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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 str...

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.

Ammonium ionic liquids are being extensively used in several applications, and hence, their effluent treatment is a significant cause of concern. Various Ag-doped SnO2 nanoparticles (2%, 3% and 5% Ag–SnO2) were developed and systematically characterized using advanced analytical instruments. Due to Ag doping in SnO2, the optical bandgap was decreased from the original 3.92 to 3.05 eV. The crystalline NPs showed particle sizes in the range of 40–100 nm. All the synthesized NPs were subjected to degradation of an emerging quaternary ammonium ionic liquid (QAIL) pollutant, Aliquat 336, in the presence of UV-vis light. The sample aliquots were analyzed by a total organic carbon (TOC) analyzer and gas chromatography–mass spectrometry (GC-MS). The 5% Ag–SnO2 catalyst (0.6 g L−1) was able to degrade all the pollutants within 300 min. The essential parameters of photodegradation such as the catalyst concentration, wastewater pH and catalyst recycling were investigated. In a typical study, urban wastewater, which is also an emerging cause of concern, is spiked with the pollutant to evaluate other constituents' effects. It was observed that the proposed photocatalytic methodology could degrade all the pollutants with extended irradiation time. The detailed reaction kinetics with rate constants are presented. For the first time, based on the GC-MS study, the selected QAIL pollutant's degradation pathway is predicted. The original QAIL pollutant was sequentially degraded into CO2 and H2O through the intermediates dioctyl amine, primary amine and pentaldehyde. At the end, the degradation results of QAIL were compared with those of the other reported aromatic ILs.

Boron based compounds have been looked upon as possible replacements to conventional toxic hypergolic fuels in propellant system. In an attempt to add to the pool of boron based hypergols, a series of new amine borane/ cyanoborane zwitterionic compounds were developed. Their hypergolic reactivity, performance parameters and physico-chemical properties were examined, in detail. The unsymmetrical dimethyl hydrazine (UDMH) based zwitterions, UDMH-borane and UDMH-bisborane displayed strikingly lower ignition delay times of 2.2 and 2 ms, respectively and high specific impulse 241 and 245 s, respectively. The pyridinium-cyanoborohydride exhibited high heat of formation (146 kJ/mol) than UDMH. While all the developed compounds exhibited higher density than the UDMH. Chemical stability of UDMH-borane was investigated at different environmental conditions; it was found to be stable for longer duration. Low ignition delay, good thermal and chemical stability, positive heat of formation, high specific impulse, ease of synthesis, and commercially available starting materials are the promising features of these compounds which make them attractive prospects in revolutionizing the area of green hypergolic fuel in liquid as well as hybrid rocket propulsion.

Objective: Selective removal of phenol from organic solvent mixture (benzene + toluene + hexane) or other petroleum by-products have a major concern. Hence, the experiments were conducted on the removal of phenol from synthetically prepared phenolic organic waste by using a green process, ionic liquids. Methods: The ionic liquids, 1-ethyl-3-methyl imidazolium cyanoborohydride, and 1- butyl-3-methyl imidazolium hexafluorophosphate were used for the extraction study. The effect of various operating parameters such as the type of ionic liquids, effluent temperature, extraction time, and the phase volume ratio of ionic liquid and phenol has been studied in details. The ionic liquid, 1-ethyl-3-methyl imidazolium cyanoborohydride selectively extracted 95 % of the phenol from the synthetically prepared organic oil mixture of benzene and toluene, with an initial phenol concentration was 100 ppm. Further, ionic liquids were recycled and reused for six consecutive studies with removal efficiency of about 74%. Additionally, a batch reactor study was conducted to find the process viability for industrial use and 92% phenol removal efficiency was achieved. Results: The study demonstrates the selective removal of phenol from petroleum oil using ionic liquids is a simple and environmentally friendly process for industrial use. Conclusion: This method cannot only extract phenol but also phenol-derived compounds may be extracted from hydrocarbon oil.

With an aim to prepare phase change material (PCM) as self-sustaining film from poly(ethylene glycol) (PEG) having reduced hydrophilicity, cross-linking of PEG and hydroxy-terminated poly(dimethyl siloxane) (HTPDMS) was done by using tetraethyl orthosilicate (TEOS) as a cross-linking agent. Following the confirmation of the crosslinked polymer using FTIR and 13C-solid state NMR, the crystallization properties were studied using X-ray diffraction and polarized optical microscopy. DSC analysis indicated an increase in enthalpy with increasing concentration of PEG. The enthalpy of fusion and crystallization was observed to reach a maximum of 125 and 104 J g−1 respectively. Contact angle of 89.5° has been achieved for polymer with highest concentration of HTPDMS. The material with lowest PEG concentration was film forming in nature. This material can be extensively used as a thermal energy storage material particularly, in smart packaging.

