PVC-zeolite nanoparticle-surfactant anion exchanger membrane: preparation, characterization, and its application in development of ion-selective electrode for detection of sulfate

Anion sensing properties of electrospun nanofibers incorporating a thiourea-based chromoionophore in methanol

To sense hydrophilic anions in protic solvents, we fabricated polymethylmethacrylate (PMMA) nanofibers incorporating 4-nitrophenyl azo thiourea polymer as a chromoionophore. When methanol solutions containing anions contacted the PMMA nanofiber, a bathochromic shift from 386 nm was observed in the absorption maximum of the chromoionophore. This spectral change is due to hydrogen bond formation between the urea moiety of the thiourea-based polymer and anions penetrating the nanofiber. This spectral change was not observed in PMMA film incorporating the same anion sensor, and the difference is attributed to the much larger specific surface area of the nanofiber compared to the film. As a result, many anions could react with the anion-sensing polymers in the nanofiber and induce a large spectral response.

Determination of Sulfate Ion with 2-Aminoperimidine Hydrobromide Using an Optode Based on Tetrabromophenolphthalein Ethyl Ester Membrane

An optode method for the determination of sulfate ion was developed. The optode membrane is 2-nitrophenyl octyl ether-plasticized poly(vinyl chloride) membrane containing tetrabromophenolphthalein ethyl ester. The method is based on formation of an ion associate between the excess of 2-aminoperimidine hydrobromide (Ap) and sulfate ion in the sample solution, and detection of the concentration of the remaining Ap ion by the optode. Under the optimal conditions, a good linear relationship was found to exist between the absorbance of the optode membrane, and concentrations of sulfate ion in a concentration range from 20 to 400 μM. The developed optode method was applied to the determination of sulfate ion in environmental water samples.

Adsorption of Cr(VI) by Natural Clinoptilolite Zeolite from Aqueous Solutions: Isotherms and Kinetics

The main aim of this study was to evaluate the efficiency of natural zeolite for Cr(VI) removal from aqueous solutions. Following simple modification of adsorbent, the effect of operational parameters including pH (2–10), adsorbent dosage (2–20 g/L), contact time (5–150 min) and Cr(VI) concentration (10–50 mg/L) were studied according to one-factor-at-a-time procedure. The maximum Cr(VI) removal of 99.53% was obtained at initial pH of 2, contact time of 30 min, adsorbent dosage of 8 g/L and initial chromium concentration of 10 mg/L. The Freundlich isotherm was best fitted with experimental data (R2 = 0.951). Also, type 1pseudo second order kinetic model showed the most correlation (R2 = 1) with the experimental data. According to obtained results, it can be concluded that the application of clay-like adsorbents such as natural clinoptilolite zeolite can be considered as an efficient alternative for final treatment of effluents containing Cr(VI).