Figures (7)  Tables (4)

    • Figure 1. 

      Synthesis of magnetic hydrochar through hydrothermal carbonization.

    • Figure 2. 

      (a) FTIR, (b) XRD, and (c) XPS analysis of flax shives and eucalyptus sawdust hydrochar.

    • Figure 3. 

      The high-resolution XPS spectra of (a) C 1s, (b) O 1s, (c) N 1s, and (d) Fe 2p.

    • Figure 4. 

      (a), (b) VSM, and (c), (d) BET analysis of flax shives and eucalyptus sawdust hydrochar.

    • Figure 5. 

      The surface morphology of (a)–(c) FS-HC, (d)–(f) FS-Fe-HC, (g)–(i) ES-HC, and (j)–(l) ES-Fe-HC.

    • Figure 6. 

      Removal efficiency influenced by (a) adsorbent dose, (b) initial concentration of PCP, (c) pH, (d) point of zero charge, (e) contact time, and (f) reusability.

    • Figure 7. 

      Kinetic analysis of PCP adsorption using (a) FS-Fe-HC, and (b) ES-Fe-HC, and isotherm model fitting for PCP adsorption using (c) FS-Fe-HC, and (d) ES-Fe-HC.

    • Biomass Flax shives Eucalyptus sawdust
      Proximate analysis (wt%)
      Moisture 1.04 ± 0.15 1.36 ± 0.04
      Volatile 95.99 97.64
      Fixed carbon 2.48 1.91
      Ash 1.78 ± 0.25 0.72 ± 0.27
      Biochemical analysis (wt%)
      Cellulose 45 ± 5.92 42 ± 5.38
      Hemicellulose 29.67 ± 4.91 27 ± 5.01
      Lignin 25 ± 1.82 31 ± 2.45

      Table 1. 

      Proximate and biochemical analysis of flax shives and eucalyptus sawdust

    • Biomass BET surface area (SBET) (m2/g) Total pore volume (cm3/g) Average pore diameter (nm)
      FS-HC 4.3803 0.0269 12.29
      ES-HC 0.8796 0.0548 125.52
      FS-Fe-HC 118.49 0.4271 7.21
      ES-Fe-HC 87.74 0.4393 10.01

      Table 2. 

      BET analysis of FS-HC, ES-HC, FS-Fe-HC, and ES-Fe-HC

    • Adsorbent Adsorbent dose (g/L) Time (h) PCP (mg/L) pH Removal efficiency (%) Ref.
      Flax shives hydrochar 0.1 0.33 10 3 81 [25]
      Fe3O4−SiO2 decorated carbon nanotubes 0.5 2 100 2.5 98 [54]
      Carbon nanotubes 0.35 1 1 − 88 [59]
      Fungal biomass 1 6 1 3 100 [53]
      Sunflower seed waste 40 1 5 2.5 84 [60]
      FS-Fe-HC 0.4 1 10 4 95 This study
      ES-Fe-HC 0.3 0.58 10 4 88 This study

      Table 3. 

      Summary of different biomass waste-based adsorbents for PCP removal

    • FS-Fe-HC ES-Fe-HC
      Kinetics Pseudo-first order model Qe(exp) (mg/g) 1.227 1.336
      Qe(cal) (mg/g) 1.21 ± 0.01 1.31 ± 0.008
      k1 (min−1) 0.32 ± 0.02 0.001 ± 0.01
      R2 0.995 0.997
      χ2 0.0006 0.0005
      Pseudo-second order model Qe(cal) (mg/g) 1.23 ± 0.01 1.36 ± 0.03
      k2 (g/mg/min) 0.73 ± 0.14 1.0 ± 0.55
      R2 0.992 0.969
      χ2 0.001 0.005
      Isotherm models Langmuir model Qm (mg/g) 2.58 ± 0.64 57.99 ± 6.71
      KL (L/mg) 0.63 ± 0.29 1.22 ± 0.34
      RL 0.137 0.075
      R2 0.928 0.957
      KF 0.93 ± 0.09 28.92 ± 2.5
      χ2 0.02 9.56
      Freundlich model 1/n 0.628 0.492
      n 1.59 ± 0.36 2.03 ± 0.44
      R2 0.861 0.860
      χ2 0.039 31.08
      Temkin model AT (L/g) 5.88 ± 0.76 10.51 ± 1.63
      bT 0.583 ± 0.04 13.49 ± 0.98
      R2 0.971 0.973
      χ2 0.008 5.96

      Table 4. 

      Kinetics and isotherm models for PCP adsorption using FS-Fe-HC and ES-Fe-HC