Reusable alginate-based hybrid granular activated carbon from sugarcane bagasse residues for secondary decolorization of clear liquor in sugar refining

• Alginate-based GAC was developed at 1:2 (w/w) ratio of leached ash and SCB-AC. • The selected SCB hybrid GAC reduced clear liquor color to 187 IU (63%) at pH 7. • 4-cycle regeneration with 40% ethanol retained >80% efficiency with no deformation. • Low flow rate (0.1 ml/min) in continuous column prolonged breakthrough time. • Reusable hybrid GAC can be applied to secondary decolorization in sugar refining. To overcome limitations associated with powdered adsorbents in sugar refining and to support the valorization of sugar industry byproducts, alginate-based hybrid granular activated carbons (GACs) were developed by incorporating sugarcane bagasse-derived activated carbon (SCB-AC) and acid-leached sugarcane bagasse ash (L-SCBA) into calcium alginate hydrogels. Among the five formulations evaluated, the hybrid GAC with a 1:2 weight ratio of L-SCBA to SCB-AC (L-SCBA1:SCB-AC2) achieved a decolorization efficiency of approximately 63% in batch experiments using synthetic clear liquor (500 IU, pH 7), reducing the effluent color to 187 IU within the typical industrial target of 200 ± 50 IU. Although this formulation exhibited a relatively low BET surface area (282 m 2 /g), it outperformed a commercial hybrid GAC (MPS1:CPAC2). This was probably due to the presence of surface functional groups and its pH-responsive adsorption behavior. Regeneration with 40% ethanol under mild conditions preserved over 80% decolorization efficiency across four consecutive cycles, without observable granule deformation. Fixed-bed column in continuous experiments further confirmed that lower flow rates extended breakthrough time, while performance declined in actual clear liquor presumably due to diffusion limitations from inorganic impurities and increased viscosity. These results demonstrate the potential of SCB-based hybrid GACs as a promising, reusable, and scalable alternative to conventional powdered activated carbon for secondary decolorization of clear liquor in sugar refining, applicable in both batch and column modes.