HF HCl Research Articles

Acid hydrolysis conditions for quantification of meningococcal X polysaccharide in a pentavalent vaccine using HPAEC-PAD/ESI-MS

A selective and sensitive method was evaluated for quantitation of meningococcal X (Men X) polysaccharide in pentavalent meningococcal A, C, W, Y and X conjugate vaccine using different acid hydrolysis conditions like HCl, TFA, HF, HF-TFA, and HF–HCl. High-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) using CarboPac PA10 column was used to identify the hydrolyzed products based on retention time and its comparison with monosaccharide standards. Complete release of glucosamine (GlcN) from Men X in monovalent bulk and pentavalent vaccine samples was achieved using HF hydrolysis at 80 °C for 2 h. The Men X HF-hydrolyzed polysaccharide to glucosamine along with the reference standard was identified using collision-induced dissociation (CID) electrospray mass spectroscopy and the MS/MS fragments of m/z 162, m/z 144 and m/z 84. Meningococcal polysaccharide concentration was determined with a correlation coefficient r2 >0.99 using polysaccharide reference standard. The serogroups A, W, and Y were converted to their monosaccharides units and quantified using this method however, milder acid hydrolysis 0.1 M HCl 80 °C 2 h for release of sialic acid for Men C polysaccharide was found to be more suitable. These methods will provide necessary tools and prove to be beneficial to laboratories developing new saccharide-based vaccine combinations.

Chemical processing of fossil phyllocarid cuticle: a comparison of micro- and macrofossil remains

Cuticular remains of the phyllocarid crustaceans Caryocaris? and Ceratiocaris? obtained via maceration of macrofossil remains in hydrofluoric acid are compared with dispersed fragments isolated using both the low-manipulation HF extraction and the standard HCl–HF–HCl method. The studied specimens were obtained from Ordovician and Silurian shales of the Šárka and Požáry formations (Prague Basin, Barrandian area, Czech Republic). This methodological approach allows a direct comparison of macrofossil remains with microfossils in residue. The differences in residues obtained through the two bulk-rock extraction methods are also discussed.

Effect of acidification on microscopic properties and pore structure of coal

Acidification is a common method for removing minerals from coal. In this study, four groups of acidification samples were evaluated: raw coal (Raw), hydrofluoric acid (HF), hydrochloric acid (HCl), and mixed HF–HCl acid (Mix) groups. The concentrations of ash and various elements in the sample groups were measured by industrial and elemental analyses. The Mix solution most effectively removed the minerals from coal, with an ash removal fraction of 87.87%. The microscopic characteristics of the four groups were studied using Fourier-transform infrared (FT-IR) and carbon nuclear magnetic resonance spectroscopy (13C NMR). The oxygen-containing functional groups of the coal samples increased after acidification by 76.07%, 14.49%, and 51.06% for the HF, HCl, and Mix groups, respectively. In addition, the content of aliphatic structures decreased during acidification. The adiposity of the Mix, HCl, and HF groups decreased by 16.36%, 8.50%, and 12.73 %, respectively. The results of CO2 and liquid nitrogen adsorption showed that the cumulative pore volume of the HF and Mix groups increased by 24.90% and 21.39%, respectively, while that of the HCl group decreased by 3.23% compared to the Raw group. The changes in the coal microstructures were observed for both micropores and mesopores. The aliphatic content was inversely proportional to the pore volume, whereas some oxygen-containing functional groups enhanced the pore volume. These findings contribute to the body of knowledge related to coal-seam acidification.

A novel purification method for fluoride or chloride molten salts based on the redox of hydrogen on a nickel electrode.

A novel purification process was proposed for molten salts based on the polarization of a hydrogen electrode on nickel, i.e., H+/H2, Ni electrode. The features of the H+/H2, Ni electrode in typical chloride and fluoride molten salts were investigated. Consistent current electrolysis was performed in a feasible polarization range, and the deoxidation efficiency was higher than that of the traditional chemical or electrochemical purification methods in both chloride and fluoride molten salts. Only H2 was used as a purification source gas, and almost no toxic HF or corrosive HCl emissions were used or occurred in the new process. The application range of the proposed method was also discussed.

