Sulphuric Acid Concentration Research Articles

Dosimetry aspects of a non-diffusing genipin–gelatin gel

Genipin–gelatin gel shows promise as a stable, three-dimensional dosimeter for use in quality assurance for radiotherapy treatments. Genipin creates cross-links in gelatin, forming a blue colour that bleaches quantitatively upon irradiation. A formulation suitable for dosimetry was investigated by varying the concentrations of genipin, gelatin and sulphuric acid and determining the dose sensitivity. An important parameter of the gel preparation that affects dose sensitivity is the temperature at which the cross-linking reaction takes place. The most suitable formulation for dose measurements in 1cm pathlength cuvettes was found to be made from 50μM genipin, 4% w/w gelatin and 100mM sulphuric acid in the final gel. An evaluation of the diffusion coefficient of chromophores in this gel dosimeter demonstrated that this genipin–gelatin gel is a non-diffusing dosimeter. This dosimeter was also evaluated for stability, dose sensitivity, irradiation and measurement temperature dependence and dose rate dependence. No appreciable dependence on dose rate in the range 0.4–40Gymin−1 was found. No appreciable dependence on measurement temperature between 15 and 23°C was found. A slight dependence on irradiation temperature was found and this was used to determine the product of the molar linear absorption coefficient and the radiation chemical yield. Finally, the dosimeter measurement uncertainty was evaluated and this was used to determine the dose resolution. Although the focus of this work is on a genipin–gelatin gel dosimeter, the measurement and calibration techniques presented may be applied to any gel dosimetry system measured spectrophotometrically.

Solvent extraction of tantalum(V) from aqueous sulphate/fluoride solution using trioctyl phosphine oxide in MIBK

Tantalite–columbite with a combined Ta–Nb content of 33% was leached using 20M hydrofluoric acid. The acidity of the leach was adjusted with sulphuric acid and the tantalum–niobium content was extracted using methyl isobutyl ketone (MIBK) and trioctyl phosphine oxide (TOPO), with kerosene and xylene as diluents. Stripping and precipitation of the extracted species was performed using 30% V/V ammonia solution. Both tantalum and niobium were extracted to different extents, with greater degree of extraction observed for tantalum. The extraction of tantalum was found to be dependent on the concentration of sulphuric acid added. For systems involving TOPO as extractant, kerosene proved to be a better diluent than xylene. Synergism was observed with respect to tantalum extraction when 20g/l solution of TOPO in MIBK was used as the extractant. The number of extraction stages can be greatly reduced using a TOPO — MIBK blend in place of MIBK or TOPO only.

Humidity-dependent phase state of SOA particles from biogenic and anthropogenic precursors

Abstract. The physical phase state (solid, semi-solid, or liquid) of secondary organic aerosol (SOA) particles has important implications for a number of atmospheric processes. We report the phase state of SOA particles spanning a wide range of oxygen to carbon ratios (O / C), used here as a surrogate for SOA oxidation level, produced in a flow tube reactor by photo-oxidation of various atmospherically relevant surrogate anthropogenic and biogenic volatile organic compounds (VOCs). The phase state of laboratory-generated SOA was determined by the particle bounce behavior after inertial impaction on a polished steel substrate. The measured bounce fraction was evaluated as a function of relative humidity and SOA oxidation level (O / C) measured by an Aerodyne high resolution time of flight aerosol mass spectrometer (HR-ToF AMS). The main findings of the study are: (1) biogenic and anthropogenic SOA particles are found to be amorphous solid or semi-solid based on the measured bounced fraction (BF), which was typically higher than 0.6 on a 0 to 1 scale. A decrease in the BF is observed for most systems after the SOA is exposed to relative humidity of at least 80% RH, corresponding to a RH at impaction of 55%. (2) Long-chain alkanes have a low BF (indicating a "liquid-like", less viscous phase) particles at low oxidation levels (BF < 0.2 ± 0.05 for O / C = 0.1). However, BF increases substantially upon increasing oxidation. (3) Increasing the concentration of sulphuric acid (H2SO4) in solid SOA particles (here tested for longifolene SOA) causes a decrease in BF levels. (4) In the majority of cases the bounce behavior of the various SOA systems did not show correlation with the particle O / C. Rather, the molar mass of the gas-phase VOC precursor showed a positive correlation with the resistance to the RH-induced phase change of the formed SOA particles.

