Hydrochloric Acid Concentration Research Articles

Arsenazo III-spectrophotometry for the determination of thorium content

ABSTRACT The complexation interaction between arsenazo III chromogenic agent and tetravalent thorium ion (Th4+) is the theoretical basis for the determination of thorium by spectrophotometry. In this paper, the effects of the acidity, temperature, interfering ions and Th4+ concentration on the absorbance and stability of arsenazo III-Th4+ solution by spectrophotometry were systematically studied. The results showed that the solutions to be tested had high absorbance values and stability only when the concentration of hydrochloric acid was greater than 6 mol·L−1. The absorbance decreased only 0.02 when the temperature was changed from 15°C to 40°C. The absorbance of arsenazo III-Th4+ solution at 662 nm showed a good linear relationship with the concentration of Th4+ under the same experimental environment (R2 = 0.9986), and the apparent molar absorption coefficient was 9.95 × 104 L·mol−1·cm−1, showing that thorium can be accurately quantitatively measured according to the Lambert-Beer law under these conditions.

Physical and Chemical Characteristics of Green Algae Halimeda opuntia Calcium Powder Extracted Using Hydrochloric Acid

Halimeda opuntia is one of the macroalgae species whose utilization is still slightly known. In the open sea, H. opuntia holds an important role in changing carbon dioxide (CO2) to calcium carbonate (CaCO3). This led to previous research analyzing the calcium content of H. opuntia, which showed 30.30%. However, the information about calcium powder extraction using HCl from H. opuntia has not been reported. This research aimed to observe the physical and chemical characteristics of calcium obtained from H. opuntia extracted using different hydrochloric acid (HCl) concentrations. The method used in this research was experimental laboratories with a completely randomized design (CRD) using different HCl concentrations (1N, 2N, and 3N). The extraction results were analyzed for yield value, moisture, ash, fat, protein, carbohydrate, calcium, color, Scanning Electron Microscope (SEM), particle size, and X-Ray Diffraction (XRD). Data were then analyzed using Analysis of Variance (ANOVA). The use of different HCl concentrations showed significant effect (p0.05) on ash content (91.95±0.47%), carbohydrate content (7.26±0.57%), lightness (L*) (86.21±0.83), yellowness or blueness (b*) (8.81±0.02), E (11.33±0.54), and whiteness index (WI) (83.62±0.70%), where the calcium extracted by 1N HCl (CH1) showed the best result. The SEM microstructural analysis showed a non-porous surface and a single cubical shape in CH1. Diffractogram pattern of calcium extracted from H. opuntia using different concentrations of HCl done by XRD exhibited the same pattern as CaCO3 for all samples. HCl solvent at 1 N can produce calcium powder from H. opuntia with high calcium content and better color characteristics.

Effects of Fuel Hydrochloric Acid Contamination on Selected Metals

Chlorinated organic compounds, as contaminants in marine fuels, have caused severe damage, affecting both main and auxiliary engines. Contaminated fuels can cause serious damage to an engine and its components, corroding fuel pumps and blocking filters, for example. This affects the operation of the engine, and, in the most severe cases, vessel safety. This study considered fossil diesel containing hydrochloric acid as a possible product formed under certain conditions in fuel contaminated with COCs and its effects on carbon steel, stainless steel, tempering steel, and aluminum. Five fuel samples with different concentrations of hydrochloric acid were prepared, plus one sample of diesel and water. Metal bars were partially immersed in the fuel samples and stored at room temperature for approximately one month. A visual assessment found corrosion across the entire surface of all metal bars when exposed to fuel samples containing hydrochloric acid. Even the smallest acid content (25 ppm) caused corrosion, and the effects were already observable after only two days of exposure. Despite their acid contamination, the measured fuel properties fulfilled the standard for automotive fuels at the beginning of the test. The water in the diesel sample did not cause any visible corrosion.

