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The degradation of nitroaromatics/toxic energetic compounds contaminated water is a major cause of concern. W-doped TiO 2 nanoparticles (NPs) were synthesized in ionic liquid, ethyl methyl imidazolium dicyanamide (EMIM-DCA) by a solvothermal method. The developed NPs were sintered at 500 °C and characterized by UV-Vis-DRS, FT-IR, FE-SEM, XRD, XPS, and BET techniques. The 30-40-nm-sized NPs were subjected to photocatalytic degradation of the toxic energetic compound, tetryl (2,4,6-trinitrophenylmethylnitramine) under UV-Vis light. Various operating parameters such as the effect of concentration of catalyst, pH of feed phase, oxidizing agents, and recycling of catalyst were studied in detail. For the first time, the degradation-mechanism pathway and kinetics of tetryl were evaluated. The degradation products were precisely analyzed by using HPLC, GC-MS, and TOC techniques. The USEPA has prescribed a drinking water limit of 0.02 mg L -1 , and it was found that 0.5 g of 4% W-TiO 2 could totally degrade tetryl (50 mg L -1 ) within 8 h. The kinetic rate constant of 4% W-TiO 2 was 0.356 h -1 , whereas pure TiO 2 showed 0.207 h -1 .

Dioxins and dioxin-like chemicals are predominantly produced by thermal processes such as incineration and combustion at concentrations in the range of 10-100 ng of I-TEQ/kg (I-TEQ = international toxic equivalents). In this work, a new approach for the removal of dioxins from high-temperature vapor streams using facilitated supported ionic liquid membranes (SILMs) is proposed. The use of ceramic membranes containing specific ionic liquids, with extremely low volatility, for dioxin removal from incineration sources is proposed owing to their stability at very high temperatures. Supported liquid membranes were prepared by successfully immobilizing the ionic liquids tri-C(8)-C(10)-alkylmethylammonium dicyanamide ([Aliquat][DCA]) and 1-n-octyl-3-methylimidazolium dicyanamide ([Omim][DCA]) inside the porous structure of ceramic membranes. The porous inorganic membranes tested were made of titanium oxide (TiO(2)), with a nominal pore size of 30 nm, and aluminum oxide (Al(2)O(3)), with a nominal pore size of 100 nm. The ionic liquids were characterized, and the membrane performance was assessed for the removal of dioxins. Different materials (membrane pore size, type of ionic liquid, and dioxin) and different operating conditions (temperature and flow rate) were tested to evaluate the efficiency of SILMs for dioxin removal. All membranes prepared were stable at temperatures up to 200 °C. Experiments with model incineration gas were also carried out, and the results obtained validate the potential of using ceramic membranes with immobilized ionic liquids for the removal of dioxins from high-temperature vapor sources.

The present investigation deals with separation of various types of nitrophenols using SILM technique. Several ionic liquids were developed and the SILM parameters such as role of ILs, feed and strip phase concentration, wastewater pH, salt effect and mixture of pollutants were thoroughly investigated. The percentage extraction and stripping, flux, apparent rate constants and selectivity were evaluated. The selected ammonium IL being more polar than the imidazolium IL showed better separation of 2-nitrophenol. The SILM constituting an ammonium IL with SCN anion exhibited extraction efficiency of >96% and Ka: 0.264 h−1. The change in feed concentration showed maximum transport of nitrophenol at 300 ppm concentration (Ka: 0.673 h−1). The membranes were repeated for 4 cycles which demonstrated good stability for runs of more than 48 hours. The selectivity of 2-nitrophenol, 2,4-dinitrophenol, 2,4,6- trinitrophenol over nitrobenzene was 26, 36 and 58, respectively. The morphology of membranes was studied by using FTIR and FE-SEM and the transport mechanism was elucidated. With the optimized parameters, a concentration factor of 7 can be achieved in the present SILM system. The application of SILM including ammonium IL with SCN anion shows a promising potential for the treatment of various types of nitrophenol bearing wastewater. [ABSTRACT FROM AUTHOR]

The degradation of nitroaromatics/toxic energetic compounds contaminated water is a major cause of concern. W-doped TiO2 nanoparticles (NPs) were synthesized in ionic liquid, ethyl methyl imidazolium dicyanamide (EMIM-DCA) by a solvothermal method. The developed NPs were sintered at 500 °C and characterized by UV-Vis-DRS, FT-IR, FE-SEM, XRD, XPS, and BET techniques. The 30–40-nm-sized NPs were subjected to photocatalytic degradation of the toxic energetic compound, tetryl (2,4,6-trinitrophenylmethylnitramine) under UV-Vis light. Various operating parameters such as the effect of concentration of catalyst, pH of feed phase, oxidizing agents, and recycling of catalyst were studied in detail. For the first time, the degradation-mechanism pathway and kinetics of tetryl were evaluated. The degradation products were precisely analyzed by using HPLC, GC-MS, and TOC techniques. The USEPA has prescribed a drinking water limit of 0.02 mg L−1, and it was found that 0.5 g of 4% W-TiO2 could totally degrade tetryl (50 mg L−1) within 8 h. The kinetic rate constant of 4% W-TiO2 was 0.356 h−1, whereas pure TiO2 showed 0.207 h−1. [ABSTRACT FROM AUTHOR]

