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Nitrogen-functionalized graphene oxide (GO) nanocatalysts were prepared using ammonia, methylamine, ethylamine, and hydrazine hydrate as a nitrogen source. Nanocatalysts samples were thoroughly characterized using XRD, Raman, FTIR, XPS, FESEM, TEM, and TGA techniques. Quantitative and qualitative analyses of surface acidic and basic sites were done by NH3- and CO2-TPD techniques. Nanocatalysts were further examined for DMC production via transesterification reaction of propylene carbonate (PC) with CH3OH. Quantitative analysis of nitrogen-containing functional groups in the prepared sample with respect to other functional moieties was performed. Among various nanocatalysts, ammonia functionalized GO (AGO) was found to be the best for DMC production. At optimized reaction conditions of temperature (180 °C), time (6 h), and catalyst dose (1 wt% with respect PC), the highest DMC yield of ∼50% was observed. Reusability studies using AGO nanocatalyst were conducted up to four consecutive test cycles to evaluate catalysts' potentiality towards DMC synthesis. Thus, N-functionalized GO is a useful metal-free nanocatalyst that could also be explored for other chemical processes.

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.

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.

Inexpensive and nontoxic metal-free heteroatom (P, N, and O) enriched high surface area nanoporous materials (CHNM and HNM) as efficient heterogeneous catalysts for the conversion of epoxides to cyclic carbonates by utilizing CO2 is reported. The catalysts were made by condensing the heteroatom enriched precursor with melamine and pyrrole to produce HNM and CHNM, respectively. The catalysis was carried out under mild experimental conditions, i.e. 100 °C reaction temperature and 4 bar CO2 pressure under solvent-free conditions. Almost 100% conversion can be realized using HNM as a catalyst and this superior performance was attributed to the presence of larger heteroatoms as compared to CHNM, although the latter has 159% specific surface area and 115% pore volume as compared to the former. The obtained results are discussed in terms of the Lewis acid–Lewis base interaction, textural properties and the frameworks of the catalysts and the reactants.

Co(II) porphyrins have been utilized as efficient and selective catalysts for the extractive oxidative desulfurization reaction on the refractory dibenzothiophene (DBT) in [Formula: see text]-dodecane (model middle distillate fuel oil). The acetonitrile was taken as extracting polar solvent and H2O2 was used as oxidant. The reaction optimization was done with respect to DBT:catalyst molar ratio; DBT:H2O2 molar ratio; extracting solvent: CH3CN/[Formula: see text]-dodecane volume ratio; reaction temperature and time. Under the optimized conditions, a maximum of [Formula: see text]98% DBT removal was achieved by using the meso-tetrakis(4[Formula: see text] methoxyphenyl)porphyrinatocobalt(II) as catalyst under mild conditions at 50[Formula: see text]C.

The main objective of the present work was to understand the interactive behaviour of various operating parameters including concentration of pollutants during binary electrochemical mineralization of the two nitrogenous heterocyclic pollutants in the aqueous solution. Indole and pyrrole were selected as pollutants, whereas Pt/Ti was selected as anode and cathode. The effects of different operating parameters like current density, solution conductivity, initial concentration of the pollutants and time were studied. Taguchi method was used to optimize these operating parameters for obtaining the ultimate rate of degradation for the nitrogenous compounds. There were basically two responses, i.e. chemical oxygen demand (COD) degradation and specific energy consumption. These responses were maximized and minimized, respectively. At the optimum condition, removal efficiencies of pyrrole, indole and COD were found to be 46.1%, 62.4% and 61.4%, respectively. The optimum value of specific energy consumption was found to be 159.5 kWh per kg COD removed. Possible mineralization pathways are also proposed on the basis of the identified intermediates by gas chromatography coupled with mass spectroscopy. The operating cost was also calculated for the binary lab-scale treatment of the indole and pyrrole and compared with reported cost analysis for the electrochemical treatment.

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...

