Increasing H2SO4 Concentration Research Articles

Novel dialkylphosphinic acid modified Merrifield resins: Synthesis, characterization, and their adsorption and separation behaviors for zirconium and hafnium

Deep separation of Zr and Hf has always been a great challenging due to their very similar physicochemical properties. In this study, we established a method to synthesize two novel extraction chromatographic resins which graft dialkylphosphinic acid groups through amide group. The dialkylphosphinic acid modified resins were characterized by FT-IR, EA, SEM-EDS, XPS, and BET. Their adsorption and separation behaviors for Zr and Hf were investigated, and the adsorption mechanism was studied. The Zr and Hf adsorption onto Mer-CON-POOH-272 and Mer-CON-POOH-HYY2 both fit pseudo-second order model and Langmuir isotherm model. Mer-CON-POOH-HYY2 has stronger affinity to Zr and Hf than Mer-CON-POOH-272. Mer-CON-POOH-272 has a theoretical maximum loading capacity of 5.663 mg·g−1 Zr and 11.111 mg·g−1 Hf, while Mer-CON-POOH-HYY2 has a higher theoretical maximum loading capacity of 8.376 mg·g−1 Zr and 13.157 mg·g−1 Hf. Dialkylphosphinic acids are the functional groups of Mer-CON-POOH-272 and Mer-CON-POOH-HYY2 that interact with Zr and Hf during adsorption. They adsorb Zr and Hf through cation exchange mechanism, which can be expressed as M(SO4)32– + 2HL ⇌ M(SO4)L2 +.2H+ + 2SO42-. With increasing H2SO4 concentration, the Zr and Hf extraction percentages and their separation efficiency reduce. The DFT calculation reveals that the adsorption process is accompanied by charge transfer. Adsorption occurs mainly at P = O and P-O positions. The affinity of the two resins for Hf is higher than that of Zr, which is the reason why the resin preferentially adsorbs Hf.

Dissolution behavior and improvement approach for gallium extraction from zinc refinery residues

Aiming at solving low Ga leaching efficiency during actual industrial production in Danxia Smelter, chemical composition, phases and morphologies of various zinc refinery residues were characterized using ICP−AES, XRD and SEM−EDS. Compared with the normal material, Ga was embedded in the jarosite phase from the special zinc refinery residue, causing difficulty in Ga leaching. During the oxidation pressure leaching, the dissolution behaviors of Ga, As and Fe presented similar variation tendency. Namely, a sufficient H2SO4 concentration and liquid-to-solid ratio promoted the dissolution of Ga, Fe and As, whereas higher reaction temperature and oxygen partial pressure weakened the leaching. Based on the results, leaching parameters were optimized for enhancing Ga recovery. Through weakening the 1st oxidation pressure leaching (by decreasing reaction temperature and total pressure to 90 °C and 0.2 MPa, respectively) and strengthening the 3rd atmospheric leaching (by increasing H2SO4 concentration and reaction temperature to 160 g/L and 85 °C, respectively), the leaching efficiency of Ga increased from 77.83% to 96.46%.

Crucial role of sulfonated ionic liquids as promoter for efficient production of valuable carboxylic acids by H5PMo10V2O40-catalyzed aerobic oxidation of lignite

To explore the effect of adding acidic ionic liquids (ILs) to the heteropoly acid/H2SO4 catalytic system on the aerobic oxidation of lignite, acidic ILs functionalized with -SO3H were synthesized accordingly and mixed with H5PMo10V2O40 (HPA-2) in various molar ratios. The optimum combination of HPA-2 and 1-methyl-3-(4-sulfobutyl) imidazolium (MIMBS) with molar ratio of 0.3 showed excellent performance for the catalytic oxidation of lignite, with the yields of carboxylic acids (CAs) (including benzene carboxylic acids, formic acid and acetic acid) reaching 326.21 ± 12.86 mg/g lignite, which considerably exceeded the 136.08 ± 6.23 mg/g lignite of pure HPA-2. Highest occupied molecular orbital energy of CAs calculated by Gaussian 09 on 6-31G(d) basis set and Hammett function analysis confirmed that the oxidative activity and acidity of the catalytic system could be moderately modulated by sulfonated ILs, thereby increasing the yield of CAs. In addition, the effect of H2SO4 concentration on the oxidation of lignite was investigated via the HPA-2/H2SO4/MIMBS system with different molar ratios, and the results showed that CAs yield increased first and then decreased with increasing H2SO4 concentration, but the concentration of H2SO4 at the maximum yield of CAs was significantly reduced from 0.28 wt% to 0.14 wt% once MIMBS was added. A possible process for the catalytic oxidation of lignite by sulfonated ILs/HPA-2/H2SO4 in aerobic aqueous solution is proposed, which generally involves the reactions of hydrolysis, oxidation and re-oxidation. Due to the good reproducibility, the robust homogeneous catalytic system of HPA-2/sulphonated ILs has the advantages of including increased yields of CAs and reduced H2SO4 dosage, which will pave the way for the efficient utilization of lignite.