Extended study on the synthesis of amorphous titanium phosphates with tailored sorption properties

The influence of concentrations of both TiO2 and H2SO4 in the syntheses of amorphous titanium phosphates (TiP) is reported. IR, XRD, TGA, BET and NMR techniques were used to characterise the isolated TiP products. The concentration of sulphuric acid in the initial synthesis plays a major role in the structural diversity and sorption properties of the final ionites. In the primary solutions, Ti(IV) is in monomeric, polymeric and colloidal forms. Upon addition of H3PO4 the presence of monomeric titanium ensures formation of the Ti(HPO4)2 phase. The polymeric Ti(IV) is responsible for formation of the titanium hydroxo-phosphate phase, Ti(OH)2(HPO4), whilst the colloidal form of Ti(IV) appears to have a role in coagulation of a minor Ti(OH)4 phase in an amorphous TiP. It is found that TiP ion-exchange capacities gradually increase with an increase of both TiO2 and H2SO4 concentrations and reach a maximum value of 3.8mg-eqg−1 when TiO2 is 70–100gL−1 and H2SO4 is 480–560gL−1. Analyses of compositional, structural and sorption data allowed 3D correlation diagrams to be built that can facilitate fabrication of TiP with tailored sorption properties.

Thermodynamic model for acidic Fe(II) sulphate from solubility data

Acidic ferrous sulphate solutions are generated in a large scale in the hydro- and pyrometallurgical industries. They are also produced in the steel industry and titanium dioxide production. Acid mine drainage has long been a significant environmental problem in the coal and metal sulphide mining. The demand of recycling and reuse of materials has increased significantly especially in EU. Dumping and land filling a neutralised deposit is not an option anymore. Thus, efficient techniques of recycling and reuse of sulphuric acid and/or metal sulphates from the side streams are needed.When developing alternative solutions, a better understanding of the thermodynamic behaviour of the FeSO4–H2SO4–H2O system is needed. In the present study a thermodynamic model of this system has been developed, in order to yield a thermodynamically consistent set of values for the solubility of iron sulphate in a wide temperature and concentration range. The current model presents the experimental data available with a good accuracy and consistently up to 100°C, and sulphuric acid concentrations up to 10mol/kg. The model also predicts well the solubility measurements available in dilute sulphuric acid solutions at 160–220°C.

Acid Hydrolysis and Utilization of Distillers' Grains

Distillers' grains (DG) has high cellulose contents and is suitable for conversion to reducing sugar under dilute acid conditions. The effects of the hydrolysis conditions, including acid concentration, solid to liquid ratio, reaction temperature and time, were discussed, as well as the changes of microstructure and groups after hydrolysis. The conversion rate of reducing sugar could reach 25.07% (g/100g DG) when the hydrolysis conditions are as follows: the concentration of sulphuric acid is 5% (wt), the temperature is 120 °C, the ratio of sulphuric acid solution volume (mL) to weight of DG (g) is 30:1 and the reaction time is 10 h.

