Search

The electrochemical reduction of nitrate and ammonium ion oxidation has been performed with the cathode (Al) and anode (Ti/RuO₂) in the explosive industry wastewater polluted with a significant quantity of NO₃– and NH₄⁺. For this, the influences of various other cathode materials (Fe, Cu, and C), the current density (j = 35.71 to 142.86 A m–²), wastewater pH (pH = 3–12), and treatment time (t = 180 min) were analyzed for nitrate ion reduction, ammonium ion oxidation, nitrite ion generation, and total nitrogen (TN) degradation. The maximum nitrate removal and TN removal efficiencies were found to be ≈51 and ≈63% at j = 142.86 A m–² and wastewater natural pH after 180 min treatment time, respectively. In this condition, SEC was calculated to be 74.4 kWh (kg NO₃– reduced)⁻¹. The mechanistic analysis suggested that the atomic hydrogen molecules, H⁺, and e– help in the nitrate ion reduction and the available Cl– ion in the wastewater helps in the oxidation of the ammonium ion into gaseous nitrogen through the electrochemical process. The new and used electrodes were characterized by FE-SEM, AFM, and XRD techniques. Electrodes were also characterized within untreated and treated wastewater through CV and EIS analysis. The in situ generated oxidizing species were identified by the p-nitrosodimethylaniline (RNO) bleaching test. Pseudo-first-order and nᵗʰ-order kinetic models were applied, and the reaction rate was calculated to understand the reaction rate of the nitrate reduction. The approximate operational cost estimation has been performed for the lab-scale batch reactor treatment of the explosive industry wastewater. No scum or sludge was produced throughout the treatment process. This study helps to understand the parametric, mechanistic, and kinetic aspects of electrochemical nitrate reduction and oxidation of the previously present and produced ammonium ion in the explosive industry wastewater.

This study reports an electrochemical reduction of the NO3− along with oxidation of the in-situ generated NH4+ with maximum selectivity of the N2 gas as the final-product. The use of aluminum as a cathode and Ti/RuO2 as an anode showed enhanced electrochemical nitrate reduction at the cathode and oxidation of the ammonium ion at the anode. Effects of various parameters like initial NO3− concentration (Co = 100−400 mg L−1), a dose of the Cl− as NaCl (NaCl = 100−400 mg L−1), current density applied (j = 83.3-333.3 A m−2), solution pH (pH = 4–10) and electrolysis time (t = 0−120 min) were studied in terms of NO3− reduction and total nitrogen (TN) removal efficiencies. Current efficiency (CE) was elaborated with respect to end products like N2, NO2− and NH4+. Specific electrical energy consumption (SEC) was calculated in kWh kg−1 NO3− removed for the electrochemical process. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized for understanding the oxidation/reduction mechanism over electrodes and the characteristics of the electrodes in a different solution. The studied mechanism suggested a circular conversion of NO3− through complex processes into the N2 gas as the final product. The ultimate nitrate and TN degradation efficiency of ≈95 % with N2 selectivity of ≈100 % were achieved at the optimum condition of Co = 100 mg L−1, NaCl = 300 mg L−1, j = 333.3 A m−2, pH = 6 and time = 120 min with SEC = 927.4 kW h kg−1 NO3− removed. The 1st, 2nd, and nth-order kinetic models were used for the reaction kinetics. FE-SEM, XRD, and AFM techniques were used for the characterization of the electrodes before and after all the electrochemical runs. The operating cost was calculated for lab-scale treatment along with a comparison with previous studies. No sludge or scum got produced for each electrochemical run. Finally, this study delivers a superior perceptive for electrochemical characteristics of Al at the cathode side and Ti/RuO2 at anode side as well as electrochemical NO3− reduction and oxidation of the generated NH4+, simultaneously.

Present study proposed a sorption and desorption approach of aqueous mercury ion (Hg2+) on sulfur impregnated attapulgite (ATPS) adsorbent. Morphological characterization of natural and impregnated ATP confirmed the mesoporous nature of ATPS-adsorbents. The presence of various types of functional groups on the surface of ATPS was confirmed by using the zeta-potential measurement, X-ray fluorescence (XRF), and FT-IR analysis. Batch adsorption tests were carried out to detect the optimum condition of temperature for sulfur impregnation, and the results illustrated that the best adsorbent (ATPS-500) produced via the impregnation at 500 °C, with the highest equilibrium uptake of Hg2+ at initial pH 7. Different parameters like solution pHo, initial concentration of mercury (Co), temperature (T), contact time (t) and the effect of co-existing ions were optimized. Optimum pH and equilibrium contact time at the optimum dose of adsorbent (m) = 0.02 g in 50 mL and Co = 2.0 mg L − 1 were found to be pH~5 and 24 h at T = 313 K for ATPS-500.The best representation of adsorption kinetic was followed by the pseudo-first order kinetic model. The adsorption of Hg2+ions onto ATPS-500 was found to be endothermic. The heat of adsorption and changes in the entropy of Hg2+ions sorption on ATPS-500 were determined as 10.35 kJ mol−1 and 0.16 kJ mol−1 K − 1, respectively. Thermal regeneration represented that ATPS-500 was used for five desorption–sorption cycles with excellent efficiency of Hg2+ in each cycle.

