Showing papers in "Research on Chemical Intermediates in 2016"

Adsorption performance of continuous fixed bed column for the removal of methylene blue (MB) dye using Eucalyptus sheathiana bark biomass

Abstract: In this study, the adsorptive effectiveness of sustainable and cost-effective eucalyptus bark biomass in the removal of methylene blue (MB) dye from its aqueous solution has been tested using a packed bed up-flow column experiment. A series of column experiments using raw eucalyptus bark was performed to determine the breakthrough curves with varying inlet MB dye flow rate (10–15 mL min−1), initial MB dye concentration (50–100 mg L−1) and adsorbent bed height (10–15 cm). High bed height, low flow rate and high initial dye concentration were found to be the better conditions for maximum dye adsorption. To predict the breakthrough curves and to determine the characteristic parameters of the column dynamics for industrial applications and for process design, Thomas model, Yoon–Nelson model and bed depth service time model were applied to experimental breakthrough data. All models were found suitable for describing the dynamic behaviour of the column, with respect to MB flow rate, initial dye concentration and adsorbent bed height. The findings revealed that eucalyptus bark biomass has a high adsorption potential for the removal of MB dye from aqueous solutions in a column system, and that it could be used to treat dye-containing effluents.

Mesoporous graphitic carbon nitride materials: synthesis and modifications

Abstract: Graphitic carbon nitride (g-C3N4), as a kind of polymeric semiconductor that has unique electronic structure and excellent chemical stability, has attracted increasing attention of researchers. Moreover, the raw materials for the preparation of g-C3N4 are various and easily accessible. All of these have provided favorable advantages for the fast development of g-C3N4. Compared to bulk g-C3N4, mesoporous g-C3N4 has more prominent natures, such as high specific surface area, large pore volume, and the increased amount of surface active sites. Therefore, great efforts have been devoted to develop mesoporous g-C3N4 (MCN). Up to now, many methods have been explored for the synthesis of MCN, such as hard-template method, soft-template method, template-free method, sol–gel method, and so on. Among these methods, the hard template method is used most widely. In this paper, the recent research on the synthesis of MCN was reviewed. In addition, the modifications to the obtained MCN, which lead to performance enhancement of the MCN for better applications, were also summarized.

Green synthesis of silver nanoparticles using Solanum indicum L. and their antibacterial, splenocyte cytotoxic potentials

Abstract: Green synthesis of silver nanoparticles was carried out using Solanum indicum L. plant extract as a reducing agent. The morphology of the AgNPs was determined by transmission electron microscopy. Scanning electron microscopy and energy-dispersive spectroscopy (EDX) were used to characterize the nanoparticles obtained from S. indicum L. The EDX analysis of the nanoparticles dispersion, using a range of 2–4 keV, confirmed the presence of elemental silver, without any contamination. The green synthesized AgNPs were evaluated against the pathogens such as Staphylococcus sp., (Accession No. KC688883) and Klebsiella sp., (Accession No. KC899845). The AgNPs (1–4 mM) extensively inhibit the growth of the pathogens. Cytotoxic potential of the synthesized AgNPs was analyzed against rat splenocytes. The percentage of viable cells was diminished according to the increasing concentration of AgNPs.

Photodegradation mechanisms of phenol in the photocatalytic process

Abstract: Investigating the photodegradation pathways of phenol, as well as the efficiency of photocatalysis by commercial TiO2 is the main task in this present work. Commercial TiO2 particles with the following characteristics: 96 % anatase, 4 % rutile, and 400 nm particles size were used as catalyst source. The photocatalytic process was carried out by mixing 100 ppm of phenol solution and 0.9 g/L of TiO2 particles with magnetic stirrer under UV-C light with 210 nm wavelength. UV–Vis spectrophotometer and COD measurement were used to evaluate the efficiency of photocatalysis. On the other hand, the formed intermediate products during phenol photodegradation were identified by LC–MS, UV–Vis spectrophotometer, and photoluminescence techniques. The results indicated that phenol was removed completely after 24 h of UV-C irradiation. The absorbance peak of phenol slightly decreased during the first 16 h. However, the peak dramatically reduced and disappeared at 24 h of irradiation. This degradation mechanism also occurred similarly to the COD value. There were two phases in photocatalysis of phenol. In phase-I, phenol was decomposed to hydroxylated compounds such as catechol, benzoquinone, and complexes with two benzene rings. In the mineralization phase, hydroxylated compounds were mineralized strongly by hydroxyl radicals, hydrogen radicals, and UV energy to form short-chain organic compounds such as formic acid, glycerol, and oxalic acid. Finally, hydrocarbon chains were broken easily and removed in the forms of carbon dioxide and water.

