Weak Acid Solution Research Articles

Investigating the Effects of Surface Adsorbates on Gold and Palladium Deposition on Carbon

Surface functional groups have a strong influence on the deposition and final state of nanoparticles adsorbed on to the surface, a role discussed by Professor Spencer in his work. This tribute to Spencer explores the formation of hydroxyls, thiosulfates, sulfites and sulfur atoms on carbon (HOPG) surfaces and their effect on the deposition of gold and palladium from aqueous solutions. Hydroxyls formed from ammonium hydroxide treatment have identical behaviour to those formed by acid treatment, and gold adsorption from Au3+ solutions gives Au0 initially, with Au3+ formed at higher concentrations on these surfaces. In contrast, palladium adsorption is hindered by the presence of the hydroxyls and there is no indication of any reduction to the metallic state. Ammonium thiosulfate adsorbs dissociatively from aqueous solutions on HOPG if the surface is pre-activated by the presence of surface hydroxyls. At low concentrations of ammonium thiosulfate, adsorbed sulfite and sulfur are formed in equimolar concentrations whereas adsorption of high concentrations of ammonium thiosulfate gives some degree of molecular adsorption, with evidence in XP spectra for an ammonium ion and a sulfur 2p peak at 282.9 eV attributed to the undissociated thiosulfate ion. Both sulfur and the sulfite are stable at the surface in neutral solutions but the sulfite desorbs when treated with acidified solutions (~ pH ≤ 6). These two groups are also stable at 373 K but begin to desorb by 473 K. Exposure to a weak chloroauric acid solution causes the desorption of the sulfite and formation of a gold species with an XP binding energy of 84.6 eV; we cannot determine from the present data whether this peak is due to a Au(I) state or very small nanoparticles of Au(0).Graphic

Alpha energy dependence of alpha induced liquid radioluminescense

The presence of alpha radiation causes weak nitric acid solutions to emit ultraviolet light.

Extraction of impurities from phosphorite ore in concentration and processing

The article presents a review of the reports on the composition and properties of phosphorite ore from the Polpino deposit and on the problems connected with the ore processing by dry fractional crushing–sifting separation. The content of impurities in this ore exceeds the standard, which eliminates technological capability of straight sulfuric acid treatment of the ore for wet-process phosphoric acid production. The attempted wet processing of the ore by solutions of weak organic acids, selected because of their availability, regenerative capacity and environmental safety, is described. It is found that the organic acids are lo w-effective in extraction of alkaline-earth metal impurities: extraction is not higher than 3.5 and 9.5 % with acetic and formic acids, respectively; total recovery of Al2O3 and Fe2O3 is not higher than 2.0 and 8.0 %, and is factually independent of concentration of the acids. The authors prove straight processability of phosphorite ore by sulfuric acid treatment with production of compound fertilizers, including selective removal of impurities and carbonate minerals, and controlled recovery of iron and aluminium. The optimization parameters of the process are concentration of nitric acid, the acid–ore interaction time and temperature. These parameters should ensure complete extraction of the target component to solution (99.0 %), as well as controlled removal of iron impurities (18.0–20.0 %) and aluminium impurities (31–32 %), which have an adverse influence on rheological properties of suspensions. Thus, the article proves technological capability of straight processing of Polpino phosphorite resources containing Р2О5–15.3 %, CaO–27.42 %, MgO–0.95 %, Fe2O3–2.58 % and Al2O3–3.65 % without pretreatment.

Chronic Metabolic Acidosis Elicits Hypertension via Upregulation of Intrarenal Angiotensin II and Induction of Oxidative Stress