In this work, an ionic liquid (IL) based electrode material was synthesized for the supercapacitor application. Initially, manganese dioxide (MnO2) nanoparticles have been prepared by a sol-gel method using IL, Aliquat HTA-1 as a capping agent. The effect of IL on the morphology of MnO2 nanoparticles has been investigated by using scanning and transmission electron microscopy. The morphology reveals formation of the nanorods in presence of IL and spherical nanoparticles in absence of IL. The X-ray diffraction measurements disclose a tetragonal crystal structure pattern of α-MnO2 with a crystallite size of about 20 nm. Optical properties of MnO2 have been studied by UV–Vis and emission spectroscopy. The emission spectra of MnO2 in presence of IL exhibits emission band which shows a red shift by 30 nm. The supercapacitor study has been carried out using cyclic voltammetry, and charge-discharge with MnO2 as an electrode material and 5% IL as supporting electrolyte. As evidenced by the electrochemical measurements, the MnO2 with IL generates a substantial pseudocapacitance reaching a maximum value of up to 453 Fg−1. Moreover, the supercapacitor is assembled with IL capped MnO2 as a positive and a negative electrode which resulted in high specific capacitance and better rate capability.

The degradation of nitroaromatics/toxic energetic compounds contaminated water is a major cause of concern. W-doped TiO

In this study, we have reported the synthesis of copolymers of poly(ethylene glycol) acrylate (PEGA) with methyl methacrylate (MMA) in various ratios which can be utilized as polymeric phase change materials (PCMs). The monomer reactivity ratio of PEGA copolymers was determined by Fineman-Ross method. The values of r1 (PEGA) and r2 (MMA) were found to be 0.8164 and 0.3371 respectively. The thermal analysis performed by DSC indicated high fusion enthalpy of 168 J·g−1 at 55 °C for the feed ratio of 40:60 of PEGA:MMA (Copolymer mole fraction of 76:24). The crystallization behaviour shows the presence of spherulites but of smaller size compared to PEG and with reduced crystallization ability. The results point out the capabilities of PEGA to function as an effective PCM which can be utilized for numerous thermal energy storage applications.

The current demilitarization processes employ open burning/open detonation which is not permitted by the environmental protection agency. Therefore, a systematic study has been carried out to convert waste/rejected nitramine propellant (NP) and fuel-rich-based propellant (FRP) into liquid fertilizer by digesting in dilute nitric acid followed by neutralization with potassium hydroxide and phosphoric acid. The obtained liquid fertilizers were fully characterized for nitrate, phosphate and ammonium ions along with potassium. Further, the effect of liquid fertilizers of NP and FRP on cluster bean plants was studied by taking different concentrations from 25 to 150 mL, and their effects on germination pattern, shoot growth, thickness of stem, size and number of leaves, number of pods and length over a full-grown period of plants were investigated. The results reveal that the germination index increases as the content of liquid fertilizer increases and the same trend was observed with respect to root and shoot growth. Also, broadness and the number of leaves showed an encouraging effect as concentration increases. Further, the final product, i.e. the number of pods of cluster bean and length in each pod was found to be more for liquid fertilizer of NP compared to FRP-based liquid fertilizer.

A novel cross-linked self-sustaining film was prepared by reaction of carboxyl-capped poly(ethylene glycol) (PEG) with epoxy resin, followed by incorporation of the prepared material (named modified epoxy, ME) into an epoxy matrix. Self-sustaining films were obtained with up to 60 wt% ME in the epoxy matrix. Fourier-transform infrared spectroscopy (FTIR) and 13C nuclear magnetic resonance (NMR) were used for chemical characterization of the samples. Differential scanning calorimetry (DSC) study exhibited maximum enthalpy for PCM film reaching up to 41 J g−1. The X-ray diffraction (XRD) and polarized optical microscopy (POM) indicated lesser degree of crystallinity of PEG segments due to constriction by crosslinked epoxy resin. Dynamic mechanical analysis (DMA) results indicate that the blend of epoxy and ME is compatible up to 30 wt% ME and there is distinct phase separation beyond this composition.

For efficient energy storage, hyperbranched (HB) architecture was adopted to prepare a series of HB polyurethanes via A2 + B3 approach with isocyanate terminated poly(ethylene glycol) (PEG) as branching unit and phloroglucinol (PG) as aromatic core. The chemical structure of the HB polymer was confirmed using FTIR and NMR. The gel permeation chromatography and solution viscosities indicate polymers of moderately high molecular weights. The thermal behavior and crystalline properties were investigated using differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, and polarized optical microscopy. A high fusion enthalpy of 146.6 J g–1 at transition temperature of 56 °C was achieved. Thermal stability was found to be quite high (up to 300 °C), and thermal reliability was retained with no chemical degradation after thermal cycling. The polymer exhibited crystalline to amorphous phase change above the transition temperatures and back, which makes it attractive as a polymeric phase chan...