Reductive leaching behaviour of manganese and cobalt phases in laterite and manganese ores

The reductive leaching behaviour of manganese (Mn) and cobalt (Co) in a laterite and a pure manganese ore was investigated by varying and optimising various leaching parameters for the recovery of Mn and Co. The effect of different reducing agents (FeSO4, Na2SO3), sulfuric acid concentration, reductant/ore mass ratio, leaching time, and reaction temperature on the dissolution of Mn and Co from the laterite and manganese ores were studied. Furthermore, the kinetics of Mn and Co leaching from laterite ore was studied. The Mn and Co recovery from both ores increased with increasing H2SO4 concentration, reductant/ore mass ratio, leaching time, and reaction temperature. Based on the manganese and cobalt extraction efficiency, FeSO4 was the best reductant among the two evaluated reductants. The optimum leaching of Mn and Co from the laterite ore occurred at a H2SO4 concentration of 0.51 M, a reductant/ore mass ratio of 2.7, a leaching time of 5 h, and a reaction temperature of 363.15 K. For the manganese ore the optimum leaching of these elements at the same temperature occurred at a higher H2SO4 concentration of 1.02 M, a reductant/ore mass ratio of 2.4, and a shorter leaching time of 2 h. The results from the optimization studies showed that the leaching trends of Mn and Co phases in the manganese ore are similar to those of the Mn and Co phases in the laterite ore. Moreover, Co was co-leached together with Mn suggesting a degree of correlation of cobalt to manganese mineral phases in both, the laterite, and the manganese ores. The kinetics of the reductive leaching of Mn and Co for the laterite ore could well be described by the Avrami model reflected by high correlation coefficient values of R2 > 0.95. The leaching of Mn and Co occurred rapidly at the initial leaching stage but gradually slowed down with prolonged leaching time. This was indicated by the modal parameter (n) values that were <1, at varying reaction temperatures. The experiments showed further that Mn and Co leaching in laterite ore is a diffusion-controlled reaction, which was indicated by the apparent activation energy of 11.7 kJ mol−1 and 11.1 kJ mol−1, respectively.

Eutectic freeze crystallization for recovery of NiSO4 and CoSO4 hydrates from sulfate solutions

In this study, eutectic freeze crystallization (EFC) was investigated to recover NiSO4 and CoSO4 hydrates from aqueous and dilute sulfuric acid solutions of metal sulfates. Binary phase diagrams were established using a combination of thermodynamic modeling and experimental data. The mixed-solvent electrolyte (MSE) model was employed to model solid–liquid phase equilibria. The predicted binary phase diagrams from the model were in good agreement with the experimental results. Experimental eutectic temperatures and eutectic metal sulfate concentrations for the NiSO4-H2O and CoSO4-H2O systems are −3.3 °C and 20.8 wt% and −2.9 °C and 19.3 wt%, respectively. For NiSO4-H2SO4-H2O and CoSO4-H2SO4-H2O systems, the eutectic temperature and eutectic metal sulfate concentration decrease with increasing H2SO4 concentration. Batch experiments were performed to study the EFC of different sulfate solutions, including 25- wt% NiSO4 in H2O, 20- wt% NiSO4 in 0.5 mol/kg H2SO4, 25- wt% CoSO4 in H2O, and 20- wt% CoSO4 in 0.5 mol/kg H2SO4. The results show that controlling the supersaturation allows high-quality ice and salt crystals to be recovered as separate phases under eutectic conditions, with the crystalline salts in the form of heptahydrates. This study shows that EFC can be a promising alternative to evaporative crystallization for recovering NiSO4 and CoSO4 hydrates from sulfate solutions.

