Mineral Acid

Almond shell is a food waste that is utilized as bioadsorbent for the uptake of Eriochrome Black T (EBT) and Malachite Green (MG) dyes from aqueous solutions. The biomaterial was characterized by specific surface area (BET), scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, and X-ray diffraction. The effects of the initial pH of solutions, particle size, adsorbent dosage, initial dye concentration, contact time, and temperature on the EBT and MG adsorption were studied using batch contact mode at 22 °C. Rapid sorption dynamics following a second-order kinetic model were shown by kinetic studies. The adsorption equilibrium data were fitted well to the Freundlich isotherm for EBT and MG as anionic and cationic dyes, respectively. The adsorption of pollutants was exothermic (DH 0 = -1.7 kJ mol -1 for EBT and -32 kJ mol -1 for MG). The reaction was accompanied by a decrease in entropy (DS 0 \ 0 for EBT and MG). Negative values of DG 0 showed the spontaneity of the MG adsorption process. However, positive values of DG 0 showed that the EBT uptake by almond shell is not a spontaneous reaction. The results indicate that almond shell is a promising alternative for the biosorption of anionic (EBT) and cationic (MG) dyes from aqueous solutions.

The effect of organophosphorous moieties of three acid ligands, D2EHPA, PC88A and Cyanex 272, dissolved in light liquid paraffin, on extraction of U(VI) and mineral acid was studied using the Bulk-Liquid Membrane (BLM) technique. A kinetic model was developed to predict the concentration of acid and U(VI) in the feed, organic and the strip phases during extraction. Acid extraction by complexing ligands was found to be significant. The extraction of U(VI) by these three acidic ligands in different mineral acids followed the order HNO 3 N HCl N H 2 SO 4 . The distribution coefficient for acid and U(VI) extraction increased with increase in '-OR' moieties in the acid ligands i.e. in the order D2EHPA N PC88A N Cyanex 272. The suitability of a ligand for liquid emulsion membrane (LEM) application depends upon the ratio of rates of extraction of U(VI) and acid (HNO 3 ). The study showed that the ratios are in the order D2EHPA N PC88A N Cyanex 272.

Center for Adsorption and Reaction Engineering on Surface (CARES), Department of Chemistry,<br> Sidho-Kanho-Birsha University, Purulia-723 104, West Bengal, India<br> E-mail: nagendranath_mahata.chem@skbu.ac.in<br> Manuscript received online 04 December 2020, accepted 24 December 2020 Esterification of carboxylic acid is a very important class of reaction in organic synthesis. Comparative kinetic studies of esterification<br> of acetic acid with methanol catalysed by heteropoly and mineral Bronsted acids, viz. phosphotungstic acid, hydrochloric<br> acid, sulphuric acid, and nitric acid were carried out. The investigation was done in the temperature range of 308<br> to 328 K. HCl exhibited distinctively higher catalytic activity than the other three Bronsted acids. Specific reaction rate with<br> H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub> also was found to be excellent, particularly at higher temperature.

In this study, three raw Brazilian clays from João Pessoa, Paraíba State (Aço AP, AVL and Verde Lodo) were characterized before and after purification and acid activation. Several instrumental techniques were used, and the raw clays were classified as dioctahedral smectites with different compositions, where the AVL sample had the highest content of montmorillonite. In addition, analyses showed modification in clay mineral compositions, mainly due to removal of impurities and octahedral sheet cation leaching during acid activation, which resulted in specific areas ranging from 42 to 93 m 2 g -1 and increase of the Brønsted/Lewis acid site ratio, until 1.52 (AVL). Then, methyl esterification reactions were performed using the acid-activated clays as catalysts. The maximum acid conversions obtained were of 92 and 64%, for acetic acid using activated AVL and for lauric acid using activated Verde Lodo, respectively, and these data were correlated mainly to the Brønsted-Lowry acidity.