Perfluorooctanoic acid (PFOA) is a chemical used for both commercial and industrial applications. It has turned out to be worldwide anxiety owing to its extensive existence in the water bodies and subsequent harmful ecological effects. This study illustrates the significance of hybrid aerated electrocoagulation (EC) and modified peroxi-coagulation (PC) for the PFOA degradation in an aqueous solution. Consumable iron plate electrodes were employed as an electrode pair in both EC and modified PC processes. The laboratory tests were conducted in a batch reactor with a functioning capacity of 1 L. Aeration improved the EC process performance considerably. Higher than 56% PFOA and 38% defluorination occurred after 60 min of electrolysis with EC being operated at a pH of 3.6 and applied a current density of 78.34 Am−2. The performance of the modified PC process was considerably higher than that of the aerated EC process. More than 90% PFOA, 87%total organic carbon (TOC), and 71% deflorination were attained with modified PC process after 60 min of electrolysis operated at 78.34 Am−2 and initial pH of 3.6 when 50 mM hydrogen peroxide (H2O2) was added. The superior performance of the modified PC than aerated EC is mostly owing to the attack of in-site produced OH• radicals. PFOA decayed stepwise into small‒chain perfluoro carboxylic acids (PFCAs) and fluoride ions during modified PC oxidation.

In the present study, reduced graphene oxide-supported zinc oxide nanocatalysts (rGO/ZnO) with varying graphene contents (1, 2, 5, and 10%) were synthesized and employed for the production of dimet...

This paper deals with the hazards associated with a liquefied petroleum gas (LPG) bottling plant. Due to the release of LPG, different possible hazards, such as fireball, jet fire and vapour cloud explosion (VCE), may take place in the bottling plant. Each critical stages of bottling plants are briefly discussed and modelled in ALOHA and PHAST, and their simulated consequences of results are compared. In this article, the complete bottling plant has been divided into various risk zones which are expected accidental areas (like tank storage area, small domestic cylinder storage area, and LPG pump and compressor area). The risks during handling and the use of LPG have been analysed and modelled and their results are compared. Among all the accident scenarios, fireball was found to be the most dangerous condition in the bullet and small cylinder storage units. Overall, bullet storage unit was found to be the most hazardous section having the most destructive damage (with an overpressure of 0.41 bar), which causes complete destruction, large number of injuries and fatalities (within a distance of 215 m) in case of VCE and having a thermal intensity of 37.5 kW/m2 which causes deaths due to burn up to the largest distance (324 m) in the case of fireball.

Present paper evaluates the catalytic activity of Ce/Al2O3 (CeAl) catalyst for the oxidative removal of sulfur from model oil (dibenzothiophene, DBT, dissolved in iso-octane). CeAl catalyst synthes...

Transesterification of propylene carbonate (PC) and ethanol is a potent non-phosgene route for the synthesis of diethyl carbonate (DEC). In the present study, hydroxyapatite was synthesized and modified using Zn and Mg (Zn/HAP and Mg/HAP). Modified hydroxyapatite was used as catalyst for the synthesis of DEC. The thermal analysis of the catalytic precursor was studied using thermogravimetric-differential thermal analysis. The structural analysis, surface morphology, and nature of active sites over the catalyst surface were studied using techniques such as Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, and CO2 temperature-programmed desorption. Effects of reaction conditions like reaction temperature, reaction time and ethanol/PC molar ratio on DEC yield were also studied. The effects of Mg and Zn on HAP were found to be promotional for the synthesis of DEC using PC and ethanol. Mg/HAP was found to be the best among the three catalysts studied owing to its high basicity. Maximum DEC yield of 52.1 % was obtained in 5 h at 433 K using Mg/HAP catalyst.

Two kinetic models, i.e., schemes, surface adsorbed nitrogen as divergent (SND) and surface adsorbed NO as divergent (SNOD) towards NH4+ and N2 production, were developed to model simultaneous electrochemical reduction of the nitrate ion (NO3−) and oxidation of by-products. Experimental data for electrochemical reduction was collected in synthetic nitrate solution and actual wastewater using Al and Ti/RuO2 as cathode and anode, respectively. Sum of square errors (SSE) and Akaike's information criterion (AIC) analysis showed that the SND model well-represented all the concentration profiles of nitrogen species with the variation in all the operating parameters. Desorption of nitrite ion from the cathode surface was the rate-determining step for the SND kinetic model. Mechanistic and kinetic analysis suggested that N2 gas was the main product. However, NO2− gets formed as the by-product in the alkaline environment, whereas, NO2− and NH4+ were the by-products in the acidic environment.

In this paper, we report a simple two-step approach for the synthesis of large graphene oxide (GO) sheets with lateral dimensions of ≈10 μm or greater. The first step is a pretreatment step involving electrochemical exfoliation of graphite electrode to produce graphene in a mixture of H2SO4 and H3PO4. The second step is the oxidation step, where oxidation of exfoliated graphene sheets was performed using KMnO4 as the oxidizing agent. The oxidation was carried out for different times ranging from 1 to 12 h at ∼60 °C. Prepared GO batches were characterized using a number of spectroscopy and microscopy techniques such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and UV–visible spectroscopy. Raman and thermogravimetric analysis techniques were used to study the degree of oxidation in the as-synthesized GO batches. The UV–visible absorption spectrum showed an intense peak at 230 nm and an adjacent band at 300 nm corresponding to π–π* and n−π* transitions in all samples. Normalized FTIR plots were used to calculate the relative percentages of oxygen-containing functional groups, which were found to be maximum in GO (6 h). Boehm titration was used to quantify the functional groups present on the GO surface. Overall GO sheets obtained after 6 h of oxidation, GO (6 h), were found to be the best. XRD pattern of GO (6 h) revealed a characteristic peak at 2θ = 8.88°, with the corresponding interplanar spacing between the layers being 0.995 nm, which is among the best with respect to the previous methods reported in the literature. Raman spectroscopy showed that the degree of defect (ID/IG) area ratio for GO (6 h) was 1.24, which is higher than that obtained for GO (1.18) prepared by widely used Marcano’s approach.

