Use Of Mineral Acids Research Articles

Mesoporous Silica with an Alveolar Construction Obtained by Eco-Friendly Treatment of Rice Husks.

The high silicon content in rice plant waste, specifically rice husks, makes this waste by-product attractive for the extraction and valorization of silicon oxide, which is widely used as an inert support in catalysis, drug delivery and molecular sieving. The procedures currently used for the treatment of plant biomass make extensive use of mineral acids (HCl, H2SO4, HNO3), which, besides them being potential environmental pollutants, reduce the yield and worsen the chemical-physical properties of the product. In this study, an evaluation of the easy treatment of rice husks by benchmarking different, more eco-friendly carboxylic acids in order to obtain a mesoporous SiO2 with an alveolar structure and a relatively high surface area and pore volume (300-420 m2/g, 0.37-0.46 cm3/g) is presented. The obtained mesoporous silicas are characterized by worm-like pores with a narrow size distribution and a maximum in the range of 3.4-3.5 nm. The mesoporous structure of the obtained materials was also confirmed by TEM. The complete removal of the organic part of the rice husks in the final materials was evidenced by thermogravimetric analysis. The high purity of the obtained mesoporous silica was detected using ICP analysis (98.8 wt. %). The structure peculiarities of the obtained mesoporous silicas were also characterized by solid-state NMR and ATR-FTIR spectroscopies. The morphology of the mesoporous silica was investigated by SEM.

Solubility in manganese sulfate-ammonium sulfate-water system

The production of phosphorus-containing fertilizers involves the use of mineral acids and phosphate raw materials. In the production process and finished fertilizers, the existence of calcium phosphates, ammonium, sulfuric or nitric and phosphoric acids is possible. Enriched superphosphate contains monocalcium phosphate, calcium sulfate dihydrate, phosphoric acid. During ammoniation, monoammonium phosphate can also be formed. The solubility of the components in the manganese sulfate-ammonium sulfate-water system was studied by the visual-polythermal method in the temperature range from -1.0°С to 27.0°С. The phase diagram limits the regions of ice crystallization, ammonium sulfate, manganese sulfate and chemical compound. A solubility diagram was plotted and a new compound (ammonium sulfate + marganes sulfate + water) (NH4)2Mn(SO4)2*6H2O was isolated. The new compound was identified by chemical, X-ray diffraction, thermogravimetric and IR spectroscopic analyses. To physicochemically substantiate the behavior of marganese sulfate under the conditions of production of enriched superphosphate, the interaction of marganese sulfate with monocalcium phosphate was studied by the method of isomolar series in 0.01 M solutions.

Pretreatment of beechwood with polyoxometalate-based catalysts towards the production of polyunsaturated fatty acids by Crypthecodinium cohnii

In the present work, a novel OxiOrganosolv pretreatment was developed for the fractionation of beechwood. Τhe process employs a mixture of water and common organic solvents, polyoxometalate complexes (POMs) as homogeneous catalysts and O2 that acts as an oxidative agent enabling their regeneration. Due to their strong oxidizing ability and redox reversibility, POMs can achieve efficient biomass fractionation by catalyzing simultaneously hemicellulose hydrolysis and oxidation of lignin ether bonds that leads to its depolymerization, dissolution in the organic solvent and removal from the cellulose-rich pulp. According to the results, both commercially available phosphomolybdic acid (HPMo) and also the in-house produced Fe- and Cu- exchanged salts successfully promoted delignification and hemicellulose removal compared to the OxiOrganosolv pretreatment in the absence of catalyst. Most importantly, catalytic lignin depolymerization was achieved without the use of mineral acids that are typically used in a traditional organosolv. Evaluation of the enzymatic digestibility of the pulps revealed HPMo as the most favorable catalyst for increased saccharification yields and production of sugar-rich hydrolysates that were further used as carbon sources for fermentation and production of ω-3 polyunsaturated fatty acids (ω-3 PUFAs) from the heterotrophic microalgae Crypthecodinium cohnii. Hydrolysates produced from HPMo and Fe-PMo-assisted OxiOrganosolv pretreatment supported cell growth and led to high accumulation of ω-3 PUFAs, while severe inhibition was observed with the hydrolysates from Cu-PMo pretreated biomass. This study demonstrates the possibility of using POMs as catalysts for efficient biomass delignification with the aim to obtain sugar-rich streams that can be utilized for the production of nutraceuticals.

Sustainable Production of Bioethanol Using Levulinic Acid Pretreated Sawdust.