Chronic metabolic acidosis (CMA) can be a consequence of persistent hypertension but could potentially play a role in invoking hypertension. Currently, there is a scarcity of studies examining the outcome of induced chronic acidosis on blood pressure regulation. This study investigates CMA as a cause of hypertension. Chronic acidosis was induced in Sprague Dawley rats (100–150 g) by providing a weak acid solution of 0.28 M ammonium chloride (NH4Cl) in tap water for 8 weeks. To determine whether the rats were acidotic, blood pH was measured, while blood pressure (BP) was monitored by tail-cuff plethysmography weekly. Rats were divided into five groups: control, CMA, CMA ± spironolactone, captopril, and tempol. Serum sodium and potassium; renal interstitial fluid (for Angiotensin II concentration); and kidney proximal tubules (for Na+/K+ ATPase- α1 concentration) were analyzed. Reactive oxygen species (ROS) were detected in renal cortical homogenates using electron paramagnetic resonance (EPR). In the CMA rats, a sustained elevation in mean arterial pressure (MAP) associated with a significant decrease in blood pH was observed compared to that of control over the 8 weeks. A significant decrease in MAP was observed in acidotic rats treated with captopril/tempol, whereas spironolactone treatment caused no decrease in MAP as compared to that of the CMA group. The interstitial angiotensin II was increased in the CMA group but decreased in the CMA with captopril and tempol groups. In addition, the urinary sodium was decreased, and the serum sodium levels increased significantly in the CMA groups as compared to that of control. However, the acidotic groups with captopril and tempol showed reduced levels of serum sodium and an elevation in urinary sodium as compared to that of the CMA group. In addition, there was a significant increase in plasma renin and no change in plasma aldosterone in the CMA group with no significant differences in plasma renin or aldosterone observed during spironolactone, captopril, or tempol treatments. The increased expression of Na+/K+ ATPase-α1 in the CMA group suggests that active transport of Na+ to the blood could be causative of the observed hypertension. Furthermore, the EPR analysis confirmed an elevation in superoxide (O2-) radical levels in the CMA group, but the tempol/captopril treated acidotic groups showed less (O2-) compared to that of either the CMA group or control. Taken together, our data suggest that induction of CMA could potentially be causative of hypertension, while the mechanisms underlying the increased BP could be through the activation of intrarenal Ang II and induction of oxidative stress.

Comparison of Extraction Ability between a Mixture of Alamine 336/Aliquat 336 and D2EHPA and Ionic Liquid ALi-D2 from Weak Hydrochloric Acid Solution

The development of extraction systems to improve the extraction efficiency of metals using commercial extractants and ionic liquids is of importance. The extraction behavior of Co(II) between mixture of Alamine 336/Aliquat 336 and D2EHPA and synthesized ionic liquid ALi-D2 was compared in this work. Some factors, such as equilibrium pH, properties of the extractants, and concentration of components in the mixture had a remarkable effect on the extraction of Co(II). The interactions occurring in the mixtures as well as the change in solution pH were analyzed. Co(II) was completely extracted by ionic liquid when equilibrium pH was higher than 6.5, while it was difficult to extract Co(II) by employing the mixture of D2EHPA and Alamine 336/Aliquat 336. The formation of ionic liquid in the mixture of D2EHPA and Aliquat 336 was verified through FT-IR spectra. In addition, the competition extraction of hydrogen ion and Co(II) by ionic liquid ALi-D2 was explained. Among the three kinds of extractants, the ionic liquid showed the best extraction efficiency for Co(II) and pH control from weak acidic solutions. The present study provides valuable information on the extraction behavior of metal ion by the mixtures of commercial extractants, and thus can give some light on the development of metal extraction systems.

Polymeric copper(II) diethylenetriaminepentaacetates for gas adsorptions

A series of copper(II) diethylenetriaminepentaacetates [Cu(H4dtpa)Cl]·KCl·3.5H2O (1), Kn[Cu(H2dtpa)]n·2nH2O (2), K3[Cu(dtpa)]·3H2O (3) and Kn[Cu2(dtpa)]n·4nH2O (4) (H5dtpa = N,N,N′,N″,N″-diethylenetriamine-pentaacetic acid) have been obtained from the direct reactions of copper(II) chloride with diethylenetriaminepentaacetic acid in acidic or weak acidic solutions. pH values show obvious impacts for the coordination modes of DTPA with the formations of monomer, one dimensional (1D) and three dimensional (3D) structures respectively. The four complexes are well characterized by elemental analysis, IR, X-ray structural analyses and theoretical bond valence calculations. There exist free carboxy and amino groups in 1, which indicates that strong acidity can weaken the coordination of DTPA. Complex 4 is a 3D metal organic framework with small holes of diameter 3.3 Å, which can adsorb oxygen for 12.83 mg/g under 29.9 bar. It is thermal stable up to 150 °C based on simulated and experimental XRD patterns.