In this study, zinc ferrocyanide nano-composite materials were synthesized and developed by reaction of aqueous K4Fe(CN)6·3H2O and ZnCl2 in the presence of tri-block copolymer and tert-butanol. The synthesized catalysts were characterized by CO2- and NH3-temperature-programmed desorption (TPD), N2-sorption, SEM, TEM, XRD and used for transesterification reactions. The zinc ferrocyanide catalyst showed a sharp cube shaped structure with a high amount of basic sites. The zinc ferrocyanide catalyst showed type IV isotherm with H3 hysteresis loop. BET surface area and pore volume were found to be 125 m2/g and 0.1395 cm3/g, respectively. The transesterification of Jatropha oil using Fe-Zn-1 showed the maximum 94.5% jatropha oil conversion. The prepared catalyst can be easily recovered and successfully reused after five times. The slight loss of activity of Fe-Zn-1 catalyst can be attributed to the deposition of the reaction products on the active sites and the blockage of the pores. Overall, the zinc ferrocyanide catalyst activity was found to be directly dependent upon both the textural and surface basic/acidic properties.

The present review compiles and critically evaluates studies on the synthesis of dimethyl carbonate (DMC) using different techniques and catalysts with reaction conditions, a wide range of applicat...

The disposal and management of sulfur-rich sludges (SRS) are challenging issues for the industries due to their adverse environmental impact. The present study reports the detailed characterizations and assessment of the thermo-kinetics of sludge generated from the sulfuric acid plant. In addition, the sulfur was retrieved with the help of the evaporation–condensation method. In the active devitalization zone (200–400 °C), a substantial mass loss (91 ± 3%) was observed, primarily due to the vaporization of sulfur. The isoconversional model-free methods were used to appraise kinetic parameters for the pyrolytic process. The average activation energy (64.5 kJ mol−1) estimated by the Starink method admired the less energy-intensive process and validated the occurrence of thermochemical reactions at low temperatures. The thermodynamic parameters and frequency factor calculated at 10 °C min−1 were ΔG* = 149.1 kJ mol−1, ΔH* = 59.8 kJ mol−1, ΔS* = −0.157 kJ mol−1K−1, and A = 2.1 × 105 s−1. Criado's Z-master plot revealed the dominance of the diffusion mechanism on the process. The efficient recovery of sulfur (≈96% with purity 99 ± 0.5%) was achieved at 440 °C by evaporation–condensation technique, and the findings closely complemented the kinetic and thermodynamic parameters. This study provides a background for a better understanding SRS and efficient sulfur recovery.

The FeCl2/K2CO3 catalyst system was used successfully for the synthesis of oil soluble N-benzylated cobalt phthalocyaninetetrasulfonamide by the reaction of benzyl alcohol on water-soluble ...

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...

Present study deals with the binary batch adsorption of aniline (AN) and nitrobenzene (NB) onto granular-activated carbon (GAC). For single component, the adsorptive uptake of AN and NB increased a...

In the present work, a detailed thermo-kinetics of hazardous sulfur-rich sludge generated from the corn processing industry was performed for acquiring the optimum parameters for the efficient recovery of sulfur using the evaporation-condensation technique. Sulfur in the sludge was found to be 79 ± 3% (wt%) as estimated by the Bureau of Indian Standards method. A weight loss of 77 ± 3% was found in the active devolatilization zone from ≈ 200–400 °C. The online FTIR confirmed the evolution of mainly sulfur vapors (S8) along with some sulfur dioxide (SO2) and disulfur (S2). The thermogravimetric data (TG) was used to evaluate the kinetic parameters with the help of model-free methods, and Z-master plots determined additional insight into the reaction mechanism. Furthermore, the calculated activation energy (Ea) was used to determine the thermodynamic feasibility. The average Ea values appraised by FM, FWO, sDAEM, and ST models were 55.43, 72.04, 62.33, and 62.67 kJ mol−1, respectively. Overall, 91.2% of sulfur was successfully recovered at 400 °C, having 99 ± 0.5% purity. The approximate cost analysis of the sulfur recovery process was also estimated to check the economic viability. Recovered sulfur could be directly used for industrial and agricultural applications without any further purification.