Hydrolytic purification of industrially extracted mimosa tannin

Tannins, which can be extracted from certain tree barks, are polyphenolic compounds, that gain a lot of interest in industry, as they can be utilized to replace petroleum-based chemicals. Currently, they are used in the leather industry, as flocculants or as adhesives. To further increase their potential, an increase in purity is necessary. To do so, various methods are available, in this study we present a 2-step approach consisting of (i) depolymerization and cleavage of glycosidic bonds and (ii) separation of phenolic-rich and phenolic-poor fractions. Commercially available mimosa tannin is treated with various concentrations of hydrochloric and sulfuric acid (0.4 M and 0.8 M) and separated with chromatographic resin. Resulting fractions are characterized by UV/Vis spectroscopy for phenolic content and antioxidant activity, infrared spectroscopy, NMR, HPLC-DAD and GPC to determine their composition and molecular size as well as their reactivity towards formaldehyde. It was observed that mild acidic cleavage with 0.4 M HCl results in more phenol-rich material (TPC 1124 µgGAE mg−1) while 0.8 M sulfuric acid leads to tannin fractions with higher antioxidative properties. Amberlite resin yields fractions with higher reactivity towards formaldehyde (gel time below 60 s compared to over 90 originally) while the Sephadex fractions present the highest values for total phenolic content.

Modification of sand fertility parameters during cleaning and purification process

The use of sand as a substrate in nutritional studies is frequent, but there is no formal protocol for cleaning and purifying this substrate for various agronomic studies, including those related to plant nutrition. The study aimed to evaluate the changes in chemical attributes resulting from the cleaning and purification of common construction sand. The experimental study, of a quantitative nature, was carried out under greenhouse and laboratory conditions. An experiment was carried out whose treatments were levels of hydrochloric acid (HCl) concentration, immersion times in the acid solution, and purification in an autoclave. It was found that sterilization in an autoclave significantly decreased the pH of the sand and increased the phosphorus content. From a day of rest with HCl, the decrease in the pH of the sand was significant. On the other hand, the phosphorus content increased linearly with the immersion time in HCl. The use of HCl completely eliminated the levels of potassium, calcium, magnesium, and copper, and significantly decreased the contents of iron and manganese (above 70%) and zinc (above 80%). To exhaust or significantly decrease the levels of nutrients present in the sand, one should use 3% HCl, without rest, for phosphorus and one day of incubation for potassium, calcium, magnesium, and copper, iron, manganese, and zinc.

Physicochemical properties and antibacterial activity evaluation of new indigo extract from Baphicacanthus cusia (Nees) Bremek prepared by chemical conversion method

The effect of acidolysis time, hydrochloric acid concentration, ozonization time and pH on the yield of indigo were investigated by single factor experiment using dried leaves of Baphicacanthus cusia (Nees) Bremek (DLB) as raw material. On this basis, the technological condition for preparing new indigo extract (NIE) by directional chemical conversion method was optimized by orthogonal experiment. Then, the physiochemical properties of NIE were analyzed by combustion assay, nitric acid assay, thin layer chromatography identification assay, moisture detection and water-soluble pigment observation assay. Moreover, UPLC-Q-TOF-MS/MS technology was utilized to compare chemical composition difference between the NIE and traditional indigo naturalis (TIN). Finally, NIE emulsion was prepared by ultrasound assisted high pressure homogenization method and its stability, antibacterial activity as well as antibacterial mechanism were evaluated. The experimental results showed that optimum process for preparing NIE were hydrochloric acid concentration of 2 %, ozonization time of 3 min, pH of 7 and acidolysis time of 1 h; Under this condition, the content and yield of indigo in the NIE were significantly improved, which could reach up to 42.6 ± 0.28 % and 2.26 ± 0.04 %, separately. NIE possessed similar physiochemical properties with TIN described in Chinese pharmacopoeia 2020, and had more diverse active ingredients than TIN. The prepared NIE emulsion demonstrated excellent stability, whether at dark or bright place, and no matter at low temperature (4 ℃) or room temperature (25 ℃), the particle size, PDI, pH and indigo content of which displayed little variation. In addition, the NIE emulsion owned good inhibitory activity against S. aureus, and its MIC and MBC values were 40 and 80 μg/mL, respectively. Moreover, NIE emulsion exhibited antibacterial effect by influencing cell membrane integrity, Ca2+-Mg2+-ATPase activity on the cell membrane and intracellular Ca2+ levels of S. aureus. All of above results will lay the foundation for the green and sustainable utilization of Baphicacanthus cusia (Nees) Bremek.

