Ming Duan

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

AbstractMontmorillonite (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 ...

Inhibitive Performance of 1,4/1,6-Bis(α-Alkyl Pyridinium ) Butane/Hexane Dibromide on A3 Steel

1,6-bis(α-alkyl pyridinium ) hexane dibromide was synthesized and confirmed by 1H NMR, 13C NMR, FT-IR and MS. The inhibitive effect of the gemini surfactants for A3 steel in 20% hydrochloric acid was evaluated by gravimetric measurement and electrochemical method. The results indicated that the inhibitive efficiency of the gemini surfactants was affected by the concentration, the length of alkyl chain and spacer in the gemini surfactants. The inhibition rate increased with concentration, the surfactants with four methylenes as spacer showed a slightly better anticorrosive performance than those with six methylenes, and the gemini surfactants with decyl chains exhibited the best inhibitive efficiency. The adsorption of these gemini surfactants on the surface of A3 steel was in accordance with Langmuir isotherm. The electrochemical experiment revealed that the gemini surfactants were mix-type inhibitors. The current density decreased noticeably with the concentration while the charge-transfer resistance increased. The pyridinium rings and positively charged nitrogen atoms in the gemini molecule adsorbed on A3 steel surface and the alkyl chains formed a hydrophobic layer by virtue of self-assembly property of surfactants. Therefore the corrosion of A3 steel was effectively inhibited by the gemini surfactants.