The need for eco-friendly fuels has given a fillip to search for new molecules and their cost-effective synthesis. A series of ceria-strontium (CexSr1−xO2; x = 0 to 1) catalysts were prepared by a citric acid assisted sol–gel method. These catalysts were characterized by BET, XRD, SEM-EDAX, ICP-MS, FTIR, NH3-TPD and CO2-TPD techniques and tested for the synthesis of dimethyl carbonate (DMC) in a batch reactor for the transesterification of ethylene carbonate (EC). The activity of the synthesized catalysts was found to be closely related to basic and acidic sites, and the surface area of the catalysts. The catalyst, Ce0.6Sr0.4, showed highest basicity and acidity, and was found to be most effective in the formation of DMC from transesterification of EC. Reactions were carried out by varying the particle size (50–800 μm) and agitation speed (200–600 rpm) for minimizing the internal mass transfer resistance and the external mass transfer resistance, respectively. Further, Ce0.6Sr0.4 catalyst was used to optimize the reaction conditions such as methanol/EC molar ratio (in the range of 4–12), catalyst dose (in the range of 2–5 wt% of EC), reaction time (in the range of 2–6 h) and temperature (in the range of 100–180 °C) for DMC yield and EC conversion. At the optimum conditions of methanol/EC molar ratio of 8, 3 wt% of catalyst, 5 h reaction time and 150 °C temperature, the DMC selectivity was 87% and EC conversion of 82%, with a reaction rate of ∼0.547 mol/L.h (with respect to EC). The reusability of the Ce0.6Sr0.4 catalyst for EC conversion with turn-over frequency and DMC selectivity were also studied.

Reutilizing the shavings of willow wood (Salix alba), a waste biomass from cricket bat manufacturing units of Kashmir (India) through pyrolysis, would prove to be a promising way for bioenergy production. The thermal degradation of this waste biomass was carried out under inert atmosphere using thermogravimetric analysis (TGA), at three different heating rates of 10, 25, and 50 K min−1. The kinetic and thermodynamic analyses were performed using isoconversional models of Kissenger-Akahira-Sunrose (KAS) and Ozawa-Flynn-Wall (OFW). The heating value of the willow wood shavings was found to be 18.03 MJ kg−1. The values of activation energy were found to be in the range of around 41.5 to 167.8 kJ mol−1 through conversion points of 0.2 to 0.8. The average value of change in Gibbs free energy were calculated to be of the order of 183.2 and 182 kJ mol−1 using KAS and OFW models, respectively. The thermal degradation reaction mechanism was predicted using Coats-Redfern method which showed that the one-dimensional diffusion model and first-order kinetic reaction model were best suited to represent the degradation process involving both exothermic and endothermic reactions. The thermodynamic parameters including pre-exponential factor, changes in enthalpy, and entropy reflect an enormous potential of the Salix alba shavings as low-cost waste biomass for bioenergy production.

The prediction of adsorption equilibria in multicomponent systems is of prime importance. Therefore, the equilibrium adsorption data for the following multicomponent systems have been studied. The present paper deals with the simultaneous removal phenol (P), 4-chlorophenol (CP), 4-nitrophenol (NP) and catechol (C), resorcinol (R), hydroquinone (HQ) onto modified activated carbon (MAC) from ternary mixtures. The BET surface area of SC was found to be 934 m2/g, whereas BJH adsorption/desorption surface area of pores is 53.03/58.15 m2/g. The equilibrium adsorption data were obtained at different initial concentrations (C0 = 50–1000 mg/L), 12 h contact time, 30°C temperature, MAC dosage of 10 mg/L at solution pH. Equilibrium isotherms for the ternary adsorption of P–CP–NP and C–R–HQ onto MAC have been analyzed by using non-modified Langmuir, modified Langmuir, extended Langmuir, extended Freundlich and Sheindorf–Rebuhn–Sheintuch (SRS) models. The competitive Sheindorf–Rebuhn–Sheintuch (SRS) model fits for both ternary adsorption equilibrium data satisfactorily and adequately.

In the present study, simultaneous adsorption of quinoline and pyridine onto adsorbents such as granular activated carbon (GAC) and bagasse fly ash (BFA) from pyridine–quinoline binary aqueous solution was studied at various temperatures (288–318 K). Gathered equilibrium adsorption data were further analysed using various multicomponent competitive isotherm models such as non-modified and modified competitive Langmuir isotherms, extended-Langmuir isotherm, extended-Freundlich model, Sheindorf–Rebuhn–Sheintuch (SRS) model, and non-modified and modified competitive Redlich–Peterson isotherm model. It was observed that increase in pyridine concentration decreased the total adsorption yield and the individual adsorption yield for both the quinoline and pyridine for both the adsorbents GAC and BFA at all the temperatures studied. Identical trend was observed during the equilibrium uptake of pyridine on to GAC and BFA with an increase in quinoline concentration. The extended-Freundlich model satisfactorily represented the binary adsorption equilibrium data of quinoline and pyridine onto GAC and BFA.

Highly acidic (pH

Propylene carbonate is an important organic carbonate having wide applications. In the present work, thermodynamic analysis of propylene carbonate synthesis routes was performed. Benson group contribution method and Rozicka–Domalski model were used to estimate the heat of formation and the heat capacities of some of the components, respectively. Urea alcoholysis was found to be a favorable method for producing propylene carbonate under mild conditions. This route was further studied experimentally using various MgAl and ZnAl hydrotalcite derived catalysts. The catalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption–desorption, and Fourier transform infrared spectroscopy (FTIR) techniques. Yield of PC was found to be strongly correlated to the basicity of catalysts. Addition of a third element, Ca or La, was found to reduce the surface area of the catalysts. Fluorinated MgAlO (MgAlO-F) was found to possess greater basicity than MgAlO and greater catalyt...