Adsorption of Cu(II) on soil humin: batch and spectroscopy studies

Understanding the interactions of humic substances with metal ions is of great importance in forecasting the behaviors and fates of trace metals in the environment. Humin is the least understood humic substance fraction due to its close association with the mineral matrix in soil. In this study, humin was prepared from three zonal soils (i.e., dark brown soil, yellow brown soil, and latosol) in eastern China by demineralization using HF–HCl solution after removing alkaline-soluble humic substance fractions. The adsorption properties of Cu(II) onto both humin and humic acid were examined using batch and spectroscopy (SEM, EDS, FTIR, XPS, and XAS) techniques. With respect to humic acid, humin was more aliphatic and less polar. The adsorption kinetics of humin and humic acid were best fit with pseudo-second-order kinetics equation, and the adsorption isotherms were well depicted by the Langmuir model. However, the quantity of adsorbed Cu(II) on humin was inferior to that of Cu(II) adsorbed onto humic acid. After adsorption, the surface morphology of humin and humic acid changed. Carboxyl, hydroxyl, aromatic N, and primary amine N on the surfaces of the two humic substance fractions took part in Cu(II) adsorption, and Cu(II) was bound with O/N and C atoms via inner-sphere complexation. Our results suggested that humin and humic acid had different adsorption capacity but similar adsorption mechanisms toward Cu(II).

Analysis of morphological, optical and thermal properties of porous p-type indium phosphide p-InP(100) prepared by the vapor etching method

In this paper we report for the first time, the effect of halogenic acids (HCl and HF) on the morphological, optical and thermal properties of porous p-InP layers (p-InP-Ls). The samples were elaborated by a vapor phase etching (VE) method with two halogenic acids (1M HF and 1M HCl). The recording of the porous surfaces' morphology was carried out by Scanning Electron Microscopy (SEM). The porous p-InP-Ls formed using 1M HCl steam was found to have a micro-porous structure in which the pores were distributed on the p-InP(100) substrate. The UV-Visible spectrum revealed that the porous p-InP-Ls formed by 1M HCl steam displayed a greater absorbance capacity in the visible range than the other layer which is formed using 1M HF steam. In addition, it was found that the band gap energy (Eg) of porous p-InP-Ls formed by 1M HCl steam was greater (1.254 eV) than the unetched p-InP substrate (1.228 eV), which was attributed to the quantum size effect. FTIR spectrum showed the presence of peaks related to P-Cl bonds. The thermal conductivity and thermal diffusivity of the porous p-InP-Ls were determined by the photo-thermal deflection technique, which studies the variation of the photothermal signal with the square root of the modulation frequency. The result showed that the vapor of halogenated acids (especially HCl steam) clearly affected the thermal properties.

Investigation of change in different properties of sandstone and dolomite samples during matrix acidizing using chelating agents

Properties of rock, such as effective porosity, permeability and pore size distribution (PSD), are generally referred to as petrophysical properties. These properties are among the most significant for reservoir evaluation. Acid stimulation treatments are usually used in sandstones to mitigate the impact of formation damage, with the aim of restoring or enhancing the natural matrix permeability and consequently boosting the well productivity. Hydrochloric acid (HCl) is commonly used in the preflush stage to remove calcium and other metal ions, preventing the development of calcium fluoride (CaF2) and other silicate precipitates that could block the pore throats, while an acid mixture (HF–HCl combination) is usually preferred as the main stimulation fluid for the removal of quartz and remaining metal ions. However, sometimes the application of these acids can lead to other problems, including fast reactions, corrosion of pipes, environmental hazards, precipitation reactions and formation damage due to the incompatibility of HCl with clay minerals, so chelating agents have been proposed as an alternative for matrix stimulation fluids. In this study, three different chelating agents, ethylenediaminetetraacetic acid (EDTA), N-(2-hydroxyethyl) ethylenediamine-N,N′,N′-triacetic acid (HEDTA) and N-acetyl-l-glutamic acid (GLDA), have been used to stimulate Berea sandstone, Colton tight sandstone and Guelph dolomite samples. Core flood experiments were conducted on 1.5 × 3 (in2) core plugs, at a temperature below 180 °F. A slow injection rate of (1–0.5 cc/min) was chosen for the treatment fluid, promoting the dissolution of ions by increasing the contact time between the fluid and the rock. Furthermore, nuclear magnetic resonance, wettability and micro-computed tomography (CT scan) analyses were employed to evaluate the effect of the acid treatment on formation properties such as porosity, PSD, pore topology, wettability and pore structure. After exposing the samples to HEDTA, large wormholes were detected in their pore network, demonstrating that HEDTA has the highest potential to create new pore spaces when compared to GLDA and EDTA when reacted with both types of samples.

