Enhanced adsorption of hydroxyl contained/anionic dyes on non functionalized NiSiO2 core-shell nanoparticles: Kinetic and thermodynamic profile

A green and low-cost adsorbent with both magnetic property and high adsorption capacity was prepared on the basis of nickel magnetic core with silica shell. The surface of the prepared NiSiO2 composite was not modified. The influence of different functional groups and different charged of the dyes on the adsorption process on the non functionalized NiSiO2 have been studied. The results indicated that synthesized adsorbent exhibited higher adsorption capacity for dyes with negative charge/hydroxyl groups as compared to dyes with positive charge/without hydroxyl groups due to the hydrogen bonding interaction and electrostatic interaction between the adsorbent and dyes. Adsorption kinetics and isotherms experiments were carried out and the results indicated that the adsorption process was fitted by pseudo second order kinetics and Freundlich model. The binding of these dyes with magnetic adsorbent surface mainly involves physical adsorption according to D-R model. Furthermore, the adsorption process is spontaneous and endothermic as studied from adsorption thermodynamics. The value of Delta H degree and mean free energy further confirmed that physical adsorption is the major adsorption process. After regeneration, the adsorbent still shows high adsorption capacity even for 4 cycles of desorption-adsorption.