Concentrated Sulfuric Acid Research Articles

Pretreatment of refractory gold ore by curing with concentrated sulfuric acid

Pretreatment of refractory gold ore by curing with concentrated sulfuric acid

Solution-recrystallization mechanism of g-C3N4 and its inhibitory effect on polysulfide shuttling through cross-linked porous network structure with carbon nanotubes

Lithium-sulfur batteries have the advantages of high specific capacitance density and high theoretical capacity, which are attracting more and more attention in the field of energy storage. However, in practice, there are still many difficulties, such as the poor conductivity of sulfur, the large volume expansion of sulfur, and the shuttle effect of polysulfides, which lead to rapid capacity degradation and poor cycling stability. Here, we utilize g-C3N4 which is soluble in concentrated H2SO4 and has a good solution-recrystallization reversible property, alcohol was used as deprotonation solvent, the g-C3N4/CNT composites were prepared by the method of solution-recrystallization as sulfur host. The dissolution and precipitation mechanism of g-C3N4 in concentrated sulfuric acid and the composite mechanism with CNT were revealed. The g-C3N4/CNT/S cathode exhibit excellent electrochemical properties. The capacity of SPCNT11 can still be maintained to 1013 mAh·g−1 after 200 cycles at 0.2 C, with a capacity retention rate of 73.2%. Even at rate of 4C, the SPCNT11 material still has a capacity of 547 mAh·g−1 after 450 cycles. The first-principle calculation results further reveal that the interaction between g-C3N4 and CNT produces conjugated effect, the constrain of g-C3N4 to electrons is weakened, enhances its conductivity, and thus realizes the effect of promoting polysulfide transformation.

Optimized Ilmenite Leachate by Wet Mechanical Activation for the Synthesis of TiO<sub>2</sub> Nanoparticles through Sulfate Route

The extraction of ilmenite minerals using the sulfate route is one of the commercial methods for producing titanium dioxide (TiO2) materials. The sulfate process requires a high concentration of sulfuric acid to achieve high extraction yield of titanium. However, this process also results in the generation of high amounts of sulfuric acid waste. Modifying ilmenite minerals is thought to be one of approaches in reducing the consumption of highly concentrated sulfuric acid. In the current study, we investigated the effect of the ilmenite-to-water mass ratio (ITWR) on the wet-ball milling process to enhance the dissolution of titanium from the ilmenite mineral. The results revealed that increasing the water amount from 10 to 70% wt has decreased the particle size from 167.60 to 0.55 μm and increased the titanium yield from 479.36 to 1228.89 ppm. On the basis of investigation, it was shown there is a significant relationship between the ilmenite-to-water mass ratio and titanium dissolution, highlighting the importance of an optimal ratio for achieving maximum dissolving yield. The obtained TiO2 nanoparticles provide the average crystallite size of 4.16 nm, with rutile and anatase phase, and spherical morphology.

Decoration with electronegative 2D materials based on chemical transition layers on CFR-PEEK implants for promoting osteogenesis

Due to the unique lamellar structures, physicochemical and biological properties, electronegative two-dimensional (2D) materials have been explored for surface modification of carbon fibers reinforced polyetheretherketone (CFR-PEEK) composite. Deposition of electronegative 2D materials based on a porous surface created by concentrated H2SO4 has been studied to promote osteogenesis of CFR-PEEK. Generally, a porous layer will be pre-built on CFR-PEEK through severe corrosion of concentrated sulfuric acid to help the loading of 2D materials. However, the severe corrosion will greatly reduce surface mechanical strength, especially wear resistance and hardness, which increases the risk of collapse or even peeling of the bioactive coating by external force. Herein, instead of the severe corrosion, a mild corrosion by concentrated HNO3 was applied to modify the surface of CFR-PEEK to pre-create a dense transition layer for the further surface decoration of electronegative 2D materials (graphene oxide (GO) and black phosphorus (BP), representatively). The results indicated that hardness and wear resistance of the dense transition layer were markedly higher than those of the porous layer. Although GO and BP can be both loaded on these two transition layers, –SO3H on the porous transition layer showed moderate cytotoxicity, while –NO2 on the dense transition layer showed good cytocompatibility. The dense transition layer displayed higher mineralized deposition in vitro and new bone formation rate in vivo than the porous transition layer, moreover, GO and BP coatings improved osteogenesis. This work offers inspirations for the construction of electronegative 2D material coating on CFR-PEEK based on chemical transition layers.