Liquid–liquid equilibrium data for the system consisting of toluene,n-heptane and Aliquat 336 ionic liquid was obtained at 303.15 K and atmospheric pressure. The values of distribution coefficient and selectivity were evaluated. Mathematical model relating distribution coefficient and dispersion, dipolar interaction and hydrogen bonding has been developed. Hansen’s solubility parameters were used to determine the parameters. The model was applied for various ionic liquids as solvents. The model predicted the trends similar to the trend reported in the literature. Thus model can predict better solvent for the given extraction application. This methodology has great potential to act as a knowledge-based framework to aid development of new tailor-made solvents. This will save cost and time in experimentation and analysis. [ABSTRACT FROM PUBLISHER]

Hypergolic ionic liquids (HILs) have gained significant importance in recent years as green space propellants. It is mainly due to their attractive physicochemical properties, such as high density, negligible vapor pressure and wide liquid range. More importantly, they show low ignition delay with storable oxidizers viz. white fuming nitric acid (WFNA), red fuming nitric acid (RFNA), dinitrogen tetroxide (N2O4) and hydrogen peroxide (H2O2). Therefore, investigation into the performance parameters of HILs, such as specific impulse (Isp), density and vacuum-specific impulse (ρIsp & Ivac), and characteristics velocity (C*), has received enormous attention. In the present study, 14 HILs have been selected for evaluation of their performance parameters using the NASA-CEC-71 program. Amongst them, three HILs have been developed in the laboratory by the authors. The effects of oxidizers, oxidizer to fuel ratio, heat of formation, hydrogen content of the HIL, and the chamber pressure parameters were studied in detail. The performance of HILs was also compared with that of a proven fuel, UDMH. The HILs 1-ethyl-3-methyl imidazolium cyanoborohydride, [EMIM][BH3CN], and 1,3-diallyl imidazolium cyanoborohydride, [diAIM][BH3CN], were particularly promising with all the oxidizers. The H2O2 seems to be a good potential oxidizer as it exhibited a higher value of ρIsp for most of the HILs than the UDMH. A propellant based on high-density HIL as a fuel and H2O2 as an oxidizer can be classified as a green propellant. Thus, the investigation helps in designing or selecting the best combination of HIL and oxidizer for rocket applications. [ABSTRACT FROM AUTHOR]

Exploring ultrafast igniting and hydrolytically stable ionic liquids (ILs) has a wide scope in hypergolic rocket fuels. The hydrophobicities of ILs, induced by a smart change in alkyl substituents of imidazolium cations with energy-rich cyanoborohydride, [BH3CN]− and dicyanamide, [DCA]− anions were examined for the first time. The physico-chemical properties and performance of ILs were also studied. Consequently, hydrolytic stability in terms of moisture study of all the ILs was thoroughly investigated under standard environmental conditions. The analysis indicates that the IL 14, 1-allyl-3-octyl imidazolium cyanoborohydride is most hydrophobic and hydrolytically stable. Studies evaluating the role of the cationic hydrocarbon chain and the nature of anions of ILs on the properties of hypergolic fuel were carried out. All the ILs are liquid at room temperature and exhibit a positive heat of formation. IL 10, 1,3-diallyl-imidazolium cyanoborohydride exhibited the shortest ignition delay of 1.9 ms with WFNA and IL 11, 1-allyl-3-ethyl imidazolium cyanoborohydride presented the lowest viscosity of 16.62 mPa s. Therefore, these ILs can be suggested as potential candidates for replacing acutely toxic and carcinogenic hydrazine and its methylated derivatives as hypergolic fuels. [ABSTRACT FROM AUTHOR]