Use of Cyanex 572 as an effective extractant for the recovery of Mo(VI) and V(V) from HDS spent catalyst leach liquor

In this study, the extraction of Mo(VI) and V(V) from the simulated leach liquor of hydrodesulfurization spent catalyst was studied. The commercial extractant Cyanex 572 was used for the extraction of both Mo(VI) and V(V). At the low pH region, the extraction of Mo(VI) was higher than that of V(V). At higher pH, the extraction of V(V) was more but, the co-extraction of Mo, Fe and Al was also more. By increasing H2SO4 concentration in the feed solution from 0.25 to 5.0 mol/L, molybdenum extraction decreased from 96% to 70% and remained constant after 1 mol/L H2SO4. The extraction of V(V) was less than that of Mo(VI). With increasing Cyanex 572 concentration from 1 to 10%, Mo(VI) extraction increased from 20.1% to 97.6%, whereas V(V) extraction increased to 9.1% only. The co-extraction of Al, Ni, Fe and Co was not observed. From the slope analysis data, it was observed that two moles of H+ were released during the extraction of Mo(VI) and one mole of H+ was released during the extraction of V(V). Similarly, two and three moles of Cyanex 572 were associated with the extraction of Mo(VI) and V(V), respectively. The extracted species of Mo(VI) and V(V) were MoO2.A2.H2A2 and VO2.A.5HA, respectively. The McCabe-Thiele diagram for Mo(VI) showed three stages at A:O ratio of 2:1 for quantitative extraction of Mo(VI). From the loaded organic V(V) was removed by scrubbing with 0.3 g/L Mo solution followed by Mo stripping with (NH4)2CO3. After that, V(V) extraction was carried out with the same extractant at pH 2.0 in three counter-current stages at A:O ratio of 1:1, and from the loaded organic, V was selectively stripped with (NH4)2CO3. The thermodynamic parameters such as ΔHo, ΔSo and ΔGo were also determined.

Effect of sulfur content in the crude oil to the corrosion behavior of internal surface of API 5L X65 petroleum pipeline steel

This work discussed the corrosion behavior of the internal surface of pipeline steel caused by the composition of petroleum products, particularly crude oil. Internal and external pipeline corrosion is the notable cause of pipeline failure in Malaysia&#8217;s oil and gas industry. However, internal corrosion is preferred to be concerned in this work because it involved one of the major corrosive media in the crude oil, such as sulfur content. This project aim is to find the sulfur concentration in the crude oil using Fourier transform infrared spectroscopy and atomic absorption spectroscopy. The corrosion rate, corrosion current and corrosion potential of the API 5L X65 grade carbon steel pipeline in different simulated H2SO4 solution concentrations were carried out using the Tafel extrapolation technique. The corrosion properties of the samples were morphologically measured by means of optical microscope, scanning electron microscope and energy dispersive X-ray analyses. The results showed that the corrosion rate of the pipeline steel significantly increased with the increasing H2SO4 concentrations. The corrosion products formed on the pipeline steel surfaces were mainly composed of iron sulfate, iron sulfide and iron oxide. These findings are crucial to understanding the corrosion behavior caused by the crude oil and should be further investigate with the other possible influence factors such as temperature and petroleum&#8217;s flowing velocity.

Physico-chemical characteristics of nanocellulose at the variation of catalytic hydrolysis process

In this work, the influence of various sulfuric acid (H2SO4) concentration is studied towards the crystallinity, particle size distribution, thermal stability, and morphology of the synthesized nanocellulose (NCC) during the esterification process. Different concentrations of H2SO4 (40%, 58%, 64% and 78%) was utilized to achieve the optimal properties of NCC. The as-produced NCC was characterized by Fourier Transmission Infra-Red (FTIR) analysis that confirmed the attachment of sulphate ions (SO4−3) to C-6 of the glucose ring. Moreover, the hydrogen ions (H+) weakened the C-6 of cellulose chains by attacking the glycosidic linkages resulting in the formation of NCC. The X-Ray Diffraction (XRD) analysis revealed an increase in the crystallinity index with increasing H2SO4 concentration till 78%. NCC represented a needle shaped like structure having a particle size of 10–18 nm in diameter as observed under Atomic Force Microscopy (AFM) and Fourier Emission Scanning Electron Microscopy (FESEM). Furthermore, Dynamic Light Scattering (DSL) analysis recorded the particle size of the NCC as less than 20 nm in diameter. Thus, owing to various H2SO4 concentration the particle size, crystallinity, and features of NCC are substantially affected.

