N-benzyl-N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine as corrosion inhibitor of steel in 1 M HCl

The inhibition effect of a new bipyrazole derivative namely N-benzyl-N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]amine (BBPA) on the corrosion of steel in 1 M HCl is studied at 308 K. Weight-loss measurements, potentiodynamic polarisation, linear polarisation and impedance spectroscopy (EIS) methods were used. Results show that BBPA is a good inhibitor and inhibition efficiency reaches 87% at 5 · 10^− 4 M. The values of the inhibition efficiency calculated from these techniques are reasonably in good agreement. Polarisation curves revealed that this organic compound acts as a mixed-type inhibitor. The temperature effect on the corrosion behaviour of steel in 1 M HCl with and without BBPA at 5 · 10^− 4 M is studied in the temperature range 308-353 K. The associated activation energy is determined. The adsorption of BBPA on the steel surface obeys to the Langmuir's adsorption isotherm. EIS measurements show that the transfer resistance increases with the inhibitor concentration. Efficiency is explained by the theoretical studies.     

Influence of substitution of phenyl group by naphthyl in a diphenylthiourea molecule on corrosion inhibition of cold-rolled steel in 0.5 M H2SO4

N,N′-Diphenylthiourea (DPTU) and N-naphthyl-N′-phenylthiourea (NPTU) synthesized in our laboratory, were tested as inhibitors for the corrosion of cold-rolled steel in 0.5 M H₂SO₄ by weight loss and electrochemical measurements. The studies clearly reveal that when we substitutes a phenyl group in N,N′-diphenylthiourea (DPTU) by naphthyl group to obtain N-naphthyl-N′-phenylthiourea (NPTU), the inhibition efficiency increases from 80 to 96% at 2 × 10⁻⁴ M. Polarization curves show that NPTU acts as mixed type inhibitor whereas DPTU predominates as cathodic inhibitor. Changes in impedance parameters (charge transfer resistance, R _t, and double layer capacitance, C _dl) were indicative of adsorption of DPTU and NPTU on the metal surface, leading to the formation of protective films. The degree of the surface coverage of the adsorbed inhibitors is determined by ac impedance technique, and it was found that the adsorption of these inhibitors on the cold-rolled steel surface obeys the Langmuir adsorption isotherm. The effect of the temperature on the corrosion behavior with addition of 10⁻⁴ M of DPTU and NPTU was studied in the temperature range 20–50 °C. Results show that the rate of corrosion of mild steel increased with increasing temperature both in the presence of inhibitors and in their absence. Activation energies in the presence and absence of DPTU and NPTU were obtained by measuring the temperature dependence of the corrosion current. The reactivity of these compounds was analyzed through theoretical calculations based on density functional theory to explain the different efficiency of these compounds as corrosion inhibitors.     

Amine-impregnated MCM-41 in post-combustion CO2 capture: Synthesis,characterization, isotherm modelling

In this study, a composite mesoporous silica material MCM-41 (Mobil composite matter) is impregnated with monoethanolamine (MEA) as primary linear amine, benzylamine (BZA) as primary cyclic amine and N-(2-aminoethyl) ethanolamine (AEEA) as secondary diamine and the effects of amine loading, amine type, CO₂ partial pressure and adsorption temperatures on the CO₂ adsorption are investigated. The CO₂ adsorption performances of MCM-41 and amine impregnated MCM-41 samples are studied up to 1 bar of CO₂ partial pressure and the temperature range of 25–60 °C. The amine loadings (% impregnation) are optimized for maximum CO₂ uptake. The materials are characterised using N₂ adsorption/desorption isotherm, Fourier Transform Infrared (FT-IR) Spectroscopy, Thermogravimetric (TGA) and Elemental (CHNS) analysis. The materials have shown good structural and thermal stability. The MCM-41-40%AEEA, MCM-41-40%BZA and MCM-41-50%MEA samples are exhibited the CO₂ adsorption capacity of 2.34 mmol/g (102.98 mg/g), 0.908 mmol/g (39.96 mg/g) and 1.47 mmol/g (64.69 mg/g) respectively. The CO₂ uptake of MCM-41-40%AEEA is 3.5 times higher than that of in MCM-41 (0.68 mmol/g) and it is also the highest reported value as di-amine impregnated MCM-41. The results indicated that the adsorption capacities of the materials (MCM-41 and MCM-41-40%AEEA) are decreased with an increase of adsorption temperature in the range of 25–60 °C. The Freundlich, Langmuir, Sips and Toth isotherm models are used to correlate and predict experimental CO₂ adsorption data. The Sips and Toth isotherm models are found to be better fitted with the experimental data. The isosteric heat of adsorption of MCM-41 and MCM-41-40%AEEA samples are also calculated from Van’t Hoff plot using iSorbHP-win instrumental analysis software in the experimental temperature range.     