A series of low-cost, pyridinium cation-based hypergolic ionic liquids (HIL) containing amine, butyl, or allyl substituents with cyanoborohydride [BH3CN]− and dicyanamide [DCA]− anions were developed and characterized. The investigated physicochemical properties include melting and decomposition temperature, viscosity, density, heat of formation (Δ Hf) and specific impulse ( Isp). The ignition delay (ID) of all HILs was tested with the oxidizer RFNA. The HIL, 1-allyl 4-amino pyridinium dicyanamide, exhibited highest density (1.139 g cm−3) amongst the known pyridinium HILs. The heats of formation predicted on the basis of Gaussian 09 suit programs were within the range of − 30 to 356 kJ mol−1. The structure of HIL, 1-butyl 4-aminopyridinium cyanoborohydride, was examined by single-crystal X-ray diffraction, which revealed hydrogen bonding between anion and cation as N1−H1N ⋅⋅⋅N3=2.07 Å, N1−H2N ⋅⋅⋅H1B1=2.18 Å, and N1−H2N ⋅⋅⋅H2B1=2.21 Å, respectively. HIL (1-allyl 4-aminopyridiniun cyanoborohydride) exhibited highest Isp of 228 s amongst the designed series. [ABSTRACT FROM AUTHOR]

Deep desulfurization of diesel fuel has attracted the attention of a growing number of scientists and engineers due to the stringent regulations imposed on the presence of sulfur in fuel (10 ppm). To bring down the concentration of sulfur compounds to less than 10 ppm is very challenging and demands newer technologies. Novel processes are being proposed for this purpose. It is observed that ionic liquids as class of green solvents can play a major role in the deep desulfurization of diesel fuel. For this reason, this review focuses on the current status in application of ionic liquids for achieving ultra-low-sulfur diesel (ULSD). To get a comprehensive perspective about the topic, other techniques of desulfurization are also discussed in brief in the introduction. Here we propose that the appropriate removal method should be selected according to different systems. To achieve deep desulfurization using ionic liquids, a better understanding regarding the regeneration of ionic liquids is vitally important. [ABSTRACT FROM AUTHOR]

Dioxins are highly toxic compounds that mainly originate from incineration and combustion sources. In this work, a new, simple, and efficient approach for the absorption of dioxins from gaseous streams using thermally stable ionic liquids is proposed. The absorption process of nonchlorinated and chlorinated dibenzo-p-dioxin compounds was studied in the temperature range 100-200 °C. Imidazolium-, ammonium-, and guanidinium-based ionic liquids were designed for this specific purpose. It was observed that imidazolium cations having long alkyl side chains exhibit the highest absorption capacities, whereas the anion dicyanoamide [DCA] possesses higher absorption capacity than other anions studied. In a typical experiment, it was found that the ionic liquid 1-n-octyl-3-methyl imidazolium dicyanoamide [C8mim][DCA] can absorb more than 14% by weight of dibenzo-p-dioxin, 2-chlorodibenzo-p-dioxin, and 1 ,2,3,4-tetrachlorodibenzo-p-dioxin from a gaseous stream. A process for desorption of dioxins from the ionic liquid was tested, revealing that complete desorption can be achieved under a high vacuum. Additionally, the feasibility of the process was examined by carrying out experiments under real operating conditions of incineration and combustion processes. The success of the method heavily relies upon the design and selection of specific ionic liquids having enhanced affinity for the aromatic compound functionality present in dioxins and, simultaneously, possessing extremely low volatility and high chemical and thermal stability. [ABSTRACT FROM AUTHOR]

There is a growing demand for functional silica-based porous materials in the market. In this regard, PEG-linked bis-imidazolium chloride silsesquioxane (PIMAILS, an ionic liquid) was functionalized on polyhedral oligomeric silsesquioxanes (POSS). The materials were characterized with FT-IR, 1H and 13C NMR. The structural morphology of the adsorbent was analyzed with BET, TEM and FE-SEM techniques. The NMR results imply that during the PIMAILS loading over the POSS framework, the O–CH 3 bond was cleaved out and the ionic liquid bridge was attached to the Si vertices of the POSS cage. The BET surface area of 853 m2 g−1 indicates higher porosity of the material. The ion exchanger has smooth and round-shaped morphology with continuous porous structures and an average particle size of 20–40 nm. The porous framework contains imidazolium binding sites, which have ion-exchange capability and was used to separate Cr(VI) ion from wastewater. With neat POSS and POSS-IL, comparative adsorption of Cr(VI) was carried out at different contact times, wastewater pH and initial concentrations. Maximum removal of 92% of Cr(VI) from an aqueous solution was achieved with POSS-IL at pH 2. The results showed that the adsorption adequately fit the linear Langmuir model and second-order kinetics. After adsorption, the adsorbents and treated solutions were further analyzed with XPS and ion chromatography instruments, indicating ion exchange mediated adsorption for the POSS-IL. [Display omitted] • Imidazolium-based ionic liquid successfully impregnated over POSS framework. • Morphological studies imply that POSS-IL has good porous characteristics. • Post-adsorption analysis confirmed that clear ion exchange (Cl−↔CrO 4 2−) takes place. • POSS-IL has a comparatively higher ion-exchange capacity at pH 2.0. [ABSTRACT FROM AUTHOR]