Figures (6)  Tables (1)

    • Figure 1. 

      (a) SEM image, (b) EDS spectrum, (c) XRD pattern, and (d) FTIR spectrum of nMgO/Py-HyC.

    • Figure 2. 

      (a) Adsorption isotherms and (b) thermodynamic plot of fluoride ions on nMgO/Py-HyC.

    • Figure 3. 

      Effects of pH on F− adsorption by nMgO/Py-HyC.

    • Figure 4. 

      Effect of coexisting (a) SO42−, (b) NO3−, and (c) HCO3− on F− adsorption by nMgO/Py-HyC.

    • Figure 5. 

      (a), (b) SEM images and EDS spectra of nMgO/Py-HyC after fluoride adsorption; (c) FTIR spectra, and (d) XRD patterns before and after fluoride adsorption.

    • Figure 6. 

      XPS spectra of nMgO/Py-HyC before and after the adsorption of fluoride ion.

    • Adsorbent material Adsorption
      capacity (mg/g)      		 Dosage
      (mg/L)      		 pH Mechanisms Ref.
      Mn-modified natural bentonite 2.64 40 6.2 Electrostatic interaction; ion exchange; surface complexation [48]
      Natural clay adsorbent 16.05 20 6 ± 0.5 Ion exchange; electrostatic interaction; surface adsorption [49]
      MnO2/graphene oxide composite 2.52 0.5–2.0 7.0 ± 0.5 Electrostatic interaction; surface complexation [50]
      Zr-based MOFs 40.26 4 5.0 Ligand exchange; electrostatic interaction;
      metal–fluoride complexation      		 [51]
      UiO-66/CF composite 295.00 200 7.0 ± 0.5 Anion exchange; Zr–F complexation; electrostatic attraction [52]
      Corn stalk biochar 75.20 1,000 7.0 AlCl3 modification increases aluminum active sites [53]
      Fe3O4/mSiO2/mLDH 28.52 1,000 6.0 Anion exchange; electrostatic interaction; surface complexation [54]
      Co/Mg/Al-LDH 38.01 500 5.0 Anion exchange; surface complexation [55]
      Mg/Al/La-LDHs 62.33 1,000 6.0 Anion exchange; ligand exchange; electrostatic attraction [56]
      MgO-modified biochar 83.05 1,000 8.0 ± 0.2 Mg–F complexation; precipitation; electrostatic attraction [46]
      MgO/RH 63.47 1.0 7.0 Biochar preparation followed by MgO loading and calcination [57]
      MgO/SCG 141.98 1.0 7.0 Biochar preparation followed by MgO loading and calcination [57]
      nMgO/Py-HyC 469.64 1.0 7.0 ± 0.1 Hydrothermal pre-carbonization followed by one-step
      MgCl2-assisted pyrolytic modification      		 This study

      Table 1. 

      The performance and mechanisms of F− removal by different materials