Nickel and its isotopes in organic-rich sediments: implications for oceanic budgets and a potential record of ancient seawater

Nickel (Ni) is a biologically active element that displays a nutrient-like depth distribution in the modern oceans. Recent studies of Ni isotopes have highlighted the fact that, in common with many other transition metals, the Ni stable isotope composition, expressed as δ60Ni, of the dissolved phase is heavier than the inputs, at +1.3 to +1.7‰. The sedimentary outputs that control the high δ60Ni of the ocean, coupled with records for past seawater, could potentially yield new information on the past Earth system, but these are currently not well understood. Here we present the first Ni abundance and isotope data for a key output, that associated with Ni uptake into organic matter, at productive upwelling regions and elsewhere. We investigate the distribution of Ni and its isotopes in two fractions separated from the bulk sediment, an HF-digestible fraction, extracted with HF–HCl, and an organic-sulphide-rich fraction. The organic-sulphide fractions exhibit a range in δ60Ni, from +0.86 to +1.83. Systematic relationships between Ni concentrations, total organic carbon and Ni isotopes suggest that the organic-sulphide fraction originates in the photic zone, and is delivered to the sediment as a closed system, despite the possibility of transfer of Ni to sulphide within it. Authigenic Ni in the bulk sediment is dominated by the HF-digestible fraction which, in Ni-enriched sediments where the detrital correction is small, is very close to the modern deep ocean, at δ60Ni = +1.2‰. These data suggest that organic-rich sediments beneath upwelling zones, while they are an important output flux of Ni from the oceans, do not solve the isotope balance problem because their δ60Ni is almost identical to modern seawater. On the other hand, the approach adopted here involving the analysis of the two fractions, both traces the fractionation imparted by biological uptake as well as recording the δ60Ni of contemporary seawater, suggesting potential for understanding the past oceans.

On The Mechanism of the Anisotropic Dissolution of Silicon in Chlorine Containing Hydrofluoric Acid Solutions

The wet-chemical acidic treatment of silicon wafer surfaces is very important in photovoltaic, microelectronic and further industries. Recent works report on new mixtures for acidic anisotropic etching mixtures based on hydrofluoric acid HF and hydrochloric acid HCl with an added oxidant. The aim of this work was to get an insight into the reactions during the etching process of silicon in the system HF-HCl-Cl2. The etching mixtures, gaseous reaction products, as well as the generated silicon surfaces were investigated by 19F, 29Si, and 35Cl NMR, ion chromatography (IC), iodometric titration, FT-IR spectroscopy, diffuse reflectance FT-IR spectroscopy (DRIFT) as well as scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDX). A reaction scheme for the anisotropic dissolution of silicon in chlorine containing aqueous HF-solutions is proposed, which involves dissolved Cl2 as the oxidizing agent, coordination of fluoride/chloride ions and formation of a hydrophilic surface. These steps are similar to the well known alkaline anisotropic etching of silicon.

Etching Silicon with Aqueous Acidic Ozone Solutions: Reactivity Studies and Surface Investigations

Aqueous acidic ozone (O3)-containing solutions are increasingly used for silicon treatment in photovoltaic and semiconductor industries. We studied the behavior of aqueous hydrofluoric acid (HF)-containing solutions (i.e., HF–O3, HF–H2SO4–O3, and HF–HCl–O3 mixtures) toward boron-doped solar-grade (100) silicon wafers. The solubility of O3 and etching rates at 20 °C were investigated. The mixtures were analyzed for the potential oxidizing species by UV–vis and Raman spectroscopy. Concentrations of O3 (aq), O3 (g), and Cl2 (aq) were determined by titrimetric volumetric analysis. F–, Cl–, and SO42– ion contents were determined by ion chromatography. Model experiments were performed to investigate the oxidation of H-terminated silicon surfaces by H2O–O2, H2O–O3, H2O–H2SO4–O3, and H2O–HCl–O3 mixtures. The oxidation was monitored by diffuse reflection infrared Fourier transformation (DRIFT) spectroscopy. The resulting surfaces were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectrosc...

