Abstract
Expanded vermiculite (EVMT) modified with polyethylenimine (PEI) was developed, characterized, and evaluated as a promising adsorbent efficacious aquatic adsorption of Thorium (Th(IV)) ions. The foremost adsorptive chemical groups and surface morphologies of EVMT and PEI modified-EVMT (PEI-EVMT) were investigated by FTIR spectroscopy and SEM/EDX techniques. The change in Th(IV) adsorption yield with respect to the experimental parameters was methodically studied using factorial design analysis. The isotherm modeling studies showed that the adsorption data were in good correlation with the non-linear Langmuir model and the adsorption capacity of the PEI-EVMT adsorbent was determined to be as 872.2 mg g−1 during the 30 min contact time at pH 5 and 20°C. The kinetic studies demonstrated that the pseudo-second-order kinetic model is well appropriate for recognizing Th(IV) adsorption mechanism onto PEI-EVMT composite. The negative ΔG° (between -19.02 kJ.mol−1 and -16.76 kJ.mol−1) showing the spontaneity of Th(IV) adsorption onto PEI-EVMT composite in a temperature range of 293 to 333 K. The negative ΔH (-34.90 kJ.mol−1) proved that the adsorption proceeded exothermically under the studied temperature range. The ΔS value (-53.97 J.mol−1.K−1) demonstrated the decreased randomness throughout Th(IV) adsorption onto PEI-EVMT composite. The adsorption efficiency of PEI-EVMT composite for the removal of 5 mL of 10 mg L−1 Th(IV) ions in wastewater samples was found 90%. The desorption/desorption yield of the composite adsorbent was determined as 94/92%, 87/81%, 74/70%, 46/40, and 32/25% after the first, third, 5th, 8th, and 10th cycle, respectively. All obtained results revealed that the developed PEI-EVMT composite can be used as a promising adsorbent for considerable elimination of Th(IV) from aquatic media.