Silica-coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40; synthesis, preparation, and application as an efficient, magnetic, green catalyst for one-pot synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives

Abstract: A powerful, magnetic, supported, acid catalyst, NiFe2O4@SiO2–H3PW12O40, was prepared by chemical support of Keggin (H3PW12O40) heteropolyacid (HPA) on silica-coated NiFe2O4 magnetic nanoparticles. XRD, TEM, SEM, VSM, and FTIR confirmed that the keggin HPA is well dispersed on the surface of silica-coated NiFe2O4 magnetic nanoparticles. The magnetically recoverable catalyst could be easily recycled at least six times without significant loss of catalytic activity. After full characterization, its catalytic activity was investigated in the synthesis of tetrahydrobenzo[b]pyran and pyrano[2,3-c]pyrazole derivatives. (1) Novel silica-coated magnetic NiFe2O4 nanoparticles-supported H3PW12O40 was fabricated and characterized. (2) Recyclability of the catalyst. (3) Avoiding use of corrosive acid catalysts. (4) Green chemistry.

Reductive amination of furfural toward furfurylamine with aqueous ammonia under hydrogen over Ru-supported catalyst

Abstract: Poly(N-vinyl-2-pyrrolidone)-capped ruthenium-supported hydroxyapatite (Ru-PVP/HAP) shows significant activity for the synthesis of furfurylamine (FAM) via the reductive amination of furfural. As-prepared 5 wt% Ru-PVP/HAP affords 50 % yield of FAM in 25 % NH3 aqueous solution under pressurized H2 gas (2.5 atm), and the highest yield approaches 60 % at 4.0 H2 atm. Comparison between the activities over four Ru-supported HAP catalysts prepared with different methods and the results of X-ray absorption spectroscopy suggested that the metallic Ru cluster is the active center for the reductive amination of furfural. Transmission electron microscope and inductively-coupled plasma analysis indicated that the as-prepared 5 wt% Ru-PVP/HAP catalyst possessed 4.0 wt% PVP-capped Ru clusters with average diameter of 1.7 ± 0.3 nm on HAP support. It was also demonstrated that the reductive amination approach with Ru-PVP/HAP catalyst, NH3 aq. and pressurized H2 gas has capability for transformation of aromatic aldehydes to the corresponding aromatic amines. According to these results, it is concluded that Ru(0) cluster supported on HAP will represent a suitable catalyst for widely-usable reductive amination to convert an aldehyde functionality towards an amine.

Tragia plukenetii extract as an eco-friendly inhibitor for mild steel corrosion in HCl 1 M acidic medium

Abstract: A Tragia plukenetii (T. plukenetii) plant extract for use as a low-cost and efficient corrosion inhibitor for mild steel (MS) in 1 M HCl medium has been studied using various methods involving weight loss calculation, electrochemical impedance spectroscopy, and Tafel polarization. The maximum corrosion inhibition efficiency was found to be 88 % at 500 ppm. It was found that the T. plukenetii extract’s inhibition efficiency increased with the inhibitor concentration. The polarization measurement showed that the T. plukenetii plant extract acts as good mixed-type inhibitor. Thermodynamic investigations showed the change in enthalpy, entropy, and free energy. The adsorption mechanism of the extract was investigated using UV–Visible, FT-IR, Raman spectroscopy, and wide-angle X-ray diffraction studies. The inhibitor solution, investigated on the basis of the atomic absorption spectra for MS, revealed decreased dissolution of Fe in the presence of the plant extract. Surface analysis of the metal with and without the plant extract was carried out by using scanning electron microscopy and energy-dispersive X-ray spectroscopy.