In this study, thermodynamic analysis of various possible synthesis routes of diethyl carbonates (DEC), a benign organic carbonate, was carried out and a comparative analysis was performed. Chemical equilibrium constants at standard conditions were calculated using Gibbs free energy of the system. The Benson group contribution method was used to estimate standard heat of formation and standard entropy change of some raw materials/components like dimethyl carbonate. Variation of heat capacity (Cp) with temperature was estimated for different components from the Rozicka-Domalski model. Variation of chemical equilibrium constants with temperature and pressure was studied for various routes. Synthesis of DEC from ethylene carbonate (EC) was also found to be better considering equilibrium constants at room temperature. The CO2 route was found to be the most unfavourable route for DEC synthesis due to stability of CO2 molecules. Moreover, DEC synthesis through the urea route was found to be best at high temperatures since the equilibrium constants were found to increase exponentially. Experiments were conducted for DEC synthesis using the EC route at two temperatures. Activity coefficients were calculated using the UNIFAC model. Experimentally and theoretically determined chemical equilibrium constant values were found to be similar. PRO/II was also used to minimize Gibbs free energy of the system and estimate the equilibrium constants and the results were comparable with those obtained by the equilibrium constant method and the trend was found to be the same for both the methods.

Diethyl carbonate (DEC) is a linear organic carbonate which has applications as a fuel additive, in production of polycarbonates, and as a solvent in lithium ion batteries. Ethanolysis of urea, as compared to other methods of DEC synthesis, has an edge having requirements of cheap and abundant raw materials. However, only few studies have been reported due to low acidity of ethanol. In the present study, cerium-zinc based oxides in various molar ratios were used for DEC synthesis from ethanol and urea. These catalysts were prepared by auto combustion technique and characterized by thermogravimetric analysis (TGA), Raman spectroscopy, X-ray diffraction (XRD), N 2 adsorption-desorption, field emission scanning electron microscope (FE-SEM), energy dispersive X-ray (EDX), Fourier transform infra-red (FTIR), and NH 3 - and CO 2 -temperature programmed desorption (TPD) methods. No additional phases except pure Ce and Zn oxide were observed in the catalyst from XRD analysis. Effects of pore surface area and surface acidity/basicity were found to be profound in the synthesis of DEC. DEC yield of 28.8% was obtained at 190 °C and 5 h using Ce 0.1 -Zn 0.9 mixed oxide. Effect of operating parameters such as ethanol/urea molar ratio, temperature, time and catalyst concentration were also studied.

Carbon dioxide has generated great interest in recent years because of its potential usage as an alternative to traditional sources of carbon such as natural gas, petroleum and coal. In this paper, CO2 in combination with methanol was used for dimethyl carbonate (DMC) synthesis in presence of cerium-calcium mixed oxide catalysts. Catalysts with different Ce/Ca molar ratios were synthesized using surfactant templating method and characterized by powder X-ray diffraction (XRD), Raman spectroscopy, N2–sorption, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and temperature-programmed desorption (TPD) of CO2 and NH3. The direct conversion of CO2 was found to be highly dependent upon the acidity and basicity of catalysts. Brunauer-Emmett-Teller (BET) surface area of Ce3 Ca1, Ce1 Ca1 and Ce1 Ca3 was found to be 102, 82, 109 m2/g, respectively, and the average pore diameter was 9, 12 and 5 nm, respectively. The Ce1 Ca1 catalyst performed the best due to its combined acidic-basic properties. In addition, the catalyst was reused up to five cycles without significant loss of performance.

The present paper assesses the adsorption capability of rice husk ash (RHA) to adsorb catechol (C) along with phenol (P) and resorcinol (R) individually and simultaneously from aqueous solution in both single and binary solutions using batch experiments. Equilibrium isotherm data were collected at 30°C by carrying out experimental runs for 24 h contact time with pre-optimized RHA dosage of 20 mg/L and initial concentration variation of individual components in the range of 50–500 mg/L. The equilibrium adsorption data for single component were fitted in three adsorption isotherm models, namely the Langmuir, the Freundlich and the Redlich–Peterson. Equilibrium adsorption data of binary aqueous solution of catechol–phenol, catechol–resorcinol and the parameter evaluated from single adsorption isotherm were fitted in various multi-component adsorption isotherm models. Extended Langmuir model which assumes overlapping of sites for different adsorbates better represented the binary isotherm data for bot...

Electrochemical oxidation of 4-chlorophenol (CP) was investigated (in terms of chemical oxygen demand (COD) and CP removal efficiencies) by using a dimensionally stable anode (DSA) namely ruthenium oxide coated titanium (Ti/RuO 2 ) electrode. Effect of process conditions such as current density ( j ), electrolyte concentration ( m ), initial pH (pH o ), time ( t ) and initial CP concentration ( C o ) has been studied. Current efficiency (CE) and specific energy consumption (SEC) were also measured. Gas chromatograph-mass spectrometry (GC/MS) analysis was used to understand the CP mineralization mechanism which has been established on the basis of intermediates identified such as benzoquinone, hydroquinone and organic acids. Reaction kinetics was expressed by pseudo-first order kinetic model. Maximum COD removal efficiency of 96.7% and CP removal efficiency of 97.2%, respectively, was observed at j = 222.22 A/m 2 , t = 180 min, pH o = 5.2 and m = 400 mg/l with SEC = 655 kWh/kg COD. Operating cost based on the studies performed on laboratory scale EC reactor has been calculated and compared with those reported for other pollutants degradation.

