Selective Dinitrogen Conversion to Ammonia Using Water and Visible Light through Plasmon‐induced Charge Separation

The generation of ammonia from atmospheric nitrogen and water using sunlight is a preferable approach to obtaining ammonia as an energy carrier and potentially represents a new paradigm for achieving a low‐carbon and sustainable‐energy society. Herein, we report the selective conversion of dinitrogen into ammonia through plasmon‐induced charge separation by using a strontium titanate (SrTiO₃) photoelectrode loaded with gold nanoparticles (Au‐NPs) and a zirconium/zirconium oxide (Zr/ZrO_x) thin film. We observed the simultaneous stoichiometric production of ammonia and oxygen from nitrogen and water under visible‐light irradiation.     

Tailoring Morphology of PVDF-HFP Membrane via One-step Reactive Vapor Induced Phase Separation for Efficient Oil-Water Separation

Poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP) receives increasing attention in membrane separation field based on its advantages such as high mechanical strength, thermal and chemical stability. However, controlling the microporous structure is still challenging.In this work, we attempted to tailor the morphology of PVDF-HFP membrane via a one-step reactive vapor induced phase separation method.Namely, PVDF-HFP was dissolved in a volatile solvent and then was cast in an ammonia water vapor atmosphere. After complete evaporation of solvent, membranes with adjustable porous structure were prepared, and the microstructures of the membranes were analyzed by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and X-ray diffraction characterizations. Based on the results, a mechanism of dehydrofluorination induced cross-linking of PVDF-HFP has been suggested to understand the morphology tailoring.To our knowledge, this is the first report of one-step reactive vapor induced phase separation strategy to tailor morphology of PVDF-HFP membrane. In addition, the membranes prepared in the ammonia water vapor exhibited enhanced mechanical strength and achieved satisfactory separation efficiency for water-in-oil emulsions, suggesting promising potential.     

A Superamphiphobic Coating with an Ammonia‐Triggered Transition to Superhydrophilic and Superoleophobic for Oil–Water Separation

Superhydrophilic and superoleophobic materials are very attractive for efficient and cost‐effective oil–water separation, but also very challenging to prepare. Reported herein is a new superamphiphobic coating that turns superhydrophilic and superoleophobic upon ammonia exposure. The coating is prepared from a mixture of silica nanoparticles and heptadecafluorononanoic acid‐modified TiO₂ sol by a facile dip‐coating method. Commonly used materials, including polyester fabric and polyurethane sponge, modified with this coating show unusual capabilities for controllable filtration of an oil–water mixture and selective removal of water from bulk oil. We anticipate that this novel coating may lead to the development of advanced oil–water separation techniques.     

Spatially Separated Photosystem II and a Silicon Photoelectrochemical Cell for Overall Water Splitting: A Natural–Artificial Photosynthetic Hybrid

Integrating natural and artificial photosynthetic platforms is an important approach to developing solar‐driven hybrid systems with exceptional function over the individual components. A natural–artificial photosynthetic hybrid platform is formed by wiring photosystem II (PSII) and a platinum‐decorated silicon photoelectrochemical (PEC) cell in a tandem manner based on a photocatalytic‐PEC Z‐scheme design. Although the individual components cannot achieve overall water splitting, the hybrid platform demonstrated the capability of unassisted solar‐driven overall water splitting. Moreover, H₂ and O₂ evolution can be separated in this system, which is ascribed to the functionality afforded by the unconventional Z‐scheme design. Furthermore, the tandem configuration and the spatial separation between PSII and artificial components provide more opportunities to develop efficient natural–artificial hybrid photosynthesis systems.     