Optimization of cobia fish (Rachycentron canadum) gelatin extraction with response surface methodology

Cobia fish or often called sea cork fish, is a fish that has thick meat which is nutritionally equivalent to salmon meat. Cobia fish is usually sold in the form of fish fillets and the bones becomes solid waste, which has the potential to be a raw material for fish gelatin. Gelatin is a bone and skin collagen hydrolysis product that can be used for food and nonfood industries. The quality of fish gelatin is influenced by the extraction process, such as acid concentration, temperature, and extraction time. This study aims to determine the effect of hydrochloric acid concentration, temperature, extraction time, and the optimal process of making cobia fish bone gelatin using the response surface methodology with the Box Behnken model. The data was processed using Design Expert 11 software. The model suggested by the software was the cubic model. The optimum extraction conditions obtained were using a concentration of 5.53% hydrochloric acid, a temperature of 90oC, and a stirring time of 6.42 mins would produce a yield of 12.38% and gel strength of 229.14 bloom. The verification results by extracting cobia fish gelatin with optimum conditions obtained a yield of 11.22% and gel strength of 227.60 bloom. The proximate analysis of cobia fish gelatin extracted under optimum conditions was found to contain 6.43% water content, 8.27% ash content, 4.65% fat content, 68.47% protein content, and 12.18% carbohydrate by different. Cobia fish gelatin microstructure is in the form of thick strands with a soft sponge.

Study on the Pb(II) adsorption mechanism on acid‐modified ceramsite made from sewage sludge and industrial solid wastes

AbstractCeramsite was made from sludge, phosphogypsum, and red mud and then modified with different concentrations of hydrochloric, nitric, or citric acid. The resulting composite ceramsite was subsequently utilized for the adsorption of Pb(II). The maximum adsorption capacities of hydrochloric acid– and nitric acid–modified ceramsites were 90.38 and 88.57 mg/g, respectively, which were much higher than those of unmodified ceramsite (66.86 mg/g) and citric acid–modified ceramsite (57.85 mg/g). The variation of isoelectric point, acidic and basic groups, and Fourier transform infrared spectra of ceramsite were compared before and after adsorption. A decrease of isoelectric point implied weakening of electrostatic repulsion between Pb(II) and the modified ceramsite. Functional groups, such as O─H, C═O (or C═C), and Si─O─Si (or Al─O─Al), were involved in the adsorption. In addition, phenol hydroxyl, which exhibited a significant increase in modified ceramsite and a noticeable decrease after adsorption, was the most important group. Besides, the modified ceramsite had larger specific surface areas and pores (30.66 g/m2, .11256 cm3/g), more functional groups, and lower isoelectric points (8.57), which were favorable for adsorption. The adsorption processes described by pseudo‐second‐order kinetics were controlled by chemical adsorptions. Isothermal studies indicated that monolayer adsorption occurred on hydrochloric acid–modified ceramsite and multiple processes occurred on nitric acid– and citric acid–modified ceramsites. Thermodynamic analysis confirmed Pb(II) adsorption on modified ceramsite was spontaneous and endothermic.

A Study on the Adsorption of Methylene Blue by Acid-Modified Coal Measures Kaolin