Hydrogen production by methane cracking over Xiaolongtan lignite chars: The role of mineral matter

Hydrogen production by methane cracking over a set of demineralised Xiaolongtan lignite chars, with and without the addition of various inorganic species, has been studied using a fixed bed reactor at atmospheric pressure and 1123K in order to study the catalytic effect of mineral matter on methane cracking. The raw lignite char was prepared by pyrolysing a Xiaolongtan lignite sample in nitrogen in the fixed bed reactor at 1173K for 30min. Of the two demineralised chars, one (Char 1) was prepared by washing the parent lignite sequentially with 5N HCl, 29N HF and 12N HCl before pyrolysis while the other (Char 2) was prepared by washing the raw lignite char. For comparison, a variety of inorganic species were added into Char 1 via incipient impregnation. NaCl was added into Char 1 at a sodium content varying from 0.1wt% to 0.3wt%. CaCl2, FeCl3, KCl, and MgCl2 were also added into Char 1, respectively, with the corresponding metal content being 0.1wt% in the chars. The methane cracking experiments showed that hydrogen was the primary gas product. The demineralised chars were less effective in catalysing methane cracking than the raw char, suggesting that the mineral matter indeed promoted methane cracking. Char 2 showed higher catalytic activity than Char 1, due to its relatively higher mineral matter content and greater BET surface area. Carbon deposition during methane cracking resulted in deactivation of the chars by blocking the pores and reducing the surface areas. The added inorganic species at trace amounts in the demineralised Char 1 also enhanced the methane conversion and hydrogen yield. With increasing sodium addition up to 0.3wt%, the catalytic effect of the char increased first and then decreased. In terms of the methane conversion, the catalytic effect of the inorganic species added into Char 1 followed the order of NaCl>CaCl2≈FeCl3>MgCl2≈KCl. However, the various inorganics showed no difference in enhancing hydrogen yield.

The Removal of Titanium from Metallurgical Silicon by HF–HCL Leaching

The removal of titanium from metallurgical grade silicon (MG-Si) by HF–HCl leaching was investigated as a function of leaching time, temperature, particle size, and acid concentration. It was found that the extraction of titanium from MG-Si increased with a decrease in particle size and increase in hydrofluoric acid concentration. Titanium removal was improved very little by increasing temperature and hydrochloric acid concentration. The removal of titanium by HF–HCl took place rapidly. It was possible to remove 97% of the Ti after 0.5 h of leaching. A maximum of 99% of the Ti was removed by leaching MG-Si with 3% hydrofluoric acid and 2% hydrochloric acid at room temperature for 5 h. The main titanium-bearing Intermetallic compound in MG-Si is FeTiSi2, which cannot be attacked by hydrochloric acid but can be activated by it. Titanium is more easily removed from FeTiSi2 by hydrofluoric acid if this phase is first activated by hydrochloric acid.

Trace metals in Daihai Lake sediments, Inner Mongolia, China

A total of 29 surface sediments were collected from the Daihai Lake, China. Concentrations of metals (Cu, Pb, Zn, and Cd) were determined using HR-ICP-MS after digestion with the mixture of HNO3–HF–HCl (aqua regia), and chemically fractionated according to the modified the European Community Bureau of Reference sequential extraction procedure. Total organic carbon contents and grain size were also analyzed. Average concentrations (ppm) for Cu (39.4 ± 10.6), Pb (29.9 ± 6.1), Zn (102.6 ± 23.3), and Cd (0.21 ± 0.07) were found in the sediments. The concentrations of metals are relatively higher in the central area of lake, while lower nearby the area with a shallower water depth. Sequential extraction results show that Cu and Zn are mainly distributed in the residual fraction, while Cd is dominantly in the non-residual fraction. Enrichment factor values and geoaccumulation indexes suggest that there are not obvious enrichments of Cu, Pb, and Zn in the sediments, but Cd pollution can be found in most of the area of Daihai Lake. The sources for Cu, Pb, and Zn are attributed to atmospheric deposition, which might be mainly associated with coal combustion. Agricultural runoff in polluted soils and coal combustion might be main sources of the Cd pollution in the lake.

