Adsorption mechanism of rhein-coated Fe3O4as magnetic adsorbent based on low-field NMR

In the present study, a magnetic adsorbent, rhein-coated magnetic Fe(3)O(4)nanoparticle (RMNP), for Pb(2+)and Mg(2+)had been developed, and adsorption mechanism was studied via low-field NMR. RMNP was characterized by TEM, FTIR, and XRD. RMNP could adsorb and remove Pb(2+)and Mg(2+)from water and was successfully applied to remove Pb(2+)and Mg(2+)from wastewater, with satisfactory recovery rates and high adsorption capacities. The calculated maximum adsorption capacity for Mg(2+)and Pb(2+)was approximately 69.3 and 64.9 mg g(-1)of RMNP, respectively, which was better than some results reported. Low-field NMR results showed that Pb(2+)or Mg(2+)enhanced the T(2)relaxation time of RMNP, which suggested that RMNP selectively coordinated with Pb(2+)or Mg(2+)and led to the aggregation of RMNP, furthermore removal of Pb(2+)or Mg(2+)from water. The standard curves for oT(2)-cation concentration exhibited good line correlation. The linear ranges were from 4.2 x 10(-6)to 2.0 x 10(-4)mol L(-1)for Pb(2+)and from 5.0 x 10(-6)mol L(-1)to 1.0 x 10(-4)mol L(-1)for Mg2+, respectively. The limits of detection were 1.4 x 10(-6)mol L(-1)for Pb(2+)and 2.1 x 10(-6)mol L(-1)for Mg2+, respectively. In short, low-field NMR could clearly display the interaction between RMNP and Pb(2+)or Mg2+, even be used to detect Pb(2+)or Mg(2+)in suitable condition. Besides, this method could be expanded to study the interaction between other magnetic adsorbents and analytes.

Automated summary

In this study, a magnetic adsorbent, RMNP, was successfully developed for the removal of Pb(2+) and Mg(2+) from water with high adsorption capacities. The adsorption mechanism was studied using low-field NMR, which revealed selective coordination between RMNP and Pb(2+) or Mg(2+). The results demonstrate the potential of low-field NMR in detecting and studying interactions between magnetic adsorbents and analytes.