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.

This study reports the calculation of individual ion's activity coefficient and total minimum Gibbs energy for electrochemical denitrification of nitrate ions in synthetic and actual wastewater. The concentration of nitrate ion continuously decreased during treatment via the electrochemical method. During the treatment, nitrate ions got reduced into nitrite and ammonium ion. The individual ion activity coefficient was examined by applying Pitzer, Lin and Lee modified Debye-Huckel theory which is based on the interaction of ion-ion (long-range, i.e., LR interaction-electrostatic effect) and ion-water (short-range, i.e., SR interaction-solvation effect) in the aqueous solution. The equilibrium composition of these ions was calculated by minimizing the error between total minimum Gibbs energy calculated by using experimental and predicted compositions. The individual ion activity coefficient, which was calculated through this model, was used to measure the total minimum Gibbs energy (Gtotal). Variation of individual ion activity coefficient and Gtotal with initial nitrate ion concentration, applied current density, initial pH, and concentration of NaCl as electrolyte has been studied. It was found that the experimental and calculated composition of nitrate, nitrite, and ammonium ions were in good agreement for electrochemical denitrification of synthetic and actual wastewater.

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.

Inorganic content in wastewater stream consists of potassium, calcium, sodium, magnesium, sulfate, chloride, nitrate, etc. Among these inorganic contaminants, nitrogenous contaminants such as nitrate ( NO 3 − ) along with nitrite ( NO 2 − ) and ammonium ion ( NH 4 + ) have maximum level of concentration. Owing to high release of industrial inorganic nitrogen especially in water bodies, the disproportion of the natural nitrogen cycle happens. Efficient management of nitrogen cycle in water bodies during the 21st century is a grand challenge. The main aim during treatment of inorganic nitrogen present in wastewater is to reduce it into N2 gas as final product. Several advance methods such as electrochemical (EC) treatment, advanced catalysis treatment, and photocatalysis processes have been reported, which degrade the inorganic nitrate present in wastewater. EC treatment process is very much capable of reducing inorganic nitrate into N2 gas without producing secondary pollutants and with no sludge production. Several noble metal- and graphene-based catalysts, electro-catalysts and photocatalysts have been reported, which hybridize the reduction process as well as enhance the removal of nitrate and other inorganic nitrogen pollutants. Nanoscale-coated electrodes such as Ti/TiO2 nanotube array, nano-Ti coated, and zerovalent iron reduce the nitrate into N2. This chapter reports advancement in the reduction process of inorganic nitrate into N2 gas.

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.

This study reports preparation of biosilica from teff straw ash via sol-gel method. Teff straw ash prepared at different ashing temperatures (500, 700, and 900 °C) was treated with 2.5 N NaOH solution prior to acidification in order to extract biosilica in the form of sodium silicate solution (SSS). The effects of ashing temperatures on biosilica yield and physiochemical properties were studied. Physicochemical properties of extracted biosilica were determined by performing XRD, FE-SEM, EDX, and FTIR analysis. The carbon content and other impurities in extracted biosilica decreased with rise in ashing temperature. The biosilica yield increased with ashing temperature in the order 500 °C (49.5%) 99% for biosilica prepared from teff straw ash prepared at 900 °C.

