Low temperature ionothermal synthesis of TiO2 nanomaterials for efficient photocatalytic H2 production,dye degradation and photoluminescence studies

The photocatalytic hydrogen generation is a novel, eco-friendly and favourable method for production of green and clean energy using light energy. In this direction, we report low-temperature ionothermal method for the preparation of TiO₂ nanoparticles (NPs) using methoxy ethyl methyl imidazolium tris (pentafluoroethyl) trifluoro phosphate (MOEMINtf₂) as an ionic liquid (IL) at 120°C for 1 day. The synthesized nanomaterials were examined using different spectrochemical methods like UV-DRS, XRD, FT-IR, TEM, BET and TGA-DTA techniques. The mixed phase TiO₂ is obtained with 81.7% of anatase and 18.3% of rutile phase by the XRD studies, and average crystallite size is found to be ∼7 nm. The stretching of Ti-O bond (∼555 cm⁻¹) and few other bands related to ionic liquid were confirmed by FTIR spectrum. The band gap energy was observed to be ∼3.38 eV by UV-DRS analysis. TEM images reveal spherical shape with an average particles size of about 10 nm. Photocatalytic H₂ generation was carried out using TiO₂ NPs and observed the generation of 553 μmol h⁻¹ g⁻¹ via water splitting reaction. Furthermore, the prepared TiO₂ NPs employed for the photocatalytic degradation of methylene blue dye (84.54%), and photoluminescence studies confirms the obtained material can be used in optoelectronic applications with green emission.     

Green synthesis of LiZnVO4 nanoparticles and its multiple applications towards electrochemical sensor,supercapacitor, humidity sensing,photoluminescence and antioxidant activities

LiZnVO₄ nanoparticles (NPs) were synthesized by a simple combustion method using Hibiscus Rosa Sinensis leaves as a novel fuel and the prepared NPs were characterized using XRD, FT-IR, morphological analysis by SEM and TEM studies, elemental analysis by EDAX and ICP-MS. XRD data of the synthesized NPs were well-matched with the JCPDS number 038–1332 and it confirms the distorted phenacite structure of LiZnVO₄. FT-IR strengthens the bonding of M-M and M–O in LiZnVO₄. Optical characteristics of LiZnVO₄ NPs were studied by photoluminescence (PL) spectroscopy. Vanadate group of the prepared NPs originates a green emission. Examination of latent finger prints (LFP’s) showed a crystal clear patterns under near UV region (365 nm) as they are the prominent techniques in crime investigations. LiZnVO₄ NPs exhibit a strong antioxidant property and act as a good sensor to detect sodium nitrite analyte at extremely low concentrations with limit of detection of 27.5 nM. Three-electrode system supercapacitor device has been fabricated and examined the performances. Specific capacitance of LiZnVO₄ NPs based supercapacitor was found to be 88.7 F/g at a current density of 0.1 mA. Power density (P_d) and energy density (E_d) were found to be 0.51 W/g and 12.3 Wh/Kg, respectively. This device exhibits a stable CV curves up to the scan rate of 10 V/s. Furthermore, LiZnVO₄ NPs acts as an excellent material towards the humidity sensing with a sensitivity factor, sensitivity and limit of detection of 28.0, 0.3 MΩ/%RH and 5%RH, respectively. All the above studies show the diverse potentiality of LiZnVO₄ NPs.

     

Methane Hydrate Formation and Dissociation in the presence of Bentonite Clay Suspension

The present work reports the effect of bentonite clay on methane hydrate formation and dissociation in synthetic seawater of salinity 3.55 % of total dissolved salts. Extensive observations of pressure‐temperature equilibrium during formation and decomposition of methane hydrate under different conditions have been made. It is observed that phase equilibrium conditions of hydrate are affected on changing the concentration of bentonite clay in synthetic seawater. Induction time for hydrate nucleation has been measured under different concentrations of clay and subcooling conditions. The presence of bentonite clay in synthetic seawater reduces the induction time of hydrate formation. Enthalpy of hydrate dissociation is calculated by Clausius‐Clapeyron equation using measured phase equilibrium data. The amount of gas consumed during hydrate formation has been calculated using real gas equation. It is found that a larger amount of gas is consumed upon addition of bentonite clay in synthetic seawater.     

Flocculation properties of polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) synthesised by conventional and microwave assisted method

A novel polymeric flocculant based on polyacrylamide grafted carboxymethyl guar gum (CMG-g-PAM) has been synthesised by grafting polyacrylamide chains onto CMG backbone using conventional redox grafting and microwave assisted grafting methods. Under optimum grafting conditions, 82% and 96% grafting efficiencies have been observed in case of conventional and microwave assisted methods respectively. The optimum sample has been characterized using viscometry, spectroscopic analysis, elemental analysis, molecular weight and radius of gyration determination. The flocculation characteristics of grafted and ungrafted polysaccharides have been evaluated in kaolin suspension, municipal sewage wastewater and decolourization efficiency of a dye solution (methylene blue). It is evident from results that CMG-g-PAM synthesised by microwave assisted grafting method is showing best flocculation characteristics.     

