TY  - JOUR
AU  - Gebrearegay, Aster Woldu
AU  - Tesfaye, Melaku
AU  - Gizaw, Alemu
PY  - 2026
DA  - 2026/04/24
TI  - Cr(VI) Adsorptive Removal Using Raw <i>Cordia africana</i> Sawdust: Optimization of Operating Parameters, Kinetics, Isotherm, Thermodynamics, and Desorption Efficiency
JO  - Advances in Environmental and Engineering Research
SP  - 007
VL  - 07
IS  - 02
AB  - Hexavalent chromium (Cr(VI)) is a carcinogenic pollutant commonly found in wastewater from tanning and electroplating industries. This study investigates the efficiency of raw Cordia africana sawdust as a biosorbent for Cr(VI) removal. Batch adsorption experiments were conducted by varying pH (3-8), contact time (10-120 min), and Cr(VI) concentration (21-47 mg/L) using Response Surface Methodology (RSM) with Box-Behnken design. Characterization was performed using FTIR, SEM, BET, pH, and PZC analysis before and after adsorption to confirm uptake mechanisms. Desorption studies were conducted using 0.1 M HCl and 0.1 M NaOH. FTIR confirmed the presence of hydroxyl (3330 cm-1) and carboxyl (1733 cm-1) groups, with peak shifts after adsorption, indicating their involvement. SEM revealed heterogeneous surface morphology, and the BET surface area was 10.332 m2/g with PZC at 6.8. Optimal Cr(VI) removal of 84.5% occurred at pH 5.5, 47 mg/L concentration, and 10 min contact time. HCl-mediated desorption achieved 66.5% Cr(VI) recovery of efficiency, while the regenerated adsorbent maintained 78.8% of its initial capacity across three cycles. Kinetic analysis showed that the pseudo-second-order model best described adsorption (R2 = 0.996) with qe,cal (1.99 mg/g) matching the experimental value, indicating chemisorption as the rate-controlling step. Isotherm studies using non-linear regression (OriginPro 2024) revealed the Langmuir model as the best fit (R2 = 0.993, RMSE = 0.042) with a maximum capacity of 2.06 mg/g, suggesting monolayer adsorption onto homogeneous sites. The dimensionless separation factor (RL = 0.10-0.21) confirmed favorable adsorption. The Dubinin-Radushkevich model gave a mean free energy of E = 8.42 kJ mol-1, indicating an ion-exchange contribution. Thermodynamic parameters (ΔG° = -4.21 to -6.42 kJ mol-1, ΔH° = +18.7 kJ mol-1, ΔS° = +0.077 kJ mol-1 K-1) revealed spontaneous and endothermic adsorption. Comparative analysis with ten reported biosorbents shows Cordia africana sawdust performs favorably among unmodified materials (2.06 mg/g vs 1.58-1.94 mg/g range). However, raw sawdust cannot replace conventional methods like alkaline precipitation (which achieves >99% removal) due to capacity limitations and concerns about spent adsorbent disposal. The material shows potential as a low-cost supplementary treatment in resource-limited settings where waste biomass is abundant.
SN  - 2766-6190
UR  - https://doi.org/10.21926/aeer.2602007
DO  - 10.21926/aeer.2602007
ID  - Gebrearegay2026
ER  -