In the present study, biocomposites prepared from agro-based biomass were investigated for pyridine adsorption from water. Biosilica, synthesised from teff straw at ashing temperature of 900 °C, was blended with chitosan and alginate to obtain chitosan–biosilica (ChiBS) and alginate–biosilica (AlgBS). Pyridine removal efficiency was found to be affected by the adsorption parameters namely initial pyridine concentration, contact time, pH, biocomposite dosage and temperature. The optimum conditions were contact time of 240 min and biocomposite dosage of 2 g/L for both the composites, whereas optimum pH for AlgBS and ChiBS was 8.0 and 4.0, respectively. Maximum removal efficiency for initial pyridine concentration of 50 mg/L was 96 and 90%, respectively. Adsorption equilibrium data were analysed with common adsorption isotherms and kinetics equations. Langmuir model well-fitted the equilibrium data and the pseudo-second-order fitted the pyridine adsorption rate data. Furthermore, the calculated thermodynamic parameteric values indicated physical adsorption to be dominant on both ChiBS and AlgBS, and the pyridine adsorption to be endothermic in nature.

In the present work, low-cost and efficient iron oxide nanoparticle incorporated on mesoporous biochar was prepared from effluent treatment plant (ETP) sludge collected from the textile industry. This sludge contains a higher amount of Fe due to the use of ferric chloride as a coagulant in the treatment of wastewater generated during the process. The raw sludge and prepared biochar was extensively examined by various sophisticated techniques like XRF, XRD, BET, TGA, XPS, RAMAN, FTIR, FESEM, TEM, and VSM. TEM and XRD analysis confirms the presence of iron oxide nanoparticles on mesoporous biochar. The prepared biochar was found to possess BET surface area of 91 m2 g−1. Several parameters like pH, dose, initial concentration, temperature and time were optimized for the adsorptive removal of ofloxacin (OFL) from aqueous solution. Biochar (named as BTSFe) achieved ≈96% removal efficiency of OFL with a maximum adsorption capacity (qm) of 19.74 mg g−1 at optimum condition. π-π electron–donor-acceptor and H bonding were the major mechanisms responsible for the OFL adsorption. Kinetic and equilibrium thermodynamic study of showed that the adsorption of OFL was represented by the pseudo-second-order kinetics model, and the process was exothermic and spontaneous. Additionally, Redlich-Peterson and Freundlich isotherms best fitted the experimental data indicating multilayer adsorption phenomenon. Biochar was magnetically separated and thermally regenerated after each cycle for five times with a nominal overall decrease of ≈8% in removal efficiency. Leaching of iron during the adsorption process was also checked and found to be within the permissible limit. This study provides an alternative application of the textile industry sludge as an efficient, low-cost biochar for the removal of emerging pharmaceutical compounds.

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.

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.

A highly efficient G/La heterogeneous catalyst comprising of reduced graphene oxide (rGO) and lanthanum oxide (La2O3) was developed using the in-situ hydrothermal technique. Four different catalyst samples with graphene content of 0.2, 0.5, 1.0, and 2.0 were prepared and tested against dimethyl carbonate synthesis (DMC) synthesis using the transesterification method. Structural analysis by scanning electron microscopy revealed that La2O3 displayed nanorod morphology. DMC synthesis results showed that G/La-3 composite with 1% graphene content outperformed others and showed the highest DMC yield of ~84% at 180 oC. The excellent performance of G/La-3 was attributed to the synergistic effect of 2-D rGO and 1-D La2O3 nanorods, which showed the highest surface area of 76.54 m2/g. Moreover, the existence of acidic and basic active sites as identified by the temperature-programmed desorption (TPD) technique facilitates DMC production over the surface of G/La-3 catalyst. Recyclability and reusability experiments showed a gradual decrease in DMC yield owing to catalyst deactivation. It is expected that the present work provides valuable visions of the applicability of graphene/rare earth metal oxide heterogeneous catalysts in the given or similar chemical transformation processes.

This paper reports the use of novel ceria-zinc catalyst for the preparation of dimethyl carbonate (DMC) using transesterification of PC with methanol. Ceria-zinc oxide catalysts were prepared by a sol-gel method using citric acid, oxalic acid and tartaric acid as chelating agents (named as CZC, CZO, and CZT, respectively). The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, FTIR, SEM-EDX, ICP-OES, and CO2-temperature program desorption. Experimental results revealed that the catalytic performance of CZC was closely related to the surface area and presence of basic sites in the catalyst. CZC showed high selectivity and PC conversion. Effects of operating parameters such as methanol/PC molar ratio, catalyst dose, reaction temperature, reaction time were studied. The reusability of CZC as a catalyst for DMC selectivity and PC conversion with turn-over frequency (TOF) was also studied.