Effect of carbon steel microstructures and molecular structure of two new Schiff base compounds on inhibition performance in 1 M HCl solution by EIS

In this investigation, attempts have been made to study the inhibitive effect of N,N′-ortho-phenylen acetyle acetone imine (S1) and 4-[(3-{[1-(2-hydroxy phenyl) methylidene] amino} propyl] ethanemidol]-1,3-benzenediol (S2) in the concentration range of 50–400 ppm for mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T)) in 1 M hydrochloric acid by ac impedance spectroscopy. The tests were conducted in acid solutions in the absence and presence of different concentrations of S1 and S2 Schiff bases for both microstructures. A sole time constant was observed from Bode-phase angle plots in the presence of inhibitors which reveals that the action of inhibitors is through adsorption on the surface. The charge transfer resistance and inhibition efficiency increases with the increase in Schiff bases concentration for both microstructures. The perlite samples in the absence of inhibitors in 1 M hydrochloric acid indicated slightly less corrosion than martensite ones, which was because of more protective oxide layers. Furthermore in the presence of S1 and S2, these samples showed better adsorption than martensite one. Schiff base S1 showed a better inhibition against corrosion in comparison with S2. Both S1 and S2 adsorbed on steel surface according to a Langmuir adsorption isotherm model. The associated Gibbs free energies for S1 on both microstructures are more than S2.     

Synthesis and characterization of a new material based on porous silica—Chemically immobilized C,N-pyridylpyrazole for heavy metals adsorption

The immobilization of C,N-pyridylpyrazole on the surface of epoxy group containing silica gel phase for the formation of a newly synthesized material based on porous silica-bound C,N-pyridylpyrazole (SGPP) is described. The surface modification was characterized by ¹³C NMR of solid sample, elemental analysis and infrared spectra and was studied and evaluated by determination of the surface area using the BET equation, the adsorption and desorption capability using the isotherm of nitrogen and BJH pore sizes, respectively. The new material exhibits good thermal stability determined by thermogravimetry curves. The synthesized material was utilised in column and batch methods for separation and trace extraction of (Hg²⁺, Cd²⁺, Pb²⁺, Cu²⁺, Zn²⁺, K⁺, Na⁺ and Li⁺) and compared to results of classical liquid–liquid extraction with the unbound C,N-pyridylpyrazole compound. The grafting at the surface of silica does not affect complexing properties of the ligand and the material exhibits a high selectivity toward Hg(II).     

新型不对称双季铵盐表面活性剂的制备及缓蚀性能

本文以十二烷基二甲基叔胺、十六烷基二甲基叔胺、氯乙酰氯和1,3-丙二胺为原料,通过三步法制得一种新型高效、环境友好的不对称双季铵盐表面活性剂,研究了其在1 mol/L盐酸溶液中对2024 Al-Cu-Mg合金表面的缓蚀性能和机理.通过红外光谱和核磁共振氢谱对其结构进行表征;通过表面张力获得其临界胶束浓度(CMC);利用...     

Electrochemical and thermodynamic studies to evaluate inhibition effect of 2-[(4-phenoxy-phenylimino)methyl]-phenol in 1 M HCl on mild steel

Inhibition of the corrosion of mild steel in 1.0 M HCl solution by a Schiff base compound named 2-[(4-phenoxy-phenylimino)methyl]-phenol (APS) was investigated at different temperatures (25–55 °C) using electrochemical measurements. The inhibition efficiency increased as APS concentration and temperature increased. It was found that adsorption for APS on mild steel complies with the Langmuir adsorption isotherm in all studied temperature. Thermodynamic parameters (ΔG_ads, ΔH_ads and ΔS_ads) for APS adsorption on mild steel were found out and discussed at each temperature. Time dependency of mild steel in 1.0 M HCl solution in the absence and presence of APS was also studied. The surface morphology of mild steel was examined via SEM analysis.     