Fabrication of Glycidyl Methacrylate (GMA) Grafted Cellulose from Rice Straw

The purpose of this study was to prepare and characterize cellulose grafted with glycidyl methacrylate (GMA). Cellulose was isolated from rice straw by chemical method. The acid concentration used during the hydrolysis process affects the size of the cellulose produced, therefore in this study different concentrations of sulfuric acid (50%, 60%, and 70%) were used. Particle Size Analyzer (PSA) results showed the best concentration of sulfuric acid was 50%. Glycidyl methacrylate-grafted cellulose (GMA-g-C) was prepared by different concentration of GMA (15%, 20%, and 25%). GMA-g-C particles were characterized by FT-IR and XRD. FT-IR spectra confirmed the formation of GMA-g-C and XRD data showed the decrease in crystallinity of cellulose after grafting process. The optimum grafting conditions were obtained at 20% GMA with a grafting percentage (Pg) of 233.3% and grafting efficiency (GE) of 27.26%.

Ultra high density carbon fiber derived from isotactic polypropylene fiber without skin‐core structure

AbstractPolypropylene (PP)‐based carbon fibers were prepared by sulfonation process of isotactic PP fibers with concentrated sulfuric acid, followed by stress‐less carbonization under nitrogen atmosphere. The stabilization behaviors of PP fiber under different sulfonation temperatures and time were discussed. The carbonization behavior of the stabilized PP fibers under different carbonization temperatures, as well as the mechanical performance of the obtained carbon fibers were investigated. The results indicated that linear PP molecule were effectively converted into thermally stable structure at higher temperature (≥130°C) in short time (2 h) through sulfonation‐desulfonation reaction, among which ordered graphite structure has been formed prior to the carbonization process. Meanwhile, the carbon fibers were considerably densified by increasing the sulfonation temperature and carbonization temperature, and a bulk density of 1.96 g/cm3 was achieved. Moreover, the temperature and time of the sulfonation process as well as the temperature of the carbonization process were regulated, and carbon fibers with tensile strength of 262.3 MPa was obtained, which was superior to that of 208.1 MPa for the linear low density polyethylene‐based carbon fibers reported previously. Isotactic PP was proved to be a promising candidate to develop carbon fibers with tunable graphite structure and mechanical performance.

Studies on (polytrimethylene terephthalate)/graphene oxide/f-MWCNT hybrid nanocomposites

Natural resource-driven approaches to bioengineering plastics are being developed to compete in the automobiles, power, and other sectors. Polytrimethylene terephthalate (PTT) is a particular of them, and it was chosen for the current investigation to build an advanced nanocomposite material. Using a twin-screw micro compounder, injection moulded PTT/Graphene-Oxide (GO)/Carboxyl functionalized Multiwall Carbon nanotube (f-MWCNT) hybrid nanocomposites were prepared. The impact of GO and f-MWCNT reinforcement on the composite’s thermal and mechanical characteristics of hybrid nanocomposites was examined. GO was synthesized from the graphite powder by modified Hummer’s method and MWCNTs were functionalized using the concentrated sulfuric acid (H2SO4) and nitric acid (HNO3) with a volume ratio of 3:1 in an ultrasonic bath at room temperature. In all formulations, the investigation was done at a constant filler amount of 2 wt%. To understand the chemical interaction between PTT and nanofiller, Raman spectroscopy was used and to examine the state of dispersion, scanning electron microscopy (SEM) was systematically analysed. In comparison to pristine PTT, the water absorption, tensile strength, flexural strength and impact strength of hybrid nanocomposites were improved marginally. It was also observed that GO has more prominent in increasing the mechanical properties of the hybrid and f-MWCNT in thermal properties. The 3-D geometrical bridge between GO (2-D) and f-MWCNT (1-D) made the hybrid more dispersible and effective for different applications.

