Adsorption of Cu<sup>2<hsp></hsp>+</sup> and methylene blue on dodecyl sulfobetaine surfactant-modified montmorillonite: Fid-Bau Portal

Adsorption of Cu²⁺ and methylene blue on dodecyl sulfobetaine surfactant-modified montmorillonite

Fan, Hongwei / Zhou, Limei / Jiang, Xiaohui / Huang, Qiang / Lang, Wencheng

Abstract The dodecyl sulfobetaine surfactant-modified montmorillonite (Mt-SB12) was synthesized using montmorillonite (Mt) and dodecyl sulfobetaine surfactant. The as-prepared material was used as adsorbent for removal of Cu²⁺ and methylene blue (MB) in single and binary systems. In the single systems, the results showed that the kinetics of adsorption followed the linear pseudo-second-kinetic model. The results of interlayer diffusion indicated that MB had higher diffusion rate than Cu²⁺. For the Mt-SB12, the isotherm results showed that MB adsorption followed the Langmuir and Cu²⁺ adsorption followed the Freundlich isotherm. The adsorption capacities for Cu²⁺ and MB at 298K and pH5 were (10.2 and 254.0) mg/g, respectively. For the Mt, Cu²⁺ and MB adsorptions both followed the Langmuir. The adsorption capacities for Cu²⁺ and MB at 298K and pH5 were (9.5 and 150.2) mg/g, respectively. So the dodecyl sulfobetaine surfactant-modified Mt is more beneficial to adsorb MB than Mt. Dubinin–Radushkevitch (D–R) equation indicated Cu²⁺ and MB adsorptions were chemical ion exchange adsorption and adsorption thermodynamics showed they were spontaneous and endothermic processes. In binary systems, Cu²⁺ and MB showed competitive adsorption. The adsorption capacity of Cu²⁺ or MB would be decreased with the increased concentration of another adsorbate. Mt-SB12 exhibited relative higher affinity and selectivity to MB.

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Highlights • Mt-SB12 exhibited good adsorption capacities for Cu²⁺ and Methylene blue (MB). • The kinetics of adsorption followed the linear pseudo-second-kinetic model. • The adsorptions were chemical ion exchange, spontaneous and endothermic processes. • In binary systems, Cu²⁺ and MB showed competitive adsorption. • Mt-SB12 exhibited relative higher affinity and selectivity to MB.