-diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett–Teller (BET) analysis, differential thermal analysis (DTA), and thermogravimetric analysis (TGA) were used for their characterization. It was demonstrated that the surface morphology of both materials is rough and contains pores that could entrap different pollutants, as well as functional groups that can attach metal ions. In order to examine the feasibility of these materials for use as biosorbents for heavy metals, adsorption experiments were performed. The results for the removal of Cu(II) ions from aqueous solution reveal capabilities suggesting that both materials have potential to be used as promising, efficient and low-cost biosorbents.

Keywords:

• Biosorption
• Brunauer–Emmett–Teller analysis
• Bulgarian herbs
• copper(II) ions
• differential thermal analysis
• Fourier transform infrared spectroscopy
• scanning electron microscopy
• thermogravimetric analysis
• X-ray-diffraction

Acknowledgments

The authors thank to the program for supporting young scientists and Ph.D. students from the Bulgarian Academy of Sciences – 2017 (Project No DFNP-17-35/25.07.2017) for the financial support.