The sustainability and economic viability of the bioethanol production process from lignocellulosic biomass depend on efficient and effective pretreatment of biomass. Traditional pretreatment strategies implicating the use of mineral acids, alkalis, and organic solvents release toxic effluents and the formation of inhibitory compounds posing detrimental effects on the environment and interfering with the enzymatic saccharification process, respectively. Ionic liquids (ILs) as green solvents were used to overcome this issue, but the deep eutectic solvent as an emerging class of ionic liquids performed better in terms of making the process environmentally and economically viable. The green solvent-based pretreatment strategy applied in the current research was levulinic, acid-based natural deep eutectic solvent (NADES). Three different hydrogen bond acceptors (HBAs)—acetamide, betaine, and choline chloride—in combination with levulinic acid as hydrogen bond donor (HBD) in (HBD: HBA) molar ratio 2:1, were screened for biomass pretreatment. The best deep eutectic solvent was levulinic acid: choline chloride in an optimized molar ratio of 1:0.5, resulting in 91% delignification. The physicochemical parametric optimization of saccharification exhibited maximum enzymatic hydrolysis of 25.87% with 125 mg of pretreated sawdust via simultaneous addition of three thermostable cellulases [i.e., endo-1,4-β-D-glucanase (240 U), exo-1,4-β-D-glucanase (180 U), and β-glucosidase (320 U)] for 5 h of incubation at 75°C. The reducing sugar slurry obtained from the saccharified biomass was then added to a fermentation medium for bioethanol production, and a maximum of 11.82% of production was obtained at 30°C, 72 h, and 180 rpm using a 2.5% 24 h old Saccharomyces cerevisiae seed culture. The current study revealed that the levulinic-based deep eutectic solvent exhibited remarkable delignification, which led to the efficient enzymatic hydrolysis of sawdust and hence bioethanol production. Furthermore, it will prospect new avenues in bioethanol production using a deep eutectic solvent. Deep eutectic solvent overcame the issues posed by ionic liquids: toxicity, expensive and complex preparation, and non-biodegradability.

Investigation on the Beneficiation of Fluorite-ore using a mixture of Oleic acid and Palmitic acid via Froth Flotation

Fluorite (fluorspar), an important industrial mineral ore, is one of the major raw materials for the production of hydrofluoric acid. Naturally occurring fluorite ore contains gangue minerals, primarily silica (SiO2) and calcite (CaCO3). The beneficiation of fluorspar is needed to mitigate the severity of operational issues. Several studies on fluorspar beneficiation using the froth floatation technique have been executed, but the process is restricted by the use of minerals acids to remove calcite. In this study, a novel scheme for fluorspar beneficiation was investigated for the floatation of fluorite and depression of calcite and other gangue minerals simultaneously without the use of mineral acids. Moreover, mixtures of saturated and unsaturated fatty acids (oleic acid and palmitic acid) were used instead of mineral acids. Various parameters were investigated, such as the weight percent of the feed-slurry, feed pH, the effect of reagents on the process selectivity, and the effect of feed boiling and dilution on the up-gradation of fluorspar. The adopted methodology with tested reagents resulted a 67 wt. % reduction of CO32- and 75 wt. % reduction of SiO2 in gangue material at a pH 10 for the feed slurry. Fluorspar purity increased from 65-75 wt. % to 95 wt. % after the boiling and dilution steps, respectively.

Intensification of leaching of rare earth metals from phosphogypsum

Phosphogypsum is a by-product obtained in the processing of apatite concentrates in the phosphate fertilizers industry. Mining enterprises at the Khibiny deposits generate over 8 Mtpa of phosphogypsum. The stale phosphogypsum reserves in the dumps here reach 200 Mt, with an average content of rare earth elements (REE) of 0.4 % wt. In phosphogypsum (CaSO4·2H2O), rare earth metals are present in both water-soluble and hard-to-recover forms. Chemical recovery methods based on the use of various mineral acids as leaching agents are most common. Considering that rare-earth metals may form soluble complexes with citrate ions used as an eluent, the effects of sodium citrate solutions were studied. Preliminary thermal activation of samples at up to 300 °C leads to lower lanthanum, cerium, and neodymium recoveries caused by the compaction of the phosphogypsum crystal lattice due to the removal of its crystallization water. Exposure to ultrasound has no significant effect on the recovery. A significant REM recovery improvement is ensured by phosphogypsum exposure to ionizing radiation. The resulting defects in the crystal structure of the material allow the eluent solution to easily penetrate into the crystal lattice. Here, however, waste storage time is the key factor for the REM recovery efficiency. Water treatment of any freshly mined material after exposure to ionizing radiation eliminates the use of mineral acids as leaching agents and improves REM recovery.The work was carried out with the financial support of the Russian Science Foundation (project No. 19-19-00377).

