Figures (18)  Tables (6)

    • Figure 1. 

      (a) Adsorption and desorption curves, and (b) pore size distribution of MAHC.

    • Figure 2. 

      SEM images of MAHC at different magnifications. (a) 41,000×, and (b) 19,000×.

    • Figure 3. 

      (a) EDX results of MAHC element composition at the surface, (b) C, (c) O, (d) Fe, and (e) Cu.

    • Figure 4. 

      FTIR spectra of (a) sawdust, (b) hydrochar, (c) activated carbon, and (d) and MAHC.

    • Figure 5. 

      Thermal degradation characteristics of MAHC.

    • Figure 6. 

      Van Krevelen diagram.

    • Figure 7. 

      Zeta potential results of MAHC at different pH levels.

    • Figure 8. 

      Effect of pH level on the adsorption efficiency of MAHC obtained at MB concentration of 5 ppm, 24 °C, and (a) 25 ppm MAHC, (b) 50 ppm MAHC, and (c) 75 ppm MAHC.

    • Figure 9. 

      Effect of (a) MB concentration, (b) MAHC amount, and (c) temperature on adsorption capacity.

    • Figure 10. 

      (a) Langmuir, (b) Freundlich, and (c) Temkin adsorption isotherms for MB adsorption at 50 ppm MB, pH = 10, MAHC = 5–20 ppm, and 24 °C.

    • Figure 11. 

      Kinetic fits for MB adsorption on MAHC at (a) 24 °C, (b) 34 °C, and (c) 44 °C, using the pseudo-first-order model.

    • Figure 12. 

      Kinetic fits for MB adsorption on MAHC at (a) 24 °C, (b) 34 °C, and (c) 44 °C, using the pseudo-second-order model.

    • Figure 13. 

      Kinetic fits for MB adsorption on MAHC at (a) 24 °C, (b) 34 °C, and (c) 44 °C using the intraparticle diffusion model.

    • Figure 14. 

      (a) Adsorption/desorption isotherm of used MAHC, and (b) comparison of specific surface area and total pore volume between fresh MAHC and used MAHC.

    • Figure 15. 

      XPS survey scan results of MAHC before and after MB adsorption.

    • Figure 16. 

      Breakthrough curve of MAHC to treat the MB solution.

    • Figure 17. 

      MB adsorption experiment in a fixed bed column over 180 min.

    • Figure 18. 

      (a) Electrical conductivity, and the concentration of (b) total N, (c) total P, and (d) total K in the effluent over 360 min.

    • Property Value
      Electrical conductivity (μs/cm) 2,961
      Total nitrogen (mg/g) 588
      Total phosphorus (mg/g) 1,219
      Total potassium (mg/g) 1,269

      Table 1. 

      Analysis of real wastewater provided by a local potato processing facility

    • C H O1 N S2 Ash3
      Sawdust 47.76 5.90 44.34 n.d. n.d. 2.00
      Hydrochar 53.45 3.28 38.18 n.d. n.d. 5.09
      Activated hydrochar 78.42 2.72 7.88 0.28 n.d. 10.70
      MAHC 79.13 1.26 12.23 0.22 n.d. 7.16
      1 Oxygen content was estimated by difference. 2 n.d. represents not detectable. 3 Ash content was measured using thermal gravimetric analysis in air up to 900 °C and held at 900 °C for 30 min.

      Table 2. 

      Elemental composition of sawdust, hydrochar, activated hydrochar, and MAHC

    • Iodine number Value (mg/g)
      This study 612.3
      Sludge-derived activated carbon using ZnCl2[36] 531.8
      Sludge-derived activated carbon using KCl[36] 376.0
      Sludge-derived activated carbon using ZnCl2 and H2SO4[36] 446.9
      Sludge-derived activated carbon using ZnCl2 and KOH[36] 363.9
      Sludge-derived activated carbon using KOH[36] 439.0
      Acorn shell-derived activated carbon using ZnCl2[37] 37–1,209
      Calgon carbon (powdered activated carbon) > 500
      CS corporation (powdered activated carbon) 500–2,500

      Table 3. 

      Iodine number of MAHC compared with the literature and commercial activated carbon

    • Isotherm model Parameter Values
      Langmuir qm (mg/g) 2,651.606
      kL(L/mg) 0.005017
      R2 0.66229
      Freundlich 1/nf 0.81246
      kf (mg/g)(L/mg)1/n 22.15648
      R2 0.97576
      Temkin bt 0.006205
      kT (L/mg) 0.075853
      R2 0.97114

      Table 4. 

      Isotherm model parameters

    • T Pseudo-first-order Pseudo-second-order
      qe (mg/g) k1 (min−1) R2 qe (mg/g) k2 (min−1) R2
      24 °C 299.8643 0.20532 0.86046 543.4783 0.001539 0.9992
      34 °C 463.8448 0.85966 0.73901 854.7009 0.000724 0.9931
      44 °C 1437.47 0.12354 0.98077 1968.206 9.39E-05 0.9779

      Table 5. 

      Kinetic model fitting parameters for the pseudo-first-order and pseudo-second-order models

    • Temperature Stage Kp (mg/(g·min1/2)) C (mg/g) R2
      24 °C First stage 289.7151 0 1
      Second stage 118.5603 169.5876 0.99787
      Third stage 23.48912 404.37198 0.99186
      34 °C First stage 379.8602 6.56063 0.9974
      Second stage 109.46267 376.3959 0.98987
      Third stage 77.83848 439.9813 0.97312
      44 °C First stage 340.61243 73.82852 0.98758

      Table 6. 

      Kinetic model fitting parameters for the intraparticle diffusion model