The present study reports an ultrasound-photocatalysis based hybrid method for effective degradation/mineralization of a bio-recalcitrant pharmaceutical pollutant, namely ofloxacin (OFLX). To understand the role of different techniques, individual and various combined ultrasound and ultraviolet along with H2O2, TiO2, and ZnO photo-catalyst were investigated in different protocols to understand synergistic effects and mechanistic insight of the mineralization process. Photocatalysts were characterized by FTIR, FE-SEM, TEM, EDX, BET, and EIS analysis. A significant synergistic index of 3.1 for mineralization of OFLX was obtained during the combined US/UV/H2O2/ZnO method due to higher oxidizing ( OH) radical formation as compared to other binary and ternary hybrid methods. OFLX degradation and total organic carbon removal were 94.2% and 45.1%, respectively, using US/UV/H2O2/ZnO method at operating condition of H2O2/OFLX stoichiometric molar ratio = 5, ZnO dosage = 0.40 g L−1, 40 kHz ultrasonic frequency, 125 W UV power, reaction time of 120 min and pH 6.3 (natural pH). Kinetics of the degradation was well-represented by the power-law kinetic model with an order of reaction being 2.2 and 1.9 for US + UV + H2O2 + TiO2 and US + UV + H2O2 + ZnO, respectively. Besides, specific energy consumption (SEC), electrical energy per order (EEO), and the operating cost (OC) of each method employed was determined. A detailed OFLX degradation pathway has been suggested, and possible reasons for synergy are identified and discussed.

A full factorial central composite design (CCD) method has been used to design the experiments for extractive desulphurization of straight run gas oil (SRGO) containing 0.013 g/g (1.3 wt%) sulphur in packed bed extractor using N-N-dimethyl formamide (DMF) as solvent. The operational parameters namely water concentration (WC) in main solvent, solvent to feed ratio (S/F), and extraction temperature (TE) which affect the sulphur removal and yield were used as input variables in design of experiments. Considering the trade-off between sulphur removal and yield, multi-response optimization with desirability function approach has been used to estimate the optimized value of these operating parameters so as to maximize sulphur removal and yield of extracted straight run gas oil (ESRGO). Optimum values of selected variables were: water content in solvent = 2.91, solvent to feed ratio = 1.70 and extraction temperature = 46.4 °C. At the maximum desirability value, ESRGO yield and percent sulphur removal were 81.67 and 60.53%, respectively. Since, importance of sulphur removal and yield would depend on the secondary process to be selected for reducing the sulphur to 50–10 ppm, an analysis of goal importance effect on optimized value of operational parameters for maximum desirability has also been presented and discussed. This article is protected by copyright. All rights reserved

The simultaneous adsorption of a sulfur compound [dibenzothiophene (DBT)] and a nitrogenous compound [quinoline (QN)] was studied on nickel-loaded granular activated carbon (Ni–GAC). Taguchi’s L27 methodology was used to investigate the effect of various operating parameters and optimize them. Parameters studied during simultaneous adsorption included the initial DBT/QN concentration (Co,i), Ni–GAC dose, temperature, and contact time. The Ni–GAC dose was found to be the most significant factor, while the interaction between Co,i values was also significant. Optimized parameters of Taguchi experiment were further used for determining binary isotherm behavior. The adsorption capacity of Ni–GAC for QN adsorption was found to be greater than that for DBT. Among various multi-component empirical models, the extended Freundlich model best followed the binary isotherm experimental data at 303 K. DBT and QN adsorption data were also analyzed and represented by models based on ideal and real adsorbed solution theo...

Cylindrical rod-shaped copper succinate nanoparticles were prepared using the electrochemical method. Taguchi robust design was applied to optimize experimental parameters such as succinic ion concentration (Co), current applied (Iap), and pH (pH). The obtained copper succinate nano-rods were further thermally treated at different temperatures to produce copper oxide (CuO) nano-disks. At optimum conditions of Iap = 0.5 A, pH = 7, and Co = 0.25, the maximum productivity of copper nanoparticles before and after calcination at 500 °C was 1.53 g and 1.06 g, respectively. Products were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-visible spectrophotometry to determine their various physicochemical characteristics.

This paper deals with the analysis of hazards associated with accidental release of high pressure from gas-pipeline transportation system. Simplified equations which are related to the fluid properties, operating pressure, the diameter of pipeline, hole or rupture diameter and the length of the pipeline have been used for the hazard analysis due to pipeline failure. The kind of release (i.e. leak) through a hole or the complete rupture was found not to affect the effective release rate because of an increase in the operating pressure. Among various gases, the release rate of butane with lower value of specific heat ratio (γ) is found to be always higher than that of propane and methane which have higher value of γ. Decay coefficient, defined as the ratio of release rate at any instant and to the initial maximum release rate, decreases with an increase in the leak (or hole) size. The accident affected distance increases with an increase in the hole size. During the leakage of natural gas and petroleum gas pipeline, affected distance of hazard is slightly higher for fire as compared to other events. The simplified models can be used with confidence to estimate the hazard distance or hazard area. The procedure developed will be helpful for safety management or emergency response planning for the pipeline transportation of the natural gas and petroleum gas.

This paper presents an analysis and simulation of an accident involving a liquefied petroleum gas (LPG) truck tanker in Kannur, Kerala, India. During the accident, a truck tanker hit a divider and overturned. A crack in the bottom pipe caused leakage of LPG for about 20 min forming a large vapor cloud, which got ignited, creating a fireball and a boiling liquid expanding vapor explosion (BLEVE) situation in the LPG tank with subsequent fire and explosion. Many fatalities and injuries were reported along with burning of trees, houses, shops, vehicles, etc. In the present study, ALOHA (Area Locations of Hazardous Atmospheres) and PHAST (Process Hazard Analysis Software Tool) software have been used to model and simulate the accident scenario. Modeling and simulation results of the fireball, jet flame radiation and explosion overpressure agree well with the actual loss reported from the site. The effects of the fireball scenario were more significant in comparison to that of the jet fire scenario.

