Concentrated HCl Solutions Research Articles

Importance of Internal Porosity for Glucan Adsorption in Mesoporous Carbon Materials.

To better understand the adsorption of long-chain poly(1 → 4)-β-D-glucans on carbon surfaces as well as interactions responsible for this adsorption, we use a comparative study involving mesoporous carbon-silica composite materials that have been etched to varying degrees and all-atom molecular dynamics simulations. The materials synthesized as part of this etching study consist of an as-synthesized composite material (MCN-MSN), MCN-MSN-0.5 (composite materials consisting of 50% carbon by mass), MCN-MSN-0.3 (composite materials consisting of 70% carbon by mass), and MCN, in which silica etching was conducted using an aqueous ethanolic solution of either NaOH or HF. Data for the adsorption of long-chain glucans to these materials from concentrated aqueous HCl (37 wt %) solution demonstrate a direct relationship between the amount of β-glu adsorption and the magnitude of exposed carbon mesopore surface area, which systematically increases and is also accompanied by an increase in the mesopore size during silica etching. This demonstrates β-glu adsorption as occurring on internal carbon mesopores rather than exclusively on the external carbon surface. These experimental data on adsorption were corroborated by molecular dynamics (MD) simulations of β-glu adsorption to a graphene bilayer separated by a distance of 3.2 nm, chosen to correspond to the carbon mesopore diameter of the experimental system. Simulation results using a variety of β-glu solvent systems demonstrate the rapid adsorption of a β-glu strand on the graphitic carbon surface via axial coupling and are consistent with experimentally observed trends in fast adsorption kinetics. Solvent-mediated effects such as small-scale hydrophobicity and preferential interactions with ions are shown to play important roles in modulating glucan adsorption to carbon surfaces, whereas experimental data on hydrophobically modified silica demonstrate that hydrophobicity in and of itself is insufficient to cause β-glu adsorption from concentrated aqueous HCl solution.

Electrochemical kinetics of the hydrogen reaction on platinum in concentrated HCl(aq)

The hydrogen reaction in concentrated HCl(aq) solutions is a key reaction for the CuCl(aq)/HCl(aq) electrolytic cell. Here, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) were used to obtain new data for the hydrogen reaction on platinum submerged in highly concentrated acidic solutions at 25 °C and 0.1 MPa. LSV and EIS data were collected for Pt in 0.5 mol/L H 2 SO 4 (aq), 1 mol/L HCl(aq) and 7.71 mol/L HCl(aq) solutions. It was found that exchange current density ( j 0 ) values varied between 1 and 2 mA/cm 2 . An equivalent circuit model was used to obtain comparable j 0 and limiting current density values from EIS data relative to values obtained with LSV data. It was found that as the concentration of acid increased, a noticeable decrease in the performance was observed. • New electrochemical data for the hydrogen reaction on platinum in strong acids • EIS and LSV data fittings provided similar limiting and exchange current densities. • As the concentration of HCl increased, the exchange current density decreased.

Synergistic Extraction of Rhodium(III) from Hydrochloric Acid Solution with Tri-n-octylamine and Sulfide-type Extractants

Synergistic extraction of Rh(III) from relatively concentrated HCl solution was studied using two mixed solvents (di-n-hexyl sulfide (DHS)–tri-n-octylamine (TOA) and N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (TDGA)–TOA) in chloroform. The Rh(III) extraction efficiency is poor when 0.5 M TOA, DHS, or TDGA is used independently. In contrast, the 0.5 M TDGA–0.5 M TOA and 0.5 M DHS–0.5 M TOA mixed solvents extract ˜90% and ˜70% of Rh(III), respectively, at maximum. Slope analyses and Job’s plots for the distribution ratios of Rh(III) at 2 M HCl show that the apparent stoichiometry of Rh(III):TOA:(DHS or TDGA) in the extracted complex is 1:2:1.

Minimizing Unintentional Strain and Doping of Single-Layer Graphene on SiO2 in Aqueous Environments by Acid Treatments.

