Figures (13)  Tables (4)

    • Figure 1. 

      (a) FE-SEM image of FNAC, (b) nitrogen adsorption isotherms for prepared FNAC.

    • Figure 2. 

      FT-IR Spectra of FNAC.

    • Figure 3. 

      (a) XPS spectra of FNAC [C 1s], (b) XPS spectra of FNAC [O 1s].

    • Figure 4. 

      Influence of pH on % removal of BB3 at [BB3] = 100 mg/L, FNAC dose = 0.10 g/100 mL, temperature = 298 K, and contact time = 140 min.

    • Figure 5. 

      Influence of FNAC dose on % removal and adsorption capacity of BB3 at [BB3] = 500 mg/L, pH = 6.5 ± 0.1, temperature = 298 K, and contact time = 140 min.

    • Figure 6. 

      Influence of BB3 and contact time on % removal of BB3 at FNAC dose = 0.10 g/100 mL, pH = 6.5 ± 0.1, temperature = 298 K, and contact time = 140 min.

    • Figure 7. 

      Plot of the Langmuir isotherm model for the adsorption of BB3 on FNAC.

    • Figure 8. 

      Plot of Freundlich isotherm model for the adsorption of BB3 on FNAC.

    • Figure 9. 

      Pseudo-second order plot for adsorption of BB3 on FNAC at FNAC dose = 0.10 g/100 mL, pH = 6.5 ± 0.1, temperature = 298 K, and contact time = 140 min.

    • Figure 10. 

      Pseudo-first order plot for adsorption of BB3 ions on FNAC at FNAC dose = 0.10 g/100 mL, pH = 6.5 ± 0.1, temperature = 298 K, and contact time = 140 min.

    • Figure 11. 

      Intraparticle diffusion plot for adsorption of BB3 ions on FNAC at FNAC dose = 0.10 g/100 mL, pH = 6.5 ± 0.1, temperature = 298 K, and contact time = 140 min.

    • Figure 12. 

      Mechanism of adsorption of BB3 dye on the FNAC surface.

    • Figure 13. 

      (a) Effect of solvent on regeneration of FNAC. (b) FNAC reusability.

    • Isotherm Isotherm constant Constant values
      Langmuir qmax (mg/g) 389.1
      R2 0.9986
      RL 0.0169
      Freundlich KF (mg/g) 84.63
      1/n 0.3453
      R2 0.8981

      Table 1. 

      Langmuir and Freundlich isotherm constants for the BB3 adsorption onto FNAC.

    • Adsorbent Surface area (m2/g) qmax (mg/g)/
      % removal      		 Ref.
      Heveabra siliensis seed coat 1,225 227.27 [27]
      Silybum marianum stem 122.56 36.8 [28]
      Waste ash 935 2.73 [29]
      Persea americana nuts 1,593 625 [30]
      Cedar sawdust 1.33 85.3 [31]
      Carbon-silica composite 297 1,295.9 [32]
      Sugar cane bagasse − 72.32% [33]
      Macadamia seed husks 99.0% [34]
      Fox nut shell 1,813.2 374.6 Current study

      Table 2. 

      Evaluative analyses of the adsorption capacity of BB3 across various adsorbent substrates.

    • Kinetic models Parameters Initial dye concentration (mg/L)
      100 200 300 400 500
      Pseudo-first order kinetic qe (mg/g) 52.71 66.91 72.85 85.72 155.94
      k1 (min−1) 0.0685 0.0457 0.0278 0.0340 0.0660
      R2 0.9575 0.9861 0.9357 0.9447 0.9613
      Pseudo-second order kinetic qe (mg/g) 100.5 196.08 285.71 357.14 384.61
      k2 [/g(mg·min)] 0.00337 0.00171 0.0010 0.0009 0.00112
      R2 0.9994 0.9982 0.9953 0.9992 0.9968
      qe (mg/g) [experimental] 97.2 191.5 281.7 343.6 374.6

      Table 3. 

      Variables computed from the PFO and PSO kinetic model.

    • Temp (K) ∆S° [J(K·mol)] ∆H° (kJ/mol) ∆G° (kJ/mol)
      298 −123.72 ± 5.19 −43.62 ± 2.07 −6.751 ± 0.39
      303 −6.133 ± 0.42
      308 −5.514 ± 0.33

      Table 4. 

      Thermodynamic parameters concerning the adsorptive elimination of BB3 by FNAC.