Separation of niobium and tantalum from Mozambican tantalite by ammonium bifluoride digestion and octanol solvent extraction

Tantalite ore from Mozambique was digested using molten ammonium bifluoride (NH4HF2) as an alternative to hydrofluoric acid. Niobium and tantalum were extracted from the water-leached filtrate using 1- and 2-octanol as extractants. The main process variables are time, temperature and the bifluoride-to-ore mass ratio, for the bifluoride treatment step, along with the sulphuric acid concentration of the aqueous filtrate, and the solvent-extraction contact time. The optimum parameters obtained for the bifluoride treatment were a reaction time of 3h, a reaction temperature of 250°C, and a tantalite-to-bifluoride mass ratio of 1:30. Under these conditions, up to 97.24% of Nb and 98.66% of Ta were recovered. Introduction of sulphuric acid (H2SO4) into the aqueous phase increases the extraction of Nb and Ta with octanol. It is shown that a 5M to 6M sulphuric acid concentration results in good extraction of tantalum. An acid concentration higher than 5M must be used for efficient extraction of niobium. A contact time of 10min between the feed solution and the solvent is required. McCabe–Thiele equilibrium diagrams constructed from the experimental data suggest that two and three extraction stages are sufficient for almost complete extraction of Ta and Nb respectively, at optimum extraction conditions.

Optimization of tartaric/sulphuric acid anodizing process using Doehlert design

The aim of this study was to investigate the influence of tartaric/sulphuric acid anodizing parameters (bath temperature, anodic current density, sulphuric acid and tartaric acid concentrations) on the anodic oxide layer properties. A Doehlert design was implemented to optimize this process. Four responses were retained, namely: growth rate, microhardness, dissolution rate and weight loss after abrasion of the anodic oxide layer. A multicriteria optimization using desirability function was performed in order to find a compromise between maximization of growth rate and microhardness and minimization of dissolution rate and weight loss after abrasion.Under the determined optimal anodizing conditions (Ctart=23.1gL−1, 8.6°C, 2.1Adm−2, Csul=151gL−1), the estimated response values were 0.59μmmin−1, 3.64gm−2min−1, 446HV and 70gm−2 for growth rate, dissolution rate, microhardness and weight loss after abrasion, respectively. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy, atomic force microscopy and glow-discharge optical emission spectroscopy.

SO2 crossover flux of Nafion® and sFS-PBI membranes using a chronocoulometric (CC) monitoring technique

Abstract A chronocoulometric electrochemical measuring technique was used to evaluate the gas flux and permeation properties of sulphuric acid dissolved SO2 across various polymeric membranes, using an in-house assembled permeation setup. This was done in the temperature and differential pressure range of 298–353 K and 0–2 bar respectively. The sulphuric acid concentration was varied between 30 and 90 wt%. The electrochemically measured current due to SO2 oxidation at the platinum electrode was converted to molar gas flux using Faraday's law. The flux was found to decrease as the temperature increased for all the evaluated membranes for example from 2.16×10−8±0.15 mol s−1 cm−2 at 298 K to 1.46×10−8±0.15 mol s−1 cm−2 at 353 K for Nafion® 112. The flux was found to increase with increasing Δp across the membrane and decrease with increasing acid concentration. From the flux data we were able to calculate the SO2 permeation, diffusion and solubility parameters for the various membranes.The measured and calculated values were compared to existing literature values. The lowest SO2 crossover was observed at high temperatures, low differential pressures and high H2SO4 concentrations.

Dissolution kinetics and thermodynamic analysis of vanadium trioxide during pressure oxidation

The dissolution kinetics of vanadium trioxide in sulphuric acid-oxygen medium was examined. It was determined that the concentration of sulphuric acid and stirring speed above 800 r·min−1 did not significantly affect vanadium extraction. The dissolution rate increased with increasing temperature and oxygen partial pressure, but decreased with increasing particle size. The dissolution kinetics was controlled by the chemical reaction at the surface with the estimated activation energy of 43.46 kJ·mol−1. The leaching mechanism was confirmed by characterizing vanadium trioxide and the dissolution residue using SEM-EDS analysis. Combined with thermodynamic calculation, the pressure leaching of vanadium trioxide in the temperature range (100 to 140 °C) studied occurs as follows: V2O3 + O2 + H2SO4 = (VO2)2SO4 + H2O.