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.

A novel bifunctional mesoporous organosilica, PEG-functionalized bis-prolinium chloride bridged mesoporous organosilica (BPBMO) was synthesized by reacting the precursor, PEG-functionalized bis-prolinium chloride bridged organosilane (BPRIL) with tetraethyl orthosilicate (TEOS) in the presence of surfactant. The chemical conformation of BPBMO was investigated by using Fourier transform infrared (FTIR), thermogravimentric analysis (TGA), 13C, and 29Si cross-polarization/magic angle spinning (CP/MAS) NMR techniques. The characterization represents PEG-linked-prolinium (−N+Cl–) and carboxyl (−COOH) entities, constructing the dicationic framework through siloxane (Si–O–Si) linkages. The pore-wall distribution and the periodicity of BPBMO retained during the synthesis were examined by small-angle X-ray scattering (SAXS), Brunauer-Emmett-Teller-Barrett-Joyner-Halenda (BET-BJH), and transmission electron microscopy (TEM) techniques. The results revealed BPBMO as a spherical shaped solid (50–100 nm) having mesopo...

In the present work, hyperbranched polyurethanes were prepared by using oligomeric A 2 + B 3 approach. The synthesis of hyperbranched polymers was carried out by reaction of trimethylolpropane (TMP) with poly(ethylene glycol) (PEG) terminated isophorone diisocyanate (IPDI). The prepared hyperbranched polymers were confirmed by Fourier transform infrared spectroscopy (FTIR) and 1 H nuclear magnetic resonance ( 1 H NMR). The crystallization properties studied with X-ray diffraction (XRD) and polarized optical microscopy (POM) indicated that hyperbranched polymers had crystalline structure and degree of crystallization reduces with introduction of hard segment. The maximum latent heat of fusion was found to be 145 J g −1 at 55 °C. Field emission scanning electron microscopy (FESEM) showed presence of homogeneous structure and thermogravimetric analysis (TGA) results indicated that the materials have good thermal stability. Thermal reliability tests from 20 thermal cycles demonstrate that enthalpy of hyperbranched polyurethanes improves with thermal cycling without any chemical degradation. These materials can be successfully used as polymeric phase change materials for thermal energy storage applications.

In this work we report efficient molecularly imprinted polymer (MIP) based carbon paste electrode sensor for the determination of diphenylamine in aged propellant. Initially, diphenylamine (DPA)-MIP was synthesized by using methacrylic acid (monomer) and ethylene glycol dimethyacrylate (cross-linker). Developed DPA-MIP was analyzed by Fourier transform infrared spectroscopy and Field-emission scanning electron microscopy. The sensor was incorporated as electrode in cyclic voltammetry. The sensor response was linear in the range of 0.5–3 mM DPA concentration. The lower detection limit obtained for sensor was 0.1 mM. The developed sensor was used for the determination of DPA in propellant systems. Same electrode was used for three repeated analysis without significant decrease in efficiency.

The research on phase change materials (PCM) has evolved significantly in the last few decades due to the need to manage the demands of energy requirements. Polyethylene glycol (PEG) is established as an organic solid–liquid PCM offering a wide range of enthalpies and phase transition temperatures as a function of its molecular weight. Herein, we have focussed on three aspects including preparation methods, microencapsulation and applications. An attempt has been made to focus on thermal conductivity enhancement methods used in the preparation of PEG based PCMs to give way for the commercial utility of these materials. The concluding remarks address the future directions for investigation, challenges and new possibilities for practical implementation of these materials.

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.

In this research, lignin, an abundant bioresource and a natural polymer, is investigated for its use as the supporting material while poly(ethylene glycol) (PEG) has been used as the working element. Various ratios of PEG and lignin were studied and the shape-stabilized phase change material (SSPCM) was prepared using microwave assisted blending, which proves to be one of the efficient and green ways of preparing the blends. The chemical structure of the PCM blend was confirmed using FTIR spectroscopy. The thermal and crystalline properties were investigated using differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction. The morphology was studied with field-emission scanning electron microscopy (FESEM), energy dispersive X ray spectroscopy (EDAX) and polarized optical microscopy (POM) suggesting a homogeneous network formation of the composite. Maximum loading of PEG was found to be 70%, giving enthalpy of 100.91 J/g. The prepared PCM exhibited excellent thermal reliability even after 100 thermal cycles. This novel PCM blend of PEG and lignin is considered as a promising candidate in terms of reliability and renewability making it suitable for various thermal energy storage applications.