Syngas Production from Methane Dry Reforming Over Ni/Al2O3 Catalyst

Abstract: We evaluated dry reforming of methane in a tubular fixed-bed reactor at various reaction temperatures from 923 to 973 K using different reactant compositions over 10 % Ni/Al2O3 catalyst prepared by a wet impregnation method. Both NiO and NiAl2O4 phases were formed on the catalyst surface during calcination, and the 10 % Ni/Al2O3 catalyst possessed high surface area of 106.36 m2 g−1 with fine metal dispersion. The low activation energy observed for formation of NiAl2O4 phase during calcination indicated strong interaction between the NiO form and the γ-Al2O3 support. The NiO phase was completely reduced to metallic Ni0 form via H2 reduction. The conversions of CO2 and CH4 increased noticeably with increasing CO2 partial pressure, and the H2/CO ratio was always below unity, regardless of reaction conditions. The yield of H2 was enhanced with growing CO2 partial pressure, approaching a highest value of about 70 %. The heterogeneous nature of the deposited carbon was evident from the coexistence of carbon nanofibers and graphitic carbon. In addition, the amount of filamentous carbon appeared to be slightly less than that of graphitic carbon. However, these deposited carbons were completely removed by O2 at below 900 K during temperature-programmed oxidation.

Fruit juice of Citrus limon as a biodegradable and reusable catalyst for facile, eco-friendly and green synthesis of 3,4-disubstituted isoxazol-5(4H)-ones and dihydropyrano[2,3-c]-pyrazole derivatives

Abstract: Fruit juice of Citrus limon (lemon juice) has been utilized as a natural and renewable catalyst for the green and environmentally friendly preparation of 3,4-disubstituted isoxazol-5(4H)-one derivatives and 6-amino-1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile derivatives in hydroalcoholic media at 90 °C. A one-pot three-component reaction of β-oxoesters with hydroxylamine hydrochloride and various aromatic aldehydes afforded 3,4-disubstituted isoxazole-5(4H)-one derivatives in excellent yields. The rate constant (K = 6.12 × 10−2 min−1 at 25 °C) for the formation of isoxazole derivative (1g) was also calculated. Similarly, a four-component reaction of ethyl acetoacetate, hydrazine hydrate, aryl aldehydes, and malononitrile gives pyrano[2,3-c]-pyrazole derivatives in very good yields. After completion of the reaction, the products were isolated by simple filtration. A simple work-up process, high product yields, short reaction times, and the use of an inexpensive and biodegradable catalyst are the advanced rewards of the present protocol.

Theoretical evaluation of triazine derivatives as steel corrosion inhibitors: DFT and Monte Carlo simulation approaches

Abstract: Density functional theory (DFT) calculations and atomistic Monte Carlo simulations were performed on hexahydro-1,3,5-triphenyl-s-triazine (Inh1), hexahydro-1,3,5-p-tolyl-s-triazine (Inh2), hexahydro-1,3,5-p-methoxyphenyl-s-triazine (Inh3), hexahydro-1,3,5-p-aminophenyl-s-triazine (Inh4), hexahydro-1,3,5-p-nitrophenyl-s-triazine (Inh5) molecules in order to study their reactivity and adsorption behaviour towards steel corrosion. DFT results indicate that the active sites of the molecules were mainly located on the N atoms of the triazine ring and on the aromatic rings containing substituted polar groups. Monte Carlo simulations were applied to search for the most stable configuration for the adsorption of the inhibitor molecules on Fe(110) surface both in vacuum and in aqueous solution. The investigated molecules exhibited strong interactions with iron surface. In aqueous solution all the investigated molecules displaced water molecules and were strongly attracted to the Fe surface as evident in their large negative adsorption energies compared to that in vacuum. The DFT reactivity indicators as well as the adsorption strength from the outputs of Monte Carlo simulations of the studied molecules on Fe(110) surface in vacuum and in the presence of water follow the trend: Inh4 > Inh3 > Inh2 > Inh1 > Inh5. The theoretical data obtained are in good agreement with the experimental inhibition efficiency results earlier reported.