Extractive desulfurization of synthetic and actual gas oil with various solvents was carried out to understand the fruitfulness of studies on solvent screening using synthetic carrier phases. Solvent extraction of various model sulfur compounds from two synthetic carrier phases of different composition was carried out using N,N-dimethylformamide (DMF) solvent to illustrate the effect of the sulfur compound molecular structure on its extractability and interaction with the carrier phase composition. Removal of sulfur compounds from the synthetic carrier phase followed the order: BT ≈ DBT > 4-methyl-DBT > 3-methyl BT ≈ 4,6-dimethyl-DBT > 2-N-octylthiophene ≫ 1-dodecanethiol. Thereafter, extraction of actual straight run gas oil (SRGO), cracked gas oil (CGO), and their mixtures was studied using DMF to understand the effect of their composition on extraction performance. Performance parameters such as yield of raffinate, degree of sulfur removal, distribution coefficient, and performance factor were found to be quite different for different gas oil streams. Thereafter, models were developed for correlating performance of extraction in terms of degree of sulfur removal (Dsr), yield (Y) of extracted gas oil with composition of gas oil and operating conditions. A performance factor (Pf,α) (defined as the summation of Dsr and Y with the weight factor (α) to Dsr) model was used to estimate the optimum operating conditions to maximize the extraction performance. Results indicate that the value of the weight factor (α) affects operating conditions, Dsr and Y, significantly and should be chosen with utmost care in light of downstream process capabilities and overall process economics.

Diethyl carbonate (DEC) is a well-known linear organic carbonate that has wide applications. Besides its use as a fuel additive, DEC is an excellent electrolyte for lithium ion batteries and is used for the production of polycarbonates, which are globally used engineering plastics. The synthesis of DEC from CO2 helps in CO2 mitigation. It was earlier synthesized by phosgenation of ethanol, which is a toxic and dangerous process. Certain non-phosgene routes have been developed in recent years, which include oxidative carbonylation of ethanol, trans-esterification of carbonate, alcoholysis of urea, ethanolysis of CO2 and the ethyl nitrite route for DEC synthesis. This review underlines various non-phosgene methods for the synthesis of DEC by critically evaluating the catalysts used, operating conditions and mechanism of synthesis. The performances of various catalysts have been compared graphically along with the identification of problems and potential solutions. Certain engineering aspects, including kinetics and thermodynamics of the various routes, have also been highlighted. The shortcomings and research gaps have been explicitly mentioned and discussed along with required future developments and research work for DEC synthesis.

In this paper, a series of CexZr1−xO2 solid solution spheres were synthesized by exo- and endo-templating methods and tested for dimethyl carbonate (DMC) synthesis using direct conversion of CO2. The synthesized catalysts were characterized by X-ray diffraction (XRD), N2-physisorption, scanning electron microscopy (SEM), and CO2/NH3-temperature-programmed desorption (TPD). Formation of CexZr1−xO2 solid solutions with tetragonal and cubic crystal structures depending on cerium/zirconium compositions was confirmed by XRD analysis. The specific surface area of the mixed oxide decreased and the average pore diameter increased with an increase in the ceria content, with the exception of the mixed oxides with x = 0.4–0.5 i.e. Ce0.4Zr0.6O2 and Ce0.5Zr0.5O2. The basic and acidic site density of the synthesized catalysts was in the order: ZrO2 < CeO2 < Ce0.5Zr0.5O2, and the basic and acidic site density per unit area followed the same order. The best Ce0.5Zr0.5O2 catalyst was further used for the optimization of reaction conditions such as reaction time, reaction temperature, catalyst dose and reusability for DMC synthesis. Furthermore, study of chemical equilibrium modeling was done using the Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid reaction condition so as to calculate change of Gibbs free energy (ΔG°) and heat of reaction (ΔH°).

The present research deals with the treatment of agri-based pulp and paper mill wastewater by continuous electrocoagulation (CEC) process using iron (Fe) as an electrode material. Effects of flow rates (dm3 h−1): 0.5–4.0 and residence time (τ): 0.5–4.0 h were investigated on degradation of chemical oxygen demand (COD), color, total solid (TS), turbidity, specific energy consumption (SEC), instantaneous current efficiency (ICE) and electrochemical degradation index (EDI). At flow rates of 1.0 and 0.5 dm3 h−1, COD removal efficiency of 78.20 and 82.15%; and color removal efficiency of 79 and 90%, respectively, was achieved. TS concentration of wastewater slurry was also reduced by 65% after 3 h residence time with flow rate of 1 dm3 h−1. The specific energy consumption (kW h per kgCODremoved) was decreased from 16.3 to 14.3 with decrease in τ from 4 to 1 h. At a supply charge concentration of 0.62 A h dm−3, the current efficiency (CE) values were 310% and 274% after τ = 2 and 1 h, respectively. Dissolution and consumption of electrodes were also studied with a change in flow rates. Sludge obtained after the CEC process was analyzed for settling and filterability characteristics, morphology and elemental analysis, point of zero charge, physicochemical and elemental characterization, and TS concentration. The operating cost of the process was also calculated based on the electrical energy and electrode consumption and was found to be 61.0 Indian Rupees (0.9 USD) for the treatment of 1 m3 of wastewater.

The surge in biodiesel production in recent years has resulted in enhanced research interest in the conversion of glycerol to other valuable chemicals such as glycerol carbonate (GLC). In the present study, the catalytic transesterification of glycerol with dimethyl carbonate (DMC) for the production of GLC was studied with calcium–lanthanum mixed-oxide catalysts at different Ca/La molar ratios. These catalysts were synthesized using an exo- and endotemplating method. The physicochemical characteristics of the catalysts were determined using powder X-ray diffraction (XRD), N2 sorption, scanning electron microscopy (SEM), and temperature-programmed desorption (TPD) of CO2 and NH3. The transesterification of glycerol was found to be highly dependent on the basicity of the catalysts. The catalyst with a Ca/La molar ratio of 3 (3CaLa) showed the highest glycerol conversion and GLC yield. Optimization of the reaction parameters and reusability of the catalyst were studied with the 3CaLa catalyst in terms of gl...