The zero-valent copper (Cu(0)) nanoparticles were prepared by chemical reduction method. The morphology of nanoparticles was investigated by using X ray diffraction, scanning electron microscopy-energy dispersive X ray, UV-visible spectrophotometer and Brunauer-Emmett-Teller surface area analyser. The Cu(0) nanoparticles along with reducing agents, NaBH4/5% acidified alcohol were used for the dechlorination of chloroaromatics at room temperature. Chlorobenzene (Cl-B), chlorotoluene (Cl-T), chloropyridine (Cl-Py) and chlorobiphenyl (Cl-BPh) were selected as the contaminants. The effect of various operating parameters such as pH, concentration of the catalyst and reducing agent (NaBH4), and recycling of the catalyst on dechlorination were studied. Nearly complete dechlorination of all the chloroaromatics were achieved in the presence of Cu(0) nanoparticles (2.5 g L(-1)) and NaBH4 (1.0 g L(-1)) within 12 h. On the contrary, approximately 70% of dechlorination was observed in the presence of 5% acidified alcohol at similar experimental conditions. The dechlorination mechanism highlighted the importance of Cu(0) nanoparticles as a surface mediator. The kinetics of the dechlorination of chloroaromatics was investigated and compared with chloroaliphatics. The dechlorination rate differed from 0.23 h(-1) (Cl-B) to 0.15 h(-1) (Cl-BPh) in the presence of Cu(0) nanoparticles and NaBH4. The effectiveness of Cu(0) nanoparticles with NaBH4 (1 g L(-1)) and 5% acidified alcohol as electron donors were studied by oxidation-reduction potential and observed to be -1016 mV and -670 mV, respectively. Final products of the dechlorination were benzene, toluene, pyridine and biphenyl, as identified by gas chromatograph mass spectrometer and nuclear magnetic resonance spectroscopy.

Development of novel periodic mesoporous organosilicas (PMOs) were carried out by designing precursor, PEG-linked bis-imidazolium chloride bridged silsesquioxanes (PIMAILS, an ionic liquid). The involvement of tetraethyl ortho silicate (TEOS) as a template in an acidic medium led to the formation of a silica hybrid material (PMO-T). Contrary, in the absence of TEOS, PIMAILS self-assembled in a basic environment over the cationic surfactant, cetyl trimethyl ammonium bromide (CTAB) to form the silica hybrid material (PMO-S). The availability of surface silanols and ionic liquid (IL) in both the PMOs were verified using FT-IR and 13 C solid NMR. Further, they were quantified using 29 Si solid state NMR technique. The results depicted 3 times better loading of the precursor in the framework of PMO-S than PMO-T. Larger surface areas and higher porosities were found in PMO-S than PMO-T while analyzed using BET-BJH technique. Thermogravimetric (TG) analysis revealed nearly 2.2 times higher weight losses (%) from PMO-S than PMO-T, which validate the results of silica solid state NMR. Powder XRD analysis showed well-defined hkl reflections (110) and (200) from PMO-S in contrast of PMO-T, describing the periodic arrangement of IL within PMO-S. Finally ion-exchange capacities of these materials were estimated by employing them for recovery of W(VI). The PMO-S, which has higher percentage of IL in the framework, achieved better separation of W(VI) than PMO-T.

Hypergolic fuel has unique importance in missiles and satellite launch vehicles. Hydrazine and its derivatives (Monomethyl hydrazine, MMH and Unsymmetrical Dimethyl Hydrazine, UDMH) are the continuous choices of fuel in bipropellant though it is carcinogenic and toxic. Development of new, green and cost-effective fuel blends based on trust-worthy, ionic liquid and biofuel in different volume proportion have been reported. The blends exhibit reasonably good stability (chemical and thermal), low viscosity (η 1 g/cm3), low ignition delay and high performance in comparison with UDMH - a proven liquid fuel presently being used as promising fuels for liquid rocket application. The reported blends appear to be a technologically promising, eco-friendly and affordable fuel blend to replace currently used liquid toxic fuels.

A series of semi-interpenetrating polymer networks (IPN) of poly(2-hydroxyethyl methacrylate) (poly(HEMA)) and crosslinked polyethylene glycol (PEG) were prepared by simultaneous IPN polymerisation technique. Tetraethyl orthosilicate (TEOS) was used for crosslinking. The prepared semi-IPNs were characterized by Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance (13C-NMR), X-ray diffraction (XRD), polarized optical microscopy (POM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), swelling studies and contact angle measurements. The river like pattern of fractured cross section of the SEM micrograph of IPNs indicated no phase separation and also siloxane moiety placement on matrix-air interface. The semi-IPN samples are found to possess crystalline spherulites and the crystallinity reduces as the percentage of poly(HEMA) increases as demonstrated by XRD and POM. Maximum melting enthalpy obtained from DSC thermogram was around 145 J/g. The contact angle studies show that the relative hydrophobicity of the semi-IPNs increases with increase in content of HEMA in the semi-IPNs. These materials show satisfactory latent heat storage capacity and good thermal reliability for application as phase change material (PCM).

