Fingerprinting of Octane Rating Gasoline and its Contaminants Using Synchronous Fluorescence Spectroscopy.

Fuel fraud has proliferated due to underlying economic advantage in nearly every nation. For the purpose of detecting adulteration and providing real-time quality assurance, non-destructive oil analysis is crucial. This paper reports the simple approach for fingerprinting undiluted petroleum products including gasoline from various brands, diesel, and kerosene oil in comparison with organic solvents using synchronous fluorescence spectroscopy and hierarchical cluster analysis. Fluorescence-based successful detection of adulterated samples is demonstrated in imported RON 92 gasoline, synthetically adulterated with kerosene oil (KO) in proportions up to 70%. Compared to gasoline, kerosene oil has a lower relative poly aromatic hydrocarbons, as the amount of kerosene oil (KO) increases, the KO peak at 352 nm rises, but the gasoline's peak intensity decreases in the range of 371-500 nm. It is noteworthy that imported fuel grades RON 92 and RON 95 are comparable to each other and surprisingly clustered with RON 91 from the Attock refinery presenting concerns about quality. Similarly, the Shell website mentions that Shell V-Power is RON 99 but interestingly it clusters with retail fuel samples acquired from PSO filling stations and PSO RON 95 showing disagreement with the claim that the fuel is high octane. Another use for this technique in oil exploration was the detection of adulterants and successfully spotted methanol, ethanol, and kerosene oil in the tainted samples. These findings suggest SFS as an accurate, and low-cost testing tool for gasoline fingerprinting and contamination screening.

Correlation between Magnetic and Dielectric Response of CoFe2O4:Li1+/Zn2+ Nanopowders Having Improved Structural and Morphological Properties.

The vast applicability of spinel cobalt ferrite due to its unique characteristics implies the need for further exploration of its properties. In this regard, structural modification at the O-site of spinel with Li1+/Zn2+ was studied in detail for exploration of the correlation between structural, magnetic, and dielectric properties of the doped derivatives. The CTAB-assisted coprecipitation method was adopted for the synthesis of the desired compositions owing to its cost effectiveness and size controlling ability. Redistribution of cations at T- and O-sites resulted in the expansion of the crystal lattice, but no distortion of the cubic structure was observed, which further supports the flexible crystal structure of spinel for accommodating larger Li1+/Zn2+ cations. Moreover, an XPS analysis confirmed the co-existence of the most stable oxidation states of Zn2+, Li1+, Co2+, and Fe3+ ions with unstable Co3+ and Fe2+ ions as well, which induces the probability of hopping mechanisms to a certain extent and is a well-established behavior of cobalt ferrite nanoparticles. The experimental results showed that Li1+/Zn2+ co-doped samples exhibit the best magnetic properties at dopant concentration x = 0.3. However, increasing the dopant content causes disturbance at both sites, resulting in decreasing magnetic parameters. It is quite evident from the results that dielectric parameters are closely associated with each other. Therefore, dopant content at x = 0.1 is considered the threshold value exhibiting the highest dielectric parameters, whereas any further increase would result in decreasing the dielectric parameters. The reduced dielectric properties and enhanced magnetic properties make the investigated samples a potential candidate for magnetic recording devices.

Thermo-catalytic decomposition of polystyrene waste: Comparative analysis using different kinetic models.

Due to a huge increase in polymer production, a tremendous increase in municipal solid waste is observed. Every year the existing landfills for disposal of waste polymers decrease and the effective recycling techniques for waste polymers are getting more and more important. In this work pyrolysis of waste polystyrene was performed in the presence of a laboratory synthesized copper oxide. The samples were pyrolyzed at different heating rates that is, 5°Cmin-1, 10°Cmin-1, 15°Cmin-1 and 20°Cmin-1 in a thermogravimetric analyzer in inert atmosphere using nitrogen. Thermogravimetric data were interpreted using various model fitting (Coats-Redfern) and model free methods (Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Friedman). Thermodynamic parameters for the reaction were also determined. The activation energy calculated applying Coats-Redfern, Ozawa-Flynn-Wall, Kissinger-Akahira-Sunose and Friedman models were found in the ranges 105-148.48 kJmol-1, 99.41-140.52 kJmol-1, 103.67-149.15 kJmol-1 and 99.93-141.25 kJmol-1, respectively. The lowest activation energy for polystyrene degradation in the presence of copper oxide indicates the suitability of catalyst for the decomposition reaction to take place at lower temperature. Moreover, the obtained kinetics and thermodynamic parameters would be very helpful in determining the reaction mechanism of the solid waste in a real system.

