Selective Anionic Dye Adsorption from Multi-Dye Mixtures Using Modified Silica Nanoparticles Derived from Sugar Cane Bagasse Ash

Power plants burning sugar cane typically generate bottom sugar cane bagasse ash (BSBA) as a byproduct. Since BSBA is rich in silica (SiO₂), it offers potential applications in dye adsorbent production. In this study, silica nanoparticles (SiO₂NPs) were synthesized from BSBA via a sol-gel method, with cetyltrimethylammonium bromide (CTAB) added during synthesis to reverse the surface charge from -28.96 to +12.06 mV, thus enhancing the adsorption of anionic dyes. The material was evaluated for methylene blue (MB), methyl orange (MO), congo red (CR), and reactive orange 16 (RO16) adsorption in single, binary, ternary, and quaternary dye systems. SiO₂NPs@CTAB showed high selectivity for anionic dyes, achieving adsorption capacities of 135.81, 159.76, and 135.59 mg g^-1 for MO, CR, and RO16, respectively. These findings confirm that SiO₂NPs@CTAB is highly selective and efficient in removing anionic dyes, while BSBA is demonstrated to be a cost-effective and sustainable silica source, promoting environmental benefits through the use of industrial waste byproducts.