Sepiolite functionalized with N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt. Part II: Sorption of Ni2+ ions from water

Abstract

Abstract: The sorption of Ni²⁺ on the sepiolite functionalized by covalent grafting of N-[3-(trimethoxysilyl)propyl]ethylenediamine triacetic acid trisodium salt, MSEAS, was studied in batch experiments as a function of the initial metal concentration, the equilibration time, pH value, and temperature. The modification of sepiolite resulted in an enhanced Ni²⁺ retention with a capacity of 0.261 mmol/g at 298 K. The retention of Ni²⁺ ions occurred dominantly by specific sorption and exchange of Mg²⁺ ions from the sepiolite structure. The sorption process followed pseudo-second-order kinetics. The sorption equilibrium results were best described by the non-linear form of the Langmuir Sorption Equation. The values of the thermodynamic parameters (enthalpy, free energy and entropy) were calculated from temperature dependent sorption isotherms and these values showed that the sorption of Ni²⁺ onto modified sepiolite was endothermic.