A Study of the Effect of the Concentration of Constituents on the Characteristics of a Cross-Linked Polyacrylamide Gel

Abstract

Polymer gels have long been used for water shutoff in petroleum production operations. A polymer gel is prepared by a combination of water, polymer, and cross-linker. The gelation or cross-linking reaction between the polymer and cross-linker results in the formation of a three-dimensional polymer network known as gel, which forms a barrier to water flow. Polyacrylamides along with cross-linkers such as metal ions (Al³⁺, Cr³⁺, Zr⁴⁺, etc.) and organic compounds such as resins, glutaraldehyde, phenol/formaldehyde, etc., have been used by the oil industry for this purpose. Most of these gels have been successfully applied in the field and good results have been obtained. In the present study, polyacrylamide (PAM) was cross-linked with hydroquinone (HQ) and hexamethylene tetramine (HMTA). The gel formed by cross-linking HQ and HMTA with PAM had high mechanical strength and was stable for long periods of time. The kinetic parameters of this system were determined by viscosity measurement at a temperature of 85°C.     

The effect of zirconia ions on corrosion performance of sol–gel coated galvanized steel

Currently, galvanized steel is treated with hexavalent chrome passivation. Sol–gel coating has been found to be a potential replacement for the hazardous hexavalent chrome passivation treatment. The aim of this work is to study the effect of zirconyl nitrate on corrosion behavior of sol–gel coating. Aminopropyl-trimethoxysilane and 3-glycidoxypropyltrimethoxysilane were employed as precursors to prepare the sol–gel-based silane coating. The sol–gel film was deposited on galvanized steel sheet by dip coating method. The chemical properties of sol–gel solution and coated films were analyzed by infrared spectroscopy. Morphology of the film was characterized by scanning electron microscope. The corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization curve, and salt spray test. The results indicated that zirconia-doped coatings have better corrosion resistance in comparison with their undoped counterparts. The coating doped with 0.5% zirconyl nitrate provides better corrosion protection due to the inhibitive action of zirconia ion.     

Effect of Branched Alcohols on Phase Behavior and Physicochemical Properties of Winsor IV Microemulsions

The microemulsion phase behavior and physicochemical properties of surfactant–water–alcohol–oil systems are the pioneer laboratory study as a function of alcohol, water content and temperature to develop an experimental investigation for a better understanding of the microstructure of a single phase microemulsion and its stability under reservoir condition during hydraulic fracturing to recover the residual trapped oil. Viscosified surfactants are used as an efficient proppant conducting medium in hydraulic fracturing applications. The physicochemical properties of microemulsions are very helpful for characterization of microemulsions to justify their abilities and screening of surfactants. In the study, two branched alcohols, 2-methyl butan-2-ol, 3-methyl butan-1-ol selected as the cosurfactant in the proposed microemulsion system and their effect in tailoring the viscosity of microemulsions were studied. Microemulsion regions elucidated from Winsor’s pseudophase model of an oleate surfactant show a signatory distribution pattern of components between different domains with non-polar and asymmetric geometry of cosurfactant directs macromolecular alignments; their alignment contributes to a viscous microemulsions (gel) regime. The effect of surfactant and alkali, and the experimental temperature on the rheological properties of the lamellar mesophase were investigated. Phase transit regions and exact microemulsion and viscous microemulsion magnitudes were elucidated with the help of conductivity and viscosity studies of the ternary system as a function of the aqueous fraction and were in good agreement with Winsor’s pseudophase model. Dynamic and steady shear rheological studies showed that the gel is viscoelastic in nature, sustain viscosity and elastic modulus values appropriate for proppant suspension under high shear conditions. The proppant suspension and thermal behavior of ideal gel composition was found to be suitable for Coal Bed Methane and soft rock, clay reservoir stimulation.     

Assessment of spontaneous heating susceptibility of Indian coals—A new approach

The article enumerates a new electro-chemical method, viz. wet oxidation potential technique for assessing the susceptibility of coal to spontaneous combustion. In the present investigation, 600 experiments with 50 coal samples collected from fiery and non-fiery seams covering different geographical locations in India were carried out. Physicochemical characteristics of coal like moisture, volatile matter, oxygen, and hydrogen contents have been correlated with the results of wet oxidation potential method carried out at different experimental conditions. Analysis of the results indicates that the experiments of the wet oxidation potential method should be carried out with 0.2N KMnO₄ solution in 1N KOH at 45°C to achieve optimum results. Results of this method are corroborating with field observations and also give good correlation with results obtained from the crossing point temperature method.     

Effect of Hydrophobic Modification on the Properties of Polymer‐Blended Microemulsion Gels

Phase behavior of sodium oleate (NaOl)/isoamyl alcohol‐based lamellar gel phase in cedar oil/water medium in the presence of the nonionic polymer hydroxyethyl cellulose (HEC) and its hydrophobic modified product (HMHEC) is investigated for the development of polymer‐embedded surfactant gels. HMHEC is more soluble in oil‐in‐water (o/w) microemulsions, but nonionic HEC shows limited solubility in the lamellar microemulsion (o/w type). Quantitative estimation of rate of adsorption of the polymer on lamellae bilayers can be easily done by Sudan solubilization and methylene blue complexation methods. Addition of HMHEC to the lamellar gel phase increases the polymer solubilization limit of lamellar gels as well as the viscoelasticity and thermal stability. The polymer‐embedded microemulsion gel acts as a “clean gel” since it exhibits good solubilization in different hydrocarbon media at ambient conditions. Elastic modulus of the polymer‐embedded gel influences directly the suspension performance of gels at high temperature and yields a reasonable sand‐settling velocity acceptable according to fracturing standards. The thermal characteristics and viscoelastic properties of polymer‐embedded gel were found to be suitable for moderate‐temperature reservoir stimulation where the bottom hole temperature is in the range 70–75 °C. Already a large amount of experimental data on pure microemulsions (without polymer) exists. Our studies indicate that the developed polymer‐embedded microemulsion gel has great potential as a model system for the study of polymer–microemulsion interactions.