Mild and green synthesis of tetrahydrobenzopyran, pyranopyrimidinone and polyhydroquinoline derivatives and DFT study on product structures

Abstract: The multicomponent synthesis of 4H-benzo[b]pyran, pyranopyrimidinone and polyhydroquinoline derivatives has been achieved using catalytic amounts of calcium hydrogen phosphate in aqueous medium as a green, inexpensive and environmentally benign media The process is operationally simple and has good to excellent yields Moreover, computational parameters of some products were obtained using density functional theory at the B3LYP/6-311++G(d,p) basis set and correlated to experimental results

Recent synthetic scenario on imidazo[1,2-a]pyridines chemical intermediate

Abstract: Of the biologically important benzene fused heterocycles, the most important are those containing a ring-junction nitrogen. The majority of ring junction systems do not occur naturally, but they have been important from a theoretical viewpoint, for preparation of potentially active analogues. The imidazo[1,2-a] pyridines are an important class of nitrogen ring junction heterocyclic compounds. They have huge applications in medicinal chemistry and drug molecule production. Thus, the initial discussion focuses on synthetic strategies of imidazo[1,2-a] pyridines, and later we disclose the reactivity of the imidazo[1,2-a]pyridines. This review is intended to summarize and discuss the most recent developments of synthesis and reactivity of imidazo[1,2-a]pyridines, mainly the contributions after 2007.

Synthesis and anti-inflammatory activities of 4H-chromene and chromeno[2,3-b]pyridine derivatives

Abstract: Several derivatives of 4H-chromene and chromeno[2,3-b]pyridine were efficiently prepared under microwave irradiation in a one-pot reaction, and their anti-inflammatory activities were evaluated. Six synthetic products (1b, 1c, 1h, 2d, 2j, and 2l) exhibited more powerfully inhibited the production of tumor necrosis factor-α-induced nitric oxide (NO) than quercetin and exhibited comparable cell viability in both human and porcine chondrocytes. In particular, 2d at dosages of 10 and 20 mg/kg had a very potent anti-inflammatory effect by suppressing the formation of carrageenan-induced rat paw edema and prostaglandin E2. The results herein suggest that these compounds may have potential as structural templates in the design and development of new anti-inflammatory drugs.

Ag/SiO 2 as a recyclable catalyst for the facile green synthesis of 3-methyl-4-(phenyl)methylene-isoxazole-5(4 H )-ones

Abstract: An efficient and facile green method for synthesis of 3-methyl-4-(phenyl)methylene-isoxazole-5(4H)-one (4a-m) via room temperature reaction of hydroxylamine, ethylacetoacetate and substituted aromatic aldehydes is designed, using Ag/SiO2 as catalyst with water as solvent. This protocol offers several advantages, such as it being a benign, energy conserving and eco-friendly reaction with products obtained in excellent yields (88–93 %). The reaction requires relatively short reaction times (< 1 h), a simple workup procedure with good atom efficiency and easily recoverable catalyst. The heterogeneous catalyst, Ag/SiO2, was fully characterized and is reusable without loss of activity for up to seven cycles with marginal activity loss.

Copper(II) acetate monohydrate: an efficient and eco-friendly catalyst for the one-pot multi-component synthesis of biologically active spiropyrans and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives under solvent-free conditions

Abstract: We have studied the catalytic ability of copper(II) acetate monohydrate as a mild, environmentally benign, natural and economical catalyst for the multi-component efficient synthesis of biologically active spiro-4H-pyran derivatives and 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives with excellent yields and short reaction times. The most important advantages of this procedure are its mild, non-toxic and inexpensive catalyst, one-pot synthesis, environmentally benign nature, solvent-free conditions, simple operational procedures, and highly efficient conditions.

