Sunflower seed pulp ash as an efficient and eco-friendly adsorbent for Congo red uptake: characteristics, kinetics, and optimization

Abstract

This investigation focused on the Congo red uptake, as the azo dye, from an aqueous environment. Herein, ash derived from sunflower seed pulp waste (SSPA) was used as an eco-friendly low-cost adsorbent. Based on the BET results, the specific active surface area of SSPA was approximately 102 m2/g. The effect of the initial analyte concentration (10–50 mg/L), the concentration of the adsorbent (1–5 g/L), and the processing time (10–240 min) on the rate of Congo red uptake was also evaluated and optimized. According to the results, the maximum dye removal from synthetic solution (91.89%) was achieved at a dye concentration of 50 mg/L, an adsorbent concentration of 3 g/L, and a processing time of 180 min. The maximum SSPA capacity for Congo red uptake from aquatic solution was 15.34 mg/g, achieving under optimized operational conditions. The adsorption process of SSPA also follows a pseudo-second-order kinetic model (qe = 15.85 mg/g; R2 > 0.99), considering the results of BET and FTIR, suggesting that the rate-controlling step in analyte removal is the chemical interaction between functional groups in SSPA and used dye. Finally, the SSPA washing with different solvents showed that the adsorbent treated with 1 M sodium hydroxide still performed well after his five reuses. HIGHLIGHTS Sunflower seed pulp ash (SSPA) was prepared and applied as an eco-friendly low-cost adsorbent for Congo red uptake.; Experiments showed the rate-controlling step in dye adsorption is the chemical interaction of functional groups between SSPA and Congo red.; According to the washing process of the adsorbent used by different solvents, one molar solution had a high capacity to wash the SSPA.;

Keywords

• adsorption
• ash
• congo red dye
• kinetic modeling
• sunflower seed pulp