Surface Complexation Models of Pertechnetate on Biochar/Montmorillonite Composite-Batch and Dynamic Sorption Study.

Area of Science:

• Materials Science
• Environmental Chemistry
• Radiochemistry

Background:

• Liquid wastes pose environmental risks due to radioactive contaminants like technetium (Tc (VII)).
• Developing efficient sorbent materials is crucial for the safe separation and management of Tc (VII).
• Biochar and its composites are promising candidates for adsorbing heavy metals and radionuclides.

Purpose of the Study:

• To evaluate the efficacy of two biochar-based sorbents, BC1 and BC2a, for technetium (Tc (VII)) removal from liquid waste.
• To investigate the surface properties and sorption characteristics of the biochar sorbents.
• To assess the influence of pH and kinetics on Tc (VII) sorption dynamics.

Main Methods:

• Preparation of biochar (BC1) from bamboo and its composite with montmorillonite K10 (BC2a).
• Characterization of sorbent surface properties using X-ray fluorescence (XRF) and potentiometric titration.
• Application of Chemical Equilibrium Model (CEM) and Ion Exchange Model (IExM) for surface group analysis.
• Monitoring of Tc (VII) sorption, including equilibrium isotherms, pH effects, and kinetic studies.
• Mathematical-physical modeling of sorption dynamics.

Main Results:

• Both BC1 and BC2a sorbents demonstrated good performance for Tc (VII) separation.
• BC2a exhibited higher sorption capacity and faster kinetics compared to BC1, attributed to the montmorillonite content.
• The optimal pH for Tc (VII) sorption was found to be 2-3.
• Sorption is influenced by surface group protonation and the anionic forms of Tc (VII) and Re (VII) (TcO₄^-, ReO₄^-).

Conclusions:

• Bamboo-derived biochar composites, particularly BC2a, are effective materials for the separation of Tc (VII) from liquid wastes.
• The enhanced properties of BC2a make it a more advantageous sorbent for Tc (VII) remediation.
• Understanding the role of pH and surface chemistry is key to optimizing Tc (VII) removal processes.