In this paper, coal measure kaolin after flotation decarburization was made into an adsorbent by ball milling and acid modification to absorb methylene blue in water, achieving the treatment of waste with waste. The objective of this paper is to expand the application of coal measure kaolin, reduce its stock, and lower the raw material cost of adsorbents while treating wastewater containing methylene blue. The optimum milling time, acid boiling conditions, and adsorption conditions were investigated. Furthermore, the adsorption mechanism was investigated by kinetic calculation. The results show that the optimum milling time is 7 h. Relatively good acid modification conditions include a boiling temperature of 100 °C, a stirring time of 135 min, a stirring speed of 1000 r·min−1, and a concentration of hydrochloric acid of 8 mol·L−1. When 0.05 g of flotation kaolin adsorbent was used to adsorb the solution with pH 12 and a methylene blue concentration of 100 mg·L−1, the optimal adsorption conditions were a 38.05 °C adsorption temperature, a 160 r·min−1 stirring speed, and a 31.02 min stirring time. Under these optimal conditions, the adsorption quantity reached 39.92 mg·g−1. The adsorption process involves physical adsorption and spontaneous adsorption. The adsorption type is known as the quasi-second-order adsorption kinetic model. The adsorption form is heterogeneous adsorption in which a monolayer and a multi-molecular layer coexist.

Hot-pressure acid leaching changes grain boundaries to deeply remove impurities in quartz sand

High-purity quartz sand is a crucial raw material for advanced industries such as photovoltaics. However, due to the limited availability of high-quality ore sources, there is currently no method to prepare high-purity quartz sand using alternative minerals, leading to a shortage of high-purity quartz sand resources. This study aims to explore the mechanism of efficiently purifying quartz sand through a comparative analysis of hot-pressure acid leaching (HPAL) and atmospheric-pressure acid leaching (APAL), providing a theoretical foundation for preparing high-purity quartz sand using alternative minerals. The results indicate that, during the HPAL process, the combined action of temperature and pressure transforms closed grain boundaries (CGBs) into open grain boundaries (OGBs), increasing the degree of openness of OGBs. The opening of CGBs provides additional channels for the leaching agent to penetrate the quartz, exposing it to more internal impurities. Under conditions of hydrochloric acid (HCl) concentration (3 M), liquid-to-solid ratio (5:1), stirring speed (450 rpm), and holding time (2 h), elemental contents of iron (Fe), aluminum (Al), potassium (K), and sodium (Na) after APAL (363 K, atmospheric pressure) were reduced to 63.9 μg/g, 58.7 μg/g, 21.3 μg/g, and 7.3 μg/g, respectively. However, after HPAL (473 K, 1.5 MPa), these values decreased significantly to 4.7 μg/g, 30.9 μg/g, 3.6 μg/g, and 4.9 μg/g. This paper elucidates the mechanism of HPAL efficiently removing impurities in quartz sand through grain boundaries (GBs), providing a new direction and theoretical basis for the preparation of high-purity quartz sand.

A new derivatizing reagent for the determination of 5-nitro-2-furaldehyde in trout muscle by liquid chromatography-tandem mass spectrometry

The 5-nitro-2-furaldehyde (5-NF) is an aldehyde aromatic organic compound that has been envisaged as an alternative marker for detecting nitrofurazone treatment abuse and to avoid the false positive results induced by the semicarbazide. Analyzing 5-NF presents challenges, and its derivatization reaction with hydrazine reagents is required to enhance the capability of its detection and its identification. This study aims at developping an analytical method for 5-NF determination in trout muscle samples based on chemical derivatization prior to analysis by liquid chromatography–tandem mass spectrometry. Four commercially available hydrazine reagents, namely: N,N-Dimethylhydrazine (DMH), 4-Hydrazinobenzoic acid (HBA), 2,4-Dichlorophenylhydrazine (2,4-DCPH) and 2,6-Dichlorophenylhydrazine (2,6-DCPH) were proposed for the first time as derivatizing reagents in the analysis of 5-NF. The derivatization reaction was simultaneously performed along with the extraction method in acidic condition using ultrasonic assistance and followed by liquid extraction using acetonitrile. The efficiency of the chemical reaction with 5-NF was examined and the reaction conditions including the concentration of hydrochloric acid, pH, temperature, reaction time and the concentration of the derivatizing reagents were optimized. Experiments with fortified samples demonstrated that 2,4-DCPH derivatizing reagent at 20 mM for 20 min of ultrasonic treatment under acidic condition (pH 4) gave an effective sample derivatization method for 5-NF analysis. Under the optimized conditions, the calibration curves were linear from 0.25 to 2 μg kg−1 with coefficient of determination >0.99. The recoveries ranged from 89 % to 116 % and precision was less than 13 %. The limit of detection and quantification were 0.1 and 0.2 μg kg−1, respectively.

