Adsorption of Ni 2+ ions by phosphate and carbonate adsorbents

The adsorption of Ni2+ ions by sorbents based on dolomite thermally activated at 800 °C (D-800), phosphated dolomite (PD), and Zr-modified PD (PD-Zr) was studied. It was found that D-800 sample was characterized by the highest sorption capacity (364 mg/g), while at the initial concentration of Ni2+ ions of 300 mg/L, the purification of aqueous solutions to the MPC standards for drinking water (< 0.1 mg/L) was achieved, and at C0 (Ni2+) of 50 mg/L, deep purification to a residual concentration of < 0.01 mg/L occurred. It was revealed that the absorption of Ni2+ ions by the D-800 sorbent is due to the heterogeneous precipitation of nickel hydroxicarbonate, and in the case of the PD sorbent, nickel hydrophosphate is formed. The results of desorption of Ni2+ ions from saturated sorbents indicated the occurrence of ion exchange with the participation of amorphous zirconium phosphate for the PD-Zr sample. The lowest desorption degree (<1 %) was demonstrated by samples D-800 and PD. In the dynamic sorption process, the granular sorbent D-800 provided purification of more than 1000 column volumes of solution with C 0 (Ni2+) 10 mg/L below the MPC standards for drinking water at a linear filtration rate of 20 m/h.