Optimized Demineralization Technique for the Measurement of Stable Isotope Ratios of Nonexchangeable H in Soil Organic Matter

To make use of the isotope ratio of nonexchangeable hydrogen (δ(2)H(n (nonexchangeable))) of bulk soil organic matter (SOM), the mineral matrix (containing structural water of clay minerals) must be separated from SOM and samples need to be analyzed after H isotope equilibration. We present a novel technique for demineralization of soil samples with HF and dilute HCl and recovery of the SOM fraction solubilized in the HF demineralization solution via solid-phase extraction. Compared with existing techniques, organic C (C(org)) and organic N (N(org)) recovery of demineralized SOM concentrates was significantly increased (C(org) recovery using existing techniques vs new demineralization method: 58% vs 78%; N(org) recovery: 60% vs 78%). Chemicals used for the demineralization treatment did not affect δ(2)H(n) values as revealed by spiking with deuterated water. The new demineralization method minimized organic matter losses and thus artificial H isotope fractionation, opening up the opportunity to use δ(2)H(n) analyses of SOM as a new tool in paleoclimatology or geospatial forensics.

White-light-emitting Liquefiable Silicon Nanocrystals

Abstract White-light-emitting silicon nanocrystals (Si NCs) have been prepared from Si powder through a facile route including HF–HCl etching. Owing to a broad size distribution, the light emission spectrum covers the whole visible wavelength range with full width at half-maximum (FWHM) of 230 nm. Covalent attachment of octyl monolayers to the Si surface changes the physical nature of the NCs from a solid into a solvent-free liquid, and affords them high thermal stability of photoluminescence (PL) even under ambient conditions.

The effect of pyridine treatment on phase Q: Orgueil and Allende

Abstract– Marrocchi et al. (2005) reported that low‐temperature fractions of heavy noble gases were largely removed upon pyridine treatment of the Orgueil CI meteorite. As pyridine is known to induce the swelling of the macromolecular network of organic matter, they concluded that the low‐temperature phase Q is macromolecular organic carbon. However, Busemann et al. (2008) showed that pyridine had no significant effect on the noble gas contents for other very primitive meteorites, such as CM and CR. Therefore, we prepared an HF–HCl residue and the pyridine‐treated residue of Orgueil, and re‐examined the results of Marrocchi et al. (2005) by analyzing all noble gases. We confirmed that heavy noble gases are surely removed by the pyridine treatment, but the degree of the loss of heavy noble gases is generally small, and is even smaller for the lighter noble gases. Furthermore, we could not observe the evidence of Xe isotopic ratios by removing only phase Q after the pyridine treatment. We further prepared the HF–HCl residue and the pyridine‐treated residue of the Allende CV3 meteorite and performed noble gas analyses. For Allende, there is no significant change in the elemental abundances after the pyridine treatment. These results suggest that only Orgueil is special, and it is likely that the gas loss of the Orgueil residue is due to the loss of some kind of organic matter that was formed and that adsorbed the fractionated Q and HL gases during the aqueous alteration within the parent body of Orgueil.

An attempt to characterize phase Q: Noble gas, Raman spectroscopy and transmission electron microscopy in residues prepared from the Allende meteorite

We have prepared a HF–HCl residue and its oxidized residue of the Allende meteorite and have measured the elemental concentrations and the isotopic compositions of noble gases. In the HF–HCl reside, noble gases are enriched in colloidal fraction compared to the non-colloidal fraction by a factor of 2–4. The heavy noble gases were evidently lost after the oxidization, indicating that phase Q (carrier of planetary heavy noble gases) was removed by the oxidation. The Raman spectroscopic parameters show that the colloidal fraction of the HF–HCl residue is more amorphous compared to the non-colloidal fraction. As the ion irradiation converts carbon into a more amorphous form, our result indicates that the “plasma model” is more plausible than the “labyrinth model” as the origin of phase Q. TEM (Transmission Electron Microscope) observations also show such a trace of ion irradiation. While the TEM observations did not show any large difference between the HF–HCl residue and its oxidized residue, the Raman spectroscopic parameters changed discretely resulting from the oxidization. This observation indicates that the oxidization not only dissolved and removed oxidized carbon, but also changed the carbon structure itself to a more amorphous (disordered) state. The Raman spectroscopic results indicate the possibility that release of Q-gas during oxidation is not accompanied by mass loss and that the release of Q-gas simply resulted from rearrangement of carbon structure during oxidation.