The effects of treating SiO2/Si with either acidic or alkaline solutions on single-layer graphene were investigated using Raman microscopy. It is well-known that in air graphene on SiO2 is unintentionally strained and hole-doped to different degrees, varying widely by sample. It is also known that various amine compounds act as electron donors to graphitic materials. In this study, a SiO2/Si substrate was simply dipped in either a concentrated HCl solution or pH 9.0 NaOH solution and then rinsed, prior to transferring graphene on it. The G and 2D peaks were followed at a fixed position on a single-layer graphene flake in water and various concentrations of pH 7.4 tris(hydroxymethyl)aminomethane (Tris) buffer. The results demonstrate that these treatments reduce the sample variation, improve the stability against Tris, and even bring some graphene samples close to a freestanding state. The Raman analysis reveals that the main effect of dipping is to relieve strain. The undoping effect on some samples is explained by the HCl solution becoming trapped between the graphene and SiO2 surface.

Preparation of the Nanoceria Powder from Bastnasite

A novel process was developed to obtain high content of ceria powder directly from bastnasite mineral. The bastnasite was roasted with NaHCO3 at 550 oC for 2 h, washed with water and dilute HCl respectively to remove impurities, and finally calcined in air. TG-DTA, XRD, XRF, SEM was used to characterize the decomposition process of bastnasite, crystalline phase, the chemical composition, and morphology of the product. The results showed that the concentration of HCl solution was the most important factor in the leaching process, and the calcining temperature of bastnasite mineral should be controlled below 600 oC. The optimal technological parameters were suggested as follows: leaching temperature at 45 oC, for 45min in 3 mol/L HCl, with the weight ratio of solid to liquid of 1:5, and the calcining of the leachate at 600 oC for 2 h. And the high content of ceria (TREO > 80wt %, Ceria/TREO > 85wt %) nanosized (20~100 nm) powder was obtained succeffully, which showed potential application in polishing materials.

Morphologically controlled synthesis of porous Mn2O3 microspheres and their catalytic applications on the degradation of methylene blue

Porous Mn2O3 microspheres are controllably synthesized by selectively etching MnCO3 precursor with HCl solution. Morphologies and microstructures of Mn2O3 microspheres are analyzed by SEM, TEM, XRD, and N2 sorption technique. The catalytic performances of Mn2O3 microspheres for the degradation of methylene blue (MB) are investigated, and the reaction kinetics of MB degradation is also studied. The results show it is feasible to control the morphologies of Mn2O3 microspheres by adjusting the concentration of HCl solution, and the well-developed porous Mn2O3 microspheres demonstrate good potential on MB degradation. The degradation reactions follow the pseudo-first-order kinetic model, and the degradation capabilities for MB are great dependent on BET surface areas and pore volumes of Mn2O3 microspheres.

Bulk hierarchical nanoporous palladium prepared by dealloying PdAl alloys and its electrochemical properties

Bulk hierarchical nanoporous palladium (BHNPP) materials composing both bimodal porous structure and monolithic porous structure were fabricated by chemical dealloying of Pd20Al80 alloy with sub-micrometer grain size via mechanical alloying and spark plasma sintering process (MA-SPS). The different nanoporous structures were formed in the regions where the microstructure was heterogeneous. Monolithic porous structure were formed after dealloyed of monolithic grain structure mainly composed of PdAl3 phase, and bimodal porous structure with both larger pore of hundreds nanometers and smaller pore of a few nanometers were obtained after dealloyed of nanocrystalline structure consist of PdAl3 and Al phases, respectively. Effects of dealloying time, concentration of dealloying solutions and chloride ion (Cl−) on the evolution of the microstructure of BHNPP were also studied. Ligament of BHNPP can be facility coarsen by add chloride rather than only raise the concentration of HCl solution. Moreover, the cyclic voltammetry results reveal that the BHNPP materials have superior ethanol oxidation ability.

Preparation of nanoporous silver micro-particles through ultrasonic-assisted dealloying of Mg-Ag alloy ribbons

Nanoporous silver (NPS) micro-particles were prepared successfully by combining high-intensity ultrasonic irradiation (UI) and chemical dealloying process of rapidly solidified Mg-Ag precursors. The length scale of the ligaments in NPS is 100±30 nm, which is insensitive to the concentration of the hydrochloric acid (HCl) solution and the intensity of the UI. However, smaller NPS micro-particles with a size of 50±20 μm can be obtained by dealloying the precursor ribbons in a much more concentrated HCl solution under UI. It is supposed that the cavitation phenomena induced by UI treatment may play a key role in disaggregating the precursor ribbons into the present NPS micro-particles during dealloying.