In this study, we report the synthesis of a Pb(II) ion-imprinted interpenetrating polymer network (II-IPN) by simultaneous polymerization for selective extraction of Pb(II) from printed-circuit-board (PCB) recycling unit wastewater. Initially, a polymer network was synthesized by polymerization of methacrylic acid (monomer) and ethylene glycol dimethacrylate (cross-linker) and a second polymer network by chitosan (complexing monomer) and tetraethyl orthosilicate (cross-linker). The chemical structure and morphology of the II-IPN were analyzed using Fourier transform infrared, field-emission scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. The interaction of the functionality in the II-IPN with Pb(II) through chelation was studied by X-ray photoelectron spectroscopy analysis. The maximum adsorption capacities for II-IPN and nonimprinted interpenetrating polymer network were 37.5 and 10.3 mg g–1, respectively. The largest selectivity coefficient for Pb(II) in the ...

The N-doped TiO2 photocatalyst was synthesized by the sol–gel method and characterized in detail in terms of its morphology, structure and composition. The prepared N-doped TiO2 exhibited polycrystalline structure having particle sizes of around 50–120 nm and rod-shaped geometry. The N-doped TiO2 was subsequently used for the photocatalytic degradation (PCD) of pharmaceutical micropollutants, namely ciprofloxacin HCl (CFX), naproxen (NPX) and paracetamol (PARA) and it was found that the rate of degradation of CFX and NPX is higher than that of PARA. To verify the beneficial effect of N-doped TiO2 for PCD of CFX, similar experiments were carried out using commercially available Aeroxide P-25 TiO2. It was observed that N-doped TiO2 was more efficient than Aeroxide® P-25 TiO2. It was also found that the PCD of CFX in the presence of N-doped TiO2 was highly efficient under the solar radiation as compared with artificial radiation. The effect of various operating parameters, such as adsorption of CFX, pH of the aqueous solution, effect of co-existing ions on PCD of CFX, was investigated using artificial radiation and optimum conditions were established. The intermediates formed during the PCD of CFX were identified using liquid chromatography tandem mass chromatography (LC-MS/MS). The presented results demonstrate that N-doped TiO2 photocatalyst shows excellent photocatalytic activity in the visible region for the degradation of pharmaceutical pollutants.

Aqueous waste containing low concentrations of tungsten are generated during printed circuit board (PCB) or e-waste recycling process. Study has been initiated to develop a suitable emulsion liquid membrane (ELM) technique for the separation and recovery of tungsten [W(VI)] from such waste using Aliquat 336 in hexane as a carrier and sodium hydroxide as a stripping agent. The waste, having a composition of nearly 600 ppm W(VI), 150 ppm Pb(II) and below 5 ppm concentrations of Cu(II), Mn(II), Zn(II), Co(II), Ca(II), Mg(II), Na(I) and K(I) at pH 5, was used as the feed phase. Various factors that affect the emulsion stability, as well as percentage extraction of W(VI), have been optimized to obtain maximum enrichment of W(VI). An attempt was made to recover W(VI) without making any substantial changes to the waste composition. Under optimized conditions, the extraction percentage of W(VI) was found to be 80% with 4 times enrichment in stripping phase. The separation factor for W(VI) vs. other co-ions was found to be very high thereby indicating selective recovery of W(VI) from the wastewater by using ELM process.

Chlorophenol (CP) is considered as environmentally hazardous material due to its acute toxicity, persistent nature and strong bioaccumulation. The dechlorination of 4-CP was investigated by using various catalysts such as bimetallic (Fe0/Cu0, Al0/Fe0), Pd/C, Raney Ni and Fe0 at room temperature. Among the catalysts studied, Raney Ni proved to be very economical and efficient catalyst that worked without the use of an external reducing agent. The dechlorination of 4-CP by Raney Ni was therefore further explored. Complete dechlorination of 4-CP (30 mg L−1) was achieved in 6 h at an optimum Raney Ni catalyst loading of 3 g L−1. The effect of triethylamine (TEA) and tripropylamine (TPA) was also investigated and it was observed that 100% dechlorination is possible in presence of 45 mg L−1 of TEA. The kinetics of dechlorination of 4-CP was investigated and found to be first order with a rate constant of 0.017 min−1 at 50 οC, and it enhances to 0.109 min−1 with addition of TEA. In the absence of a reducing agent, acidic to neutral pH favors dechlorination of 4-CP. The final product of dechlorination was estimated to be phenol by performing HPLC, LCMS and NMR analysis. Based on the results, a probable dechlorination mechanism of 4-CP is also proposed. It can be concluded that the catalytic hydrodechlorination is an effective and economical technique for dechlorination of 4-CP and it has a potential for the dechlorination of other toxic derivatives of chlorinated aromatics.

