Enhancement adsorption of hexavalent chromium from aqueous solution on polypyrrole using ethylamine group

<p>A novel nanospheres adsorbent was successfully prepared using functionalized 1H-Pyrrole-1-ethanamine by homopolymerization. It could be easily protonated to form double-charged repeating structural units on the surface of nanospheres. The physic-chemical properties were characterized by SEM, TGA, XPS and Zeta potential. The effects of initial pH, adsorbent dosage, contact time, initial concentration, and ionic strength were studied in detail. The maximum adsorption capacity of Chromium(VI) was about 729.09 mg g⁻¹ at room temperature. Electrostatic attraction played an important role in the adsorption process and the size of the ion group had a greater effect on the adsorption performance than the charge.</p

A Comparison of New Gemini Surfactant Modified Clay with its Monomer Modified One: Characterization and Application in Methyl Orange Removal

New gemini surfactant, glycol bis-<i>N</i>-tetradecyl nicotinate dibromide (designated E_G), and the corresponding monomer, methyl <i>N</i>-tetradecyl nicotinate bromide (E_S), were synthesized and utilized to modify sodium bentonite (Na-Bt). E_G-Bt and E_S-Bt, the surfactant modified bentonites, were then used for methyl orange (MO) removal from the dye solution. E_G was more effective than E_S at expanding the interlayer space of Na-Bt. The adsorption of E_G, E_S and MO obeyed well the pseudo-second-order kinetic model and Langmuir isotherms on Na-Bt or on the modified bentonite. However, the adsorption of E_G was more spontaneous than that of E_S, and E_G replaced more small particles, such as Na⁺ and water, than E_S did during the adsorption on Na-Bt. The elevated temperature impairs the adsorption of the surfactants, but enhances that of MO. MO absorbed more easily on E_G-Bt than on E_S-Bt. When the dosage of the surfactants used goes beyond a certain amount, the uptake of MO by E_G-Bt/E_S-Bt decreases slowly owing to desorption of the surfactants. E_G and E_S formed a complex with MO on the modified bentonite as evidenced by UV–vis spectra, and E_G exhibited the stronger interaction with MO

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

<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

Decarbonylation of Lactic Acid to Acetaldehyde over Aluminum Sulfate Catalyst

Decarbonylation of lactic acid to acetaldehyde over several solid catalysts was investigated. Among the tested catalysts, aluminum sulfate has an excellent activity. In order to further understand the main reason which influenced the catalytic activity, NH₃-TPD was used to estimate the acidity of the catalyst. According to the total acid amount, aluminum sulfate has a moderate amount. Heteropolyacids have strong acidity which caused serious carbon deposition on the surface of catalysts, resulting in a rapid deactivation of catalysts. Besides, FT-IR, XRD, and SEM were also utilized to characterize the fresh catalysts and the used. As for the aluminum sulfate catalyst, an evident adsorption band occurs in 2970 cm^–1, suggesting a formation of poly lactate on the surface of the catalyst, and led to deactivation of the catalyst. Other parameters such as reaction temperature, lactic acid concentration, and LHSV (liquid hourly space velocity) were also discussed. Inspiringly, at high LHSV, lactic acid was efficiently converted to acetaldehyde via a decarbonylation reaction. As for stability and the recovery of aluminum sulfate, deactivation of the catalyst belongs to temporary deactivation caused by poly lactate covering the active sites of the catalyst, and only at simple calcination under the air atmosphere, the catalyst may be compeletely regenerated. Under the optimal reaction conditions, conversion of lactic acid achieved 100%, and the selectivity of acetaldehyde achieved 92.1% at 380 °C over the aluminum sulfate catalyst

Self-Assembly and Anticorrosive Property of <i>N</i>‑Alkyl-4-[2-(methoxycarbonyl)vinyl]pyridinium Bromides on X70 Steel in an Acid Medium: an Experimental and Theoretical Probe

A new type of self-assembly inhibitors, <i>N</i>-alkyl-4-[2-(methoxycarbonyl)­vinyl]­pyridinium bromide surfactants (designated as PPA-<i>n</i>, <i>n</i> = 8, 10, 12, and 14), has been synthesized and characterized by various spectrum methodologies. The anticorrosive performance of PPA-<i>n</i> on X70 steel in 5 M HCl was evaluated via weight loss and electrochemical methods as well as theoretical calculation. Scanning electron microscopy, energy-dispersive spectroscopy, and X-ray photoelectron spectroscopy evidenced that PPA-<i>n</i> molecules self-assembled and formed a compact monolayer on the X70 surface, which blocked the active sites and elevated the energy barrier of the corrosion reaction of X70 steel. The inhibitory efficiency of PPA-<i>n</i> was up to 98% at 75 μM PPA-14. The inhibition capacity as well as resistance to corrosion at higher temperature increased with prolonged alkyl chain in PPA-<i>n</i>. Density functional theory calculation suggested that the ester group and pyridinium ring might be the most active sites for PPA-<i>n</i> adsorbing on the X70 steel surface via the π* orbital of the pyridinium accepting the 4s electrons of iron and empty 3d orbital of iron taking up the nonpair electrons of the O atom in PPA-<i>n</i>. The energy gap of the frontier orbitals of PPA-<i>n</i> are in the order of PPA-8 > PPA-10 > PPA-12 > PPA-14, inferring a contrary order in the inhibition efficiency