UV-assisted synthesis of reduced graphene oxide–ZnO nanorod composites immobilized on Zn foil with enhanced photocatalytic performance

Abstract: ZnO nanorods were hydrothermally grown on Zn foil in an alkaline solution and the immobilized nanorods were subsequently hybridized with reduced graphene oxide (rGO) through UV-assisted photocatalytic reduction of graphene oxide (GO). X-ray diffraction analysis confirmed the vertical growth of ZnO nanorods while the incorporation of rGO to ZnO was investigated by scanning electron microscopy and photoluminescence spectroscopy. The successful photocatalytic reduction of GO was demonstrated by means of Raman spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic behavior and photostability of the sandwich-like rGO–ZnO composite were studied through decolorization of the aqueous solution of acid orange 7 under UV-C illumination. The rGO–ZnO photocatalyst presented higher dye decomposition efficiency than pure ZnO. The hybridization of rGO and ZnO led to a 40 % increase in the pseudo-first-order kinetic model’s rate constant and an enhancement of the photostability. The role of incorporation of rGO in enhancement of the ZnO’s photostability has been elucidated in the light of specific features of the sandwich-like architecture.

TiO2/g-C3N4 nanosheets hybrid photocatalyst with enhanced photocatalytic activity under visible light irradiation

Abstract: The nanosheets TiO2/g-C3N4 hybrid material with efficient visible-light photocatalytic activity was prepared by a facile solvothermal method The as-prepared TiO2/g-C3N4 nanosheets composite was thoroughly characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, N2 adsorption–desorption analysis, UV–Vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy As evaluated by the degradation of methylene blue under visible light irradiation, TiO2/g-C3N4 hybrid composites exhibit much higher photocatalytic activity than pristine g-C3N4 and TiO2, respectively The significant enhancement in photodegradation activity over the TiO2/g-C3N4 photocatalyst can be ascribed to the combined effects of the nanosheet structure and subsequent efficient separation of photogenerated charge carriers A tentative mechanism for the photodegradation process was proposed

A review on green Lewis acids: zirconium(IV) oxydichloride octahydrate (ZrOCl2·8H2O) and zirconium(IV) tetrachloride (ZrCl4) in organic chemistry

Abstract: Lewis acids are important and interesting catalysts in most organic transformations. Among different Lewis acids, Zr(IV) species such as ZrCl4 and ZrOCl2·8H2O are allocated special attention because of their low toxicity, availability and handling, moisture stability, and low cost in comparison to some of their corresponding compounds. During recent decades, Lewis acids have been used to promote different types of organic reactions because they naturally possess mild acidity properties and, as such, can catalyze reactions selectively. This means that in the presence of various functional groups, they can operate on a specific group to produce the objective product. In this review we have focused on the reactions which have been progressed in the presence of ZrCl4 and ZrOCl2·8H2O. The study has been ordered based on the number of the reaction components and their solvent media.

Equilibrium and kinetics studies of hexavalent chromium biosorption on a novel green macroalgae Enteromorpha sp.

Abstract: This study focuses on the use of novel Enteromorpha sp. macroalgal biomass (EMAB), for the biosorption of hexavalent chromium from aqueous solutions. The biosorbent was characterized by Fourier transformer infrared spectroscopy, energy dispersive spectroscopy, and scanning electron microscopy techniques. The effect of experimental parameters such as pH, initial concentration of Cr(VI) ions, biosorbent dosage, and temperature were evaluated. The maximum biosorption capacity for Cr(VI) was observed at pH 2.0. The modeling of the experimental data at equilibrium was performed using two parameter isotherm models. Both Langmuir and Freundlich isotherm equations better fitted the equilibrium data. A contact time of different initial Cr(VI) concentrations was about 160 min to attain biosorption equilibrium. The kinetic data were fitted by models including pseudo-first-order, pseudo-second-order, and intraparticle diffusion. The pseudo-second-order and intraparticle diffusion kinetic models adequately described the kinetic data. Moreover, the thermodynamic parameters indicated that the biosorption process was spontaneous, endothermic, and increased randomness in nature. The results showed that EMAB could be used as an effective biosorbent for the removal of Cr(VI) from aqueous solution.