The present work reports the extraction behaviors of mineral acids: HClO4, HNO3, HCl and H2SO4 (commonly found in acidic bleed solutions from the hydrometallurgical route of metal extraction processes) by tri-n-octylamine (TOA) dissolved in distilled colorless kerosene. The systems have been investigated as functions of various experimental parameters, such as time, [acid], [TOA], temperature, extraction stage and the organic to aqueous phase volume ratio (O/A). Strippings was also examined. Equilibration time is less than 60 min. The acid concentration in the organic phase at equilibrium is increased with increasing initial acid concentration in the aqueous phase for all systems. However, the is after %extraction decreased with increasing initial acid concentration in the aqueous phase. The % extraction increased remarkably with increasing [TOA] for all cases. Being the ratio of the [acid] in the organic to aqueous phase at equilibrium equal to extraction ratio, D; the log D vs. lo...

Center for Adsorption and Reaction Engineering on Surface (CARES), Department of Chemistry,<br> Sidho-Kanho-Birsha University, Purulia-723 104, West Bengal, India<br> E-mail: nagendranath_mahata.chem@skbu.ac.in<br> Manuscript received online 04 December 2020, accepted 24 December 2020 Esterification of carboxylic acid is a very important class of reaction in organic synthesis. Comparative kinetic studies of esterification<br> of acetic acid with methanol catalysed by heteropoly and mineral Bronsted acids, viz. phosphotungstic acid, hydrochloric<br> acid, sulphuric acid, and nitric acid were carried out. The investigation was done in the temperature range of 308<br> to 328 K. HCl exhibited distinctively higher catalytic activity than the other three Bronsted acids. Specific reaction rate with<br> H<sub>3</sub>PW<sub>12</sub>O<sub>40</sub> also was found to be excellent, particularly at higher temperature.

Almond shell is a food waste that is utilized as bioadsorbent for the uptake of Eriochrome Black T (EBT) and Malachite Green (MG) dyes from aqueous solutions. The biomaterial was characterized by specific surface area (BET), scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, and X-ray diffraction. The effects of the initial pH of solutions, particle size, adsorbent dosage, initial dye concentration, contact time, and temperature on the EBT and MG adsorption were studied using batch contact mode at 22°C. Rapid sorption dynamics following a second-order kinetic model were shown by kinetic studies. The adsorption equilibrium data were fitted well to the Freundlich isotherm for EBT and MG as anionic and cationic dyes, respectively. The adsorption of pollutants was exothermic (DH 0 =-1.7 kJ mol-1 for EBT and-32 kJ mol-1 for MG). The reaction was accompanied by a decrease in entropy (DS 0 \ 0 for EBT and MG). Negative values of DG 0 showed the spontaneity of the MG adsorption process. However, positive values of DG 0 showed that the EBT uptake by almond shell is not a spontaneous reaction. The results indicate that almond shell is a promising alternative for the biosorption of anionic (EBT) and cationic (MG) dyes from aqueous solutions.

A study of the lixiviation of Manganiferrous Aluminosilicate Mineral in hydrochloric acid has been undertaken. Experiments on quantitative lixiviation of the mineral showed that its dissolution rate depends on hydrogen ion concentration, reaction temperature and particle size. The activation energy calculated from the experimental data was 34.19 kJ/mole and this suggests a diffusion controlled mechanism. A reaction order of 0.2 with respect to the acid concentration was also found. With 8.42 M HCl at 80°C, about 69.27% of the 10 g/L of the manganiferrous mineral was dissolved within 120 min using < 0.09 mm particle diameter.

A method for the selective extraction of mercury has been developed. The extraction of Hg(II) by 2-benzylpyridine (BPy) in benzene from dilute mineral acid solution containing iodide ions has been investigated, and variables such as concentration of acids, iodide and the extractant have been optimized. The optimum conditions for the extraction of Hg(II) by 0.1M BPy/benzene are: 0.01M (HCI, HNO3, H2SO4)+0.01M KI. The distribution coefficients and separation factors of 19 elements relative to Hg(lI), have been reported. Effect of anions such as ascorbate, acetate, citrate, oxalate and thiosulfate has also been studied. The method developed could find useful applications in selective extraction of small amounts of mercury from environmental samples.

