Effective removal of Co(II) and Sr(II) from radiocative wastes using covalent triazine frameworks: Kinetics and isotherm studies

Adsorption of pollutants onto adsorbents is extremely important for water purification systems. In this study, the dynamic adsorption of radionuclides Co(II) and Sr(II) onto covalent triazine frameworks (CTFs) was explored. The effects of the adsorption conditions such as the amount of CTF (10, 25, and 50 mg), radionuclides concentrations (0.50–500.0 mg L −1 ), and adsorption temperature (293, 303, and 313 K) on the adsorption capacity was examined. Adsorption kinetics data were analyzed by using the pseudo-first-order and pseudo-second-order kinetic models. Langmuir and Freundlich models were used for analyzing adsorption isotherms. The results showed that the Langmuir isotherm and pseudo-second-order models described the experimental data better than the other models. The adsorption equilibrium time of CTF-N and CTF-B are 600 s and 200 s. The maximum monolayer adsorption capacity (q max ) of CTF-B and CTF-N for Co(II) were determined as 50.76 mg g −1 and 60.82 mg g −1 at 303 K. The q max of CTF-B and CTF-N for Sr(II) were 43.12 mg g −1 and 55.89 mg g −1 at 303 K. Thermodynamic analyses indicated that the adsorption process of Co(II) and Sr(II) onto CTF was spontaneous (ΔG < 0) and endothermic (ΔH > 0) and was favored at higher temperature.