The inhibition of mild steel corrosion in hydrochloric acid media by two Schiff base compounds

Schiff bases of 2-({-1-methyl-3-[(2-sulfanylphenyl)imino]butylidene}-amino)-1-benzenethiol and 2-({-1,2-diphenyl-2-[(2-sulfanylphenyl)imino]ethylidene}amino)-1-benzenthiol are investigated as corrosion inhibitors in acid solution. Polarization, electrochemical impedance spectroscopy, and weight loss measurements were performed on mild steel in 15% HCl with and without the inhibitors. A significant decrease in the corrosion rate of mild steel was observed in the presence of investigated inhibitors. Polarization curves indicate that both compounds are mixed inhibitors, affecting both cathodic and anodic corrosion currents. The adsorption of inhibitors on mild steel surface in 15% HCl was found to follow Langmuir adsorption isotherm. Thermodynamic adsorption parameters (K _ads, ∆G _ads) of studied Schiff bases were calculated using the Langmuir adsorption isotherm. Activation parameters of the corrosion process such as activation energies, E _a, activation enthalpies, ∆H*, and activation entropies, ∆S*, were calculated by the obtained corrosion currents at different temperatures.     

Characterisation of structural parameters of finely divided and porous materials by a new adsorption isotherm

An adsorption isotherm log log p = C+nlog v was developed and applied earlier. The isotherm has been used to determine the structural parameters of adsorbents. The application of the isotherm has been extended to determine separation factor of mixture of gases, surface area of adsorbed monolayer from energy consideration, categorisation of micropores etc. It is shown that equation of Lewis et al. for partial adsorption and equation of Langmuir can be deduced from isotherm equation of John. Advantages of John's isotherm are enumerated.     

The inhibition action of N-(furfuryl)-N′-phenyl thiourea on the corrosion of mild steel in hydrochloric acid medium

The inhibiting effect of N-(furfuryl)-N′-phenyl thiourea (FPTU) on the corrosion of mild steel in 0.01 M HCl solution has been demonstrated using potentiodynamic polarization technique. The polarization data have shown that FPTU acts as an efficient anodic inhibitor for mild steel in acid solution. Adsorption of this compound on the mild steel surface was found to obey Temkin's adsorption isotherm. Good inhibition efficiency (> 93%) has been evidenced at 28 °C and 50 °C and inhibition is governed by chemisorption mechanism.     

Removal of disperse dye from aqueous solution by novel adsorbent prepared from biomass plant material

The adsorption of Disperse Orange 25 (3-[N-ethyl-4-(4-nitrophenylazo) phenylamino] propionitrile) onto activated carbon was investigated in a batch system with respect to contact time, carbon dosage, pH and temperature from aqueous solutions. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) adsorption models were applied to describe the equilibrium isotherms and the isotherm constants were also determined. The Langmuir isotherm model agrees with the experimental data well. Maximum adsorption capacity (q_max) of Disperse Orange 25 onto adsorbent was 118.93 mg g⁻¹ at 20 °C. The first-order, pseudo-second-order kinetic models and the intraparticle diffusion model were used to describe the kinetic data and the rate constants were evaluated as well. The experimental data fitted very well to pseudo-second-order kinetic model. The results show that activated carbon prepared from Euphorbia rigida by sulfuric acid chemical activation could be employed as low-cost material to compare with commercial activated carbon for the removal of disperse dyes from effluents.     

Adsorption of BSA onto hexagonal mesoporous silicate loaded by APTES and tannin: Isotherm,thermodynamic and kinetic studies

In the present study, hexagonal mesoporous silica (HMS) was synthesized and modified by tannic acid as a natural poly-phenol and amine (TA-A-HMS) and was applied for the adsorption of bovine serum albumin (BSA) from aqueous media. To investigate the structure of HMS and TA-A-HMS, SEM, TEM, XRD, BET and FTIR analysis were applied. The effects of pH, adsorbent dosage, contact time and temperature on the BSA adsorption were studied. After modification, BET surface area of HMS was reduced from 885?m²/g to 51?m²/g which confirms the presence of tannin and amine groups that inhibit the adsorption of nitrogen molecules. According to the results of equilibrium data, it is shown that Langmuir isotherm with maximum adsorption capacity of 1000?mg/g is the predominant model and adsorption is mono-layer. Kinetic and thermodynamic studies also reveal that adsorption kinetic followed by pseudo-second order model and the adsorption process is exothermic.     

Temperature swing adsorption of melamine on thermosensitive poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) cryogels

In the past few years, polymer-based adsorbents have been emerging as highly effective alternatives to activated carbons for pollutants removal and recovery from industrial effluents. In this article, novel thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) cryogels adsorbents were directly prepared with N-isopropylacrylamide (NIPAAm) as a thermosensitive monomer and PEG-20,000 as a porogen at −12 °C by means of an in situ free-radical redox cryopolymerization. Subsequently, PNIPAAm cryogels were further employed to adsorb and desorb melamine through temperature swing adsorption (TSA) between 25 and 50 °C. The adsorption isotherms were correlated to Langmuir and Freundlich isotherm models. Moreover, the result indicated that the developed PNIPAAm cryogels adsorbents could be utilized effectively to concentrate melamine from aqueous solutions and spiked liquid milk. The cycle of the adsorption and desorption could be repeated without much loss of the melamine adsorbing ability.     

