Construction of C8/threonine-functionalized mesoporous silica aerogel based on mixed-mode and its adsorption properties for both anionic and cationic dyes

High adsorption and desorption efficiencies for both anionic and cationic dyes are still a challenge for adsorbents to treat dyestuffs wastewater. In this study, the C8/threonine-functionalized mesoporous silica aerogel based on mixed-mode was constructed to overcome the challenge, with properties of hydrophobicity and switchable surface charge of n-octyl and threonine groups. With methylene blue and azophloxine as cationic and anionic dye models, batch tests were conducted. The consequences proofed the adsorption process was efficient and fast, and the highest adsorption quantities for methylene blue and azophloxine were estimated as 274.30 mg/g and 152.43 mg/g, respectively. Additionally, the adsorbent showed good removal efficiency and reusability. The desorption efficiencies exceeded 97% using low concentration HCl or NaOH as eluents. Mechanism investigation proved that adsorption process relied on hydrophobicity and electrostatic interactions. These results instructed that SG-C8/Thr was a promising adsorbent with excellent adsorption and desorption efficiencies for both anionic and cationic dyes.