Effect of <sup>60</sup>Co Irradiation on Boehmite\nDissolution in Caustic Solutions

Here, we examine how radiation impacts the dissolution\nbehavior\nof boehmite by subjecting dry nanoparticles of different sizes to <sup>60</sup>Co γ radiation and subsequently analyzing their dissolution\nbehavior in caustic solutions as a function of temperature. The measured\nkinetics show that irradiation with an amount 228.24 Mrad significantly\nslows the dissolution rate, particularly for smaller sizes at lower\ntemperatures. Specifically, the temperature-dependent dissolution\nrates of irradiated 20 nm boehmite versus pristine material in 3 M\nNaOH solutions were several times lower (e.g., rate constant of 0.026\nvs 0.075 h<sup>–1</sup> at 60 °C), with an apparent activation\nenergy 40 kJ mol<sup>–1</sup> higher. Although various imaging\ntechniques and X-ray diffraction measurements consistently revealed\nno obvious differences between pristine and irradiated samples, after\nirradiation significant binding energy shifts were detected in the\nX-ray photoelectron Spectroscopy peaks of Al 2p and O 1s, and a change\nin their relative intensities indicated a lower O/Al ratio. This suggests\nthat γ-irradiation may stabilize boehmite particle surfaces\nby driving their chemistry and structure toward more stable aluminum\noxide forms. This finding may help explain slower dissolution rates\nof boehmite in nuclear waste and may be useful for the development\nof more robust predictive models and effective strategies for waste\nprocessing.