Rapid analysis of cyclamate in foods and beverages by gas chromatography-electron capture detector (GC-ECD)

A rapid method for determination of sodium cyclamate in foods and beverages was developed. Sodium cyclamate was converted to N,N-dichloridecyclohexylamine by reaction with sodium hypochlorite under acid condition. N,N-dichloridecyclohexylamine was subsequently extracted by n-hexane and determined by gas chromatography. Conditions such as derivatization time, the concentration of sodium hypochlorite and sulphuric acid were optimised. Amino acids, aliphatic amines, and food additives such as preservatives, dyes and sweeteners showed no interference for quantification of cyclamate. The correlation coefficient of calibration curve was 0.9993 in the range of 5.0-250mg/L. The limits of detection (LOD) and limits of quantification (LOQ) were calculated as three or ten times the signal-to-noise ratio (S/N), respectively. The LOD and LOQ for yellow wine and fruit juice were 0.05 and 0.2mg/L, respectively. The LOD and LOQ for cake and preserved fruit were 0.25 and 0.8mg/kg, respectively. The intra-day and inter-day RSD were 0.28% and 1.1% (n=5), respectively. The method was successfully applied for determination of cyclamate in yellow wine, cake, fruit juice and preserved fruit. This method was simple, fast, and sensitive. It was suitable for the determination of cyclamate in foods and beverages for safety and quality control inspections.

Electrochemical Behavior and Thickness of Aluminium Oxide Films Studied by EIS: Laboratory and Field Studies

The technique of electrochemical impedance spectroscopy (EIS) is widely used in laboratories and industries for materials evaluation. The aim of this investigation is to monitor the thickness of the anodized (oxide) aluminium sheets (samples) by using the EIS in a laboratory and a field study at a predetermined exposure duration in the field, i.e., 0, 1, 3, 6, 9, 12 months, in 0-10 % sulphuric acid. Four experimental stations were built out of KISR in order to monitor the thickness of the anodized (oxide) layer and the electrochemical parameters of anodized aluminium sheets by using the EIS. The zero state results at 0 exposure duration, indicating that as the concentration of the sulphuric acid increased from 0-10% H2SO4, the polarization resistance was observed to decrease from 3.15E+05 to 9.80E+03 Ohms, except at a concentration of 4% H2SO4, where the polarization resistance was observed to increase from 5.20E+03 to 2.90E+04 Ohms. On the contrary, the value of the solution resistance was observed to vary several times between 1.33E+04 to 1.53E+00 Ohms as a function of the increase of the sulphuric acid concentration from 0-10% H2SO4. In similar fashion to the polarization resistance, as the concentration of the sulphuric acid increased from 0-10% H2SO4, values of the alternating current impedance were found to vary several times between 1.94E+09 to 3.95E+05 Ohms, in a non-linear fashion. A similar behavior was observed on the values of the double layer capacitance as a function of the sulphuric acid increased, from 0-10% H2SO4, in which the values of the double layer capacitance was observed to change several times from 2.24E-09 to 2.53E-06 μF. The optimum thickness of the oxide film was detected (26.5 nm) at 8% H2SO4 of the sulphuric acid concentration. In order to determine the performance of the anodized aluminium-sheet in surrounding areas of Kuwait, a plan was arranged for such a field study. The field study consists of setting up four racks of sample panels in different locations in Kuwait. The racks were installed in the main field of Kuwait Institute for Scientific Research (KISR) in Shuwaikh area, in a residential area of South Sura area, in the main field of the Petroleum Research Department and Studies Center (PRSC) of Kuwait Institute for Scientific Research (KISR), in an industrial area of Ahmadi city, and in the main field of the fishery department of Kuwait Institute for Scientific Research (KISR) in a marine area of Salmia. The investigation planned to take a sheet each three months, for a 12 months duration, in order to determine the electrochemical parameters and the oxide film thickness of the sheets by the EIS technique in the field and to compare the data with those obtained in this report, at zero state.