Nitroaromatics have been released into wastewater during its production and application, thus, contaminating the ecosystem. The stringent discharge limits of industrial effluents have led to the development of sustainable technologies for removal of nitroaromatics from wastewater. In the present investigation, separation of nitroaromatic compounds such as TNT, TNP and Tetryl from model wastewater was investigated by using supported ionic liquid membrane (SILM) process. Various aliquat 336 based ionic liquids (ILs) were synthesised and characterized, and immobilized in PTFE and PVDF supports for the preparation of SILMs. The key parameters such as type of IL and striping phase, feed phase pH, selectivity for SILM, extraction kinetics and reuse of SILM were studied, in detail. The size of IL-anion plays an important role in removal process. The SILM was found to be selective for TNP over other nitroaromatics. Maximum separation of TNP (

Hexavalent chromium [Cr(VI)], one of the most toxic contaminants, is released in the environment due to various anthropogenic activities. Exposure of Cr(VI) can pose a serious threat to the public health as well as flora and fauna. Effective treatment of Cr(VI) is, therefore, very essential from safety, health, and environment points of view. The present review focuses on the development of silica-based materials for the adsorption of Cr(VI) from wastewater. After discussing toxicity issues and general removal methods of Cr(VI), the importance of silica materials are highlighted. The silica has different shapes, sizes, surface areas, and pore diameters and, hence, can play a vital role in designing the adsorbent. They can be modified into organic, inorganic, polymeric, biological, and ionic liquid based materials. Therefore, they are broadly classified into these five categories. The adsorption isotherms and kinetics of these materials for Cr(VI) are discussed and compared with each other. Future prospect...

Ion imprinting technology is one of the most promising tools in separation and purification sciences because of its high selectivity, good stability, simplicity and low cost. It has been mainly used for selective removal, preconcentration, sensing and few miscellaneous fields. In this review article, recent methodologies in the synthesis of IIPs have been discussed. For several applications, different parameters of IIP including complexing and leaching agent, pH, relative selectivity coefficient, detection limit and adsorption capacity have been evaluated and an attempt has been made to generalize. Biomedical applications mostly include selective removal of toxic metals from human blood plasma and urine samples. Wastewater treatment involves selective removal of highly toxic metal ions like Hg(II), Pb(II), Cd(II), As(V), etc. Preconcentration covers recovery of economically important metal ions such as gold, silver, platinum and palladium. It also includes selective preconcentration of lanthanides and actinides. In sensing, various IIP-based sensors have been fabricated for detection of toxic metal ions. This review article includes almost all metal ions based on the ion-imprinted polymer. At the end, the future outlook section presents the discussion on the advancement, corresponding merits and the need of continued research in few specific areas. Graphical Abstract IIPs for the selective monitoring of metals.

The contamination of energetic materials (EMs) in wastewater during its production and application is one of the serious environmental issues. Selected hydrophobic ionic liquids (ILs) were developed, characterized and applied for the separation of EMs such as TNT, tetryl and picric acid from aqueous medium. Batch-wise extraction experiments were performed at 700 rpm in a capped glass vial at 25 °C. The IL containing anion, bis(trifluoromethanesulfonyl)imide ([NTf2]−) played a vital role in the separation of EMs due to its large ionic radius. It was, therefore, extensively used for the optimization of various process parameters. The investigation of the extraction mechanism has revealed that a C–H⋯Π interaction is present between the IL and EM. The results show the highest distribution ratio of 2095 for the tetryl amongst the other EMs used. A maximum separation factor for tetryl/TNT, TNT/picric acid and picric acid/tetryl was observed to be 1.75, 6.65 and 0.15, respectively for the IL, 1-octyl-3-methylimidazolium bis[trifluoromethanesulfonyl] imide ([OMIM][NTf2]). After the extraction, the IL was separated from the aqueous phase and repeatedly treated five times with a fresh batch of EM.

The aim of this study was to prepare MIP for the selective recognition of DPA and its combination with flash column chromatography for the continuous extraction of DPA from ammunition waste. The DPA–MIP was prepared by free radical polymerization using methacrylic acid as a complexing monomer and EGDMA as a crosslinker. Methanol and acetic acid (9 : 1) were used as a leaching agent for DPA. MIP showed maximum adsorption capacity at pH 4. The maximum experimental adsorption capacity obtained for MIP and NIP particles were 31 mg g−1 and 10.2 mg g−1, respectively. Langmuir and Freundlich adsorption isotherm models were used to analyze the experimental data of DPA adsorption on MIP. The Freundlich adsorption isotherm model fit very well with this. Pseudo first order and pseudo second order kinetic models were used to estimate the corresponding rate parameters, equilibrium capacities and correlation coefficients. The selectivity coefficients of MIP for DPA in the presence of NDPA, TNT and tetryl were 23.14, 47.07 and 52.30, respectively. Continuous extraction of DPA was done with the help of flash chromatography combined with MIP and showed more than 98% recovery. MIP has a good regeneration performance and could maintain almost the same adsorption capacity even after three adsorption–desorption cycles.