Rapid and selective determination of ammonium by fluorimetric flow injection analysis

Selective and sensitive procedures for the determination of ammonium in river water and diluted urine were developed by using flow injection analysis equipment. The methods are based on the derivatization of ammonia with o-phthaldehyde (OPA) and thioglycolate under alkaline conditions. The formed isoindole derivative is detected fluorimetrically at an excitation wavelength of 415 nm and an emission wavelength of 485 nm. The derivatization only takes 15 to 20 s at room temperature to achieve the maximum sensitivity. The optimized OPA reagent shows a surprisingly high selectivity for ammonium in the presence of many primary amines. With respect to the analysis of turbid and fluorescent sample solutions the selectivity can be improved by separating the ammonia through a microporous membrane from the OPA reagent. Without this separation step ammonia can be detected in the range between 0.05 and 100 microM with excellent linearity. After the insertion of an optimized membrane separation cell ammonia can be determined in the linear range between 0.2 microM and 20 mM.     

In-situ polymerized PLOT columns III: divinylbenzene copolymers and dimethacrylate homopolymers

Studies of divinylbenzene copolymers and dimethacrylate homopolymers indicate that the polymer pore size controls the separation of water and ammonia on porous-layer-open-tubular (PLOT) columns. To a lesser degree, the polarity of the polymers also affects the separation of a water-ammonia gas mixture. Our results demonstrate that the pore size can be regulated by controlling the cross-linking density or the chain length between the cross-linking functional groups. An optimum pore size will provide the best separation of water and ammonia.     

Rapid and selective determination of ammonium by fluorimetric flow injection analysis

Selective and sensitive procedures for the determination of ammonium in river water and diluted urine were developed by using flow injection analysis equipment. The methods are based on the derivatization of ammonia with o-phthaldehyde (OPA) and thioglycolate under alkaline conditions. The formed isoindole derivative is detected fluorimetrically at an excitation wavelength of 415 nm and an emission wavelength of 485 nm. The derivatization only takes 15 to 20 s at room temperature to achieve the maximum sensitivity. The optimized OPA reagent shows a surprisingly high selectivity for ammonium in the presence of many primary amines. With respect to the analysis of turbid and fluorescent sample solutions the selectivity can be improved by separating the ammonia through a microporous membrane from the OPA reagent. Without this separation step ammonia can be detected in the range between 0.05 and 100 μM with excellent linearity. After the insertion of an optimized membrane separation cell ammonia can be determined in the linear range between 0.2 μM and 20 mM.     

Miniaturized Optical System for Detection of Ammonia Nitrogen in Water Based on Gas-Phase Colorimetry

A small-size gas-tight optical measuring system for detection of ammonia nitrogen in water was prepared based on gas-phase ammonia induced color change of the sensing element that was made by loading bromothymol blue (BTB) in a transparent porous glass fiber membrane. The gas-tight optical measuring system consists of a gas-testing and a liquid-sample chamber connected with each other by means of tubes and a mini-pump that cycles the gas between the two chambers. A 625-nm light emitting diode (LED), a photodetector and a sensing element were mounted in the gas-testing chamber for optical response to ammonia gas released from the water in the liquid-sample chamber. Release of ammonia gas was realized by alkalinizing the water sample with NaOH. Owing to the amount accumulation of ammonia gas in the sealing system, the ammonia nitrogen detection limit of the device can be very low. A small concentration of ammonia nitrogen, as low as 0.05 mg/L, was detected. The two linear-response ranges from 0.05 mg/L to 0.26 mg/L and from 0.26 mg/L to 2.62 mg/L were obtained. A relative standard deviation of ≤1% was determined by multiple measurements of the same sample.     

Effect of the type and concentration of mobile phase additives on the separation of salbutamol sulfate enantiomers in supercritical fluid chromatography

The influence of a set of additives of various nature on the separation of salbutamol sulfate enantiomers by supercritical fluid chromatography on the stationary phase based on amylose tris(3-chloro-5-methylphenylcarbamate) is considered. The application of water and acidic additives does not lead to enantioseparation. The use of hexafluoroisopropyl alcohol as an additive allows separation to occur but leads to a strong distortion of the chromatographic peaks. The application of basic additives such as isopropylamine or ammonia provides a stable separation with high selectivity and resolution as well as with the symmetrical peak shape. The selectivity coefficient is surprisingly almost independent of the amine modifier concentration in the mobile phase.     

