Encountering Unprecedented Phase Transformation of Bentonite and Evaluating Its Extraction Efficiency To Sequester ReO 4 – (Surrogate of TcO 4 – ) from a Simulated Radwaste Solution

Herein, we report an experimental investigation unraveling the thermal behavior of raw bentonite using in situ high-temperature X-ray diffraction, illustrating partial phase transformation which is not reported elsewhere to the best of our knowledge. The Le-Bail fit to the diffraction pattern, along with the surface morphology study, substantiates the partially formed phase to be zeolite-A. Despite the transformation, raw bentonite exhibited the highest porosimetry parameters at ambient temperature, and thus, it was directly employed for the extraction of perrhenate (ReO 4 – ) ions, which are surrogates for radioactive pertechnetate ( 99 TcO 4 – ) ions, without any surface modification. The adsorption data fitted well with the Langmuir isotherm model ( R 2 = 0.978), estimating a maximum sorption capacity of 293 mg g –1 at pH ∼ 7, surpassing most minerals reported earlier. The XPS and FT-IR spectra validate the speciation of adsorbed rhenium. This work also paves the way for the extraction of 99 TcO 4 – and other toxic anions.