Coupling coagulation-flocculation-sedimentation with adsorption on biosorbent (Corncob) for the removal of textile dyes from aqueous solutions

This study evaluated the efficacy of combining the coagulation-flocculation-sedimentation (CFS) process with adsorption onto corncob biosorbent for the removal of textile dyes from aqueous solutions. The synthetic dyes tested were Bemacron Blue RS 01 (BB-RS01), a disperse dye, and Bemacid Marine N-5R (BM-N5R), an acid dye. Aluminum sulfate (Al₂ (SO₄)₃·18H₂O) was used as the coagulant, followed by superfloc 8396 as the flocculant. During coagulation, optimal parameters included coagulant doses (50-600 mg/L), flocculant doses (30-125 mg/L), and pH (2-11). For the adsorption phase, factors such as pH (2-11), temperature (25-45°C), contact time (0-480 min), and initial dye concentration (15-100 mg/L) were investigated. The corncob was characterized using FTIR, SEM, and pHpzc. Both Langmuir and Freundlich isotherm models were applied, with the Langmuir model demonstrating the best fit (0.92 < R² < 0.96). The CFS process achieved dye removal rates of 95.1% for BB-RS01 at pH 8 and 92.3% for BM-N5R at pH 6.5. Adsorption efficiency varied with solution pH, yielding removal rates of 26.19% for BB-RS01 at pH 6 and 7.69% for BM-N5R at pH 4. Maximum adsorption capacities were 99.5 mg/g for BB-RS01 and 46.08 mg/g for BM-N5R. This study demonstrates the effectiveness of coupling CFS with corncob adsorption for economical dye removal, utilizing agricultural waste as a biosorbent.