A novel removal of Ni²⁺ ions from water solutions using dispersive solid-phase extraction method with nano...

The effluent release containing heavy metals as Ni²⁺ ions has drastic risks to both the natural environment and human health. In this research, the nano Fe₃O₄/chitosan-acrylamide hydrogel was prepared as a novel nano sorbent for dispersive solid-phase extraction of Ni²⁺ ions and applied to the water sample solution. The pH, amount and type of elution solvent, the extraction time, etc. were optimized to improve the efficiency of the proposed method. Analytical parameters such as concentration factor and relative standard deviation (%) were achieved as 33.3 and 1.8%, respectively. The capacity in equilibrium sorption was calculated at 22.54 mg g^-1. Furthermore, to estimate the adsorption mode, Freundlich, Langmuir, and Temkin models were fitted with experimental isotherm data. Besides, to check the basic process of the metal adsorption mechanism, pseudo-first-order, pseudo-second-order, and Roginsky-Zeldovich models were investigated and the results were fitted with the pseudo-second-order model. The value of change in entropy (⊿S) obtained is -65.24 (J(mol K)^-1). Negative values of change in enthalpy, ⊿H in (kJ mol^-1) is -24.45 (kJ mol^-1) which indicates both physical and chemical adsorptions involved in the process of adsorption. Finally, the nano Fe₃O₄/chitosan-acrylamide hydrogel exhibited high performance to remove the Ni²⁺ ions from water sample solution.