Adsorption of uranium (VI) ions by LDH intercalated with L-methionine in acidic water: Kinetics, thermodynamics and mechanisms

The release of uranium into water bodies through nuclear industrial effluents is a great threat to the environmental and ecological security. In this work, removal of uranyl ion (UO₂²⁺) from acidic aqueous solution has been conducted by using a homemade hybrid of Layered Double Hydroxide intercalated with L-methionine (Meth-LDH). Characterization of this adsorbent was conducted by XRD, EDS, BET, FTIR and XPS analyses. The UO₂²⁺ uptake performance as well as the kinetics, thermodynamics, and mechanisms involved were studied. The results showed that the current adsorbent was efficient for uranyl ion adsorption with 99.34% removal with a maximum adsorption capacity of 217.39 mg/g from aqueous solution at pH 4 and 25 °C. The adsorption kinetics and isotherms fitted well with the pseudo-second-order and Langmuir models. The thermodynamic parameters indicated that the adsorption process was spontaneous and feasible. The high distribution coefficient (K_d = 1.25 × 10⁶ mL/g) at low pH showed promising potential of Meth-LDH for selective removal of UO₂²⁺. Based on experimental results, the formation of an amphoteric organic-inorganic hybrid of LDH adsorbent was confirmed. Moreover, the high UO₂²⁺ uptake performance was dependent on the electrostatic interactions and complexation with the specific surface chemistry of Meth-LDH.