Dilute acid and water-only hemicellulose hydrolysis are being examined as part of a multiinstitutional cooperative effort to evaluate the performance of leading cellulosic biomass pretreatment technologies on a common basis. Cellulosic biomass, such as agricultural residues and forest wastes, can have a significant mineral content. It has been shown that these minerals neutralize some of the acid during dilute acid pretreatment, reducing its effectiveness, and the higher solids loadings desired to minimize costs will require increased acid use to compensate. However, for sulfuric acid in particular, an equilibrium shift to formation of bisulfate during neutralization can further reduce hydrogen ion concentrations and compound the effect of neutralization. Because the equilibrium shift has a more pronounced effect at lower acid concentrations, additional acid is needed to compensate. Coupled with the effect of temperature on acid dissociation, these effects increase acid requirements to achieve a particular reaction rate unless minerals are removed prior to hydrolysis.

Aqueous pretreatment using homogenous acid catalyst is considered as a low-cost technology in the 27 production of lignocellulosic bioethanol. To establish the synergism of mixed acids, pilot-level aqueous pretreatments of bagasse covering a wide range of combined severity (CS) were carried out. To investigate the effect of application of mix-29 ture of acids on xylose hydrolysis as well as glucose hydrolysis via pretreatment and enzymatic hydrolysis, the following 30 three combinations of acids were explored: (1) oxalic acid + sulfuric acid (organic + mineral acid), (2) phosphoric + 31 sulfuric acid (mineral acids), and (3) ferric chloride + sulfuric acid (Lewis acid with a mineral acid). Of the pretreatments 32 evaluated, the synergism was most pronounced for the combination of sulfuric and phosphoric acid, which resulted in 33 more than 90% conversion of hemicellulose to xylose and 70% conversion of cellulose to glucose through enzymatic 34 hydrolysis. Fourier transform infrared (FTIR) studies of pretreated samples showed higher syringyl/guaiacyl (S/G) ratio 35 for sulfuric and phosphoric acid combination pretreatment, leading to higher enzymatic conversion. FTIR and dynamic 36 light scattering (DLS) experiments conducted on pretreated sugarcane bagasse provided useful correlation with regard to 37 the pretreatment type, particle size and enzymatic hydrolysis.

Orange (Citrus sinensis) and grapefruit (Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions. The peels are used under two states: fresh and residual (after essential oil extraction). Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification "DE" and on molecular weight "Mw". Results showed that the pectin yield was higher using the residual peels. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. This later was determined using four equations; Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight varied from 1.538 x10 05 to 2.47x10 05 g/mol for grapefruit pectin and from 1.639 x10 05 to 2.471 x10 05 g/mol for orange pectin.

The mechanism of acid-catalyzed hydrolysis of a series of p-substituted N,N′-diarylsulfamides was investigated in aqueous mineral acid solutions. Rate profiles, reaction activation parameters, catalytic order of strong acids, solvent isotope effects, and analysis of the kinetic data by the excess acidity method suggest a change in the mechanism from A2 to A1. While the hydrolysis proceeds with an A2 mechanism in low acidity regions, an A1 mechanism takes place in high acid concentrations.

There is currently a great deal of interest in the chemistry of hydroxamic acids. In recent years we have been studying the synthesis, structure and nucleophilicities of hydroxamic acids. This paper reports a kinetic study of reactivity of some hydroxamic acids RC(O)·N(OH)R′; R=C6H5·CH=CH, R′=4-CH3·C6H4 [p-tolylcinnamo hydroxamic acid]; R=C6H5, R′=4-CH3·C6H4 [p-tolylbenzo hydroxamic acid]; R=C6H5, R′=2-CH3·C6H4 [o-tolylbenzo hydroxamic acid] in aqueous mineral acids (HCl, HClO4 and H2SO4). The rate data of hydrolysis reaction revealed that the reactivity/stability sequence of the compounds is generally p-TBHA&gt;o-TBHA&gt;p-TCHA. An excess acidity analysis reveals that the reaction proceeds by nucleophilic attack of water molecule on the protonated substrate.

