TY  - JOUR
AU  - Gebrearegay, Aster Woldu
AU  - Tesfaye, Melakuu
AU  - Gizaw, Alemu
PY  - 2026
DA  - 2026/08/19
TI  - Dynamic Removal of Hexavalent Chromium from Aqueous Solution and Realwastewater Using Raw <i>Cordia africana</i> Sawdust in a Fixed-Bed Column System
JO  - Advances in Environmental and Engineering Research
SP  - 027
VL  - 07
IS  - 03
AB  - This study evaluated the dynamic performance of raw Cordia africana sawdust for hexavalent chromium (Cr(VI)) removal in a fixed-bed column system under varying operating conditions, using both synthetic solutions and real tannery wastewater. This represents the first comprehensive investigation combining fixed-bed operation, real wastewater validation, triple-model comparison, speciation analysis, and regeneration assessment for this locally abundant Ethiopian biomass. Fixed-bed column experiments were conducted at flow rates of 5, 8, and 10 mL/min, bed depths of 6, 9, and 12 cm, and pH 5.5 using synthetic Cr(VI) solution (47 mg/L) and real tannery wastewater. All experiments were performed in duplicate, with the optimal condition repeated in triplicate to establish measurement variability. Breakthrough curves were analyzed using Thomas, Yoon-Nelson, and BDST models with comprehensive error metrics (RMSE, MAE, AIC). Regeneration studies were conducted over three cycles using 0.1 M HCl, and comprehensive wastewater characterization was performed using ICP-OES and standard physicochemical methods. Chromium speciation analysis was conducted to assess Cr(VI) reduction during adsorption, with complete mass balance closure (99.2 ± 1.5%). Lower flow rate (5 mL/min) and greater bed depth (12 cm) improved column service time, with breakthrough time increasing from 36.0 to 50.0 min as flow rate decreased from 10 to 5 mL/min. However, the highest dynamic adsorption capacity (1.78 ± 0.06 mg/g) was observed at 10 mL/min (Run 9), reflecting faster column saturation and steeper breakthrough curves at higher hydraulic loading, rather than superior adsorbent performance. For real tannery wastewater, the adsorbent achieved 1.51 ± 0.28 mg/g—representing approximately 85% retention despite the presence of competing ions (Cu2+, Zn2+, Fe3+), high TDS (3500.97 mg/L), and elevated COD (812.00 mg/L). The Thomas and Yoon-Nelson models accurately predicted breakthrough behavior (R2 > 0.98; RMSE < 1.84 mg/L for all conditions). BDST model parameters (N0 = 1252-2132 mg/L; ka = 0.00936-0.00089 L/mg·min) confirmed decreasing adsorption driving force with bed saturation. Chromium speciation revealed partial reduction of Cr(VI) to Cr(III) during adsorption, with approximately 28% of adsorbed chromium present as Cr(III) on the spent adsorbent (mass balance closure: 99.2%). Regeneration with 0.1 M HCl maintained approximately 76% of initial capacity after three cycles. The adsorbent’s low cost ($0.10-0.15 USD/kg), natural abundance, and simple preparation requiring no chemical modification support its preliminary promise for polishing applications in resource-limited settings. This is the first report on dynamic Cr(VI) removal using raw Cordia africana sawdust with: (1) validation using real tannery wastewater, (2) comprehensive three-model comparison with error analysis (RMSE, MAE, AIC), (3) chromium speciation assessment with complete mass balance, (4) regeneration evaluation over multiple cycles, and (5) techno-economic analysis based on local Ethiopian market conditions. The combination of all five elements in a single study distinguishes this work from previous lignocellulosic biosorbent investigations.
SN  - 2766-6190
UR  - https://doi.org/10.21926/aeer.2603027
DO  - 10.21926/aeer.2603027
ID  - Gebrearegay2026
ER  -