Nickel chloride was dissolved in ultrapure water in the concentration of 5 mM and the solutions were treated both with Mn0 and with Mn12 suspension in a concentration of 850 ppm and 722 ppm, respectively, evaluated by means of ICP-MS.
Starting from the percent of nickel removed by means of the presence of the Mn12 nanoparticles, it was possible to calculate that 1 mg of Mn12 can remove 0.16 mg of [Ni.sup.2+].
The influence of pH on the ability of Mn12 to remove nickel ion from aqueous solutions was verified at four different pH values (3, 5, 7, and 8).
After 3 hours, the magnetic nanostructures were removed by means of the application of a magnet and the efficacy of the Mn12 regenerated nanostructures for nickel removal was checked by the dimethylglyoxime test.
As reported in Figure 8, the presence of [Cd.sup.2+] strongly reduced the nickel abatement in the presence of Mn12: competing adsorption of cadmium and nickel ions on the surface of the nanoparticles takes place, reducing the available sites for the absorption of [Ni.sup.2+].
Real samples of instant tea were prepared according to the procedure reported in the Materials and Methods, in order to check the efficacy of Mn12 even in complex matrices for the nickel capture.
Magnetization curves were recorded for all samples and a superparamagnetic behavior of the nanostructures obtained using 100: 0 (Mn0) and 88: 12 (Mn12) Fe: Mn weight ratio was observed.
Adsorption/desorption curves revealed that Mn12's porosity is enhanced tenfold nearly when compared to the sample Mn0.
Caption: Figure 2: SAED measurements carried out on the samples: (a) Mn0, (b) Mn12, (c) Mn25, and (d) Mn50.
Caption: Figure 5: (a) [N.sub.2] adsorption/desorption isotherms and (b) pore size distribution for Mn0 (black squares) and Mn12 (red points) samples.
Caption: Figure 6: (a) Effect of the treatment carried out by Mn0 suspension (red line) and Mn12 suspension (blue line) evaluated by means of the dimethylglyoxime test.
Caption: Figure 7: (a) Reusability of Mn12 nanostructure for [Ni.sup.2+] decontamination after EDTA treatments revealed by dimethylglyoxime test and (b) influence of the number of regenerations on the [Ni.sup.2+] removal.