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

This study focuses on the "green" conversion of glycerol to 1,2-propanediol using the Cu-Al-Zn catalyst prepared by the co-precipitation method. Different ratios of (Cu+Zn)/Al were synthesized; the Zn and Al contents were varied while the Cu was kept constant (the Zn/Al ratios were 3:1, 4:1, 5:1, and 6:1). Catalyst characterization using TPD, XRD, and SEM, showed that the synthesized catalysts consisted of hydrotalcite with basic and acidic sites. The basicity of the catalysts was found to be an important criterion for the catalytic transfer hydrogenation, with the basic sites of the catalyst increasing the conversion of glycerol. Copper appeared to have an impressive effect on the C-O/C-C cleavage of glycerol during indirect hydrogenolysis for the synthesis of 1,2-propanediol. A reaction mechanism based on the hydrogenation of ethanol at Cu sites and the formation of intermediates at the basic sites of the catalysts was proposed.

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...

Indole is a highly recalcitrant aromatic heterocyclic organic compound consisting of a five-membered nitrogen-containing pyrrole ring fused to a six-membered benzene ring. This study presents the results of the electro-chemical mineralization of indole in an aqueous solution using platinum-coated titanium (Pt/Ti) electrode. A central composite design was used to investigate the effect of four parameters namely initial pH (pHo), current density (j), conductivity (k) and treatment time (t) at 5 levels. Multiple responses namely chemical oxygen demand (COD) removal (Y 1) and specific energy consumption (Y 2) were simultaneously maximized and minimized, respectively, by optimizing the parameters affecting the mineralization of indole by using the desirability function approach. At the operating conditions of pH 8.6, j = 161 A/m2, k = 6.7 mS/cm and t = 150 min, 83.8% COD removal with specific energy consumption of 36.3 kWh/kg of COD removed was observed. Ultra performance liquid chromatography, UV–visible spectroscopy, Fourier transform infrared spectroscopy and cyclic voltammetry of the indole solution were performed at the optimum condition of the treatment so as to report a plausible mechanism of indole degradation. Field emission scanning electron microscopy analysis of electrodes before and after treatment was performed for determining the changes on anode surface during the treatment. Thermal analysis of the solid residue (scum) obtained was also performed for exploring its disposal prospects. Present study shows that electro-chemical oxidation can be used for mineralization of nitrogenous heterocyclic compounds such as indole.

Diethyl carbonate, an important member in the family of organic carbonates, is a fuel additive like dimethyl carbonate (DMC). It holds an extra edge of having better gasoline/water distribution coefficient than DMC, and also DEC is widely used as an electrolyte in lithium ion batteries. Ethanolysis of ethyl carbamate (EC) is the most economical and greener route for DEC synthesis. Zn–Al–M (M=Ca, La, Mg and Y) have been synthesized using two methods and their activity have been explored DEC systhesis from EC and ethanol. The catalysts were characterized using thermogravimetric analysis, Brunauer, Emmett and Teller surface area, N2 adsorption–desorption textural analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, temperature-programmed desorption (TPD), atomic-force microscopy and Raman spectroscopy. Pure metal oxides were observed during the XRD analysis and Al2O3 was found to be in amorphous form. Third metal oxide prepared from impregnation method was found to be present on the surface as well as in impregnated form. CO2-TPD analysis showed close correlation between the basicity and the DEC yield. Zn–Al–Mg, prepared from precipitation method, being most basic, was found to be most effective although the performances of Zn–Al–Ca and Zn–Al–La were good. The effect of precipitants was also studied by synthesizing Zn–Al–Mg using NaOH and liquid NH3 as precipitants. DEC yield of 40.2% and turn over frequency of 1055 mgDEC gcat −1 h−1 was obtained in 5 h at 190 °C using Zn–Al–Mg prepared from precipitation method. Effect of reaction conditions was also studied and equilibrium constant of the reaction was estimated using the Benson group contribution method.