Three gemini cationic surfactants as biodegradable corrosion inhibitors for carbon steel in HCl solution

Abstract: Three gemini cationic surfactants with different hydrophobic spacer chain lengths were synthesized and characterized. The inhibition effect of N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis(2-(tetradecanoyloxy)ethyl)ethane-1,2-diaminium bromide (G-2); N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis(2-(tetradecanoyloxy)ethyl) hexane-1,6-diaminium bromide (G-6); and N,N′-bis(2-hydroxyethyl)-N,N′-dimethyl-N,N′-bis (2-(tetradecanoyloxy) ethyl) dodecane-1,12-diaminium bromide (G-12) on the corrosion of carbon steel in 1.0 M HCl solution at 25–60 °C was studied by weight loss, potentiodynamic polarization, and electrochemical impedance spectroscopy. The results show that the synthesized inhibitors are effective inhibitors even at very low concentration, and the adsorption on the carbon steel surface obeys the Langmuir adsorption isotherm. Potentiodynamic polarization curves reveal that the synthesized inhibitors behave as a mixed-type inhibitor. Adsorption of used inhibitors led to a reduction in the double layer capacitance and an increase in the charge transfer resistance. Thermodynamic parameters have been obtained by adsorption theory. Surface activity and corrosion inhibition relationship were discussed. The biodegradability of the synthesized surfactants showed their readily biodegradation in the open environment and were considered as environmentally friendly corrosion inhibitors.

Enhancement of visible-light photocatalytic activity of Cu-doped TiO2 nanoparticles

Abstract: Bare TiO2 and Cu-doped TiO2 nanoparticles with different nominal doping amounts of Cu ranging from of 0.5 to 5.0 mol% were synthesized using the modified sol–gel method. The samples were physically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller-specific surface area, UV–Vis diffuse reflectance spectroscopy, zeta potential, X-ray photoelectron spectroscopy, inductively coupled plasma, and photoluminescence techniques. The Cu-doped TiO2 exhibited good photocatalytic activity in mineralization of oxalic acid and formic acid under visible light irradiation. Photomineralization of oxalic and formic acids under visible light irradiation revealed greatly enhanced photoactivity exhibited by the 2.0 mol% Cu-doped TiO2 photocatalyst compared to bare TiO2 . The enhanced photocatalytic performance arises from copper ion doping in the TiO2 structure, leading to an extended photoresponsive range, enhanced photogenerated charge separation, and transportation efficiency.

Kinetics and isotherm study on adsorption of chromium on nano crystalline iron oxide/hydroxide: linear and nonlinear analysis of isotherm and kinetic parameters

Abstract: Nano crystalline iron oxide was used as an adsorbent for removal of chromium from aqueous solutions. Linear and non-linear equations were applied to model the kinetic and isotherm data. Non-linear analysis included error analysis using the Solver addin of Microsoft Excel and Origin. Error analysis methods fitted the data better than Origin for determination of isotherm and kinetic parameters. Non-linear analysis suggests adsorption of chromium on nano crystalline iron oxide followed Langmuir isotherm. The maximum adsorption capacity of the adsorbent was found to be 11.18 mg/g. The system followed a pseudo second order model on the basis of linear and non-linear data. The Langmuir constant and partition coefficient methods were used to determine the thermodynamic parameters. Both methods suggested that the adsorption of chromium by nanocrystalline iron oxide is spontaneous and exothermic (−47.26 kJ/mol). The free energy values varied from −24.23 to −27.22 kJ/mol, and the process of removal progressed with a decrease in entropy (0.9256 kJ/mol). Thermodynamic parameters predicted by the linear Langmuir constant method suggested that the system is endothermic (9.65 kJ/mol), spontaneous, and occurs with an increase in entropy (0.1142 kJ/mol).

Aqueous extract of Argemone mexicana roots for effective protection of mild steel in an HCl environment

Abstract: The inhibition effect of aqueous Argemone mexicana root extract (AMRE) on mild steel corrosion in 1 M HCl has been studied by weight loss, Tafel polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), and atomic force microscopy techniques. Results indicate that inhibition ability of AMRE increases with the increasing amount of the extract. A maximum corrosion inhibition of 94 % is acknowledged at the extract concentration of 400 mg L−1. Polarization curves and impedance spectra reveal that both cathodic and anodic reactions are suppressed due to passive layer formation at the metal–acid interface. It is also confirmed by SEM micrographs and FTIR studies. Furthermore, the effects of acid concentration (1–5 M), immersion time (120 h) and temperature (30–60 °C) on inhibition potential of AMRE have been investigated by the weight loss method and electrochemical techniques. An adsorption mechanism is also proposed on the basis of weight loss results, which shows good agreement with the Langmuir isotherm.