Aqueous pretreatment using homogenous acid catalyst is considered as a low-cost technology in the 27 production of lignocellulosic bioethanol. To establish the synergism of mixed acids, pilot-level aqueous pretreatments of bagasse covering a wide range of combined severity (CS) were carried out. To investigate the effect of application of mix-29 ture of acids on xylose hydrolysis as well as glucose hydrolysis via pretreatment and enzymatic hydrolysis, the following 30 three combinations of acids were explored: (1) oxalic acid + sulfuric acid (organic + mineral acid), (2) phosphoric + 31 sulfuric acid (mineral acids), and (3) ferric chloride + sulfuric acid (Lewis acid with a mineral acid). Of the pretreatments 32 evaluated, the synergism was most pronounced for the combination of sulfuric and phosphoric acid, which resulted in 33 more than 90% conversion of hemicellulose to xylose and 70% conversion of cellulose to glucose through enzymatic 34 hydrolysis. Fourier transform infrared (FTIR) studies of pretreated samples showed higher syringyl/guaiacyl (S/G) ratio 35 for sulfuric and phosphoric acid combination pretreatment, leading to higher enzymatic conversion. FTIR and dynamic 36 light scattering (DLS) experiments conducted on pretreated sugarcane bagasse provided useful correlation with regard to 37 the pretreatment type, particle size and enzymatic hydrolysis.

Aqueous pretreatment using homogenous acid catalyst is considered as a low-cost technology in the 27 production of lignocellulosic bioethanol. To establish the synergism of mixed acids, pilot-level aqueous pretreatments of bagasse covering a wide range of combined severity (CS) were carried out. To investigate the effect of application of mix-29 ture of acids on xylose hydrolysis as well as glucose hydrolysis via pretreatment and enzymatic hydrolysis, the following 30 three combinations of acids were explored: (1) oxalic acid + sulfuric acid (organic + mineral acid), (2) phosphoric + 31 sulfuric acid (mineral acids), and (3) ferric chloride + sulfuric acid (Lewis acid with a mineral acid). Of the pretreatments 32 evaluated, the synergism was most pronounced for the combination of sulfuric and phosphoric acid, which resulted in 33 more than 90% conversion of hemicellulose to xylose and 70% conversion of cellulose to glucose through enzymatic 34 hydrolysis. Fourier transform infrared (FTIR) studies of pretreated samples showed higher syringyl/guaiacyl (S/G) ratio 35 for sulfuric and phosphoric acid combination pretreatment, leading to higher enzymatic conversion. FTIR and dynamic 36 light scattering (DLS) experiments conducted on pretreated sugarcane bagasse provided useful correlation with regard to 37 the pretreatment type, particle size and enzymatic hydrolysis.

In this study, three raw Brazilian clays from João Pessoa, Paraíba State (Aço AP, AVL and Verde Lodo) were characterized before and after purification and acid activation. Several instrumental techniques were used, and the raw clays were classified as dioctahedral smectites with different compositions, where the AVL sample had the highest content of montmorillonite. In addition, analyses showed modification in clay mineral compositions, mainly due to removal of impurities and octahedral sheet cation leaching during acid activation, which resulted in specific areas ranging from 42 to 93 m 2 g −1 and increase of the Brønsted/Lewis acid site ratio, until 1.52 (AVL). Then, methyl esterification reactions were performed using the acid-activated clays as catalysts. The maximum acid conversions obtained were of 92 and 64%, for acetic acid using activated AVL and for lauric acid using activated Verde Lodo, respectively, and these data were correlated mainly to the Brønsted-Lowry acidity.

