Dispersion of boron nitride nanotubes in aqueous solution with the help of ionic surfactants

We report that ammonium oleate surfactants can help the dispersion of multiwalled boron nitride nanotubes (BNNTs) in water to form a BNNT solution stable for several months, which was due to the non-covalent functionalization of nanotube surfaces. Fourier Transform Infrared Spectroscopy (FTIR) and Photoluminescence (PL) analysis with synchrotron radiation source revealed that this BNNT aqueous solution preserves the intrinsic optical properties of BNNTs. © 2009 Elsevier Ltd. All rights reserved.

Chemiluminescence from reactions with bis-cyclometalated iridium complexes in acidic aqueous solution

Chemical reactions between certain bis-cyclometalated iridium complexes, cerium(IV) and organic reducing agents in aqueous solution produce an emission of light which in some cases is more intense than that from analogous reactions with conventional ruthenium-based reagents, thus providing a new avenue for chemically-initiated luminescence detection.

Wool powders used as sorbents to remove Co2+ ions from aqueous solution

The Co2+ sorption of two wool powders was investigated using its radioisotope 57Co (T1/2=271.8 days and γ=122.1 and 136.5 keV) as a tracer. The effects of the type of buffer, the pH value, the contact time and the initial concentration of Co2+ on the sorption behaviour of wool powders were studied. The Co2+ releasing ability of wool powders and the re-use of wool powders to sorb Co2+ were also examined. The optimum sorption of Co2+ by the powders occurred at pH 8 in phosphate buffer and pH 10 in ammonium sulphate buffer. Fourier-transform infrared spectroscopy (FTIR) was used to study the changes in chemical structure of the wool after exposure to both buffer solutions. Compared to the untreated wool fibre, the fine wool powders showed rapid sorption rates and high sorption capacities for Co2+. Co2+ ions were recovered after exposing the Co2+ loaded wool to HCl (0.1 M) and buffer at pH 3 (glycine/sodium chloride). After releasing Co2+ ions from wool powders, the efficiency of wool powders re-used to sorb Co2+ was 80% of that of the fresh wool powders. It is concluded from this study that wool powder can be used as an efficient sorbent to remove and release Co2+ from solution.

Preconcentration of phenanthrene from aqueous solution by a slightly hydrophobic nonionic surfactant

The preconcentration of phenanthrene from aqueous solution was discussed. The study was carried out by using a slightly hydrophobic nonionic surfactant. The slightly hydrophobic surfactant, at proper condition enhanced the performance of the surfactant-based extraction process on polycyclic aromatic hydrocarbons (PAH). The results show that the increasing the temperature difference enhanced the preconcentration factors prominently but only slightly the recovery efficiency.

A novel cloud-point extraction process for preconcentrating selected polycyclic aromatic hydrocarbons in aqueous solution

A novel but simple cloud-point extraction (CPE) process is developed to preconcentrate the trace of selected polycyclic aromatic hydrocarbons (PAHs) with the use of the readily biodegradable nonionic surfactant Tergitol 15-S-7 as extractant. The concentrations of PAHs, mixtures of naphthalene and phenanthrene as well as pyrene, in the spiked samples were determined with the new CPE process at ambient temperature (23 °C) followed by high performance liquid chromatography (HPLC) with fluorescence detection. More than 80% of phenanthrene and pyrene, respectively, and 96% of naphthalene initially present in the aqueous solutions with concentrations near or below their aqueous solubilities were recovered using this new CPE process. Importantly Tergitol 15-S-7 does not give any fluorometric signal to interfere with fluorescence detection of PAHs in the UV range. No special washing step is, thus, required to remove surfactant before HPLC analyses. Different experimental conditions were studied. The optimum conditions for the preconcentration and determi nation of these selected PAHs at ambient temperature have been established as the following:  (1) 3 wt % surfactant; (2) addition of 0.5 M Na2SO4; (3) 10 min for equilibration time; and (4) 3000 rpm for centrifugal speed with duration of 10 min.

Effect of surface roughness and electrostatic surface potentials on forces between dissimilar surfaces in aqueous solution

The first surface force measurements under electrochemical potential control between a metal and a ceramic surface across a liquid medium (water) are reported. Our experiments also investigate and reveal how increasing levels of surface roughness and dissimilarity between the potentials of the interacting surfaces influence the strength and range of electric double layer, van der Waals, hydration, and steric forces and how this contributes to deviations from DLVO theory at small distances within aqueous solution.

Tuning radical species in graphene oxide in aqueous solution by photoirradiation

Graphene oxide (GO) possesses unusual electronic and mechanical properties, including the ability to stabilize graphene radicals (GRs). However, controlled generation of GRs remains a challenge for applications requiring large-scale production. In this study, we demonstrate controlled production of GRs by UVB irradiation of GO solutions. Electron paramagnetic resonance spectroscopy of GO solutions revealed a dose-dependent exponential growth in radical production as a function of UVB exposure time. The GRs were air-stable over a long period, both in the solution state and in freeze-dried powders, suggesting they are graphene-based phenalenyl-like radicals. The redox activity of GRs was demonstrated by their ability to oxidize the chromophore 3,5,3?,5?- tetramethylbenzidine, with oxidation capacity of GO increasing with GR content.

Ammonia nitrogen removal from aqueous solution using functionalized zeolite columns

In this study, a functionalized zeolites column was developed to remove ammonia nitrogen with a low concentration (50 mg/L) from aqueous solution. The absorption properties and regeneration capacity were investigated. Through breakthrough and elution curve for dynamic adsorption, we found the wastewater with 50 mg/L ammonia nitrogen took 7 h to flow 10 g modified zeolites column with diameters of 24 to 64 meshes at a flow rate of 2 mL/min. The saturated extent of adsorption was up to 7.95 mg/g, and the saturated adsorption time was 22 h. The process of dynamic adsorption could be fitted by the Thomas Model. The regeneration ability was optimized by 0.1 M Na2CO3 as a regenerant. With excellent absorption ability for removing ammonia nitrogen with a low concentration, the functionalized zeolites could be potentially used a high-performance adsorbent for removing ammonia nitrogen.