Comparison of MOF-5- and Cr-MOF-derived carbons for hydrogen storage application

Abstract: Nanoporous carbons which possess high surface areas and narrow pore size distributions have become one of the most important classes of porous materials with potential to be utilized for hydrogen storage. In recent times, several metal–organic frameworks (MOFs) have been shown to be promising precursors for creating nanoporous carbons due to their high surface areas and tunable pore sizes. The pore structure and surface area of the resultant carbon materials can be tuned simply by changing the calcination temperature. In this work, a zinc-based MOF (MOF-5) and a chromium-based MOF (Cr-MOF) were both used as precursors for syntheses of nanoporous carbons by the direct carbonization technique at different temperatures. The resultant carbon nanostructure from MOF-5 possessed higher surface area, higher pore volume and enhanced hydrogen storage capacity as compared to pristine MOF. Meanwhile, the derived carbons from Cr-MOF displayed lower surface areas, pore volumes and hydrogen uptake than the parent MOF due to the formation of chromium oxide and carbide species in the pores of the Cr-MOF-derived carbons.

NaBH 4 reduction of ortho and para -nitroaniline catalyzed by silver nanoparticles synthesized using Tamarindus indica seed coat extract

Abstract: This study deals with reduction of ortho and para-nitroaniline by NaBH4 with silver nanoparticles (AgNPs), synthesized by use of a green method, as catalyst. In the synthesis of the AgNPs an aqueous extract of Tamarindus indica (T. indica) seed coat was used as a reducing and capping agent. The effects of extract concentration and reaction time on formation of the AgNPs were studied by use of UV–visible (UV–Vis) spectroscopy. The stable AgNPs were characterized by dynamic light scattering (DLS), measurement of zeta potential, Fourier-transform infrared (FTIR) spectroscopy, and high-resolution transmission electron microscopy (HRTEM) with energy-dispersive spectrum analysis. Appearance of a yellow color and generation of a surface plasmon resonance peak in UV–Vis spectroscopy confirmed formation of the AgNPs. The FTIR results suggested that the phytoconstituents of T. indica seed coat extract are responsible for reduction of the Ag+ and protection of the AgNPs. HRTEM studies showed the size of the AgNPs was approximately 30–50 nm; their shape was distorted spherical. The TEM results were consistent with DLS study. The catalytic efficacy of stable AgNPs in the reduction of o and p-nitroaniline was studied by UV–Vis spectroscopy. The calculated rate constants (k) for catalytic reduction of o and p-nitroaniline by AgNPs were 2.43 × 10−3 and 6.22 × 10−3 S−1.

Corrosion inhibition of mild steel in hydrochloric acid using extract of glycine max leaves

Abstract: The activity of glycine max leaves extract against corrosion of mild steel in 0.5 M HCl solution has been investigated at different temperatures (298–328 K). Different measurements were done using weight loss, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM)–energy dispersive x-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The weight loss results indicate that glycine max leaves extract is a good inhibitor and its optimum inhibition efficiency reaches up to 91.07 % at 2 g l−1 (308 K). The adsorption of the inhibitor molecules onto the mild steel surface was found to follow the Langmuir adsorption isotherm. The values of the Gibbs free energy of adsorption strongly support physisorption of inhibitor molecules on the mild steel surface. The decrease in inhibition efficiency is observed with increasing temperature, but increases with increase in inhibitor concentration. Formation of a protective layer against acid attack on the metal surface was confirmed by use of FT-IR, XRD analysis, and SEM.