Controllable synthesis of mesoporous SBA-15 using H2SO4

ABSTRACT Mesoporous SBA-15 has been synthesised using a binary acid H2SO4 as media. The effects of H2SO4 concentration and synthesis temperature on the morphologies and mesostructures of the obtained mesoporous SBA-15 materials were studied. The results revealed that the more-ordered structure was obtained at a H2SO4 concentration of 2 M, while a higher H2SO4 concentration of 3 M led to a less-ordered structure. In addition, with increasing H2SO4 concentration from 1 to 3 M, the morphologies of SBA-15 particles transferred from rod-like to sphere-like. This work demonstrated that mesoporous SBA-15 with various textural properties and morphologies can be feasibly obtained by controlling the H2SO4 concentration and synthesis temperature.

Highly efficient smoothing of Inconel 718 via electrochemical-based isotropic etching polishing

For the highly efficient and versatile polishing of metals, isotropic etching polishing (IEP), which is based on the merging of isotropic etching holes, has been developed. In this study, the feasibility and mechanism of isotropic etching polishing of nickel-based superalloy Inconel 718 (IN718) and the polishing characteristics have been studied. The potentiodynamic experiments revealed similar trends of the cathodic, passive, second passivation, and transpassive regions in all the electrolytes, while the corrosion susceptibility of IN718 successively decreased with the increasing H2SO4 concentration in the electrolyte. The etching anisotropy of the IN718 precipitated with different phases can be experimentally transmuted to isotropic etching by modulating the electrolyte concentration and keeping electrolyte temperature equal or above the room temperature. Because of the positive correlation of the etching current with isotropic holes density and diameter, etching at higher currents is promoted for the rapid and proficient polishing. The surface evolution mechanism during IEP has been confirmed. The surface roughness initially increased due to the formation of etching holes, then decreased abruptly owing to the rapid merging of etching holes and finally achieved a smooth surface. The wet grounded surface of IN718 with a roughness of Sa 62.7 nm has been transformed into a mirror-like smooth surface with a roughness of Sa 0.86 nm within 300 s of IEP at optimized conditions and a high MRR of 2.73 mm3/min has been achieved.

Recycle of synthetic calcium fluoride and waste sulfuric acid to produce electronic grade hydrofluoric acid.

An innovative method for utilizing synthetic calcium fluoride (CaF2), recovered from fluoride-containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low-temperature production of HF via reaction of synthetic CaF2 and waste H2SO4. The impact of four factors, including H2SO4 concentration, total volume (H2SO4 + H2O)/CaF2 ratio, drying temperature of synthetic CaF2, and reaction carried out under different temperature, on HF productivity was investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. Generally, reactions carried out under low-temperature (< 100°C) had a positive impact on HF yield. The higher temperature led to an increase in absorbed-HF but a decrease in total-HF. The reaction of commercial CaF2 and 70% H2SO4 had a higher absorbed-HF yield of 61.7% than synthetic CaF2 and 70% waste H2SO4, which had a yield of 36%. This was due to the higher purity of the commercial CaF2 and fewer interference ions in H2SO4. HF productivity was lowered by CaSO4, which hindered the reaction of reactants and also the generation of fluorosulfuric acid.

