Removal of Sodium Dodecylbenzenesulfonate from Aqueous Solution Using Quaternary Ammonium-Modified Paper Fibers

This study explores the removal of the anionic surfactant sodium dodecylbenzenesulfonate (SDBS) from aqueous solution using paper fibers functionalized with quaternary ammonium groups. The paper fibers used in the adsorbent were derived from waste paper, and under alkaline conditions, the quaternary ammonium groups were grafted onto the hydroxyl groups on the cellulose 6 position via the Williamson reaction, thereby producing cationic cellulose. Through the characterization of modifier, we confirmed that the product was a dodecyl dimethyl quaternary ammonium salt. The successful modification of the paper fibers by a quaternary ammonium salt was confirmed by analyzing the structural characteristics of the fibers before and after modification. The modification rate was about 36.6%. The results of the adsorption experiment with SDBS solution showed that compared with unmodified paper fibers, the adsorption capacity of modified paper fibers for SDBS increased by about 8 times and the SDBS removal rate was 97.6%. The optimal adsorption conditions were pH 7, an adsorbent input of 0.3 g, and a shaking time of 6 h. It was determined that the adsorption process was more consistent with pseudo-second-order adsorption kinetics, and the Langmuir adsorption isotherm equation indicated that the adsorption process was monolayer adsorption, with a maximum capacity reaching 90.9 mg/g. Finally, thermodynamic analysis showed that adsorption occurred spontaneously and exothermically.