Carboxyl-functionalized biochar derived from walnut shells with enhanced aqueous adsorption of sulfonamide antibiotics

The novel HNO3-modifitied biochar (NBC) was synthesized from walnut shell. The NBC was characterized from scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectrum. The NBC was then used in the adsorption of sulfadiazine, sulfamethazine and sulfachloropyridazine from aqueous solution. The material surface has carbon/oxygen-contained groups, which is benefit for the adsorption. The results showed the adsorption ability of NBC on three sulfonamides were 32, 46, and 40 mg g−1, respectively. The kinetic was found to follow the Elovich model and the isotherm conformed Freundlich. Adsorption was more favorable at weak acidic solution. The interactions mainly include π-π EDA, electrostatic interaction, Lewis acid-base interaction, hydrophobic interaction and H-bond.

Stabilization of heavy metals in municipal solid waste incineration fly ash via CO2 uptake procedure by using various weak acids

Among various kinds of methods for the stabilization of heavy metals in municipal solid waste incineration fly ash (MSWI FA), acid leaching is the most prevalent. However, the process of heavy metals leaching in MSWI FA by various acids must be compared. In this study, we extracted the heavy metals in MSWI FA using 0.5 M solutions of strong acids (HCl, H2SO4 and HNO3), as well as weak acids (NH4Cl, (NH4)2SO4 and NH4NO3). Solidification by CO2 injection occurred in all the leaching solutions. The leaching test was performed for solids such as treated MSWI FA and the precipitates produced in the solidification process, compared with untreated MSWI FA. The solids were analyzed by using X-Ray fluorescence spectroscopy, X-Ray diffraction, and scanning electron microscopy. The leaching solutions were analyzed by inductively coupled plasma-optical emission spectroscopy. Using weak acid solutions, Zn, Pb, and Cu were leached 15–70 times, two times, and 20–150 times, respectively, more than those leached strong acids. Except H2SO4 and (NH4)2SO4 solutions, all the acids reduced the mass of MSWI FA and extracted heavy metals. The crystalline precipitates were the carbonates. HNO3 solution was found to be the most appropriate solvent for the proposed method.

Mechanisms of Hydrogen Evolution in Weak Acid Solution Investigated By Using EIS

EIS was used in this mechanistic study of the electrochemical reaction mechanisms associated with corrosion of mild steel in the presence of weak acids, such as carbonic acid found in CO2 saturated aqueous solutions. Over the past decade, comprehensive mechanistic studies using DC electrochemical techniques have indicated that direct reduction of carbonic acid is not a significant reaction in CO2 aqueous solutions, contrary to what the conventional wisdom was for a long time. The new results suggest that the only cathodic reaction is hydrogen reduction, and that the main role of carbonic acid is to increase the limiting current by the so-called buffering effect. However, the problem is that the same limiting current is obtained theoretically whether one assumes that the direct reduction of carbonic acid or the buffering effect is true. Therefore, by using DC electrochemical techniques it is impossible to distinguish these two mechanisms in the limiting current region which is always seen in the polarization sweeps. An attempt has been made here to use the EIS technique to identify the role of carbonic acid in accelerating the cathodic reaction. Results indicate that the buffering effect is dominant, as recently proposed.

Solvent Extraction Separation of Co(II) and Ni(II) from Weak Hydrochloric Acid Solution with Ionic Liquids Synthesized from Organophosphorus Acids

Solvent Extraction Separation of Co(II) and Ni(II) from Weak Hydrochloric Acid Solution with Ionic Liquids Synthesized from Organophosphorus Acids

THE DEVELOPMENT OF THE METHOD FOR THE DETERMINATION OF SULFONAMIDES AND TRIMETOPRIM RESIDUAL QUANTITIES IN MILK SAMPLES BY UPLC-MS/MS METHOD AND ITS VERIFICATION THROUGH INTERLABORATORY TESTING