Electrochemical oscillation behaviors of gold during its recovery from waste printed circuit boards through slurry electrolysis

Slurry electrolysis is an effective technology for recovering gold from waste printed circuit boards (WPCBs). However, electrochemical oscillation during the gold recovery process is a potential factor affecting power consumption. As a result, the potential oscillation behaviors of gold dissolution at a constant current were studied. These results showed that the periodic formation and dissolution of the Au-OH passive film on the anode induced electrochemical oscillation. The amplitude and frequency of electrochemical oscillation were affected by hydrochloric acid concentration, current intensity, electrode spacing, and sodium chloride concentration, among which the concentration of sodium chloride had a significant inhibitory effect. Under the following conditions: hydrochloric acid concentration of 8 mol/L, current of 0.03 A, and electrode spacing of 1.5 cm, the obtained maximum amplitude potential and frequency were 1.17 V and 0.56 Hz, respectively. The phase space reconstruction results showed that the systems evolved between the near-linear equilibrium region and the periodic oscillation region. Different factors induced two oscillation modes: top-down and bottom-up. The top-down and bottom-up oscillations induced by current intensity, hydrochloric acid concentration, and electrode spacing reduced the relative power consumption by 11.8, 17.2, and 11.8 %, respectively, and increased the relative power consumption by 14.3, 21.2, and 30.1 %, respectively. A critical value was obtained, which varied oscillation patterns and gained a region of lower power consumption. The addition of trisodium citrate and PVP can improve gold recovery rate and current efficiency by regulating process of electrochemical oscillation. This work will provide theoretical support for recovering valuable metals from WPCBs with reduced energy consumption by controlling the external conditions to switch the oscillation mode.

Application of Acid Activated Ouw’s Natural Clay (ONC) on Adsorption of Methylene Blue Dye

The application of natural clay as an adsorbent has been widely used. This is supported by the porous surface texture of the clay. However, some treatments are needed to remove impurities in natural clay before using it as an adsorbent. The common effort is to activate it with acid. This research studied the effect of hydrochloric acid concentration on the adsorption capacity of methylene blue dye. The concentrations of hydrochloric acid used were 2, 3, and 4 M. Characterization was carried out with IR, XRD, and SEM-EDX spectroscopy to see the differences in ONC characters before and after adding hydrochloric acid. The characterization results showed that ONC contained montmorillonite and quartz, and an increase in base distance was directly proportional to the increase in the concentration of hydrochloric acid used. High concentrations of hydrochloric acid caused excessive dealumination and deionization. The dealumination process was supported by IR data where there was a shift in wavenumber in the Al-O stretching vibration region from 796 cm–1 to 794 cm–1; the sharper the vibration in the Si-O region (488-468 cm–1); there was also an increase in the Si/Al ratio of pure ONC from 1.7497 to 2.2970 for 3 M ONC-HCl. The concentration of hydrochloric acid did not significantly affect the capacity of ONC as an adsorbent for methylene blue. The adsorption capacity of pure ONC obtained was 4.97215 mg/g, while for ONC-HCl 3 M was 4.97746 mg/g.

Closed-loop cleaning treatment system — resource recovery of coal gangue

ABSTRACT Coal gangue (CG) is one of the main solid wastes emitted by coal mining. It causes severe damage to the environment. CG contains high levels of valuable elements (Al, Si) and has the potential for utilization and clean disposal. Here, an environment-friendly process for separating valuable components from CG was proposed: the closed-loop system of activation-leach-separation. The results show that the decarbonization rate was close to 100% under the optimum conditions of CG particle size of 0.075 mm to 0.15 mm and activated at 800°C for 120 min. Subsequently, it was transformed into a mixed-acid system with a hydrochloric acid (HCl) concentration of 4.5 mol/L, hydrofluoric acid (HF) volume fraction of 15%, and the liquid-solid ratio of 10:1, which achieved excellent separation efficiency. The residual rate of Al in the solution was only 0.7%, and the extraction rate of Si can reach 71.6%. Further, industrial-grade AlF3 products were also recovered. By adding saturated KCl solution and reacting at 33°C for 15 min, Si was further recovered in K2SiF6, and the yield was 85.83%. Particularly, the leaching solution maintained good extraction efficiency in the subsequent three cycles, the yield of K2SiF6 was 88.29%, confirming the feasibility of the closed-loop system. This treatment embodied the environmental-friendly properties of low acid consumption and low effluent discharge, providing a feasible method for clean treatment and resource utilization of CG.