Development and validation of an acid/alkaline digestion method for efficient microplastic extraction from wastewater treatment plant effluents: Sulfuric acid concentration and contact time do matter

Accurate analysis of microplastic particles (MPs) in environmental samples requires removal of interferences during sample preparation. Wastewater samples are interference-rich and thus particularly challenging, with concentrated sulfuric acid currently deemed impractical as a reagent. Therefore, this study aimed to establish a straightforward, effective, and safe method employing concentrated sulfuric acid and potassium hydroxide to eliminate interferents from effluent samples obtained from wastewater treatment plants (WWTPs). We found that 80 % sulfuric acid at room temperature with a brief contact time of 5 min was viable through a qualitative spot test involving 37 plastics categorized into three types (I, II, and III) based on their polymer structure's oxygen position. A quantitative assessment revealed that treatments involving H2SO4 and KOH (20 %, 24 h, 48 °C), either separately or in combination, had no discernible physical impact on the overall plastics, except for a subtle one for Type III plastics (e.g., nylon and PMMA) known to be labile under harsh pH conditions. This acid/alkaline digestion (AAD) method, incorporating such conditions for H2SO4 and KOH treatments, yielded a high mass removal efficacy (97.8 ± 2.4 %, n = 13) for eliminating natural particle interferents for primary, secondary, and tertiary effluent samples. Furthermore, the AAD method allowed for the determination of MPs in effluents with high surrogate particle recoveries (e.g., 95.1 % for larger than 500 μm size fraction). This method is readily adaptable to create appropriate protocols for different types of environmental matrices.

A novel solution-based approach for PANI growth on PEDOT:PSS film to fabricate PEDOT:PSS/PANI-H2SO4 bilayer and its application in thermoelectric energy harvesting

The construction of bilayer or multilayer structures has been recognized as one of the most promising strategies for exploring high-performance organic thermoelectric materials. In this study, a novel poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate)/polyaniline (PEDOT:PSS/PANI) bilayer film was successfully fabricated through a facile solution method, wherein PANI was initially dissolved in concentrated sulfuric acid (H2SO4) to form a homogenous solution which was then applied to the PEDOT:PSS film. Benefiting from the introduction of PANI, the Seebeck coefficient of the PEDOT:PSS film was improved from 16.34 to 23.17 μV K−1, while the electrical conductivity experienced a remarkable enhancement, reaching 723.34 S cm−1. Accordingly, the resulting PEDOT:PSS/PANI-H2SO4 bilayer film demonstrated a high power factor (PF) of 38.83 μW m−1 K−2, which further increased to 44.38 μW m−1 K−2 at 380 K. Hence, this technique offers a facile method to fabricate large-scale PEDOT:PSS/PANI-H2SO4 bilayer films, expanding application fields of PANI via solution-based preparation.

Pretreatment and enzymatic hydrolysis optimization of lignocellulosic biomass for ethanol, xylitol, and phenylacetylcarbinol co-production using Candida magnoliae.

Cellulosic bioethanol production generally has a higher operating cost due to relatively expensive pretreatment strategies and low efficiency of enzymatic hydrolysis. The production of other high-value chemicals such as xylitol and phenylacetylcarbinol (PAC) is, thus, necessary to offset the cost and promote economic viability. The optimal conditions of diluted sulfuric acid pretreatment under boiling water at 95°C and subsequent enzymatic hydrolysis steps for sugarcane bagasse (SCB), rice straw (RS), and corn cob (CC) were optimized using the response surface methodology via a central composite design to simplify the process on the large-scale production. The optimal pretreatment conditions (diluted sulfuric acid concentration (% w/v), treatment time (min)) for SCB (3.36, 113), RS (3.77, 109), and CC (3.89, 112) and the optimal enzymatic hydrolysis conditions (pretreated solid concentration (% w/v), hydrolysis time (h)) for SCB (12.1, 93), RS (10.9, 61), and CC (12.0, 90) were achieved. CC xylose-rich and CC glucose-rich hydrolysates obtained from the respective optimal condition of pretreatment and enzymatic hydrolysis steps were used for xylitol and ethanol production. The statistically significant highest (p ≤ 0.05) xylitol and ethanol yields were 65% ± 1% and 86% ± 2% using Candida magnoliae TISTR 5664. C. magnoliae could statistically significantly degrade (p ≤ 0.05) the inhibitors previously formed during the pretreatment step, including up to 97% w/w hydroxymethylfurfural, 76% w/w furfural, and completely degraded acetic acid during the xylitol production. This study was the first report using the mixed whole cells harvested from xylitol and ethanol production as a biocatalyst in PAC biotransformation under a two-phase emulsion system (vegetable oil/1M phosphate (Pi) buffer). PAC concentration could be improved by 2-fold compared to a single-phase emulsion system using only 1M Pi buffer.