ДОСЛІДЖЕННЯ ПРОЦЕСУ НІТРАТНОКИСЛОТНОЇ ПЕРЕРОБКИ ФОСФОГІПСУ З ОДЕРЖАННЯМ КОНЦЕНТРАТУ РІДКІСНОЗЕМЕЛЬНИХ ЕЛЕМЕНТІВ

Investigate the process of extraction of rare earth elements from phosphogypsum by its interaction with nitric acid, concentration 25, 30 and 35%, at a ratio of "phosphogypsum: acid" 1: 2 and a temperature of 700C to obtain purified calcium sulfate. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained. Experimental studies were performed using the titrimetric method using Trilon B to determine the concentration of rare earth elements in the obtained filtrates. A review of scientific and technical literature in the field of promising methods of processing phosphogypsum. The most alternative method of processing phosphogypsum is to obtain rare earth elements by acid leaching, which is provided by the use of mineral acids. Based on the obtained data, it was found that when the acid concentration increases from 25 to 35%, the content of rare earth elements (REE) in the filtrates of the samples increases from 0.21 to 1.68 g/dm3, respectively. It was found that the degree of extraction of REE concentrate from phosphogypsum is highest at an acid concentration of 25% and is 22.8%, and with increasing concentration of HNO3, it decreases by almost 2.5 times. The optimal concentration of the nitric acid solution was determined, which is 25% and interacts with phosphogypsum for the subsequent extraction of the precipitate of rare earth elements.The optimal temperature of nitric acid processing of phosphogypsum, which is 70 0C, was revealed. Regularities of the process of extraction of concentrate of rare earth elements from phosphogypsum by acid leaching are obtained.The use of nitric acid for the production of rare earth elements from phosphogypsum and for the production of purified phosphogypsum sediment from soluble impurities scientifically substantiated. The content of rare earth elements in the filtrate was determined at various acid concentrations. The efficiency of sediment removal of rare earth elements from phosphogypsum by interaction with nitric acid at a concentration of 25, 30 and 35%, respectively, was established. Purified phosphogypsum can then be used to produce gypsum binder in the construction industry and in fertilizer technology in agriculture. Concentrate of rare earth elements can be used in medicine, metallurgy and other industries with the selection of individual elements and in general.

Carbonate Micromotors for Treatment of Construction Effluents.

Concrete in construction has recently gained media coverage for its negative CO2 footprint, but this is not the only problem associated with its use. Due to its chemical composition, freshly poured concrete changes the pH of water coming in contact with the surface to very alkaline values, requiring neutralization treatment before disposal. Conventional methods include the use of mineral acid or CO2 pumps, causing high costs to building companies. In this paper, we present a micromotor based remediation strategy, which consists of carbonate particles half-coated with citric acid. To achieve this half coverage spray coating is used for the first time to design Janus structures. The motors propel diffusiophoretically due to a self-generated gradient formed as the acid coverage dissolves. The locally lower pH contributes to the dissolution of the carbonate body. These motors have been employed to study neutralization of diluted concrete wash water (CWW) at microscopic scale and we achieve visualization of the pH changes occurring in the vicinity of motors using anthocyanine as pH indicator dye. The effect of citric acid-carbonates hybrid on neutralization of real CWW on macroscopic scale has also been studied. In addition, all employed chemicals are cheap, non-toxic and do not leave any solid residues behind.

Reusable Heterogeneous Tungstophosphoric Acid-Derived Catalyst for Green Esterification of Carboxylic Acids

Solid acid catalysts are environmentally friendly alternatives to the use of mineral acids in a range of applications, including the esterification of carboxylic acids. Here, a phosphorus- and nitrogen-doped, carbon-modified, fully heterogeneous solid acid catalyst was prepared by pyrolysis of a mixture of melamine and tungstophosphoric acid at 250, 500, and 750 °C under a nitrogen atmosphere provided. The structure of the different catalysts was evaluated by surface area measurements, XRD, XPS, Raman spectroscopy, elemental analysis, and electron microscopies. Pyrolysis at 500 °C created complex solid materials with larger surface area and significantly higher acidity, which can be attributed to WO3 formation on a heteroatomic (N,P)-carbon structure. The 500 °C-treated heterogeneous catalysts showed remarkably better activity for esterification of palmitic acid and were thus applied in the esterification of a broad range of carboxylic acids with good overall yields. Furthermore, the solid acid catalyst c...

