Adsorption of anionic azo dyes on cationic surfactant-modified corn stalks: optimization studies

Abstract

Adsorption is widely recognized as one of the most effective methods for treating wastewater contaminated with synthetic dyes. Its advantages include high efficiency, selectivity, environmental safety, and process simplicity. Research focused on optimizing the adsorption removal of commonly used anionic dyes, particularly through the utilization of novel adsorbents derived from agro-industrial wastes, holds significant importance. This study aimed to optimize the removal of anionic dyes (Acid Red 14 and Acid Orange 20) from aqueous solutions using corn stalks modified with cetylpyridinium bromide. Optimization was conducted using response surface methodology (RSM) coupled with a central composite design (CCD). We have examined the effects of pH, adsorbent dose, initial dye concentration, and temperature on the removal efficiency of both Acid Red 14 and Acid Orange 20. The developed mathematical models were validated using analysis of variance (ANOVA). The quadratic regression equations showed high coefficients of determination (R? = 0.9835 for Acid Red 14 and R? = 0.9964 for Acid Orange 20), which were statistically significant (P < 0.05). It was found that the linear effects of pH, adsorbent dose, initial dye concentration, and temperature were statistically significant for the effective removal of both dyes. Among these factors, the adsorbent dose exhibited a strong synergistic effect, while pH, initial dye concentration, and temperature showed antagonistic effects. Furthermore, the interaction between initial dye concentration and pH had a pronounced antagonistic effect on the adsorption process. Optimal conditions for maximum dye removal were determined to be a pH of 2, an adsorbent dose of 10.5 g?L–1, an initial dye concentration of 50 mg?L–1, and a temperature of 20 °C. Under these conditions, removal efficiencies of 98 % for Acid Red 14 and 99 % for Acid Orange 20 were achieved. The results obtained can contribute to the development of effective wastewater treatment technologies targeting anionic azo dyes. The use of modified agro-industrial wastes as adsorbents for anionic azo dyes offers dual benefits by reducing both treatment costs and biomass disposal issues.