In this study, reduced graphene oxide supported mesoporous zinc oxide (rGO@ZnO) was synthesized and applied for the photocatalytic mineralization of ofloxacin, an antibiotic, in the aqueous solution. In-situ rGO@ZnO nano-photocatalysts with different rGO content (0.2%, 0.5%, 1% and 2%) were synthesized using a reflux column method. The nano-photocatalyst was characterized by its structural (crystallinity), morphological, as well as optical properties with the help of powdered X-ray diffraction (P-XRD), field emission-scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectroscopy, Brauner Emmet Teller (BET), thermo-gravimetric/differential thermal analysis (TGA/DTA) and UV–vis diffuse reflectance spectroscopy (DRS). The influences of pH (5–9) and catalyst dose (400–1400 mg/dm3) with irradiation time were studied. At optimum conditions (0.5% rGO@ZnO dose of 1200 mg/dm3 for ofloxacin, pH = 7, and time = 300 min), ultimate degradation efficiency was found to be ≈99%, under UV light irradiation. The degradation kinetics fitted well with the first-order kinetic model. The photocatalytic mechanism of the enhanced photo-degradation in the presence of rGO was studied by comparing band structure with the potentials of the main reactive species ( O2− and OH), which result in the mineralization of ofloxacin. The intermediates and pathways during the mineralization were determined using liquid chromatography, which is coupled with mass spectrometry (LC–MS) analysis and a possible pathway was also proposed on the basis of identified intermediates.

A comparative study on thermal analysis of two waste biomass materials of Kashmir namely deodar (Cedrus deodara) saw dust (DSD) and rice husk (RH), was carried out at different heating rates of 10, 25, 50 and 100 °C min−1 in air and nitrogen atmospheres. The onset, peak and burnout temperatures and rates of decomposition of components were determined and compared to understand the combustion and pyrolysis kinetics of selected biomass materials using iso-conversional Kissinger-Akahira-Sunose (KAS) and Ozawa-Flynn-Wall (OFW) models. The kinetic parameters calculated were in turn used to calculate the changes in thermodynamic parameters, the enthalpy (ΔH), the Gibbs free energy (ΔG) and the entropy (ΔS). The physicochemical characterisation was carried out by elemental analyser and FTIR spectroscopy. The average activation energy values for RH were found to be 107.6 and 101.2 kJ mol−1 in air atmosphere and 85.5 and 92.1 kJ mol−1 in nitrogen atmosphere based on KAS and OFW models, respectively. The activation energy for DSD on the other hand was found to be 89.9 and 95.3 kJ mol−1 in air, 179.2 and 180.6 kJ mol−1 under nitrogen atmosphere based on KAS and OFW models, respectively. The heating values of the two biomasses (~ 10 to16 MJ kg−1) and Gibbs free energy values (between 165 to 176 kJ mol−1) indicate that the selected biomass can not only prove to be potential feedstock for pyrolysis but also can become a useful source of energy and chemicals.

Efficient removal of uranium from both aqueous and simulated seawater conditions using a nitrogen enriched nanoporous polytriazine (NENP-1), is reported. A maximum adsorption capacity of 489 mg g−1 with 97.8% adsorption efficiency was estimated at 25 °C and pH of 7, when 10 mg of NENP-1 was introduced to 10 mL of 500 mg L−1 aqueous uranium solution. Both linear and non-linear regression analyses have been performed. The adsorption follows a pseudo second order kinetics and fitted well with the Langmuir adsorption isotherm model. The negative values of ΔS (−52.08 J mol−1 K−1), ΔH (−24.37 kJ mol−1) and ΔG indicate that the uranium adsorption is a spontaneous exothermic process with a reduced entropy. Retention of 93% activity even after five consecutive cycles, achieving (0.012 mg L−1) the permissible limits of the WHO (0.015 mg L−1) and USEPA (0.03 mg L−1) and adsorption of uranium (50 mg g−1) from simulated seawater have made this a potential adsorbent for industrial applications.

The authors focus on simultaneous removal of the dibenzothiophene and quinoline by using the zinc impregnated granular activated carbon (Zn-GAC). Parameters such as adsorbent dose, initial adsorbent concentration, temperature, and contact time were optimized for the simultaneous adsorption onto Zn-GAC using the Taguchi's experimental design methodology. Adsorption of quinoline was found to be more as compared to dibenzothiophene. Overall adsorptive behavior of dibenzothiophene and quinoline was antagonistic in nature. Analysis of variance was used to maximize simultaneous desulfurization and denitrogenation, which has been validated by performing confirmation experiments.

Present study reports parametric and kinetic study for catalytic per oxidation (CPO) of pyrrole by Cu/SBA-15 catalyst using H2O2 as an oxidant. Brunauer-Emmett-Teller surface area, Fourier transform infra-red spectroscopy and thermo gravimetric-differential thermal analyses were used for the characterization of catalyst. Effects of various operating variables such as initial concentration of pyrrole (Co): 48.3–386.8 mg/L, catalytic dose (Cw): 0.5–2 g/L, stoichiometric ratio of hydrogen peroxide/pyrrole: 1–4, and reaction temperature (T): 50–60°C were studied. More than 85% pyrrole mineralization was observed at the optimum conditions of Cw = 1.5 g/L, stoichiometric ratio of hydrogen peroxide/pyrrole = 3, T = 55°C at pH = 6.1. A two-step pseudo-first-order kinetic model well-described the pyrrole mineralization by the CPO process.