This manuscript presents the results of development and adoption of the confirmatory UPLC- MS/MS method for determination of sulfonamides and trimethoprim residues in whole and powdered cow's milk samples. Sample preparation includes a recovery with water (in the case of milk powder), separation of milk fat by centrifugation at 4 °C, proteins precipitation with acetonitrile using ultrasonic intensification, extraction of analytes with a two-component mixture of organic solvents from weak acidic phosphate buffer solution, concentration of obtained extracts, degreasing and reconstitution with the mobile phase. The use of tandem-mass spectrometric detector in multiple reaction monitoring mode provides high specificity for all ten sulfonamides, which molecules contain the same structural elements, and trimethoprim, as three ion transitions were used for each of the target analytes. The approach of matrix matched calibration on the milk matrix was applied, and it allowed us to disregard taking into consideration the absolute extraction of analytes during sample preparation, as well as the influence of sample matrix components on analytes ionization. The main advantages of the developed technique are simplicity, rapidity and cost effective sample preparation, fast procedure of sample analysis (the time of chromatographic separation is 2.0 min), high selectivity, and sensitivity at the level of ≤ 0.5 μg/kg (as compared with the maximum residues level of sulfonamides in dairy products, viz. 100 μg/kg). According to the European Commission Decision 2002/657/EC, the values of CCα and CCβ for sulfonamides and trimethoprim in milk were calculated. The capability of the method was confirmed on the basis of the established validation parameters, using spiked milk samples and "added – found" approach. The method was tested during the analysis of spiked samples of whole and powdered cow's milk (CV ~ 20%). The developed technique was verified by interlaboratory comparative testing of milk powder samples for sulfonamides content. The UPLC-MS/MS method for the determination of sulfonamides and trimethoprim residues in whole and milk powder samples can be used both for routine laboratory analysis of dairy products and for the examination of suspicious or questionable samples.

Effect of mechanical stress on electrochemical corrosion of X65 carbon steel in CO2 saturated brine

Abstract Applied mechanical stress could accelerate the chemical or electrochemical process of metal corrosion in weak acid solution. Series of experimental tests were conducted in this research. The results show that there is no obvious correlation between OCP (open circuit potential) values and applied stresses. However, The LPR (linear polarization resistance)corrosion rate increased intensively under the applied stress of 400 MPa. Correspondingly, the EIS (electrochemical impedance spectroscopy) Nyquist diagrams show that all of the plots contain a semicircle over the whole frequency range and the semicircle size decreased with increasing applied stress. The real-time corrosion current square waves triggered by the mechanical stress were successfully monitored by using the potentiostatic method in CO2 saturated brine under 200 mv (above OCP), flow and lower pH condition. This result is significant for many research fields, such as petrochemistry, aerospace and nuclear industries, which suffer weak acid corrosive environment.

Polymerization and Transformation of Tungsten(VI) Species in Acidic Aqueous Solution by Electrospray Ionization Time-of-Flight Mass Spectrometry

Deep understanding of the polymerization and transformation of tungstate species in aqueous solution is of great significance for hydrometallurgical and chemical separation processes, such as solvent extraction, membrane separation and crystallization. In order to study the polymerization and transformation of tungstate species, the semi-quantitative characterization method of electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was developed. In this paper, the tungsten speciation in simulative leaching solution was investigated in detail between pH 2.5 and 7 under various conditions (e.g. acid species, initial concentration, pH), and the results indicated that HCl was more conducive than HNO3 for the polymerization of tungsten at the same pH, and HAc accelerated the polymerization of tungsten species, especially in acid solution at lower pH; the morphological changes of each tungsten species tended to be consistent with the increase of tungsten concentration; pH strongly influenced the distribution of tungsten species. Then, the polymerization and transformation laws of tungstate species are summarized. W1 (monomers) are dominant species in weak acid and neutral solution, and aggregate into oligomeric species (e.g. W2, W4, W6). Transformations also exist among W2, W4 and W6. The polymerization process from W4 and W6 species to higher poly-tungstate (W10–12) was observed with the consumption of H+. This work aims to understand the polymerization and transformation of tungsten speciation using ESI-TOF-MS, which should provide useful information for the understanding and optimizing of industrial production and environmental processes, building a bridge between micro tungsten speciation and macro industrial applications.