EFFECT OF ACTIVATED CHARCOAL PECAN SHELL (Aleurites moluccanus L. Willd) WITH VARIATIONS IN SULFURIC ACID CONCENTRATION ON DECREASED COD AND BOD LEVELS OF LAUNDRY LIQUID WASTE

Pecan shells are organic waste that can be decomposed but the texture is hard enough that it takes a long time to decompose it naturally. Various efforts to utilize pecan shell waste (Aleurites moluccanus L. Willd), one of which is as a raw material for making activated charcoal. This study aims to find out how the effect of pecan shell activated charcoal (Aleurites moluccanus L. Willd) with variations in the concentration of sulfuric acid against a decrease in Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) levels of laundry liquid waste, as well as the effectiveness of the concentration of sulfuric acid activators. The manufacture of pecan shell activated charcoal (Aleurites moluccanus L. Willd) as an adsorbent is carried out through two stages, namely the authoring stage and the activation stage. BOD testing is carried out by the Winkler titration method while COD is carried out by the closed reflux method. The concentration of sulfuric acid used is 0.5 N; 1.0 N; 1.5 N; 2.0 N; and 2.5 N with a soaking time of 2 hours. The results showed that the sulfuric acid activator that was most effective in reducing laundry liquid waste was at a concentration of 1.5 N with the largest decrease value for BOD, namely 955.56 mg/L (25.44 %) and for COD which was 1648.69 mg/L (18.56 %).

Atmospheric leaching of Ni, Co, Cu, and Zn from sulfide tailings using various oxidants

The growing demand for nickel and cobalt increases the interest in extracting metals from secondary sources, such as flotation tailings. A preferential strategy for the processing of the complex and/or low-grade secondary sources may be material integration into existing primary processes. In this research, a robust sulfuric acid leaching treatment was studied for metal extraction from sulfidic flotation tailings (Ni 0.45 %, Co 0.80 %, Cu 0.20 %, Zn 0.58 %). The impact of leaching parameters on metals extraction was studied; oxygen gas (1–2 L/min), ferric ions (0.05–0.3 M), and hydrogen peroxide (0.5–0.8 M), temperature (30–90 °C), sulfuric acid concentration (0.2–2 M), and solid–liquid ratio (50–100 g/L). It was found that after 30-minutes 20.0 % of nickel, 5.6 % of cobalt, and 33.0 % of the main impurity iron were extracted using oxygen as oxidant. Increasing temperature and sulfuric acid concentration were shown to have a positive effect on extraction. Also, with the further addition of ferric ions, cobalt extraction could be slightly increased (from 6.2 % to 8.3 %) whereas both nickel and cobalt could be increased with hydrogen peroxide (nickel 22.9 %, cobalt 14.2 %). However, the use of H2O2 can be challenging due to its high environmental footprint as well as partial decomposition by ferric ions, increasing H2O2 consumption further. The results suggest that the mineralogy of the investigated tailings limited feasible metals extraction using atmospheric conditions up to ≈ 20 % for nickel and ≈ 10 % for cobalt, with nickel distributing stronger into non-refractory minerals while cobalt reported more to pyrite. For other base metals, zinc extraction from sphalerite was shown to be efficient (up to ≈ 90 %) whereas copper extraction was limited (up to ≈ 30 %). In future, such atmospheric sulfuric acid leaching may provide a robust recovery route for non-refractory minerals present in the tailings, while full valorization of sulfide tailings matrix will require higher intensity processing with technologies such as pressure oxidation (POX), concentrated chloride leaching, bioleaching, roasting-leaching or very fine milling of the raw material prior to atmospheric leaching.