现代分析技术在水质氨氮监测中的应用

氨氮是我国水质污染物总量控制指标之一,水体中氨氮排放总量的控制对于水环境的改善具有重大的作用。针对氨氮污染的治理需要有更为准确、有效、快速的分析方法相配合。就近年来水中氨氮的测定方法进行了综述,介绍了实验室方法与在线监测方法的最新进展,比较了各自的特点及其在水环境监测中的应用。相应学科的新成果融入现代分析技术使得氨氮的分析水平有了极大的提高,这将会在今后的水环境污染治理中发挥越来越大的作用。     

Monitoring Of Nitrifying Processes In Ground Water By Ion Chromatography

Abstract

The removal of ammonia from mineral medium containing known concentrations of ammonia (up to 300 mg/L) and from ground water by biological oxidation was studied. Nitrifying bacteria were isolated from ground water containing ammonia.

Ammonium ion was determined by a standard titration technique while nitrite and nitrate ions were determined by ion chromatography (IC Supersep anion column) using 1.5 mM phtalic acid solution containing 5 % acetonitril as eluent.

Depending on its concentration in water biooxidation of ammonia lasted from 48 hours till three weeks.     

Silica with Bimodal Pores for Solid Catalysts Prepared from Water Glass

The comparison of bimodal pore structures between silica gels prepared from silicon alkoxide and from water glass was performed based on the results of phase separation tendency, mesopore formation, and atomic scale observation using ²⁹Si NMR. Macropore structure could be controlled for both the raw material systems by inducing phase separation. Although the gelation in the water glass system is much faster than that in the silicon alkoxide system, there is little difference in the atomic scale structure, mesopore evolution during processing, and phase separation tendency. The results suggest that the obtained bimodal porous silica from water glass is essentially the same as that from silicon alkoxide. Because of the low cost of water glass, water-glass-derived bimodal porous silica is applicable to industrial use.     

Janus Copper Mesh Film with Unidirectional Water Transportation Ability toward High Efficiency Oil/Water Separation

Inspired by the special asymmetric wettability and controllable permeation function of cell membranes, we report a Janus nanostructured copper mesh film with unidirectional water transportation ability. Water can permeate from the hydrophobic side to the hydrophilic side, but is retained in the opposite direction. Notably, based on this special unidirectional water permeation property, both heavy oil/water mixtures (ρ _oil>ρ _water) and light oil/water mixtures (ρ _oil<ρ _water) can be separated. Additionally, the film demonstrates high separation efficiency and good recyclability. This paper reports a new Janus film that achieved highly efficient oil/water separation based on smart control of the wettability of the film. It is believed to have the potential to be used in many practical applications, such as wastewater treatment and oil‐spill cleanup.     

金属-有机骨架材料用于废水处理

废水中的各种有害物质常常具有生物毒性或致癌性,因此如何高效、节能地处理水体污染是一个亟待解决的重要问题。金属-有机骨架材料(metal-organic frameworks, MOFs)是一种新型纳米多孔材料,具有种类多样性、结构可设计性与可调控性、高比表面积及良好的热稳定性等优点,已成为当前化学、材料学科的一个研究热点, 在多个领域显示出潜在的应用前景,尤其是在分离方面。与气相分离相比,MOFs用于液相分离的研究较少。本文综述了近年来MOFs用于含有染料、药物、醇、芳香族化合物、重金属离子及其他离子的废水处理的研究进展,重点剖析了MOFs的孔结构、骨架电荷及功能性对分离效果的影响,并结合本课题组的研究工作,对这种新型多功能材料在水处理方面的前景和今后的研究重点作了展望。     

Active Separation of Water Isotopologues by Local Molecular Motion in Microporous Framework Materials

Around 10–15 % of the world's energy consumption is accounted for by the separation and purification of chemicals. Among them is the enrichment and separation of isotopologues which are an essential aspect of modern chemistry. In their recent work, Su et al. demonstrate the separation of water isotopologues by responsive dynamic pore windows in a microporous coordination polymer with unprecedented selectivity based on an elegant mechanism.     