The epoxidation of soybean oil is industrially carried out by using peroxyacid generated in situ by reacting concentrated hydrogen peroxide with acetic or formic acid, in the presence of a mineral acid as a catalyst. The reaction is generally highly exothermic and an excessive increase of temperature is proved to occur, with clear safety issue. This unwanted phenomena is typically prevented by limiting the peroxyacid reactant amount with respect to the stoichiometry, either in semi-continuous fed-batch or in pulse-fed-batch. In this paper, starting from experiments and given kinetic data, the set of reactions have been analysed in the light of safety, by means of classical runaway criteria.

A study of the lixiviation of Manganiferrous Aluminosilicate Mineral in hydrochloric acid has been undertaken. Experiments on quantitative lixiviation of the mineral showed that its dissolution rate depends on hydrogen ion concentration, reaction temperature and particle size. The activation energy calculated from the experimental data was 34.19 kJ/mole and this suggests a diffusion controlled mechanism. A reaction order of 0.2 with respect to the acid concentration was also found. With 8.42 M HCl at 80°C, about 69.27% of the 10 g/L of the manganiferrous mineral was dissolved within 120 min using < 0.09 mm particle diameter.

Center for Adsorption and Reaction Engineering on Surface (CARES), Department of Chemistry,&lt;br&gt; Sidho-Kanho-Birsha University, Purulia-723 104, West Bengal, India&lt;br&gt; E-mail: nagendranath_mahata.chem@skbu.ac.in&lt;br&gt; Manuscript received online 04 December 2020, accepted 24 December 2020 Esterification of carboxylic acid is a very important class of reaction in organic synthesis. Comparative kinetic studies of esterification&lt;br&gt; of acetic acid with methanol catalysed by heteropoly and mineral Bronsted acids, viz. phosphotungstic acid, hydrochloric&lt;br&gt; acid, sulphuric acid, and nitric acid were carried out. The investigation was done in the temperature range of 308&lt;br&gt; to 328 K. HCl exhibited distinctively higher catalytic activity than the other three Bronsted acids. Specific reaction rate with&lt;br&gt; H&lt;sub&gt;3&lt;/sub&gt;PW&lt;sub&gt;12&lt;/sub&gt;O&lt;sub&gt;40&lt;/sub&gt; also was found to be excellent, particularly at higher temperature.

Comparison of different kinetic models at 313 K and 0.3268 mol•L-1 catalyst concentration. Experimental; Concentration based; activity based; Liu et al. [8]; Elugu et al. [9]; Bonnaillie et al. [15]; Agreda et al. [5] Catalysis, Kinetics and Reaction Engineering Kinetics of Esterification of Methanol and Acetic Acid with Mineral Homogeneous Acid

A novel procedure for the preparation of organic ammonium tribromides (OATBs) is described from their corresponding bromides. Quaternary ammonium bromides (QABs) and a N, Nʹ-heterocyclic dibromide are efficiently oxidized to their corresponding mono-tribromides and bistribromide by m-chloroperbenzoic acid (MCPBA) in presence of 2 and 4 equiv of KBr, respectively. The reactions are carried out in aq. medium without the use of any mineral acid and metal catalyst/promoters. A variety of tribromides are synthesized in very high yields including a hitherto unknown reagent viz. 1, 10-(ethane-1, 2-diyl)phenanthrolinediium bistribromide (EPDBT). EPDBT is investigated as brominating agent and found to be highly effective for selective bromination of active methylene groups of a variety of 1, 3-diketones and β-ketoesters.

In this study, three raw Brazilian clays from João Pessoa, Paraíba State (Aço AP, AVL and Verde Lodo) were characterized before and after purification and acid activation. Several instrumental techniques were used, and the raw clays were classified as dioctahedral smectites with different compositions, where the AVL sample had the highest content of montmorillonite. In addition, analyses showed modification in clay mineral compositions, mainly due to removal of impurities and octahedral sheet cation leaching during acid activation, which resulted in specific areas ranging from 42 to 93 m 2 g −1 and increase of the Brønsted/Lewis acid site ratio, until 1.52 (AVL). Then, methyl esterification reactions were performed using the acid-activated clays as catalysts. The maximum acid conversions obtained were of 92 and 64%, for acetic acid using activated AVL and for lauric acid using activated Verde Lodo, respectively, and these data were correlated mainly to the Brønsted-Lowry acidity.