Exploring moisture adsorption on cobalt-doped ZnFe2O4 for applications in atmospheric water harvesting.

Sorption-based atmospheric water harvesting (SBAWH) is a highly promising approach for extracting water from the atmosphere thanks to its sustainability, exceptional energy efficiency, and affordability. In this work, ZnFe2O4 and Zn0.4Co0.6Fe2O4 were evaluated for moisture adsorption. The desired materials were synthesized by a surfactant-assisted sol-gel method. Synthesized samples were characterized using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), and point of zero charge (PZC). Crystallinity and phase composition were evaluated by XRD analysis. Several parameters were determined using XRD analysis: lattice parameter, unit cell volume, crystallite size, and bulk density. The morphology of synthesized materials was assessed via SEM, and unveiled the acquisition of consistent, homogeneous, and uniform crystals. Elemental composition was determined through EDX spectroscopy. Water adsorption on the surface was evaluated by FTIR spectroscopy. The magnetic properties of synthesized ZnFe2O4 and cobalt-doped ZnFe2O4 ferrites were investigated using VSM. The negative charge on the Zn0.4Co0.6Fe2O4 surface was explored using PZC. Adsorption studies on synthesized materials were conducted with the help of an atmospheric water harvesting (AWH) plant created by our team. Moisture adsorption isotherms of synthesized materials were determined using a gravimetric method under varying temperature and relative humidity (45-95%) conditions. The moisture content (Mc) of Zn0.4Co0.6Fe2O4 and ZnFe2O4 was 597 mg g-1 and 104 mg g-1, respectively. Key thermodynamic properties, including isosteric heat of adsorption (Qst), change in Gibbs free energy (ΔG), and change in sorption entropy (ΔS), were evaluated. Qst was negative, which confirmed the sorption of water vapors on the material surface. ΔG and ΔS indicated that water-vapor adsorption was spontaneous and exothermic. A second-order kinetics study was carried out on synthesized materials, demonstrating their chemisorption behavior. The latter was due to the oxygen defects created by replacement of Co2+ and Fe3+ at tetrahedral and octahedral sites. Water vapors in the atmosphere became attached to the surface and deprotonation occurred, and the hydroxyl ions were formed. Water vapor attached to these hydroxyl ions. A second-order kinetics study was carried out to confirm the chemisorption behavior of synthesized materials.

QuEChERS sample preparation integrated to dispersive liquid-liquid microextraction based on solidified floating organic droplet for spectrometric determination of sudan dyes: A synergistic approach.

In this project, a synergistic approach has been proposed where a quick, easy, cheap, effective, rugged, and safe (QuEChERS) sample preparation technique was developed for the extraction of sudan III and sudan IV dyes in different spices prior to its dispersive liquid-liquid microextraction based on solidified floating organic droplet (DLLME-SFO). Initially, the sample was extracted by QuEChERS method and then preconcentrated through DLLME-SFO followed by spectrophotometric detection. All the experimental parameters i.e., volume of extraction solvent, pH, acetonitrile to water ratio, temperature, centrifugation rate and time, and sample volume were optimized. Limit of detection (LOD) calculated for sudan III and sudan IV were 0.42 and 0.35 mg/L, respectively. Excellent recoveries were obtained in the range of 98.29-99.88%. After validation through standard addition methodology, the developed QuEChERS@DLLME-SFO method was successfully applied to determine sudan (III-IV) dyes in real spices samples. Integration of QuEChERS and DLLME-SFO was found to be a suitable substitute to eliminate the usage of costly primary secondary amines and other sorbents. The synergistic approach of QuEChERS and DLLME-SFO with the aid of UV/visible spectrophotometry makes it prompt, cost effective technique with excellent analytical figures of merit.

Supramolecular solvent-based microextraction for the preconcentration of Pb2+ and Cd2+ prior to spectrophotometric detection.

