Biosorption of Pb²⁺, Cr³⁺, and Cu²⁺ by peach palm sheath modified colonized by Agaricus Blazei

Abstract

In this study, the behavior of lead (Pb²⁺), chromium (Cr³⁺), and copper (Cu²⁺) ions in several aqueous solutions during biosorption of peach palm sheath colonized with Agaricus blazei (PS + A. blazei) was evaluated. The modifications of the chemical structure of the biosorbent due to fungal growth were verified by scanning electronic microscopy (SEM) which showed the differences on the material surface. Biosorption of Pb²⁺ and Cr³⁺ was dependent of solution pH. Although in natura peach palm sheath and peach palm sheath with A. blazei growth have shown different behaviors in pH evaluations for the three metals, it was chosen to use pH 5.0 in all the other experiments due to the high biosorption values for all metal/biosorbent relations when compared to other pH values. The reaction reached equilibrium in 15 min and the pseudo-second-order model presented the best results for all metal/biosorbent interactions. The data for q_max showed that for all metals PS + A. blazei was better to retain ions when compared to in natura peach palm (PS). Peach palm sheath colonized with A. blazei presented the highest biosorption capacity when interacting with Pb²⁺ ion (53 mg g⁻¹). Biosorption isotherms were tested for the mathematical models of Langmuir, Freundlich, Dubinin–Radushkevichs and Temkin, and all of them were adequate for the equilibrium experimental data. The differences of sorption affinity are directly linked to electronegativity difference which also follows this order: Pb²⁺ > Cu²⁺ > Cr³⁺. Through thermodynamic parameters, it was verified that biosorption processes are spontaneous and exothermal.

Keywords:

• Biosorption
• Heavy metals
• Agaricus blazei
• Pewa sheath

Acknowledgements

The authors thank CAPES or the fellowship (PROSUP), CNPq for the fellowship (PEBIC) and Universidade Paranaense for the financical support.