Lithium extraction from seawater by manganese oxide ion sieve MnO2·0.5H2O

Abstract Among the current methods for lithium extraction from seawater, adsorption by manganese oxide ion sieves was considered to be the most promising one for industrial application. In this study, sol–gel, hydrothermal synthesis and two-stage heat treatment were used for preparing lithium ion sieve precursor Li 1.6 Mn 1.6 O 4 . Ion sieve MnO 2 ·0.5H 2 O was then obtained after eluting Li + from Li 1.6 Mn 1.6 O 4 by acid treatment. The crystal structure, surface morphology and adsorption properties of the ion sieve were characterized by XRD, SEM, HRTEM, adsorption isotherms and kinetics. Furthermore, the dynamic adsorption/desorption processes of granulated ion sieve were studied with concentrated seawater (saltern bittern) and HCl solution. The results showed that the ion sieve and its precursor were nearly pure spinel manganese oxides, and possessed one-dimensional nanowires morphologies. After granulation, the ion sieve exhibited good adsorption performance, and its adsorption process was in accordance with Lagergren Kinetics Equation and Langmuir Isotherm Equation. Under continuous and dynamic conditions, the ion-exchange capacity of this ion sieve for saltern bittern (pH = 10) was 10.05 mg/g, and after acid treatment, lithium-rich solution which was 30 times more concentrated than bittern (900 times than seawater) was obtained. The results implied that the ion sieve could be used for lithium extraction and enrichment in seawater system, and had a good application prospect.

Integrated computational and experimental protocol for understanding Rh(III) speciation in hydrochloric and nitric acid solutions.

Platinum group metals (PGMs), including rhodium, generated by the fission of (235)U are present in significant quantities within spent nuclear fuel located on power generation sites in the United States, the amount of which is expected to exceed natural reserves by 2030. Yet, spent fuel raffinates are highly acidic media that may result in complex speciation of the PGM. This work provides an understanding of Rh(III) speciation up to 9 M HCl and HNO3, and utilizes a combination of ultraviolet-visible (UV-vis) and capillary zone electrophoresis data, along with computationally predicted thermochemistry and simulated UV-vis spectra to approximate the relative concentrations of potential species in solution as a function of acid concentration. One Rh(III) species, [Rh(NO3)3], is observed under all conditions in HNO3 and for Rh(III) concentrations smaller than 10(-3) M. In contrast, a variety of chloridated Rh(III) species may exist simultaneously in a HCl medium. The species [RhCl2(H2O)4](+) and [RhCl3(H2O)3] are observed in HCl solutions of concentrations ranging from 0 to 1 M; the species [RhCl4(H2O)2](-), [RhCl5(H2O)](2-), and [Rh2Cl9](3-) are observed between 2 and 9 M HCl.

Methyl 3-((2-mercaptophenyl) imino) butanoate as an effective inhibitor against steel corrosion in HCl solution

Methyl 3-((2-mercaptophenyl) imino) butanoate (MMPB) was designed and synthesized as a corrosion inhibitor, which is functionalized with adjacent azole and thiol groups and a carboxylate tail. The inhibition efficiency of this compound has been investigated in different concentrations of HCl solutions. Then, the effect of temperature and inhibitor concentration was studied for further discussion about inhibition mechanism. In addition to potentiodynamic and electrochemical impedance spectroscopy, galvanic measurements were also realized for better explanation of interaction between inhibitor and metal surface. For this purpose, identical steel electrodes were immersed in separate test solutions with and without inhibitor, and then coupled to each other. The assessment of corrosion rate was realized with quantitative analysis of iron content in immersion test solutions. The corrosion current densities (icorr) were 20.40 and 200.30 μA cm−2, in the presence of 10 mM inhibitor and inhibitor-free test solutions, respectively. The energy barrier values against corrosion were also calculated in the presence and absence of inhibitor, with the help of surface coverage ratio and icorr values for different temperatures.

