Sustainable regeneration of acid orange 10 via amine-functionalized silica: A scalable fixed-bed approach

This study aims to evaluate the performance of monoamine-functionalized silica gel (MS) fixed-bed columns for the continuous removal of Acid Orange 10 (AO10) from synthetic wastewater. The operational parameters were optimized, including AO10 concentration (10–50 mg/L), bed height (0.7 – 2.5 cm), and flow rate (1- 3 mL/min). Under optimal conditions (50 mg/L AO10, 0.7 cm bed height, and 1 mL/min flow rate), the MS columns achieved a breakthrough capacity of 45.07 mg/g. Moreover, the columns maintained over 93% regeneration efficiency after five cycles using mild NaOH, in contrast to conventional activated carbon, which requires energy-intensive regeneration. Breakthrough analysis showed predictable behavior. Accelerated breakthrough occurred at higher flow rates, while increased bed heights and influent concentrations extended operation time. The adsorption mechanism, well described by the Thomas and BDST models (R² > 0.95), was dominated by electrostatically driven monolayer formation. Statistical analysis (ANOVA) revealed that flow rate and bed height were the most significant operational parameters (p < 0.05). Although lab-scale synthesis costs are still high (about $525/kg), this technology has great potential for scaling up. Its modular design allows easy expansion by adding more units vertically. The estimated projected treatment cost ($0.58/m³) is competitive with current methods. With high capacity, good reusability, and low-energy regeneration, MS columns offer a sustainable option for treating textile wastewater. These findings demonstrate the potential of functionalized silica adsorbents as a sustainable solution for industrial dye pollution.