In the present investigation, a new adsorbent has been developed by coating p-toluidine formaldehyde resin (PTFR) on silica gel (mass ratio of PTFR/silica 1 : 10). It was characterized using FT-IR, NMR, SEM, TGA and BET instruments to represent the functionality of the material. A detailed investigation on adsorption of Cr(VI) with the prepared adsorbent was performed at different temperatures. The adsorption process was evaluated on the basis of various parameters, such as pH, adsorbent dose, concentration of Cr(VI) and contact time. The Cr(VI) concentration was measured by UV-Vis spectrophotometer and ion chromatograph. It was observed that the HCrO4− gets adsorbed on the ammonium ions (–NH3+) of PTFR due to electrostatic interaction. The methyl group presenting at the para-position of the benzene ring exerts an inductive effect on the nitrogen atom of the amine group that in turn enhances protonation in the acidic medium. The maximum adsorption capacities of Cr(VI) achieved were 40.0, 41.67 and 43.47 mg g−1 at 303, 313 and 323 K, respectively. The adsorption followed both Langmuir and Freundlich isotherm models. The kinetics was pseudo second order and the thermodynamic parameters, such as ΔH°, ΔS° and ΔG°, analyzed at different temperatures, indicate that the adsorption process was spontaneous and endothermic at high temperature. The desorption of Cr(VI) from the adsorbent was carried out using 0.2 N NaOH at room temperature, and the complete recovery of Cr(VI) was confirmed by ion chromatograph.

Ionic liquids (ILs) are playing increasingly important roles in the membrane separation processes. The present manuscript discusses the removal of Pb(II) ions from aqueous solution using an emulsion ionic liquid membrane (EILM) process. Initially, the emulsion liquid membrane (ELM) was prepared by stirring strip phase (sulphuric acid) and organic phase (surfactant: span 80, extractant: D2EHPA, diluent: hexane) together under high speed agitation. Note that, the parameters of the ELM process such as emulsification speed, pH of the feed phase, treat ratio, extractant and surfactant concentrations were studied for the maximum removal of Pb(II) ions. The role of IL was explored by adding hydrophobic IL, octylmethylimidazole hexafluorophosphine ([OMIM][PF6]), in the organic phase. The performance of ELM with and without IL was compared on the basis of stability, enrichment factor and the removal efficiency for Pb(II). The results showed that the percentage of Pb(II) extraction was complete by the emulsion membrane with IL (EILM) in comparison to the 97% achieved by neat ELM. Further, the stability and the enrichment factor of the EILM were found to be 2–3 times greater than that of the ELM. The FT-IR spectroscopic analysis revealed that bond interactions between IL and membrane phase components avoided the coalescence of internal phase droplets and enhanced the emulsion stability. The results obtained in this work support the use of the IL [OMIM][PF6] as both a stabilizer and carrier for the overall improvement of the ELM process.

Submicron polypropylene (PP) fibers of three different sizes (300 nm, 600 nm, and 900 nm) were prepared via electrospinning. The fibers were blended with microglass (MG) fibers to form composite media in varying fiber concentrations to obtain PP to MG fiber surface area ratios ( AR ) of 0.5, 1 and 2. The effects of fiber size and amount of electrospun PP fibers on wettability and filtration performance of the blended PP + MG media were measured. The wettability of the filter media were characterized by a modified Washburn test and expressed as the lipophilic to hydrophilic ( L / H ) ratio. The wettability characterization shows that hydrophobicity of filter media increases with the amount and size of electrospun PP fibers. In liquid–liquid coalescence experiments the amount and fiber diameter of the electrospun PP fibers significantly affected the separation efficiency and the pressure drop as compare to MG fiber only media. The separation efficiency was greatest for the smallest fibers (300 nm) and the intermediate AR of 1.0. The pressure drop tended to increase with the amount of PP fiber and with fiber diameter.

Thermal storage cotton possessing solid–solid phase change properties was prepared by direct grafting of polyethylene glycol (PEG) on cotton fiber/cloth. Attempt has been made to characterize intermediates so that desired grafting could be obtained. The grafting was done by using urethane linkage and the grafted cotton was found to undergo solid–solid phase transition. The modified cotton was characterized by using Fourier transform infrared spectroscopy (FT-IR), 13C CPMAS, polarizing optical microscopy, differential scanning calorimetry (DSC) and thermogravimetry respectively. The DSC study revealed quite good storage effect of grafted cotton and the enthalpy of melting was found to be 55–59 J/g with a peak appearing at around 60 °C. During cooling scan, the crystallization peak appeared at around 38 °C. Further, thermogravimetric analysis confirmed good thermal stability up to 300 °C. Appreciable improvement of mechanical properties of cotton has been observed after grafting. The polarizing optical micrograph clearly showed change of morphology after grafting, i.e., the grafted PEG adhering to fiber surface.