Integrated acid leaching and biological sulfate reduction of phosphogypsum for REE recovery

Sulfuric acid leaching of phosphogypsum (PG) waste and leachate treatment in sulfate-reducing bioreactor was studied, in order to recover rare earth elements (REE) and remove sulfate from the residual solution. The challenge was to balance efficient REE extraction from PG while maintaining suitable leach solution acidity and sulfate concentration for the microorganisms in the bioreactor. Stirred tank reactor experiments were conducted for PG leaching to form the scope for suitable sulfuric acid concentration and REE leaching efficiency. According to these experiments, moderate REE leaching started already at 0.01 M H2SO4 concentration (yield 6–15%), and increased steadily when increasing H2SO4 concentration to 0.05 M (yield 34–62%). Different leachates were treated in sulfate-reducing bioreactor to understand the limits of acidity and sulfate concentration for the biological system. It was shown that bioreactor requires rather a mild leachate (<0.02 M H2SO4) to perform reliably and also precipitate REE from the influent. Finally, the precipitate from the bioreactor was collected and analyzed for both chemical and mineralogical composition. These results showed that REE were enriched in the precipitate and formed distinctive mineralogical phases in the MLA images. The method described in this research could be used to treat moderately acidic PG waste leachates with potential for REE recovery.

Electrochemical evaluation of cr-mn austenitic stainless steel in aqueous sulphuric acid and influence of thiocyanate ions

PurposeLow nickel austenitic stainless steel (ASS) has attracted much attention worldwide because of its economical price. This study aims to investigate the effect of different corrosive environments on the corrosion behavior of chrome-manganese (Cr-Mn) ASS. The tests were carried out as a function of H2SO4 concentrations, temperature and addition of ammonium thiocyanate (NH4SCN) (0.01 M). Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques were used to study the corrosion behavior of Cr-Mn ASS. It was observed that with increasing H2SO4 concentration, temperature and with the addition of NH4SCN solution, icorr, icrit and ipassive values increased. EIS data show decreasing charge transfer resistance value with increasing concentration and temperature. Higher corrosion rate with increasing temperature and concentration of H2SO4 is related to the anions (SO42−), which is responsible for reducing the stability of passive films. With the presence of 0.01 M NH4SCN thiocyanate (SCN− anion), there is a higher dilution of the passive film resulting in a higher corrosion rate. Energy-dispersive spectroscopy (EDS) analysis reveals the adsorption of sulfur on the surface in NH4SCN containing a solution. The significant presence of counter ions and the adsorbed sulfur species on the steel surface play a vital role in corrosion behavior.Design/methodology/approachAll the experiments were performed on a 3 mm thick sheet of Cr-Mn ASS (202 ASS) in hot rolled condition. The samples were then annealed at 1,050°C for 1 h, followed by water quenching. For microstructural examination, they were electrochemically etched in 10 Wt.% oxalic acid solution at 1 amp for 90 s. A computer-controlled Potentiostat (Biologic VMP-300) was used. After the cell was set up, the working electrode (WE) was electrostatically cleaned at −1 V vs saturated calomel electrode (SCE) for 30 s to remove the air-formed film. Then, WE were allowed to attain stable open circuit potential (OCP) for 1 h, following by the EIS test and potentiodynamic polarization test. The polarization test was started from a cathodic potential (−1.2 V vs SCE) and continued up to an anodic potential (1.6 V vs SCE) a scan rate of 0.1667 mV/s. EIS experiment was conducted on the same instrument by using a sinusoidal AC signal of 10 mV in a frequency range of 1,000,000 to 0.01 Hz at OCP.FindingsPotentiodynamic polarization graph shows that with the increase in sulphuric acid concentration. Increasing temperature from 20°C to 80°C in 0.5 M H2SO4 solution increases the corrosion rate (icorr) of Cr-Mn ASS. On the addition of 0.01 M NH4SCN to the sulfuric acid solution (0.1, 0.5 and 1 M) the corrosion rate increases drastically almost four to five times. EDS and XRD analysis shows the presence of sulfur over the oxide film and preferential site for dissolution of Cr and Mn at the steel surface when NH4SCN is added to the sulfuric acid solution.Originality/valueA study on the corrosion behavior of Cr-Mn ASS is scanty according to the author’s knowledge. Therefore, the present study will investigate the corrosion behavior of Cr-Mn ASS on SO4−2 anions, temperature and the addition of SCN− ion in sulfuric acid.

Thermodynamic Modeling of Calcium Sulfate Hydrates in a CaSO4-H2SO4-H2O System from 273.15 to 473.15 K up to 5 m Sulfuric Acid.