Properties of Nafion 117 in highly acidic environment of Bunsen reaction of I–S cycle

Membrane electrolysis could be used to carry out Bunsen reaction at much lower levels of excess iodine as compared to the direct contact mode because the two acid phases (sulphuric acid rich and HI rich phases) are separated by an ion exchange membrane. However, undesired permeation of ions or dissolved SO2 through membrane leads to cross-contamination of the two acid phases. Cross-contamination and resistance of membrane affect the purity of solutions and the energy required for the reaction, respectively. A two-compartment membrane electrolysis cell with Nafion 117 membrane was used to measure cross-contamination arising out of permeation of dissolved SO2 and/or sulphate ions from anolyte to catholyte and that of iodine/iodide ions from catholyte to anolyte. Permeation was obtained even in absence of current density and the flux increased rapidly with current density. At 1 A/dm2, the permeated SO2 and sulphate ions were ∼12% of total sulphate ions produced in electrolysis which was lower than about 20% of feed sulphuric acid appearing in HIx phase in direct contact mode. The permeated iodine and iodide ions together were less than 3% of iodide ions produced in electrolysis. Areal-resistance of the membrane was measured at different temperatures, and different concentrations of anolyte and catholyte. Areal-resistance of membrane in chemical environment of Bunsen reaction was about 50% more than the values reported in NaCl electrolyte and was found to increase with sulphuric acid concentration.

Kinetics of vanadium leaching from black shale in non-oxidative conditions

The leaching kinetics of vanadium from black shale under non-oxidative conditions was presented and compared with that under oxidative conditions. The effects of agitation speed, sulphuric acid concentration, temperature and particle size were determined. The morphology of the solid particles during leaching indicated that no product layer formed on the particles. The grain model with pore diffusion control provided a good description of vanadium leaching kinetics. The model gave an activation energy of 55·6 kJ mol−1, and reaction order 0·37 with respect to sulphuric acid due to diffusion and chemical reactions occurring in parallel in the porous solids. The linear relationship KD∝1/r02 found for the apparent rate constant, where r0 is initial particle radius, also supported a diffusion controlled process. The apparent activation energy was 40% larger for leaching under non-oxidative conditions than for leaching under oxidative conditions, indicating that an oxidising atmosphere had a positive effect on vanadium leaching.

Effect of Electrolyte on the Surface Smoothness Obtained by Electropolishing of Stainless Steel

Electropolishing is a surface finishing process of metals and alloys that enhances brilliant surface finishes with low surface roughness values. The most widely used electrolytes for the electropolishing of stainless steel are varying concentrations of phosphoric and sulphuric acid, and occasionally additives such as chromic acid. The objective of this study was to assess the performance of three commonly used industrial electrolytes in terms of the surface finish of electropolished stainless steel AISI 316L. Each electrolyte had varying sulphuric-phosphoric acid combinations with or without chromic acid. The following electropolishing conditions were assessed: current density, bath temperature, electropolishing time, and initial surface texture. The results revealed that adding chromic acid to the electrolyte did not significantly enhance surface finish, and electropolishing ranges were quite similar for all three electrolytes.

Effect of operating variables on performance of membrane electrolysis cell for carrying out Bunsen reaction of I–S cycle

Membrane electrolysis is coming up as one of the alternatives to direct contact mode of carrying out Bunsen reaction of I–S cycle. It has potential to reduce the use of excess iodine and water. A two-compartment membrane electrolysis cell with graphite electrodes and Nafion 117 membrane was used for Bunsen reaction. Effect of six independent variables on cell voltage was determined for current density values of up to 80 A/dm2. The variables were anolyte pressure, catholyte pressure, temperature, sulphuric acid concentration, HI concentration, and I2/HI molar ratio in catholyte. Flow rate of anolyte and catholyte were identified where mass transfer resistance was not significant before performing experiments with different independent variables. Cell voltage was analysed by identifying three different regimes based on its variation with current density and current density ranges where electrode resistance or ohmic resistance dominated are identified. Current efficiency was measured for 1 A/dm2 and was found to be close to 100% irrespective of values of the independent variable. Minimum amount of heat equivalent of electric energy required for membrane electrolysis was calculated and increase in its value with increase in sulphuric acid concentration was compared with estimate of reduction in heat required for concentration of sulphuric acid.