In this study, the dissolution of CuO in HCl, H 2 SO 4 , HNO 3 and citric acid solutions was investigated in a batch reactor employing parameters expected to affect the dissolution rate of copper such as stirring speed, temperature and acid concentration. It was found that 99.95% of copper was dissolved after 14 min with inorganic acids at 0.5 M, 25 • C and l/s = 10 ml/g while more drastic operation conditions were needed to reach the same dissolution efficiency with citric acid solution. Anions seem to be involved in the surface reaction. The dissolution kinetics of CuO was examined according to heterogeneous model and it was found that the dissolution rate was controlled by surface chemical process in all cases.

In this study, the leaching kinetics of malachite [CuCO 3 ‚Cu(OH) 2 ], an oxidized copper ore, was investigated in water saturated with ammonia gas. In the experiments, the ammonia concentration of the solution, the particle size of the ore, the temperature, the stirring speed, and the solid-to-liquid ratio were chosen as parameters. It was determined that the leaching rate of malachite increased with decreasing particle size and solid-to-liquid ratio and increasing reaction temperature, ammonia concentration, and stirring speed. The leaching kinetics was examined by statistical methods applied to the experimental data. It was found that the leaching rate fitted a pseudo-second-order kinetic model with an activation energy of 85.16 kJ‚mol -1 .

The production of metallic copper from low-grade copper ores is generally carried out by hydrometallurgical methods. Leaching is the first prerequisite of any hydrometallurgical process. Solutions containing ammonia may allow for selective leaching of the copper from the ore. In this study, the leaching kinetics of malachite, which is an oxidized copper ore, in ammonium nitrate solutions was examined. The effects of some experimental parameters on the leaching process were investigated, and a kinetic model to represent the effects of these parameters on the leaching rate was developed. It was determined that the leaching rate increased with increasing solution concentration, temperature, and agitation speed, as well as decreasing particle size. It was found that the leaching reaction followed the mixed kinetic controlled model, which includes two different leaching processes including the surface chemical reaction (303 K to 323 K [30°C to 50°C]) and diffusion through a porous product layer (323 K to 343 K [50°C to 70°C]). The activation energies of these sequential steps were determined to be 95.10 and 29.50 kJ/mol, respectively.

Lithium-ion batteries (LIBs) are secondary rechargeable power sources which increasing production also leads to large amount of waste. In order to environmentally friendly reduce the waste, this work aimed to use acetic acid as a substitute leaching agent to leach Co metals which constitutes about 72.39% wt of the battery cathode. The leaching process was done in a three-necked-flask where calcined LIB cathode powder was mixed with acetic acid solution. The variables of the leaching process under investigation were solution pH, concentration of H2O2 in the solution, S/L ratio, temperature and reaction time. Experimental results showed that only temperature significantly influenced the leaching rate of Co. Since the process was exothermic, the maximum recovery decreased as temperature increased. Conventional shrinking core model that considers diffusion and irreversible surface reaction resistances was found not sufficient to predict the kinetics of the Co leaching with acetic acid. ...

In this study, the dissolution of CuO in HCl, H 2 SO 4 , HNO 3 and citric acid solutions was investigated in a batch reactor employing parameters expected to affect the dissolution rate of copper such as stirring speed, temperature and acid concentration. It was found that 99.95% of copper was dissolved after 14 min with inorganic acids at 0.5 M, 25 • C and l/s = 10 ml/g while more drastic operation conditions were needed to reach the same dissolution efficiency with citric acid solution. Anions seem to be involved in the surface reaction. The dissolution kinetics of CuO was examined according to heterogeneous model and it was found that the dissolution rate was controlled by surface chemical process in all cases.