Transformations of cage alcohols in the presence of 2-propanol and H2SO4

A convenient approach for the synthesis of hydrocarbons by transformations of cage alcohols in the presence of 2-propanol and sulfuric acid has been proposed. Scalability, good yields and usage of readily available reagents along with synthetic convenience showed usefulness of proposed approach. This approach made it possible to obtain high preparative yields of difficult-to-reach cage hydrocarbons such as 2-methyladamantane, 2-phenyladamantane and homoadamantane. For some substrates, the potential to obtain corresponding saturated hydrocarbons or alkenylation products by varying the concentration of sulfuric acid under reaction conditions has been demonstrated.

Iron-sulfur chemistry can explain the ultraviolet absorber in the clouds of Venus.

The clouds of Venus are believed to be composed of sulfuric acid (H2SO4) and minor constituents including iron-bearing compounds, and their respective concentrations vary with height in the thick Venusian atmosphere. This study experimentally investigates possible iron-bearing mineral phases that are stable under the unique conditions within Venusian clouds. Our results demonstrate that ferric iron can react with sulfuric acid to form two mineral phases: rhomboclase [(H5O2)Fe(SO4)2·3H2O] and acid ferric sulfate [(H3O)Fe(SO4)2]. A combination of these two mineral phases and dissolved Fe3+ in varying concentrations of sulfuric acid are shown to be good candidates for explaining the 200- to 300-nm and 300- to 500-nm features of the reported unknown UV absorber. We, therefore, hypothesize a rich and largely unexplored heterogeneous chemistry in the cloud droplets of Venus that has a large effect on the optical properties of the clouds and the behavior of trace gas species throughout Venus's atmosphere.

Tailoring visible-light active TiO2/cellulose nanocomposites with controlled crystalline structure for enhanced photocatalytic performance.

This work involves a green and simple synthesis of TiO2 nanoparticles on cellulose under mild conditions without the need for calcination via hydrolysis of titanium oxysulfate (TiOSO4). The synthesis conditions, such as sulfuric acid concentration (0-10%wt), temperature (70-90℃), and time (4-8h), focused on precisely controlling the structure of TiO2 to enhance its photocatalytic effectiveness under visible light. At a lower 2.5wt% sulfuric acid concentration, pure anatase was formed on the cellulose, while an increase in the range of 5.0-7.5wt% sulfuric acid concentration yielded a rutile phase, resulting in a mixed phase of anatase and rutile on the cellulose. The pure rutile phase was found at a low temperature (70℃), while increased temperature led to the formation of the anatase phase. These results confirmed that the formation of crystalline TiO2 phase on the cellulose depended on sulfuric acid concentration and temperature for hydrolysis. Additionally, the photocatalytic properties of the obtained materials were evaluated by degradationvisible of Rhodamine B (RhB) under UV and visible light. The findings revealed that the mixed phase (anatase/rutile) of TiO2 on the cellulose demonstrated a superior photocatalytic efficiency (99.2%) compared to pure anatase (85.75%) and rutile (75.08%) when exposed to visible light.

Using the overall variation trend and fitting of Na-feldspar crystal plane spacing after chemical corrosion to prevent rock disasters

Sulfuric acid pollution, caused by acid rain, acidic wastewater, and natural acidic wastewater from mines, poses a significant risk to the stability of natural stone slopes and human stone structures. This study aims to develop a non-mechanical testing method for assessing the degree of acid corrosion in rocks, facilitating early intervention by safety engineers. The proposed method involves using XRD to measure the crystal plane spacing of Na-feldspar corroded by different concentrations of sulfuric acid, followed by mathematical analysis to determine the overall deviation degree of the crystal plane spacing. Four Deviation indices were defined to characterize the degree of acid corrosion, and all four indices increased with increasing acidity. By comparing trend charts, an optimized number of crystal planes for analysis was identified. Selecting the 100 sets of data with the largest spacing yielded similar trend results as selecting all the data. In addition, five different fitting methods were compared, and the power function fitting of Weighted Sum of squares of cumulative errors (WSSCE) was found to provide the optimal empirical formula, with a correlation coefficient exceeding 0.98.