Initial Salt Screening Procedures for Manufacturing Ibuprofen

The aim of this paper is to design initial salt screening procedures for manufacturing ibuprofen. Salt forms of a pharmaceutical acid racemic (R,S)-(±)-ibuprofen and their “developable” synthetic routes were ferreted out simultaneously through the screening of seven bases of sodium hydroxide, potassium hydroxide, l-arginine, l-histidine, l-lysine, diethanolamine, and tris(hydroxymethyl)aminomethane (THAM), and the match with the use of nine organic solvents of methanol, dimethyl sulfoxide, ethanol, N,?N-dimethylformamide, acetonitrile, isopropyl alcohol, 1,4-dioxane, acetone, and tetrahydrofuran mainly in the presence of water in 20 mL scintillation vials. Racemic (R,S)-(±)-sodium ibuprofen dihydrate, a well-known ibuprofen salt and the newly discovered racemic (R,S)-(±)-THAM ibuprofen, appeared as white-squared powders with a molecular weight of 327.42 g/mol, a melting point of 160.17°C, and the apparent solubility product, K′_sp, of 6.0 × 10^?4 M² at 25°C were successfully synthesized by the initial salt screening methods. The new amine salt of ibuprofen was monoclinic and had a space group of P2₁/c and lattice parameters of a = 17.578(8)°, b = 10.428(4)°, c = 9.991(4) Å, α = 90.00°, β = 97.17(1)°, γ = 90.00°, and V = 1,817.05(244) ų. The aspect ratio of the amine salt crystals of ibuprofen of ≈ 1.0 implied that the crystals had a better flowability than the sodium salt counterparts. This amine salt of ibuprofen was more stable in moist or dried atmospheres and was more hydrophobic than the sodium salt of ibuprofen. Moreover, the slow dissolution of this amine salt of ibuprofen might have made it less bitter and more suitable as a sustained release drug than the sodium salt of ibuprofen. The future work is to search for the different polymorphs of this amine salt of ibuprofen and to extend the initial salt screening working logics to the formation of co-crystals.     

Thermodynamics of rare-scattered element In<Superscript>3+</Superscript> adsorption by nanometer titanium oxide

A new method using nano-TiO₂ as a solid-phase extractant has been developed for the determination of trace amounts of indium. The adsorption pH curves, adsorption isotherms, and adsorption capacities were obtained. It was found that the adsorption rate of In³⁺ was more than 95% at pH 3.0–5.0. The adsorption reaches equilibrium in a short time and follows a Langmuir isotherm. From the results of thermodynamic analysis, the adsorption constant K _C , standard free energy ΔG ⁰, standard enthalpy ΔH ⁰, and standard entropy ΔS ⁰ of the adsorption process were calculated. The standard thermodynamic function changes were ΔG ⁰ < 0, ΔH ⁰ > 0, and ΔS ⁰ > 0, which indicated that the adsorption was a spontaneous increasing enthalpy and entropy driving process. The positive value of ΔS ⁰ for adsorption could be explained by the release of the attached water molecules from In³⁺ into solution as In³⁺ adsorbed on substrate and contributed to the increase in the degree of freedom at the solid-solution interface during the adsorption process. Fourier transformation infrared spectrum and x-ray diffraction investigated the structure of nano-TiO₂. The results and the thermodynamic data indicated that In³⁺ adsorption onto nano-TiO₂ was characterized by physical adsorption. The text was submitted by the authors in English.     

分散剂CTAB对碳纳米管悬浮液分散性能的影响

以十六烷基三甲基溴化铵(CTAB)为分散剂, 制备了分散性能良好的碳纳米管悬浮液. 通过测定等温吸附曲线和悬浮液的Zeta电位, 研究了CTAB对碳纳米管表面性质的影响. 结果表明, CTAB的加入使Zeta电位由-29mV变为65mV左右; 等温吸附曲线表明,CTAB在碳纳米管表面为“两阶段吸附”, CTAB浓度为9×10^-4 mol·L^-1时, 在碳纳米管表面达到饱和吸附. 通过悬浮碳纳米管浓度测定确定了所需最佳CTAB的用量为9×10^-4 mol·L^-1左右, 同时对CTAB的吸附分散机理进行了分析和讨论.     