Green approach to inhibition of corrosion of aluminum in 0.5 M HCl medium by tender arecanut seed extract: insight from gravimetric and electrochemical studies

Abstract: Tender arecanut seed (TAS) extract was assessed for its ability to hinder aluminum corrosion in 0.5 M HCl medium by means of gravimetric, polarization, and impedance techniques. Gravimetric experiments revealed an anticorrosive effect of extract constituents on aluminum surface, with the inhibition efficiency becoming more pronounced as the TAS extract concentration was increased but subdued as the exposure period was lengthened. Adsorption of TAS extract on aluminum surface was well fit by the Langmuir isotherm model. The inhibitory modality of TAS extract was elaborated in detail based on kinetic and thermodynamic calculations. Polarization studies revealed that TAS extract functioned as an inhibitor by decreasing corrosion current densities through a mixed-mode mechanism, and alternating-current (AC) impedance spectroscopy results evidenced adsorption of organic species from the extract at the aluminum–acid interface. Morphological studies of aluminum surface were carried out by atomic force microscopy. The inhibition efficiency values obtained by electrochemical measurements were consistent with those from gravimetric measurements and reflect the potential of TAS extract for corrosion inhibition of aluminum in acidic systems.

Synergistic effect of polyethylene glycols and rare earth Ce 4+ on the corrosion inhibition of carbon steel in sulfuric acid solution: electrochemical, computational, and surface morphology studies

Abstract: The inhibition effect of two selected polyethylene glycols (PEGs) with different molecular weight and the synergistic effect with rare earth Ce4+ ions on corrosion of carbon steel in 0.1 M H2SO4 solution has been investigated by using electrochemical measurements, scanning electron microscopy, and quantum chemical calculations. The inhibition efficiency (Z%) increased with increasing PEG concentration and molecular weight and decreased with increasing temperature. The adsorption of the PEGs obeyed the Langmuir adsorption isotherm. Potentiodynamic polarization studies showed that the PEGs were mixed-type inhibitors of corrosion by H2SO4. The results reveal that incorporation of PEGs with Ce4+ ions improved the inhibition performance. The Z% value for the PEGs in combination with Ce4+ was higher than the sum of the Z% values for the individual PEGs and Ce4+ ions, confirming a synergistic effect. Some quantum chemical parameters were calculated to corroborate the experimental results.

Facile one-pot synthesis of nano-zinc hydroxide by electro-dissolution of zinc as a sacrificial anode and the application for adsorption of Th4+, U4+, and Ce4+ from aqueous solution

Abstract: Facilely synthesized zinc hydroxide nanoparticles by electro-dissolution of zinc sacrificial anodes were investigated for the adsorption of thorium (Th4+), uranium (U4+) and cerium (Ce4+) from aqueous solution. Various operating parameters such as effect of pH, current density, temperature, electrode configuration, and electrode spacing on the adsorption efficiency of Th4+, U4+ and Ce4+ were studied. The results showed that the maximum removal efficiency was achieved for Th4+, U4+ and Ce4+ with zinc as anode and stainless steel as cathode at a current density of 0.2 A/dm2 and pH of 7.0. First- and second-order rate equations were applied to study the adsorption kinetics. The adsorption process follows second order kinetics model with good correlation. The Langmuir, Freundlich adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were determined. The experimental adsorption data were fitted to the Langmuir adsorption model. Thermodynamic parameters such as free energy (ΔG°), enthalpy (ΔH°), and entropy changes (ΔS°) for the adsorption of Th4+, U4+ and Ce4+ were computed to predict the nature of adsorption process. Temperature studies showed that the adsorption was endothermic and spontaneous in nature.

New Schiff base cationic surfactants as corrosion inhibitors for carbon steel in acidic medium: weight loss, electrochemical and SEM characterization techniques

Abstract: Two new Schiff base cationic surfactants were synthesized and their chemical structures confirmed using FTIR spectroscopy. The tensioactive and thermodynamic characteristics of their solutions were determined using surface tension/log concentration plots. The protection performance of the synthesized compounds against carbon steel corrosion in 1 M HCl solution was evaluated using weight loss and electrochemical techniques. The compounds were found to be excellent corrosion inhibitors, and their efficiency increased with increasing inhibitor concentration. The mode of adsorption obeyed the Langmuir adsorption isotherm. Polarization curves showed that the two compounds were mixed–type inhibitors. The temperature dependence of the corrosion rate in the absence and presence of these compounds was studied in a temperature range of 303 to 333 K using the weight loss data. Activation parameters E a, ΔH a o , and ΔS a o were determined and discussed. In addition, the presence of a protective film on the carbon steel surface was confirmed using scanning electron microscopy (SEM).