Super-resolution fluorescence imaging of PEDOT:PSS films.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a popular conduction polymer and widely used in organic electronics, bioelectronics and printed electronics. It is believed that PEDOT:PSS has a core-shell colloidal structure dispersed in the formulation. However, the size and surface functional groups of the PEDOT:PSS dispersion and films remain to be visualized. Here, we have introduced the concept of aggregation-induced emission (AIE) to super-resolution imaging for designing the cationic probe TPE-4N+ and accomplished the nanoscale optical visualization of PEDOT:PSS films through reversible electrostatic interactions. Information on the PEDOT:PSS size and surface charge has been successfully collected via super-resolution imaging. The full-width at half-maximum (FWHM) of PSS nanoparticles was observed to be approximately 30-40 nm. The super-resolution fluorescence imaging method can also be used to monitor the PEDOT:PSS film after acid treatment. It was observed that PSS chains were washed away when exposed to concentrated sulfuric acid, which explains why concentrated sulfuric acid treatment greatly improves the conductivity of the PEDOT:PSS film. Super-resolution imaging is promising as an effective method for characterizing PEDOT:PSS films.

Experimental Study on Activated Sulfur Selection from High Alkalinity Lead Zinc Flotation Tailings

This article takes the flotation tailings of a high sulfur lead-zinc mine in Inner Mongolia as the research object. XRD and BPMA automatic process mineralogical analysis systems are used to analyze the mineral composition of the tailings, and experimental research is conducted on the comprehensive recovery of pyrite through activated flotation. The results showed that using concentrated sulfuric acid as an activator, ethyl xanthate and isoamyl xanthate as a combination collector, and adopting a flotation process of “one coarse, one sweep, and two fine”, a concentrate product with a yield of 9.31% and a sulfur grade of 37.78% can be obtained, and the sulfur recovery rate in the concentrate can reach 77.13%; The comprehensive recovery and utilization of sulfur in the original flotation tailings have been achieved.

Caracterização físico-química de frutos, biometria e dormência de sementes de marula

ABSTRACT: This study recorded the physicochemical properties of the marula fruits, the biometry and breaking the dormancy in the marula seeds. Using 200 ripe fruits, the physicochemical characterization was done. From a random sample of 400 seeds, an assessment of the biometrics was performed, and the weight, length, width and thickness of the fruits and seeds were evaluated. Two experiments were conducted to study dormancy breaking using pre-germination treatments, which included immersing the marula seeds five times (0, 15, 30, 45 and 60 minutes) in concentrated sulfuric acid (96%) and water, at 65 ºC temperature. The control was time zero, using plain distilled water, with 25 seeds per treatment and four replications. The marula fruits revealed average values of 21.65 ± 3.44 g, 35.5 ± 2.38 and 34.8 ± 2.73, respectively, for weight, diameter and length. The soluble solids (SS), Hydrogenonic Potential (pH), titratable acidity (AT) and ratio (AT/SS) were 14.74 ± 1.0º Brix, 3.93 ± 0.49 pH, 0.63 ± 0.22 and 27.07 ± 12.10, respectively. For the weight of one thousand seeds, the average value was 3.576 ± 188.4 g. The mean values for the dimensions of the width, length and diameter of the seeds were 22.9 ± 2.11; 23.7 ± 2.04; and 14.9 ± 2.09 mm, respectively. The physiological quality of these seeds was enhanced by immersing the seeds from freshly picked fruits in sulfuric acid for a maximum of 30 minutes and storing them for six months.

Evaluation of Biodegradable Nylon from Cassava Starch (Tapioca Starch)

Biodegradable and bio-based plastics currently constitute a small fraction of the overall plastic market.This study aims to scrutinize the feasibility, properties, and environmental impact of producing biodegradable nylon using cassava starch as a raw material. Analysis carried out includes; Solubility, biodegradability, and water adsorption test. The results of the solubility test for the bio plastic derived from cassava starch indicated a slight solubility in water, insolubility in the polar solvent methanol and complete solubility in concentrated sulfuric acid (H2SO4) and hydro chloric acid (HCl). The analysis results reveal that the starch-based bio plastic displays a higher capacity for water absorption. Utilizing biodegradable components such as cassava starch, gelatin, and glycerol, a comprehensive performance film was successfully developed. The study demonstrated that bio plastics derived from cassava starch degrade in less than twenty-eight days, suggesting their suitability for application in the packaging industry.