Direct observation of transient species generated from protonation and deprotonation of the lowest triplet of p-nitrophenylphenol

Photo-induced proton coupled electron transfer (PCET) is essential in the biological, photosynthesis, catalysis and solar energy conversion processes. Recently, p-nitrophenylphenol (HO-Bp-NO2) has been used as a model compound to study the photo-induced PCET mechanism by using ultrafast spectroscopy. In transient absorption spectra both singlet and triplet states were observed to exhibit PCET behavior upon laser excitation of HO-Bp-NO2. When we focused on the PCET in the triplet state, a new sharp band attracted us. This band was recorded upon excitation of HO-Bp-NO2 in aprotic polar solvents, and has not been observed for p-nitrobiphenyl which is without hydroxyl substitution. In order to find out what the new band represents, acidic solutions were used as an additional proton donor considering the acidity of HO-Bp-NO2. With the help of results in strong (~10−1 mol/L) and weak (~10−4 mol/L) acidic solutions, the new band is identified as open shell singlet O-Bp-NO2H, which is generated through protonation of nitro O in 3HO-Bp-NO2 followed by deprotonation of hydroxyl. Kinetics analysis indicates that the formation of radical O-Bp-NO2 competes with O-Bp-NO2H in the way of concerted electron-proton transfer and/or proton followed electron transfers and is responsible for the low yield of O-Bp-NO2H. The results in the present work will make it clear how the 3HO-Bp-NO2 deactivates in aprotic polar solvents and provide a solid benchmark for the deeply studying the PCET mechanism in triplets of analogous aromatic nitro compounds.

Larvicidal Activity of Inorganic Salts Against Anopheles Stephensi and Culex Quinquefasciatus

Mosquitoes transmit serious human diseases, causing millions of deaths worldwide every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. In this study, the larvicidal bioassays for activities of aqueous solutions of weak acid [(NH4)2SO4 and NaH2PO4] and weak base (Na2CO3 and NaHCO3) inorganic salts against late instar larvae of disease vectors Anopheles stephensi and Culex quinquefasciatus were carried out under laboratory settings. The four inorganic salts showed varied levels of larvicidal activities after 24 h-exposure on Anopheles stephensi and Culex quinquefasciatus larvae in a dose-dependent fashion. However, the larvicidal activities were relatively higher in Na2CO3 (LC50 = 3162 and 447 ppm) and NaHCO3 (LC50 = 5623 and 398 ppm) solutions as compared to those in (NH4)2SO4 (LC50 = 7943 and 1995 ppm) and NaH2PO4 (LC50 = 7943 and 7120 ppm). The present study showed that the inorganic salts Na2CO3, NaHCO3, (NH4)2SO4 and NaH2PO4 could serve as potential larviciding agents considering their low toxicity. Therefore, this study provides a first report on the larvicidal activity of the inorganic salts on mosquito larvae of disease vectors.

Effect of mechanical stress on electrochemical corrosion of X65 carbon steel in CO2 saturated brine

Abstract Applied mechanical stress could accelerate the chemical or electrochemical process of metal corrosion in weak acid solution. Series of experimental tests were conducted in this research. The results show that there is no obvious correlation between OCP (open circuit potential) values and applied stresses. However, The LPR (linear polarization resistance)corrosion rate increased intensively under the applied stress of 400 MPa. Correspondingly, the EIS (electrochemical impedance spectroscopy) Nyquist diagrams show that all of the plots contain a semicircle over the whole frequency range and the semicircle size decreased with increasing applied stress. The real-time corrosion current square waves triggered by the mechanical stress were successfully monitored by using the potentiostatic method in CO2 saturated brine under 200 mv (above OCP), flow and lower pH condition. This result is significant for many research fields, such as petrochemistry, aerospace and nuclear industries, which suffer weak acid corrosive environment.

Instant Self-Assembly Peptide Hydrogel Encapsulation with Fibrous Alginate by Microfluidics for Infected Wound Healing.

Infected wounds caused by persistent inflammation exhibit poor vascularization and cellular infiltration. In order to rapidly control the inflammatory effect and accelerate wound healing, it is necessary to develop a novel drug vehicle addressing the need for infected wounds. Herein, we developed a novel dual-drug delivery system with micrometer-scale alginate fibers encapsulated in instant self-assembly peptide hydrogel. Short peptides with the sequence of Nap-Gly-Phe-Phe-Lys-His (Nap-GFFKH) could self-assemble outside the microfluidic-based alginate microfibers in weak acidic solution (pH ≈ 6.0) within 5 s. The gelation condition is close to the pH environment of the human skin. We further constructed recombinant bovine basic fibroblast growth factor (FGF-2) in fibrous alginate, which was encapsulated in antibiotic-loaded peptide hydrogel. The dual-drug delivery system exhibited good mechanical property and sustained release profiles, where antibiotic could be rapidly released from the peptide hydrogel, while the growth factor could be gradually released within 7 days. Both in vitro antibacterial experiments and in vivo animal experiments confirmed that such a dual-drug delivery system has good antibacterial activity and enhances wound healing property. We suggested that the dual-drug delivery system could be potentially applied for controlled drug release in infected wound healing, drug combination for melanoma therapy, and tissue engineering.