Neutron activation determination of rheumium in rocks and ores after preliminary extraction with pyridine

A simple neutron-activation method for the determination of rhenium based on a preliminary extractive separation of the latter from molybdenum and tungsten is described. The sample is decomposed with sodium peroxide, a small amount of water is added and the resulting pulp is extracted with pyridine. The extract is evaporated to dryness, the residue is dissolved in water and the solution is passed through a column packed with Dowex 50WX8 in H⁺ form to eliminate the metal impurities. The HReO₄ passed, after neutralization with ammonia, is evaporated to dryness in penals, which then are irradiated with thermal neutrons.     

Fluorometric determination of hydrazine and ammonia separately or in mixtures

Hydrazine and ammonia are often added to boiler water to inhibit corrosion. The reagents o-phthalaldehyde and mercaptoethanol have been found to form derivatives with hydrazine and ammonia which can be determined by fluorimetry. Because the optimum pH values for formation of the hydrazine and ammonia derivatives were different, analysis of mixtures of the two components without prior separation was possible. Simulated wet-lay-up boiler water samples containing 5-200-mug/ml levels of hydrazine and ammonia have been analysed with an average relative error of about 10%.     

The determination of free ammonia in ambient air with diffusion/denuder tubes

Ammonia is important in atmospheric chemistry because it neutralises acidic species and increases the pH of cloud droplets. Data on the concentration of free ammonia in the atmosphere are sparse because it is difficult to separate free ammonia from particulate ammonium salt aerosol. A manual method for the determination of free ammonia in air is described based on diffusion/denuder tube separation of ammonia from ammonium salt aerosol. When air is drawn through a tube coated with a selective absorbent (here oxalic acid) separation is achieved because the gaseous species diffuses much more rapidly to the tube wall than the particles. After the sampling period (usually 1–4 h, depending on the free ammonia concentration expected), the sorbed ammonia is washed from the tube and measured potentiometrically with an ammonia probe. The method is tested theoretically and experimentally. The absorption efficiency of the coated tubes is ca. 90%. In samples of room air containing 12–28 μg m^?3, the standard deviation is estimated as 1.0 μg m^?3. In field use, ammonia contents were in the range 0.53–5.0 μg m^?3.     

Water splits epitaxial graphene and intercalates

The adsorption and reactions of small molecules, such as water and oxygen, with graphene films is an area of active research, as graphene may hold the key to unique applications in electronics, batteries, and other technologies. Since the graphene films produced so far are typically polycrystalline, with point and line defects that can strongly affect gas adsorption, there is a need to understand their reactivity with environmentally abundant molecules that can adsorb and alter their properties. Here we report a study of the adsorption and reactions of water, oxygen, hydrogen, and ammonia on epitaxial graphene grown on Ru and Cu substrates using scanning tunneling microscopy (STM). We found that on Ru(0001) graphene line defects are extremely fragile toward chemical attack by water, which splits the graphene film into numerous fragments at temperatures as low as 90 K, followed by water intercalation under the graphene. On Cu(111) water can also split graphene but far less effectively, indicating that the chemical nature of the substrate strongly affects the reactivity of the C-C bonds in epitaxial graphene. Interestingly, no such effects were observed with other molecules, including oxygen, hydrogen, and ammonia also studied here.     

Determination of Chloroacetic Acids in Drinking Water by Reaction Gas Chromatography

A procedure was developed for determining chloroacetic acids in drinking water. The procedure is based on solid-phase extraction followed by the conversion of chloroacetic acids to trifluoroacetic esters and their separation and determination by gas–liquid chromatography with an electron capture detector. Esterification conditions were optimized. The procedure was used for analyzing samples of drinking water.