To prevent scaling and to recycle aqueous solutions in industrial processes, the thermodynamic properties of the CaSO4–H2SO4–H2O system are studied by thermodynamic modeling with the Pitzer model. The published solubility data of calcium sulfate hydrates in sulfuric acid solutions were collected and reviewed critically. Then, the CaSO4–H2SO4–H2O system was modeled using the Pitzer activity coefficient approach from critically selected experimental data to obtain optimized parameters. The model reproduces the solubility data with good accuracy up to 5 m sulfuric acid at temperatures of 283.15–368.15, 283.15–473.15, and 298.15–398.15 K for gypsum (CaSO4·2H2O), anhydrite (CaSO4), and hemihydrate (CaSO4·0.5H2O), respectively. However, at temperatures above 398.15 K and sulfuric acid concentration above 0.5 mol/kg, the solubility of anhydrite predicted by our model deviates significantly from the literature data. Our model predicts that the solubility of anhydrite would first increase but then decrease in more concentrated sulfuric acid solutions, which is in disagreement with the experimental data showing constantly increasing solubilities as a function of increasing sulfuric acid concentration. This discrepancy has been discussed. The transformations of gypsum to anhydrite and hemihydrate were predicted in sulfuric acid solutions. With increasing H2SO4 concentration, the transformation temperatures of gypsum to anhydrite and hemihydrate will decrease. Thus, gypsum is stable at low temperatures in solutions of low H2SO4 concentrations and transforms to anhydrite at high temperatures and in concentrated H2SO4 solutions, while hemihydrate is always a metastable phase. Furthermore, the predicted results were compared with previous experimental studies to verify the accuracy of the model.

Optimasi Suhu Hidrolisis dan Konsentrasi Asam Sulfat dalam Pembuatan Nanoselulosa Berbahan Dasar Serat Batang Pisang Kepok (Musa acuminata x balbisiana)

This research aims to investigate the optimal hydrolysis temperature and sulfuric acid (H2SO4) concentration in isolating nanocrystalline cellulose (NCC) from kepok banana pseudostem fiber with the best yield and water solubility. In this research, cellulose fiber was delignified with NaOH at 80°C for 5 minutes, then followed by bleaching with hydrogen peroxide (H2O2) for 30 minutes twice. NCC was isolated through acid hydrolysis with H2SO4 (40%, 45%, 50%, 55% v/v) at 45 °C, 50 °C, 55 °C, 60 °C for 1 hour and ultrasonicated for 5 minutes. NCC crystal was then characterized through Transmission Electron Microscopy (TEM), and water solubility. TEM analysis showed the isolated NCC has a measured length of 125 – 144 nm. The highest NCC yield was obtained at 60°C and 55% H2SO4 at 26.75%. This analysis showed that NCC yield increases with increasing H2SO4 concentration and hydrolysis temperature. The lowest water solubility obtained is 0%, which shows the purity of the cellulose used to isolate NCC.

A study on the low-temperature wet synthesis of hydrofluoric acid from synthetic calcium fluoride and waste sulfuric acid

An innovative method for utilizing synthetic calcium fluoride (CaF2), recovered from fluoride-containing semiconductor wastewater, and waste sulfuric acid (H2SO4) to produce hydrofluoric acid (HF) was investigated. The research was set to study the low-temperature production of HF via the reaction of synthetic CaF2 and waste H2SO4. The impact of H2SO4 concentration and total volume (H2SO4 + H2O)/CaF2 ratio, drying temperature of synthetic CaF2 on HF productivity were investigated in this study. HF yield increased with increasing H2SO4 concentration and total volume/CaF2 ratio under room temperature. In addition, the HF produced in the reactions involving the 105 °C-dried synthetic CaF2 were higher than the 600 °C-dried synthetic CaF2 ones. The study will not only find uses for this semiconductor wastes but also provide a greener alternative to the current commercial production of HF.

