Control of pertechnetate sorption on activated carbon by surface functional groups

Area of Science:

• Environmental Science
• Materials Science
• Radiochemistry

Background:

• 99Tc is a highly soluble radioisotope of concern for nuclear waste disposal due to poor natural adsorption.
• Activated carbon (AC) shows potential for removing Tc from aqueous solutions.
• Pertechnetate (TcO4-) is the dominant species of 99Tc in oxidizing environments.

Purpose of the Study:

• To evaluate the sorption capabilities of commercial activated carbons for TcO4- removal.
• To identify the relationship between AC surface functional groups and TcO4- sorption efficiency.
• To determine optimal AC characteristics for effective radioactive waste remediation.

Main Methods:

• Tested six commercial activated carbon materials for TcO4- sorption.
• Characterized sorption behavior across a pH range (4.5-9.5).
• Analyzed surface functional groups (carboxylic and phenolic) and their relation to sorption capacity (Kd values).

Main Results:

• Activated carbons were classified into Type I (high sorption) and Type II (low sorption).
• Type I materials exhibited high distribution coefficients (Kd) from 9.5x10^5 to 3.2x10^3 ml/g.
• Type II materials showed lower, constant Kd values (1.1x10^3-1.8x10^3 ml/g).
• High sorption correlated with the presence of carboxylic subgroups A and B; low sorption with phenolic and carboxylic subgroup C.

Conclusions:

• The effectiveness of AC for TcO4- removal is strongly dependent on its surface functional group distribution.
• Enhancing the formation of carboxylic subgroups A and B during AC processing can improve performance for radioactive waste management.
• Tailoring AC surface chemistry offers a viable strategy for mitigating 99Tc contamination.