Brønsted and Lewis Solid Acid Catalysts in the Valorization of Citronellal

Terpenes are valuable starting materials for the synthesis of molecules that are of interest to the flavor, fragrance, and pharmaceutical industries. However, most processes involve the use of mineral acids or homogeneous Lewis acid catalysts. Here, we report results obtained in the liquid-phase reaction of citronellal with anilines under heterogeneous catalysis conditions to give tricyclic compounds with interesting pharmacological activity. The terpenic aldehyde could be converted into octahydroacridines with a 92% yield through an intramolecular imino Diels–Alder reaction of the imine initially formed in the presence of an acidic clay such as Montmorillonite KSF. Selectivity to the desired product strongly depended on the acid sites distribution, with Brønsted acids favoring selectivity to octahydroacridine and formation of the cis isomer. Pure Lewis acids such as silica–alumina with a very low amount of alumina gave excellent results with electron-rich anilines like toluidine and p-anisidine. This protocol can be applied starting directly from essential oils such as kaffir lime oil, which has a high citronellal content.

Fertilisers production from ashes after sewage sludge combustion – A strategy towards sustainable development

Sustainable development and circular economy rules force the global fertilizer industry to develop new phosphorous recovery methods from alternative sources. In this paper a phosphorus recovery technology from Polish industrial Sewage Sludge Ashes was investigated (PolFerAsh – Polish Fertilizers form Ash). A wet method with the use of mineral acid and neutralization was proposed. Detailed characteristic of SSA from largest mono-combustion plans were given and compared to raw materials used on the market. The technological factors associated with such materials were discussed. The composition of the extracts was compared to typical industrial phosphoric acid and standard values characterizing suspension fertilizers. The most favorable conditions for selective precipitation of phosphorus compounds were revealed. The fertilizers obtained also meet EU regulations in the case of the newly discussed Cd content. The process was scaled up and a flow mass diagram was defined.

Production of 5‐hydroxymethyl furfural and levulinic acid from lignocellulose in aqueous solution and different solvents

AbstractWith the continuous development of society and a serious energy crisis, renewable energy has become highly important. As platform compounds that can produce large amounts of chemical products, 5‐hydroxymethyl furfural (5‐HMF) and levulinic acid (LA) have attracted the attention of many researchers. Production of 5‐HMF and LA with lignocellulose is currently one of the most promising research directions in biomass energy. Conventionally, production of 5‐HMF and LA with lignocellulose is typically performed in aqueous solutions containing dilute mineral acids as catalysts. Recently, advances have been reported in the use of heterogeneous catalysts for conversion of lignocellulose into 5‐HMF and LA in different solvents to eliminate the use of mineral acids. In this paper, the merits, demerits, and requirements for commercialization are outlined for 5‐HMF and LA production from lignocellulose in aqueous solution, and different solvents are reviewed. Special attention is focused on the use of green chemicals (such as γ‐valerolactone) and ionic liquids as solvents due to their clean and recoverable characteristics. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

A green and efficient approach to selective conversion of xylose and biomass hemicellulose into furfural in aqueous media using high-pressure CO2 as a sustainable catalyst

A novel approach to produce furfural from lignocellulosic biomass with green solvents without the use of mineral acids or heterogeneous catalysts.

Green Route for the Preparation of p-Aminophenol from Nitrobenzene by Catalytic Hydrogenation in Pressurized CO2/H2O System

The preparation of p-aminophenol from nitrobenzene by one-pot catalytic hydrogenation and in situ acid-catalyzed Bamberger rearrangement was first realized in a pressurized CO2/H2O system. By employing Pt–Sn/Al2O3 as catalyst, nitrobenzene could be converted to p-aminophenol with selectivity as high as 85% when the reaction was carried out at 140 °C under 5.5 MPa CO2 and 0.2 MPa H2. This new protocol is environmentally benign because it is fully rid of the use of mineral acid by the application of self-neutralizable carbonic acid.

Chloride ions enhance furfural formation from d-xylose in dilute aqueous acidic solutions

Furfural production through traditional processes is accompanied by acidic waste stream production and high energy consumption. Modern furfural production process concepts will have to consider environmental concerns and energy requirements besides economics, moreover will have to be integrated within widened biorefinery concepts. In this paper, some particular aspects of the chemistry of D-xylose reaction to furfural are addressed, with the aim to clarify the reaction mechanism leading to furfural and to define new green catalytic pathways for its production. Specifically, reducing the use of mineral acids is addressed by the introduction of alternative catalysts. In this sense, chloride salts were tested in dilute acidic solutions at temperatures between 170 and 200 °C. Results indicate that the Cl− ions promote the formation of the 1,2-enediol from the acyclic form of xylose, and thus the subsequent acid catalyzed dehydration to furfural. For this reason the presence of Cl− ions led to significant improvements with respect to the H2SO4 case. The addition of NaCl to a 50 mM HCl aqueous solution gave 90% selectivity to furfural. Among the salts tested FeCl3 showed very interesting preliminary results, producing exceptionally high xylose reaction rates.

