Insight into chitosan/mesoporous silica nanocomposites as eco-friendly adsorbent for enhanced retention of U (VI) and Sr (II) from aqueous solutions and real water.

Abstract

The chitosan chains were integrated with MCM-48 mesoporous silica in an eco-friendly composite (CH/MCM-48) of enhanced adsorption capacity. The prepared CH/MCM-48 composite was applied in systematic retention of U (VI) as well as Sr (II) ions from water as the commonly detected radioactive pollutants. It displayed promising retention capacities of 261.3\u202fmg/g and 328.6\u202fmg/g for U (VI) and Sr (II) considering the equilibrium time interval that was identified after 420\u202fmin. The composite showed the kinetic behavior of the Pseudo-First order model and the isotherm properties of the Langmuir assumption. The thermodynamic assessment of the reactions validated the retention of both U (VI) and Sr (II) ions by spontaneous, favorable, and exothermic reactions. Based on the theoretical values of entropy (-5.94\u202fkJ\u202fmol-1 (U (VI)) and -2.93\u202fkJ\u202fmol-1 (Sr (II))), Gibbs free energy (less than 20\u202fkJ\u202fmol-1), and Gaussian energy (5.77\u202fkJ\u202fmol-1 (U (VI)) and 4.56\u202fkJ\u202fmol-1 (Sr (II))) the uptake processes are related to physical adsorption reactions. The CH/MCM-48 composite is of significant recyclability and showed considerable affinities for the studied radioactive ions even in the presence of other metal ions (Cd (II), Pb (II), Zn (II), and Co (II)).