Adsorptive removal of rhodamine B using sodium dodecyl sulfate modified laterite soil

Abstract

Adsorption of the cationic dye Rhodamine B (RhB) onto surfactant modified laterite (SML) was studied in this work. The removal efficiency of Rab using laterite increased significantly after surface modification by pre-adsorption of anionic surfactant sodium dodecyl sulfate (SDS). Some experimental parameters such as pH, adsorbent amount and ionic strength were also investigated. The optimal conditions for RhB removal using SML were found to be pH 4, adsorbent amount 10 mg/mL and ionic strength 0.1 mM NaCl. Under optimum conditions, RhB removal efficiency increased from 25.77 % to 94.85 %, when using unmodified laterite and SML, respectively. After 5 regenerations of SML, the removal efficiency of RhB was still higher than 90 %. Adsorption of RhB onto SML decreased with increasing NaCl concentration from 0.1 to 200 mM, demonstrating that adsorption of RhB onto SML mainly induced by electrostatic attraction. The two-step adsorption model can fit the experimental results of RhB adsorption isotherms onto SML at different NaCl concentrations. Our results indicate that SML is a novel adsorbent to remove ionic dye from aqueous solution.