Study on Adsorption Behavior of Nickel Ions Using Silica-Based Sandwich Layered Zirconium-Titanium Phosphate Prepared by Layer-by-Layer Grafting Method.

In this study, the composite of silica-based sandwich-layered zirconium-titanium phosphate was prepared by a layer-by-layer grafting method and its adsorption properties in a diluted solution of Ni ions were specifically researched by the bath experiment method. The field-emission scanning electron microscope (FESEM) results presented the smooth surface morphology of the pristine adsorbent and a rough surface morphology of the adsorbed adsorbent and the energy dispersive analysis (EDS) results ensured the presence of the original metal element (Si, O, Ti, P, Zr) and the captured nickel element on the adsorbent. The Fourier transformed infrared spectroscopy (FTIR) revealed the new band formation of -Si-Ti-O-, -Si-Ti-O-P-, and -Si-Ti-O-P-Zr-O-, which ensured the successful modification of the silica substrate by zirconium-titanium phosphate. The specific surface area and pore size distribution analysis indicated that the pore structure was changed from type-Ⅳ to H2-type and the specific surface area (BET) of the modified composite was 337.881 m/g. In the bath experiment, the optimal pH for adsorbing Ni ions on the composite was ~8 with the equilibrium time 30 min at room temperature and the maximum sorption amount was 50.1 mg/g. The adsorption kinetics of the sorption process were corresponded to the pseudo-second-order kinetic equation and the isothermal adsorption data were fitted well to the Redlich-Peterson Model. Thermodynamic simulation results revealed the species of Ni ions and provided a reasonable pH scope for better removal of the Ni element in wastewater.