Synthesis and Surface Strengthening Modification of Silica Aerogel from Fly Ash.

This study focuses on using activated fly ash to preparate silica aerogel by the acid solution-alkali leaching method and ambient pressure drying. Additionally, to improve the performance of silica aerogel, C6H16O3Si (KH-570) and CH3Si(CH3O)3 (MTMS) modifiers were used. Finally, this paper investigated the factors affecting the desilication rate of fly ash and analyzed the structure and performance of silica aerogel. The experimental results show that: (1) The factors affecting the desilication rate are ranked as follows: hydrochloric acid concentration > solid-liquid ratio > reaction temperature > reaction time. (2) KH-570 showed the best performance, and when the volume ratio of the silica solution to it was 10:1, the density of silica aerogel reached a minimum of 183 mg/cm3. (3) The optimal process conditions are a hydrochloric acid concentration of 20 wt%, a solid-liquid ratio of 1:4, a reaction time of two hours, and a reaction temperature of 100 °C. (4) The optimal performance parameters of silica aerogel were the thermal conductivity, specific surface area, pore volume, average pore size, and contact angle values, with 0.0421 W·(m·K)-1, 487.9 m2·g-1, 1.107 cm3·g-1, 9.075 nm, and 123°, respectively. This study not only achieves the high-value utilization of fly ash, but also facilitates the effective recovery and utilization of industrial waste.

Industrial hemp hurd processing for microcrystalline cellulose production and its usage as a filler in paper

This article substantiates the possibilities of replacing commercial wood with raw materials made from industrial hemp hurd (hemp-woody core) for the production of unbleached and bleached paper pulps. A comparative analysis of the mechanical characteristics of sheets of paper prepared in the Rapid-Köthen apparatus and obtained from pulp obtained from commercial wood and hemp-woody core (HWC) was undertaken. The objective of this study was to determine the effect of mechanical refining of a pulp on the production of microcrystalline cellulose (MCC) from HWC. It was shown that an increase in the pulp refining degree from 15 °SR to 83 °SR led to a decrease in the degree of polymerisation of MCC from 272 to 75, the hydrochloric acid concentration from 73 to 45.63 g/L, and the hydrolysis time from 120 min to 60 min. With the addition of 5% MCC obtained from hemp-woody core, the mechanical properties of laboratory paper sheets from HWC were improved until they met ISO 12625-4-2017 (2017) requirements for NS-2. The results obtained support using hemp-woody core for the production of MCC.

Impregnated Polymeric Sorbent for the Removal of Noble Metal Ions from Model Chloride Solutions and the RAM Module.

Nowadays, there is a need for new sources of noble metals due to their dwindling natural resources. This paper presents studies on the sorption of noble metals such as Au(III), Pt(IV), Pd(II) and Rh(III) from model chloride solutions on a newly prepared Amberlite XAD-16-Aliquat 336 sorbent. A "warm impregnation" method without the use of toxic organic solvents was applied to impregnate the polymer matrix. The influence of such factors as hydrochloric acid concentration, sorbent mass and phase contact time was investigated. Kinetic as well as adsorption isotherm studies were carried out. The sorption capacity of the synthesized sorbent was Au(III)-94.34 mg/g, Pt(IV)-45.35 mg/g and Pd(II)-46.03 mg/g. Based on thermodynamic considerations, their sorption proved to be endothermic, as the values of ΔH° > 0. Sorption was spontaneous and favourable (ΔG° < 0). After leaching the RAM module, there was obtained a real solution, in which the metal contents were determined: 38.10 mg/g of gold and 1.76 mg/g of palladium. Totals of 99.9% of gold and 45.4% of palladium were removed from the real leaching solution, with other elements in the solution.