Study on Separation of Cobalt and Lithium Salts from Waste Mobile-phone Batteries

The metals in waste mobile-phone batteries may cause environmental pollution. In this paper, leaching with H2SO4+H2O2, P507 extraction, and sedimentation with oxalic acid and carbonic acid were used to deal with waste batteries and obtain cobalt and lithium salts by separation, which shows an easy and feasible method with less waste water disposal. The effects of sulphuric acid concentration, pH value, and lithium ions on the recovery were investigated. When the sulphuric acid concentration was over 0.4 mol/L, the loss of cobalt increased significantly. If pH value of 3.5 was used, it was easy for cobalt and lithium separation with a low cobalt loss. Over several recycles, the recovery of lithium could reach the maximum with the lithium ion concentration of 27.3 g/L. The recovery efficiencies for cobalt and lithium were 90.02% and 86.04%, respectively.

Determination of Organic Acids in Sheng-mai Injection by Ion Exclusion Chromatography

A method was developed for the separation and determination of three organic acid,viz citric acid,malic acid and succinic acid in Sheng-mai Injection by ion exclusion chromatography with suppressed conductivity detection.The chromatographic separation was performed on a Transgenomic Sep-ION-300 column(300 mm length ×7.8 mm i.d.,8 μm) at 70 ℃ and eluted with a mixture of 5 mmol/L sulphuric acid and acetone(95 ∶ 5) at the flow rate of 0.4 mL/min.The effects of the concentration of sulphuric acid,the volume ratio of acetone and column temperature were investigated and optimized.The calibration curve for citric acid,malic acid and succinic acid was in a good linearity in the range of 7.45-476.5 mg/L,14-521.0 mg/L and 3.47-222.0 mg/L,respectively.The average recovery for citric acid,malic acid and succinic acid was 97.12% with RSD 2.7%,96.9% with RSD 2.3%,and 95.09% with RSD 1.9%,respectively.The validated method was successfully applied to determination of organic acids in 15 batches of Sheng-mai Injection.

Evaluation of the potential of geopolymer mortar in the rehabilitation of buried infrastructure

Concrete pipes represent the backbone of the wastewater collection systems in many cities across North America. These pipes are in various stages of deterioration, generally due to microbiological induced corrosion and/or mechanical loading. A common method of rehabilitating these structures is the use of cementitious coatings. This paper describes the development and testing of three novel geopolymer mix designs prepared using metakaolin and fly ash (class C and F) precursors. Specimens prepared using Portland cement-silica fume blend were also tested for comparison purposes. The specimens were placed in several concentrations of sulphuric acid for a period of eight weeks. The corrosion resistance and remaining compressive strength of geopolymer mortar made from class F fly ash precursor were found to be substantially higher compared with the enhanced OPC formulation. The other geopolymer mix designs were found to perform equally or better compared with the OPC binary blend.

Effect of sulphuric acid and formalin on sporulation of Eimeria bovis oocysts

Eimeria bovis oocysts were isolated and identified after obtained the fecal sample from infected calf. Three different concentrations of sulphuric acid and of formalin were examining to observe their effect on E.bovis oocysts sporulation in addition to 2.5% potassium dichromate as a control. All different concentrations of both chemical solutions (sulphuric acid and formalin) were induced the sporulation of oocyst in addition to the control group (potassium dichromate).