Comparison of Fe/surfactant improved montmorillonite: adsorbing and in situ decomposing methylene blue and recycling use

Abstract

<p>Montmorillonite (MMt) was intercalated by polymeric Fe, or by N-ethyl dodecyl nicotinate bromide (EDNB), or by both. The improved MMt designated as Fe/MMt, EDNB/MMt, and EDNB/MMt/Fe, respectively. A comparison was performed on the improved MMt in the uptake and in the degradation of methylene blue (MB) as well as in the recycling use. The results showed that EDNB/MMt adsorbed more MB than the other two; however, Fe/MMt and EDNB/MMt/Fe acted faster than the former. The adsorption of MB on the three adsorbents followed Langmuir isotherm and pseudo-second-order kinetics. In addition, MB adsorbing on EDNB/MMt was also well described by intraparticle diffusion model. MB removal by EDNB/MMt experienced an endothermic and entropy driving process, but an exothermic and entropy declining process by the other two. pH of the solution affected MB removal. When pH of the solution is high than 10, MB uptake diminished on Fe/MMt and EDNB/MMt/Fe; however, it slightly increased on EDNB/MMt. MB could be decomposed by Fenton reagent on the improved MMt, and the adsorbents could be reused. By coupling the adsorption and degradation <i>in situ</i> by H₂O₂/Fe²⁺ or Fe³⁺, MB removal by Fe/MMt and EDNB/MMt/Fe was almost maintained in the ten cycles. So, present work deepens the understanding of modified MMt in the application of dye wastewater treatment.</p