Investigation of thermodynamic and kinetic regularities of asbestos waste leaching processes

The asbestos wastes were exploited for extraction of magnesium by agitation leaching process in atmospheric conditions, using hydrochloric acid as the leaching agent. The study was focused on investigating the kinetics of magnesium leaching. The effects of some variables, including stirring speed (150−300 r/min), leaching temperature (25−90 °C), leaching duration (10–60 min), the concentration of hydrochloric acid (150–300 g/L) and the solid - liquid ratio (1:2–1:5), on the leaching rate were carefully evaluated. It was found that increasing the stirring speed, leaching temperature, and concentration of hydrochloric acid can significantly increase the rate at which magnesium is leached. A comprehensive kinetic scrutinization was performed by fitting the experimental data with exponential kinetic equation, Yander diffusion equation, Drozdov-Rotinyan equation, and Prout-Tompkins equation. Amongst all these tested kinetic equations, the diffusion-controlled process showed a higher goodness-of-fit with experimental data. Thermodynamic aspects were also appraised carefully. The apparent activation energy for the process was calculated to be 19.8 kJ/mol, indicating a relatively low-level energy needed to initiate the process efficiently. Overall, the current study provided insight into how changing certain parameters can affect the overall performance when attempting to extract magnesium from the asbestos wastes by leaching process.

High‐Purity Template‐Free Mesoporous Silica Synthesized FROM Coal Fly Ash

AbstractThe study demonstrates a new method to create high‐purity mesoporous silica from coal fly ash without using structure‐directing agents. Divided into two stages, the process involves pre‐treating the ash with Na2CO3, calcination, cooling, washing, and drying to yield a dehydrated sample. Subsequently, silica synthesis occurs through an acid refluxing technique using thermally activated coal fly ash with Na2CO3. Key factors impacting synthesis include acid content and liquid‐to‐solid ratio. The study extensively employs various characterization methods like XRF, XRD, FTIR, and BET analysis, revealing a 99.1 % purity in silica content, a surface area of 793.51 m2/g, and a pore size of 3.9 nm. Optimal conditions for this synthesis involve 80 °C temperature, 2‐hour reaction time, 25 % hydrochloric acid concentration, and a 10 : 1 liquid‐to‐solid ratio. FTIR spectra demonstrate similarities between the obtained silica and commercial Sigma Aldrich silica. This innovative approach presents a promising avenue for generating top‐quality silica from coal fly ash, potentially diversifying applications across industries reliant on high‐performance silica materials.

Removal of High Concentrations of Arsenite from Aqueous Solutions by the Emulsion Liquid Membrane Technique

AbstractAs(III) is a dangerous species that contaminates groundwater resources and therefore water purification from this element is necessary. In this study, the removal of As(III) was investigated by the emulsion liquid membrane (ELM) technique due to the high toxicity levels of this species. The effect of various parameters such as hydrochloric acid and arsenic concentration in the feed solution, emulsion to feed ratio, surfactant concentration and type of carrier was evaluated on the arsenic separation efficiency. The results showed that the best type of carrier in terms of emulsion stability and separation efficiency of arsenic ions was di‐(2‐ethylhexyl) phosphoric acid (D2EHPA), and its optimal concentration was about 5 % (v/v). In addition, paraffin as the organic solvent performed better than the mixture of paraffin and kerosene in the separation of As(III) ions. The optimal conditions were obtained at 8 and 0.1 M HCl concentrations for the feed and the internal phases, respectively. Also, the emulsion to feed ratio of 1 : 4.5, the volume ratio of the internal phase to the membrane phase of 1 : 1 and the surfactant concentration of 5 % (v/v) led to achieving the maximum removal of arsenic ions. This work presents a broad perspective of removing As(III) ions from wastewater by carefully examining the parameters influencing the separation of this hazardous element through the ELM method.