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.

In this study, ceria-zirconia based catalysts (CeO 2 , ZrO 2 and Ce 0.5 Zr 0.5 O 2 ) were synthesized by hydrothermal method and characterized by N 2 -sorption, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Acidity and basicity of synthesized catalysts were investigated by NH 3 and CO 2 temperature-programmed desorption (TPD). Brunauer-Emmett-Teller (BET) surface area of CeO 2 , Ce 0.5 Zr 0.5 O 2 and ZrO 2 were found to be 88, 117 and 70 m 2 g −1 and average crystallite sizes was 9.48, 7.09 and 9.45 nm, respectively. These catalysts were further used for direct conversion of CO 2 with methanol for the synthesis of dimethyl carbonate (DMC). DMC yield was found to be highly dependent upon the both basicity and acidity of catalysts. Ce 0.5 Zr 0.5 O 2 catalysts showed better activity as compared to CeO 2 and ZrO 2 catalysts. Effect of reaction conditions (such as catalyst dose, reaction temperature and reaction time) and catalyst reusability was studied with Ce 0.5 Zr 0.5 O 2 catalyst. The optimum operating condition for direct conversion of CO 2 into DMC at constant pressure of 150 bar were found to be reaction time = 24 h, catalyst dose = 1.25 g and temperature = 120 °C. Moreover, chemical equilibrium modeling was performed using Peng–Robinson–Stryjek–Vera equation of state (PRSV-EoS) along with the van der Waals one-fluid (1PVDW) mixing rule to calculate the heat of reaction and Gibbs free energy change.

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.

Refineries process a number of gas oils such as straight run gas oil (SRGO), light cycle gas oil, coker gas oil and visbreaker gas oil for producing a common gas oil pool to be used as a transportation fuel. Considering stringent sulfur standards, new strategies and design modifications are being evaluated for desulfurization of these gas oils with minimum loss of oil during the desulfurization process. In this review, developments in solvent extractive desulfurization of gas oil have been discussed from both fundamental and applied point of views. Various performance indicators used for solvent evaluation/screening in computational and experimental studies are discussed. Particular emphasis has been given on latest developments in performance evaluation of organic and ionic liquid solvents for desulfurization of SRGO and other gas oils. Various possible designs of solvent recovery section to remove solvent from raffinate and extract phases for solvent recycling have been reviewed. Various potential optio...

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...

In this work, we report a strategy for synthesizing morphology-controlled hierarchical self-assembled, three dimensional (3D) porous wool ball (W-ball) like zinc oxides (ZnO) with excellent catalytic performance. A precursor, hydrozincite (Zn 5 (CO 3 ) 2 (OH) 6 ), was first synthesized via a green urea-glycerol assisted template-free hydrothermal approach, which was calcined to form crystalline 3D porous ZnO having nanostructured morphology. The effect of synthesis process parameters which control the morphology of ZnO were studied. ZnO was found to possess tunable pore characteristics with comparatively high specific surface area of 68 m 2 g −1 , and excellent acid-base surface properties. Prepared catalysts exhibited excellent photocatalytic performance for the treatment of highly toxic rhodamine B (RhB) dye under UV radiation. Zeta (ζ)-potential and dye adsorption tests were performed. Reusability experiments showed that after five cycles, catalysts exhibited 87% removal efficiency without any noticeable loss of the activity.