The study of adsorption characteristics Cu and Pb ions onto PHEMA and P(MMA-HEMA) surfaces from aqueous single solution

The adsorption characteristics of Cu²⁺ and Pb²⁺ ions onto poly2-hydroxyethyl methacrylate (PHEMA) and copolymer 2-hydroxyethyl methacrylate with monomer methyl methacrylate P(MMA-HEMA) adsorbent surfaces from aqueous single solution were investigated with respect to the changes in the pH of solution, adsorbent composition (changes in the weight percentage of MMA copolymerized with HEMA monomer), contact time and the temperature in the individual aqueous solutions. The linear correlation coefficients of Langmuir and Freundlich isotherms were obtained. The results revealed that the Langmuir isotherm fitted the experimental results better than the Freundlich isotherm. Using the Langmuir model equation, the monolayer adsorption capacity of PHEMA surface was found to be 0.840 and 3.037 mg/g for Cu²⁺ and Pb²⁺ ions and adsorption capacity of (PMMA-HEMA) was found to be 31.153 and 31.447 mg/g for Cu²⁺ and Pb²⁺ ions, respectively. Changes in the standard Gibbs free energy (ΔG⁰), standard enthalpy (ΔH⁰) and standard entropy (ΔS⁰) show that the adsorption of mentioned ions onto PHEMA and P(MMA-HEMA) are spontaneous and exothermic at 293–323 K.     

Effect of adsorbent concentration to the adsorption of phenol on hexadecyl trimethyl ammonium-bentonite

In this work, it is intended to study the effect of adsorbent concentration on the adsorption of phenol by hexadecyl trimethyl ammonium-bentonite. The experiments were conducted in two groups. The adsorption of hexadecyl trimethyl ammonium bromide (HDTMA) on bentonite was studied in the first group of experiments. It was observed that the all HDTMA was adsorbed by the bentonite, even when the amount used exceeded 100% of cation exchange capacity (CEC). After the modification of bentonite by using HDTMA in an amount equivalent to 100% of CEC, the adsorption experiments were performed at five different adsorbent concentrations ranging from 2 to 10 g/L. A type V isotherm and a non-linear increase in percent removal with adsorbent concentration were observed. The observation of the non-linear relation between the percent removal and adsorbent concentration was attributed to the effect of intra particle interactions and it was represented by a second order polynomial. Several adsorption isotherm equations were applied to the experimental data. Although, the Freundlich equation fitted fairly well, it failed to represent the plateau and the second region that appeared in the isotherm. Therefore, an equation giving the equilibrium concentration as a function of initial and adsorbent concentrations was suggested.     

Adsorption of nitrogen and oxygen in cobalt (II)-exchanged zeolite A

The cobalt (II)-exchanged zeolite A (NaCoA) was prepared by cation exchange process with zeolite A (NaA) and Co(NO₃)₂ in aqueous solution. A static volumetric system was employed to evaluate the N₂ and O₂ adsorption properties of NaCoA at 298 K. It was found that the N₂ adsorption capacity of NaCoA increased rapidly with the rising pressure, and the adsorption isotherm of N₂ became nonlinear in low pressure region. The O₂ adsorption capacity of NaCoA increased slightly with pressure. The introduction of Co²⁺ into the NaA enhanced the N₂ adsorption capacity and N₂/O₂ selectivity, which could be contributed to the π-complexation between N₂ and Co²⁺. This strong interaction brought about a series of high value for Henry's constant, Langmuir constant, adsorption selectivity and adsorption capacity of N₂ in NaCoA. Infrared spectra were also carried out to illustrate that the N₂ were bonding with Co²⁺.     

Effect of BTA on electrochemical corrosion and stress corrosion cracking behaviour of type 304 stainless steel in 1 M HCl

Effect of benzotriazole (BTA) on polarization and stress corrosion cracking (SCC) behaviour of type 304 stainless steel in 1 M HCl was investigated. The anodic polarization curves showed that with BTA additions the anodic polarization kinetics in the active region was not affected, though a reduction in critical current density, i _crit, and passive current density, i _p, was observed. However, BTA was found to influence significantly the cathodic reaction kinetics. SCC results using smooth tensile test specimens showed an increase in time-to-failure, t _f, with BTA additions. Crack growth rate studies using single-edge notched (SEN) specimens showed an increase in threshold stress intensity for SCC, K _ISCC, and a decrease in crack growth rate, da/dt, with BTA additions. While the adsorption isotherms derived from weight loss data followed a Langmuir adsorption isotherm signifying a monolayer adsorption, the adsorption isotherms derived from SCC test data deviated from this at higher BTA concentrations. The paper discusses the possible reason for this deviation.