Carboxylate-functionalized organic nanocrystals for high-capacity uranium sorbents

Area of Science:

• Materials Science
• Environmental Chemistry
• Nuclear Chemistry

Background:

• Uranium (U(VI)) contamination poses significant environmental and health risks.
• Development of efficient sorbent materials is crucial for uranium remediation.
• Existing sorbents often face limitations in capacity or selectivity.

Purpose of the Study:

• To synthesize and characterize novel carboxylate-functionalized organic nanocrystals (ONCs) as high-capacity uranium sorbents.
• To investigate the adsorption mechanism and performance of ONCs for U(VI) removal.
• To evaluate the efficacy of ONCs in complex industrial wastewater matrices.

Main Methods:

• Synthesis of perylene diimide (PDI) and naphthalene diimide (NDI) based ONCs.
• Characterization of ONC surface functional groups (carboxyl and hydroxyl).
• Uranium adsorption studies using uranyl ions, including kinetics and capacity measurements.
• Testing ONC performance in simulated nuclear industrial effluent.

Main Results:

• ONCs functionalized with carboxyl and hydroxyl groups exhibit high U(VI) adsorption capacity (up to 1393 mg/g).
• Adsorption kinetics follow a second-order model, indicating chemisorption as the rate-limiting step.
• Perylene-based ONCs show pH-independent U(VI) adsorption.
• Naphthalene-based ONCs removed 97.5% of U(VI) from simulated effluent with competing ions.

Conclusions:

• Carboxylate-functionalized ONCs are highly effective sorbents for uranium.
• The high adsorption capacity is attributed to the density of carboxyl and hydroxyl sites.
• These ONCs demonstrate potential for practical applications in nuclear waste treatment and environmental remediation.