Supramolecular solvent-based dispersive liquid-liquid microextraction technique has been developed as a preconcentration tool for the determination of trace level of Pb2+ and Cd2+. Dodecanol dispersed in tetrahydrofuran has been utilized as a supramolecular-solvent system for the extraction of analytes prior to their quantitative determination with graphite furnace atomic absorption spectrophotometer. Both Pb2+ and Cd2+, which were efficiently extracted by supramolecular solvent system, were complexed with dithizone followed by the addition of supramolecular solvent. The experimental variables that could possibly influence the extraction efficiency, i.e. pH value, temperature, sample volume, centrifugation time, rate of centrifugation, ionic strength, etc. were subjected to the optimization step. An interference study was also conducted to check the selectivity of developed method. Limit of detection calculated for Pb2+ and Cd2+ was 0.015 and 0.061 mg L-1, respectively. The limit of quantification was 0.05 and 0.2 mg L-1 for Pb2+ and Cd2+, respectively. The analytical signal was enhanced to 30 times in case of Pb2+ and 27 times in case of Cd2+. The results obtained revealed that the developed method is rapid, simple, sensitive, and efficient for the determination of both analytes in real water samples.

Preconcentration of rifampicin prior to its efficient spectroscopic determination in the wastewater samples based on a nonionic surfactant.

Every year, tuberculosis affects the lungs of millions of people and rifampicin is the commonly used medicine for its treatment due to its antibiotic nature. The frequent use of rifampicin may lead to its increased concentration in the water resources. This research work is focused on the cloud point extraction (CPE) procedure for the preconcentration of rifampicin prior to its determination in water. The UV/vis spectrophotometric method was adapted for the measurement of rifampicin content after the phase separation. Triton-X 100 was used as the nonionic surfactant which contains hydrophilic polyethylene chain feasible for the extraction of analyte. Various analytical parameters that can affect the extraction efficacy were optimized to achieve linearity of the proposed method in the concentration range of 3.54-81.41 mgL-1. The Limit of detection and quantification were 1.261 and 4.212 mgL- 1, respectively. The Preconcentration factor was 40 with relative standard deviation (%RSD) of 2.504%. The standard addition methodology was adopted for the validation of this procedure and effectively applied for the determination of rifampicin in real wastewater samples.

Fuel production from waste polystyrene via pyrolysis: Kinetics and products distribution.

In the present study polystyrene waste (PS) was collected from a drop off site in a local market and pyrolyzed at heating rates of 5, 10, 15 and 20 °C/min and temperature range 40-600 °C under nitrogen condition. The apparent activation energy (Ea) and pre-exponential factor (A) were determined using 6 different kinetic methods. Activation energy and pre-exponential factor were found in the range of 82.3 - 202.8 kJmol-1 and 3.5 × 106-7.6 × 1014 min-1 respectively. The results demonstrated that the calculated values of Ea and A vary with fraction of conversion, heating rates and the applied model. Moreover, pyrolysis of waste polystyrene was carried out in an indigenously manufactured furnace at temperatures ranging from 340 to 420 °C. The composition of liquid and gaseous fractions was determined using gas chromatography-mass spectrometry. Temperature and reaction time were optimized and the results revealed that temperature of 410 °C and exposure time of 70 min are the best conditions for maximum fuel oil production. Methane and ethane were found as the main products in the gas phase constituting about 82% of the gaseous fraction. The liquid products composed of broad range of C2 - C15 hydrocarbons depending on the pyrolytic parameters. A comparison of the composition of pyrolysis oil with standard parameters of diesel, gasoline and kerosene oil suggested that pyrolysis oil from polystyrene waste holds great promise for replacing fuel oil.

The interaction of a model active pharmaceutical with cationic surfactant and the subsequent design of drug based ionic liquid surfactants.

Interactions of active pharmaceutical ingredients (API) with surfactants remain an important research area due to the need to improve drug delivery systems. In this study, UV-Visible spectrophotometry was used to investigate the interactions between a model low molecular weight hydrophilic drug sodium valproate (SV) and cationic surfactant cetyltrimethylammonium bromide (CTAB). Changes in the spectra of SV were observed in pre- and post-micellar concentrations of CTAB. The binding constant (Kb) values and the number of drug molecules encapsulated per micelle were calculated, which posed the possibility of mixed micelle formation and strong complexation between SV and CTAB. These results were compared to those of a novel room temperature surface active ionic liquid, which was synthesized by the removal of inorganic counterions from a 1:1 mixture of CTAB and SV. In this new compound the drug now constitutes a building block of the carrier and, as such, has considerably different surfactant properties to its building blocks. In addition, enhanced solubility in a range of solvents, including simulated gastric fluid, was observed. The study provides valuable experimental evidence concerning the performance of drug based surfactant ionic liquids and how their chemical manipulation, without altering the architecture of the API, leads to control of surfactant behavior and physicochemical properties. In turn, this should feed through to improved and controlled drug release rates and delivery mechanisms, and the prevention of precipitation or formation of polymorphs typical of crystalline form APIs.