The effect of acidification on the determination of elemental carbon, char-, and soot-elemental carbon in soils and sediments

We studied the influence of acid pretreatment on the effective distinction between elemental carbon (EC) and organic carbon (OC), and between char-EC and soot-EC. Though widely employed in the pretreatment of soils and sediments for EC quantification, the use of HCl, HF, and HNO 3 could decrease soot thermal stability as acid remains, leading to an underestimation of soot-EC by thermal methods. We compared thermal optical reflectance (TOR) measurements of EC concentrations in char reference materials and in lacustrine and marine sediments following pretreatment with various acids. The results showed that pretreatment with 2 M HCl, concentrated HNO 3, 7 M HNO 3, and 1 M HNO 3 did not result in EC oxidation. However, hot concentrated HNO 3 oxidized EC significantly, leading to lower concentrations of EC, char-EC and soot-EC. By comparing the removal of potentially interfering materials, which contain little fire-derived carbon, with different acid pretreatments, we recommend the HCl–HF–HCl and concentrated (not hot) HNO 3–HF–HCl pretreatments for the determination of EC, char-EC, and soot-EC in soils and sediments using the TOR method.

Stabilisation of HF soluble and HCl resistant organic matter in sloping tropical soils under slash and burn agriculture

Soil organic matter (SOM) stabilisation on tropical sloping land can be influenced by slash burning and erosion processes. However, information on the behaviour of potentially stable components of organic matter on burned sites is scarce. This study is focused on organic matter soluble after demineralisation of the samples with hydrofluoric acid (HF soluble) and organic matter remaining after hydrolysis with hydrochloric acid (HCl resistant), which are both part of the potentially stabile OM fraction in tropical soils. The objective was to examine their contribution to carbon stabilisation along a toposequence of soil profiles sampled in a small cultivated catchment in Northern Laos with slash burning as common agricultural practice. Bulk soil as well as residues after acid hydrolysis using HCl have been analysed for chemical composition and mean residence time of SOM. The tropical soils showed similar amounts of HF soluble and HCl resistant OC, representing between 20 and 60% of the total OC of the soils. OC stabilisation at the sites is chiefly determined by mineral interactions as shown by the good correlations of the clay and the HF soluble OC contents with 14C activity. Analysis of the chemical structure by solid state 13C nuclear magnetic resonance spectroscopy ( 13C CPMAS NMR) showed that aromatic carbon contributes substantially to HCl resistant organic matter. The 14C activity of the hydrolysis residue was lower compared to the untreated soil, reaching a 14C age of around 1000 years B.P. in B horizons. This is consistent with the observation that chemical recalcitrant black carbon, produced by slash burning, may remain on site for a long time, once it is incorporated into the mineral soil.

Determination of heavy metals in soils and sediments by microwave-assisted digestion and inductively coupled plasma optical emission spectrometry analysis

The determination of the total content and the leachable aliquot by aqua regia dissolution of eight heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) in soils and sediments was developed by microwave digestion technique combined with inductively coupled plasma atomic emission spectrometry. A complete digestion of soils and sediments was achieved by using an acid mixture of HF–HCl–HNO 3 (1:3:1); the microwave-irradiated closed vessel system used for the determination of aqua regia leachable quota, proved to be a viable alternative to the traditional reflux system. The experimental study was conducted using five BCR standard reference materials (CRM 141R ‘Calcareous Loam Soil’, CRM 142 ‘Light Sandy Soil’, CRM 143 ‘Sewage Sludge Amended Soil’, CRM 277 ‘Estuarine Sediment’ and CRM 320 ‘River Sediment’) in two laboratories with different microwave ovens and ICP-OES. Calculated recovery, repeatability, and reproducibility confirm the good performance of the procedures adopted. A Nested Design statistical analysis was carried out for both procedures and showed that the major source of variability in the analysis was due to ICP-OES measurements rather than microwave-assisted dissolution.