Separation of Uranyl Ion from Different Media Using a New Cellulose Hydrazone: Adsorption Isotherms, Kinetic and Thermodynamic Studies

Cellulose dialdehyde has been prepared and reacted with thiosemicarbazide to give thiosemicarbazone modified cellulose (CTSC). A new and a relatively green methodology have been developed for the selective separation and/or preconcentration of uranyl ions. Batch and column modes were applied. The newly designed cellulose quantitatively sorbed UO2(II) ions at pH 4. While, t1/2 is 15 min which decreased with increasing temperatures and the sorption rate constant Rd equal 18.565 mg g-1 min-0.5. The recovery, relative standard deviation and detection limit are found to be > 98%, < 1.7 % and 5 mg ml-1, respectively. Optimum flow rate is 5 ml min?1 which reflect higher tendency toward complexation. Desorption was effective with 0.3 mol l?1 HNO3 and/or HCl prior to detection. Langmuir, Freundlich and Dubinin-Radushkevich isotherm models were applied to analyze the experimental data. The best interpretation for the experimental data was given by the Langmuir isotherm and the maximum adsorption capacity was found to be 90.04 ± 1.00 mg/g for UO2(II) ions. Kinetic data correlated well with the pseudo first-order kinetic model, which results as k = 0.046 min-1; indicating that the chemical sorption was the rate-limiting step. Thermodynamic parameters like Gibbs free energy (?G°), enthalpy (?H°) and entropy (?S°) were evaluated by applying the Van’t Hoff equation. The thermodynamic study indicated that the adsorption process is spontaneous and endothermic in nature. The modified cellulose (CTSC) was highly ion-selective in nature even in the presence of large concentrations of electrolytes or organic media, with a preconcentration ability for UO2(II) ions in presence of DETPA. From the column mode HETP and the number (N) of theoretical plates were found to be 0.194 ± 0.02 mm, 226 ± 4 plates g-1; respectively, from breakthrough curve and 0.20 ± 0.05 mm, 214 ± 2 plates g-1; respectively, from elution of column curve. The utility of the modified cellulose to synthetic and real samples showed RSD values of < 3% reflecting its accuracy and reproducibility.