Ceria and zinc oxide catalyst were impregnated onto various oxide supports, namely Al2O3, TiO2 and SiO2, individually by deposition-coprecipitation method. The synthesized catalysts (CZA, CZS and CZT having supports Al2O3, TiO2 and SiO2, respectively) were characterized by X-ray diffraction (XRD), NH3- and CO2-temperature programmed desorption (TPD) and N2 adsorption. These catalysts were used for synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate in a batch reactor. CZS was found to have larger average grain size as compared to CZA and CZT. Composite oxides (catalysts) were found to contain individual phases of ZnO, CeO2 and some spinel forms of Zn, Ce along with their supports. CZS having highest basicity and surface area showed better catalytic activity as compared to CZA and CZT. Effect of reaction temperature and methanol/PC molar ratio on DMC yield was studied and a reaction mechanism has been discussed. Maximum DMC yield of 77% was observed with CZS catalyst at 170 °C with methanol/PC molar ratio of 10.

In the present study, removal of sulfur and aromatic compounds from straight-run gas oil (SRGO), light cycle oil (LCO), coker gas oil (CGO), and their mixture, termed as mixed gas oil (MGO), was studied using N-methyl-2-pyrrolidone (NMP) solvent in a single-stage batch extractor and continuous countercurrent packed-bed extraction column. The effect of the extraction temperature (TE), solvent/feed ratio (S/F), and antisolvent concentration (Wc) on the degree of sulfur removal (Dsr), yield of extracted gas oil (Y%), and performance factor (Pf,α), which combines both Dsr and yield, was studied in a single-stage batch extractor. After optimization of the operating conditions for SRGO, LCO, and CGO in a single-stage batch extractor, studies on MGO were carried out in both a single-stage batch extractor and continuous countercurrent packed bed at estimated optimized values of TE, S/F, and Wc. Issues related to the loss of valuable hydrocarbons with extract and value addition to extract hydrocarbon have been add...

In this study, oxidative-extractive desulfurization (OEDS) of liquid fuel has been studied using an ionic liquid prepared by coordination of dimethyl sulfoxide (DMSO) with ZnCl2. Synthetic model liquid fuel was prepared by dissolving dibenzothiophene (DBT) in iso-octane. In addition, actual diesel was also tested for total sulfur removal. Oxidation in the OEDS process was achieved by adding hydrogen peroxide and acetic acid to the mixture. Different parameters such as oil to ionic liquid ratio, oxidant to sulfur ratio and temperature were optimized. Kinetic study was performed at different temperatures so as to calculate the reaction rate constants. Optimized conditions were also tested for their applicability on actual diesel. At the optimized conditions (oxidant to sulfur ratio = 6, oil to ionic liquid ratio = 3 and temperature = 30°C), 78% sulfur removal was observed from model oil (initial sulfur concentration = 1,000 mg/L) and 65% sulfur removal was observed for actual diesel oil (initial sulfur concentration = 140 mg/L).

A new strategy for screening of solvents for sulfur, nitrogen, and aromatic compounds removal from gas oil is presented. This ranking is based on comparative assessment of solvents’ capacity, selectivity, performance, and newly defined industrial usability indices. Twenty eight solvents comprising of six most widely used industrially proven conventional solvents and 22 imidazolium-based ionic liquids solvents were selected to illustrate the strategy. The solvents were ranked for removal of sulfur compounds namely benzothiophene, dibenzothiophene and their alkylated derivatives, and nitrogenous compounds namely quinoline, indole and carbazole from gas oil. Performance index (PI) which combines the effect of both capacity and selectivity seems to be better index than individual capacity and selectivity indices to rank the solvents. Industrial usability index (SIUI) of solvents which includes PI and process complexity factor for solvent recovery section seems more practical and realistic criteria for solvent assessment. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2257–2267, 2015

In the present study, Cu-Zn-Al (CZA) hydrotalcite catalysts prepared by the coprecipitation method and calcined at 300, 500 and 800 °C (named as CZA300, CZA500 and CZA800) were used for the synthesis of dimethyl carbonate (DMC) from methanol and propylene carbonate (PC) in a batch reactor. The physicochemical characteristics of the catalysts were analyzed by various methods such as X-ray diffraction (XRD), liquid nitrogen adsorption–desorption textural analysis, energy dispersive atomic spectra (EDAX), scanning electron microscope (SEM), Fourier transformation infrared (FTIR), and NH3- and CO2-temperature-programmed desorption (TPD). The average pore diameter of CZA300, CZA500, and CZA800 catalysts was found to be 55.6, 52.5, and 49.3 A, respectively. Pore volume distribution analysis revealed that the CZA300 and CZA500 have bimodal pore distribution with pores centered at 36 ± 1 A and 131 ± 2 A. CZA300 catalyst has the highest amount of basic sites in weak and strong regions whereas CZA500 catalyst has t...

Present study investigates mechanism of electrochemical (EC) oxidative degradation of p-nitrophenol (PNP) by ruthenium oxide coated titanium (Ti/RuO2) electrode. First, the process proficiency was determined in terms of chemical oxygen demand (COD), total organic carbon (TOC), current efficiency (CE) and specific energy consumption (SEC) under different experiment conditions of initial pH (pHo), current density (j), electrolyte concentration (m) and initial PNP concentration (Co). Maximum COD and TOC removal efficiencies of 98.9% and 81.9%, respectively, were obtained at j = 168.9 A/m2, pHo = 5.5, Co = 100 mg/L and m = 300 mg/L with SEC of 535.7 kW h/kg COD. PNP degradation mechanism has also been proposed on the basis of identification of intermediates by gas chromatograph coupled with mass spectrometry (GC/MS). Various intermediates such as quinine, benzoquinone, organic acids and small mineralization products were obtained during the EC treatment of PNP. PNP was found to be oxidized by both direct (hydroxyl radical generated via water electrolysis on anode surface) and indirect (via mediators, hypochlorous acid and active chlorine generated during chlorine oxidation in solution) EC oxidation. Kinetics of EC oxidation was represented by pseudo-first order kinetic model.