Glass fiber filter media are widely used in separation of droplets from liquid aerosols. In prior works two possible enhancements to the performance of the glass fiber media were studied: (1) the capture efficiencies were increased by augmenting the glass fibers with sub-micron sized electrospun polymer fibers, and (2) the pressure drop was decreased by modifying the filter media with insertion of 45° drainage channels. In this paper we report the simultaneous application of these two enhancements on the performance of the filter media. Filters were fabricated by inserting low surface energy woven polymer fiber drainage channels at various angles within non-woven glass fiber filter media augmented with Nylon sub-micron fibers. The effects of the presence and geometry of the drainage channels on the filter performance were evaluated experimentally. The sub-micron fibers gave the filter high coalescence and separation efficiencies while the drainage channels reduced the filter pressure drop. The micro glass fiber media augmented with 100 nm Nylon fibers and modified with Polypropylene fiber drainage channels at 45° downward angles had the overall best performance.

Fibrous filters are used to remove liquid aerosols from gas streams. Filter media capture fine liquid droplets; the captured liquid droplets coalesce to form big drops and saturate the filter media. This captured liquid typically drains from the filter by gravity. The saturation, or liquid holdup in the filter, constricts the gas flow, reduces capture efficiency, increases pressure drop, and increases the operating costs of the filter. Liquid holdup in the filter also decreases the on-stream life of the filter and requires replacing the filter, which requires shutting down the process and/or equipment being used, which adversely affects the economy of the process. Filter performance improves when the liquid saturation is reduced without reduction in capture efficiency. In this article, glass microfiber filter media are modified with nonwoven polypropylene fabric drainage structures to reduce saturation and drag resistance. The experimental results show that the geometry with embedded nonwoven drainage cha...

The surface energy, or wettability, of the fibers in coalescence filter media controls the performance of coalescing filters. High surface energy fibers capture and hold onto droplets, slowing their movement through the filter and hence increase coalescence between drops. Low surface energy fibers allow drops to slip through the filter with little or no hindrance but do not contribute significantly to the coalescence. In this work we present experimental data on the performance of composite filters made of high surface energy fibers with layers of low surface energy woven mats of fibers as drainage channels. Drainage channels provide pathways for coalesced liquid to rapidly flow out of the filter without compromising with the capture efficiency. Hence the saturation or hold-up of liquid, in the filter decreases. This reduces the pressure drop, and increases the filtration index and filter life. In this paper, filters were fabricated by layering woven and nonwoven polymer fiber drainage channels into non-woven glass fiber filter media. The effect of the presence and geometry of the drainage channels on the filter performance was evaluated. The high surface energy glass fibers provide the desired coalescence while the low surface energy polymer fibers of the drainage channels reduced the filter saturation. The experimental results show that filter media embedded with Teflon® fiber drainage channels at 45° downward angles had the overall best performance.

Fibrous coalescing filters are commonly used to separate water-in-oil emulsions. Wettability of the fibers significantly influences the filter performance. The wettability of the filter media depends on surface properties of fiber materials and porosity of the filter medium. The wettability of the filter media is characterized using modified Washburn’s equation and expressed in terms of the lipophilic to hydrophilic (L/H) ratio. In this work, layered media were prepared with varying compositions of hydrophilic micro glass fibers and hydrophobic polypropylene or polyester fibers to achieve a range of L/H values. By varying the fiber composition and thickness of hydrophilic and hydrophobic layers in the media, filter media with different wetting properties can be prepared. Water and Viscor-1487 oil (a diesel fuel calibration fluid) were used as test liquids for the wettability characterization. The filter media were tested in liquid–liquid coalescence experiments in which fine emulsions of water droplets were dispersed in the Viscor-1487 liquid. The experimental results show that the layered hydrophilic/hydrophobic structures significantly reduce the pressure drop and improve the filter performance as compared to media constructed with only micro glass fibers.

This paper discusses the fabrication and characterization of electrospun nanofiber mats made up of poly(4-methyl-1-pentene) polymer. The polymer was electrospun in different weight concentrations. The mats were characterized by their basis weight, fiber diameter distribution, contact angles, contact angle hysteresis, and air permeability. All of the electrospun nonwoven fiber mats had water contact angles greater than 150 degrees making them superhydrophobic. The permeabilities of the mats were empirically fitted to the mat basis weight by a linear relation. The experimentally measured air permeabilities were significantly larger than the permeabilities predicted by the Kuwabara model for fibrous media.