Removal of hazardous metals from MSW fly ash—An evaluation of ash leaching methods

Incineration is a commonly applied management method for municipal solid waste (MSW). However, significant amounts of potentially hazardous metal species are present in the resulting ash, and these may be leached into the environment. A common idea for cleaning the ash is to use enhanced leaching with strong mineral acids. However, due to the alkalinity of the ash, large amounts of acid are needed and this is a drawback. Therefore, this work was undertaken in order to investigate some alternative leaching media (EDTA, ammonium nitrate, ammonium chloride and a number of organic acids) and to compare them with the usual mineral acids and water. All leaching methods gave a significant increase in ash specific surface area due to removal of soluble bulk (matrix) compounds, such as CaCO 3 and alkali metal chlorides. The use of mineral acids and EDTA mobilised many elements, especially Cu, Zn and Pb, whereas the organic acids generally were not very effective as leaching agents for metals. Leaching using NH 4NO 3 was especially effective for the release of Cu. The results show that washing of MSW filter ash with alternative leaching agents is a possible way to remove hazardous metals from MSW fly ash.

Surface analysis of particulates from laboratory hood exhaust manifold

Particulate samples collected from a laboratory ventilation manifold during routine maintenance were analyzed to determine if particulate composition had changed as a result of changes in the laboratory's atmosphere. This ventilation manifold exhausts more than 100 fume hoods. The particulate samples were analyzed using static secondary ion mass spectrometry (SIMS). The negative SIMS spectra showed abundant Cl−, NO3−, and HSO4−, consistent with the use of mineral acids in the laboratory. Cluster anions containing primarily Zn (but also other transition metals) were detected, which signaled corrosion of the manifold's galvanized steel by the volatilized acids. The most abundant ions in the cation SIMS spectra were derived from cyclohexylamine (CHA), which had been used as an antiscaling agent in the facility's boiler. Steam from the boiler, which contained CHA, was used to humidify the building air; this practice stopped in 1997. The abundances of the CHA-derived ions were significantly lower in the samples collected in 2004 and 2006 than in the 1992 samples, indicating that the CHA is being slowly depleted. Changes in the relative abundances suggest exponential depletion from the manifold with rate constants that are on the order of 0.01 to 0.04 month−1. Published in 2007 John Wiley & Sons, Ltd.

A novel and environmentally benign selective route for Vitamin K 3 synthesis

The oxidation of 2-methylnaphthalene was carried out in acetic acid with aqueous hydrogen peroxide. 2-Methyl-1,4-naphthoquinone was obtained in a selectivity of nearly ≥90% at 100 °C for 3 h. The reaction has been studied by varying different parameters like concentration of hydrogen peroxide, strength of acetic acid, molar ratio of 2-methylnaphthalene to hydrogen peroxide, reaction temperature and time. Compared to the conventional preparation of Vitamin K 3, this method could be economical and ecofriendly as the use of mineral acid and chromium salts are avoided.

The Dehydration of 1,4-Butanediol to Tetrahydrofuran in Supercritical Water

The dehydration of 1,4- butanediol to tetrahydrofuran is a reaction that possesses disadvantages under conventional conditions caused by the use of mineral-acids and the corrosion problem interconnected with it. These disadvantages can be remedied by the use of pure supercritical water as reaction medium, as well as catalyst. The ionic mechanism, which exists under conventional conditions, could be validated by the examinations of this present work not only in the sub- but also in the supercritical range.

Investigating the Synthesis Potential in Supercritical Water

In order to investigate the synthesis potential of supercritical water (SCW), hydration and dehydration reactions as well as hydrolyses of various model compounds (alcohols, esters, nitriles, amides) were carried out under sub- and supercritical conditions. These reactions were carried out without involving catalysts (acids, bases) to overcome the disadvantages of common reaction conditions (e.g., the use of mineral acids, salt yields and low space-time yields). Small autoclaves or capillary-tube reactors have been used for most of the research on SCW up to now, and that is why wall effects of the corresponding reactor material could not always be excluded. For this reason, a continuous miniplant with technical dimensions was set up for the series of tests, with maximum working conditions of 500 bar and 500°C, which can be regarded as realistic upper limits for industrial applications. This article describes the miniplant and the first results of reactions of simple model substances with supercritical water.