Organic carbonates are green compounds with a wide range of applications. They are widely used for the synthesis of important industrial compounds including monomers, polymers, surfactants, plasticizers, and also used as fuel additives. They can be divided into two main classes: cyclic and linear carbonates. Dimethyl carbonate (DMC) and diethyl carbonate (DEC) are the important linear carbonates. Carbonyl and alkyl groups present in DMC and DEC make them reactive and versatile for synthesizing various other important compounds. Ethylene carbonate (EC), glycerol carbonate (GC) and propylene carbonate (PC) are well-known cyclic organic carbonates. Phosgenation of alcohols was widely used for synthesis of organic carbonates; however, toxicity of raw materials restricted use of phosgenation method. A number of new non-phosgene methods including alcoholysis of urea, carbonylation of alcohols using CO2, oxy-carbonylation of alcohols, and trans-esterfication of alcohols and carbonates have been developed...

Electrochemical method has been utilized to synthesize zinc-copper nanocomposite using aqueous succinic acid as electrolyte solution. Both copper and zinc electrodes were used as anodes, kept on each side of cathode, which itself was made of zinc. Synthesized nanoparticles were characterized by scanning electron micrograph (SEM), point energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy, UV–visible diffuse reflectance spectroscopy (UV-DRS) and X-ray diffraction (XRD) analysis so as to determine its various physico-chemical characteristics. XRD analysis showed the incorporation of pure monoclinic copper oxide within hexagonal zinc oxide within ZnO/CuO which was further reaffirmed by point EDX analysis. EDX spectrum confirmed the presence of Cu, Zn and O elements in nanocomposite. SEM micrograph indicates that the obtained ZnO/CuO nanocomposite was in spherical morphology. Optical properties investigated by UV-DRS showed decrease in maximum reflectance (~22%) due to incorporation of CuO within ZnO nanoparticle. The electrochemical response of ZnO/CuO reveals higher electrochemical activity than pure ZnO, without any modification.

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.

In this work, quinoline (a recalcitrant poly-nuclear aromatic compound) mineralization was studied by catalytic peroxidation process using ceria impregnated granular activated carbon. Various catalysts with different loading of ceria were prepared by wetness impregnation method and further characterized by liquid nitrogen adsorption–desorption technique, X-ray diffraction, scanning electron microscopy, thermo-gravimetric analysis and Fourier transform infrared spectroscopy. Effects of various parameters like ceria loading, pH, catalyst dose (C w), H2O2/quinoline molar ratio, initial concentration (C o) of quinoline, reaction temperature (T) and time on quinoline degradation and chemical oxygen demand (COD) removal efficiencies were studied. Quinoline degradation of 81.6% and COD removal of 86.5% were observed at optimum operating condition of pH = 4, C o = 100 mg/L, Ce loading = 7.5 wt%, H2O2/quinoline molar ratio = 1, C w = 0.5 g/L, T = 55 °C and reaction time = 4 h. The kinetics of the oxidation process was represented by the power law model.

Present study demonstrates reutilization of electrochemical (EC) sludge as a potential low-cost green catalyst for dye degradation. Hexagonal Fe2O3 type phase with trevorite (NiFe2O4)-type cubic phase nanocomposite material (NCM) was synthesized from solid waste sludge generated during EC treatment of textile industry wastewater with stainless steel electrode. For NCM synthesis, sludge was heated at different temperatures under controlled condition. Various synthesized NCMs were characterized by powder X-ray diffraction (PXD), energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) analysis. The synthesized NCMs were found to contain iron, chromium, nickel and oxygen in the form of α-Fe2O3 (metal: oxygen = 40:60), (Fe,Cr,Ni)2O3 and trevorite NiFe2O4, (Ni,Fe,Cr) (Fe,Cr,Ni)2O4 (metal: oxygen = 43:57). Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), pore size distribution, and atomic force microscope (AFM) analysis showed distribution of grains of different shapes and sizes. Catalytic activity of NCM was studied by the methylene red dye degradation by using the catalytic wet peroxidation process. Zeta potential study was performed under different pH so as to determine the performance of the NCMs during dye degradation.