Fe-quaterpyridine complex: a comprehensive DFT study on the mechanism of CO2-to-CO conversion

Catalytic conversion of carbon dioxide can solve many of the environmental problems caused by it. Iron-quaterpyridine is one of the most promising class of CO2-to-CO conversion molecular catalysts. In the present investigation, the geometry, electronic structure and catalytic property of iron-quaterpyridine complex [FeX(qpy)]X+ (X = 0–2) were explored theoretically with density functional theory (DFT). It is found that both monovalent and neutral iron-quaterpyridine complexes can bind and activate carbon dioxide in weak acid solution effectively, but Fe0(qpy) can generate inactive metal-carbonyl species Fe0(qpy)CO after activating carbon dioxide, resulting in catalyst deactivation. With respect to [FeI(qpy)]+, the catalyst can be recovered as CO in [FeI(qpy)]+CO is easy to release. Otherwise, the extra electrons will make it deeply reduced to the inactive species Fe0(qpy)CO. Furthermore, the photo-physical properties of some species involved in the reaction were investigated theoretically with time-dependent density functional theory (TD-DFT). The current investigation provides further insight into the adsorption and catalytic properties of iron-quaterpyridine complex toward CO2 activation, which plays a crucial role in the activation of CO2. In Fe0(qpy)CO2, the two oxygen atoms have negative charges of − 0.780 and − 0.754 e, respectively, and there is a very negative electrostatic potential (MESP) near the two oxygen atoms, which means the oxygen atom in neutral Fe0(qpy)CO2 adduct should be more easily to bind with H+ ion in acid solution.

Introducing Iterative Methods to Undergraduate Chemistry Students—A Spreadsheet-Based Approach

A bachelor’s degree program in chemistry typically starts with basic concepts in mathematics, physics, and chemistry. Those principles are very important because they pave the ground for future advanced studies and, therefore, one needs to present them in a clear but rigorous way. One example is provided by the mathematical notion of an iterative process which acquires a significant relevance in chemistry. The popular Newton–Raphson algorithm has been selected to exemplify how iterative methods work as it is highly effective and suitable for undergraduate students. Additionally, this work presents a straightforward and interactive pedagogical tool, created with the widespread Microsoft Office Excel, which can be applied in a classroom to solve nonlinear equations numerically. Four pervasive topics in undergraduate programs are given to illustrate the importance of iterative processes, namely the calculation of pH of a weak acid solution, the molar volume of a real gas, the molecular geometry delivered by VSEPR theory, and the conformational analysis of 1,2-dichloroethane molecule.

Recycled indium tin oxide transparent conductive electrode for polymer solar cells

Reuse of electrode substrate is one of the most important schemes to reduce the cost and thus promote the application of polymer solar cells. The present paper developed a procedure for cleaning the surface of indium tin oxide (ITO) from abandoned polymer solar cells, and studied the effects of recycled ITO on the performance of PBDB-T-2F:IT-4F and PTB7:PC71BM solar cells. The results showed that the active layer, interface layers and top electrode can be completely cleaned from ITO substrate by treating in chloroform and weak acid solutions. Moreover, it was found that the recycled ITO can be applied in the fabrication of new polymer solar cells again, and a higher power conversion efficiency (13.21%) of PBDB-T-2F:IT-4F solar cell based on recycled ITO, compared to that based on original ITO (12.86%), has been demonstrated. The enhanced performance of solar cell mainly originated from the reduced carrier recombination of photogenerated charges by optimizing the morphology of recycled ITO. Therefore, this work demonstrated the feasibility of the development of low-cost and high-efficiency polymer solar cells via recycled ITO substrate.