The structure and vibrational features of proton disolvates in water-ethanol solutions of HCl: the combined spectroscopic and theoretical study

The infrared (IR) spectra of water–ethanol (EtOH) solutions of HCl are measured over a wide range of acid concentration at fixed H2O―EtOH ratios (1 : 1, 1 : 2, and 1 : 40). In these systems, different proton disolvates with (quasi)symmetrical H-bonds are formed. Their structure and vibrational features are revealed by the density functional theory method coupled with the polarizable continuum model of solvation. In dilute acidic solutions, the Zundel-type H5O2+ ion is mainly formed. In concentrated HCl solutions, the ions (H2O···H···O(H)Et)+ and (Et(H)O···H···O(H)Et)+ with the quasi-symmetrical O···H+···O unit having O···O separation <2.45 A appear. The first ion characterized by the IR-intensive band around 1800 cm−1 is mainly formed in the 1 : 1 water–ethanol systems. The second ion exists in the 1 : 2 and 1 : 40 water–ethanol systems. Its spectroscopic signatures are the groups of the IR-intensive bands around 800 and 1050 cm−1. In highly concentrated HCl solutions with the 1 : 40 water–ethanol ratio, a neutral Et(H)O···H+···Cl− complex exists. Copyright © 2013 John Wiley & Sons, Ltd.

Effects of concentration and temperature on the corrosion properties of the Fe–Ni–Mn alloy in HCl solutions

The electrochemical behaviour and corrosion resistance of glassy Fe68.6Ni28.2Mn3.2 (at%) specimens were studied in different concentrations of HCl solutions. The results indicated that the corrosion rate increased with increasing concentration of the HCl solutions. Electrochemical impedance spectroscopy results were analysed by fitting the experimental data to an equivalent circuit using the ZSim Demo program, and suitable equivalent circuit models were determined. The results obtained from the impedance and polarization measurements are in good agreement. The thermodynamic parameters were evaluated for the corrosion process and discussed.

Linear sweep voltammetry measurements and factorial design model of hydrogen production by HCl/CuCl electrolysis

CuCl electrolysis is considered a key process in the Cu–Cl cycle of hydrogen production where H2 gas is produced by oxidation of CuCl particles dissolved in concentrated HCl solution. A lower electrochemical cell voltage than water electrolysis is a significant advantage of CuCl electrolysis and makes this process attractive for hydrogen production. In order to achieve integration of the electrolysis process with hydrolysis and decomposition reactions of the Cu–Cl cycle, experimental development of this process and analysis of operational factors are presented in this paper. A lab-scale CuCl electrolysis unit is fabricated and the influence of operating parameters including HCl and CuCl concentrations, applied current density, temperature, and solution flow rates on the cell potential and hydrogen production rate are experimentally investigated and analyzed. The present test bench and measurement techniques are described for characterization of the experiment. A fractional factorial design is performed, based on design of experiment methods, to find a correlation between cell voltage and operation factors. The present model predicts the effects of various operating variables on the cell voltage to provide new insight into integration of the electrolysis process. Close agreement between measured and theoretical hydrogen production rate, with the current efficiency of about 93%, indicates high accuracy of the experimental tests.

Adsorption kinetic, isotherm and thermodynamic studies of Sr2+ onto hexagonal tungsten oxide

Hexagonal tungsten oxide (hex-WO3) with exchangeable sodium and ammonium cations located in hexagonal channel was synthesized by a facile hydrothermal treatment of sodium tungstate dihydrate in concentrated HCl solution in the presence of ammonium sulfate. An attempt was made to assess the potential of hex-WO3 for the adsorption of Sr2+ ions from acidic radioactive waste solutions. Adsorption of Sr2+ reached equilibrium very quickly in 2 h in acidic aqueous solution. Maximum removal of Sr2+ ions occurred at pH 4. Equilibrium studies showed that the extent of Sr2+ ions uptake by hex-WO3 was better described by the Freundlich isotherm in comparison with the Langmuir model. The thermodynamic parameters showed that the adsorption of Sr2+ ions onto hex-WO3 was spontaneous and exothermic under the studied conditions.

Ions with strong symmetric H-bonds and their solvation in aqueous-ethanolic solutions of HCl

Ion-molecular interactions in the HCl-EtOH-H2O system are studied by means of multiple frustrated total internal reflection IR spectroscopy over a wide range of concentrations of the components. It is demonstrated that, in the investigated solutions, the acid is fully bound into ions and uncharged complexes formed by strong symmetric or quasi-symmetric H-bonds. There is a competition between H2O and EtOH molecules during the formation of the (H5C2(H)O…H…O(H)C2H5)+, (H2O…H…OH2)+, and (H2O…H…O(H)C2H5)+ proton disolvates. In dilute solutions of HCl in 2: 1 and 1: 1 EtOH-H2O mixtures, (H2O…H…OH2)+ proton dihydrates are mainly formed, whereas in concentrated HCl solutions, under conditions of a partial solvation of ions by solvent molecules, predominantly (H2O…H…O(H)C2H5)+ mixed proton disolvates arise. In concentrated solutions of HCl in EtOH with low water content, the acid is partially bound into (H5C2(H)O…H+…Cl−) uncharged complexes with the participation of the Cl− anion.