Dissolution Behavior of Rare-Earth Metal in H2SO4-H3PO4-H3PW12O40 Solution

The dissolution behavior of a rare-earth element in H2SO4-H3PO4-H3PW12O40 solution has been investigated. The results showed that La2(SO4)3 dissolution increased with increasing H3PO4 or H3PW12O40 concentration in single H3PO4 or H3PW12O40 solution. The presence of H3PW12O40 can improve La2(SO4)3 dissolution owing to its coordination toward La3+ in H3PO4-H3PW12O40 mixed solution. However, La2(SO4)3 dissolution decreased gradually with increasing H2SO4 concentration in H2SO4-H3PW12O40 mixed solution. In these solutions, increasing the temperature showed an adverse effect on La2(SO4)3 dissolution. In H2SO4-H3PO4-H3PW12O40 solution, when the concentration of H2SO4 or/and H3PO4 was lower, increasing the H3PO4 concentration or decreasing the temperature was beneficial to La2(SO4)3 dissolution. However, when H2SO4 or H3PO4 reached a certain concentration, some H3PW12O40 precipitated from the mixed solution. Furthermore, increasing the H3PO4 concentration was found to be harmful, while increasing the temperature could increase La2(SO4)3 dissolution. Nevertheless, increasing the H2SO4 concentration showed an adverse effect on La2(SO4)3 dissolution regardless of the H3PO4 concentration.

Galvanic displacement reaction of nickel to form one-dimensional trigonal tellurium structures in acidic solutions

Trigonal tellurium micro-wires and tubes were synthesized by galvanic displacement of nickel in acidic sulfate solutions where the growth mechanism was elucidated using various electroanalytical methods and material characterization. The effects of solution composition, including concentrations of tellurium precursor and sulfate, were studied. The transition from micro-wires to tubes with an increase in HTeO2+ concentration was observed, which might be attributed to the comparable diffusion length scale of tellurium on the cylindrical seed surface to the radius of the seed. On the other hand, increasing H2SO4 concentration led to transformation of microtubes to microwires owing to reduction deposition rate and limited mass transfer of HTeO2+ ions. The effect of other anions (i.e., Cl− and NO3−) on galvanic displacement reaction was also studied. As a strong oxidant, HNO3 dissolved nickel faster than SO4−2 and Cl−, but showed slower tellurium deposition tellurium nanowires, which might be due to co-reduction of nitrate ions. The preferential adsorption of Cl− increased both dissolution of nickel and the deposition of tellurium, resulting in larger tellurium microtubes.

Effect of H2SO4 concentration on cellulose isolation from palm empty fruit bunches.

Isolation of cellulose from palm empty fruit bunches had been conducted. Isolation was conducted with H2O2 30% and H2SO4 with various concentrations (20, 30, 40, and 50%). Hydrolysis and bleaching processes were performed for 90 minutes. The obtained cellulose was characterized by Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). FTIR analysis confirmed the typical bands of cellulose in the sample. XRD patterns showed increasing H2SO4 concentration on hydrolysis process increased crystallinity of cellulose. However, at H2SO4 concentration more than 40% the crystallinity of cellulose reduced. It was due to the reduction of crystalline part of cellulose.

Revealing sulfuric acid concentration impact on comprehensive performance of vanadium electrolytes and flow batteries

H2SO4 concentration has an important influence on the performance of vanadium electrolytes and flow batteries. However, the comprehensive research is still inadequate. In this work, a series of electrolytes with 1.5 M vanadium ions (V2+, V3+, V3.5+, VO2+ and VO2+) in various concentrations of H2SO4 (1.5 M, 2.0 M, 2.5 M, 3.0 M, 3.5 M and 4.0 M) are prepared and their physicochemical properties, electrochemical activities, single-cell performances, and static stability are studied in detail. The conductivity and viscosity of the electrolytes increase with increasing H2SO4 concentration. Besides, the electrochemical properties are improved in higher concentration of H2SO4 except for the charge transfer resistance and hydrogen evaluation reaction. Meanwhile, the single-cell performances with 3.0–4.0 M of H2SO4 are superior to those with 1.5–2.5 M of H2SO4. However, V3+ in 4.0 M H2SO4 is not stable enough to store for a long time at room temperature. The above results indicate that 3.0 M and 3.5 M of H2SO4 should be used as supporting electrolytes to achieve efficient and stable vanadium flow batteries. This work may also provide a guide for study and practical application of vanadium flow batteries.