Synthesis and properties of compounds of formamidindium disulfide with d-element tetrahalide anions

Products of reactions of salts of d elements with formamidine disulfide dihydrochloride (FDSH2Cl2) in concentrated HCl and HBr solutions were synthesized and characterized. The following compounds were obtained: FDSH2[CuCl4] · H2O, FDSH2[CoCl4], FDSH2[ZnCl4], FDSH2[HgCl4], and FDSH2[HgBr4]. The identity of these compounds was confirmed by X-ray diffraction; their compositions were derived from the results of chemical analysis and thermal analysis. The IR and Raman scattering spectra of the compounds indicate the presence therein of FDSH22+ cation. It was established that FDSH22+ transforms into formamidindium trisulfide cation (NH2)2C-S-S-S-C(NH2)22+ upon storage in air in hydrochloric acid solution.

Chromatographic isolation of carrier-free 103Pd from solutions of proton-irradiated rhodium

Ion-exchange behavior of Pd in microconcentrations (C Pd = 0.02–0.05 μg cm−3) and of Rh (C Rh = 2–15 μg cm−3) on Dowex-1×8 strongly basic anion exchanger (100–200 mesh) from HCl solutions of various concentrations was studied. The effect of oxidant (KBrO3) addition on the sorption of microamounts of Pd under these conditions was examined, and the optimal oxidant amount was determined. Based on the results obtained, a procedure was developed and implemented for the production of large amounts of carrier-free 103Pd of high chemical, radionuclidic, radioisotopic, and radiochemical purity for nuclear medicine.

CO and trans-cinnamaldehyde as corrosion inhibitors of I825, L80-13Cr and N80 alloys in concentrated HCl solutions at high pressure and temperature

In this paper, corrosion inhibition by chemisorbed CO, at high pressure and temperature, on a high-Ni ferrous alloy (Incoloy 825) and two high-Fe alloys (13Cr-L80 (Uniloy-420) and N80 steels) in very aggressive conditions (15% (w/w) HCl solution) is described. CO was either directly dosed into the electrolyte, or produced by dehydration of formic acid. It is shown that CO is a very good corrosion inhibitor, the inhibiting effect being even higher at high pressure and temperature than at normal pressure and room temperature. The effect of combining CO with a common acid corrosion inhibitor, trans-cinnamaldehyde (TCA), at high pressure and temperature, was also studied. Under these conditions, the polymerization of TCA may be favored, leading to a thin film on the metal surface that appears to serve as a barrier to corrosion. It was found that, when CO is used in combination with TCA, the inhibiting effect of the latter is considerably intensified.

Separating 2,3-butanediol from fermentation broth using n-butylaldehyde

In this paper, a complete separation process for 2,3-butanediol fermentation broth has been developed using reactive-extraction and reactive-distillation. n-Butylaldehyde can be used as both reactant and extractant in the process. Equilibrium and kinetics were studied on the reaction between 2,3-butanediol and n-butylaldehyde using different catalysts. Pseudo-Homogeneous model was used to describe the reaction behavior. The kinetic parameters were determined by analyzing experimental data. The results revealed that the reaction enthalpy ΔrH0=−21.58±1.63kJmol−1. The reaction rate was found to increase with increasing reaction temperature and had a linear correlation with catalyst amount. The activity energy for H2SO4 system and HCl system was 57.52±5.35 and 58.14±5.06kJmol−1, respectively. Feasible operation conditions have been obtained as follows: volume ratio of n-butylaldehyde to fermentation broth is 0.2; feed molar ratio of water and 2-propyl-4,5-dimethyl-1,3-dioxolane (n-butylaldehyde 2,3-butanediol acetal) for hydrolysis is 3.0; theoretical plate number for reactive-distillation column is 10 with concentration of HCl solution of 0.5mol/L. With the above conditions, more than 90% of 2,3-butanediol can be recovered from fermentation broth by reactive-extraction process and the purity of final product can be over 99%.