Initial Acid Concentration Research Articles

Ultrasonic Assisted and Neural Network Model for Adsorption of of humic acid (HAs) by Synthesised CM-β-CD-Fe3O4NPs from Aqueous Solutions

ABSTRACT In the present study, the applicability of CM-β-CD-Fe3O4NPs synthesis for eliminating humic acid rapidly from aqueous solutions. Identical techniques including BET, FT-IR, XRD and SEM have been utilised to characterise this novel material. The investigation showed the applicability of CM-β-CD-Fe3O4NPs as an available, suitable and low-cost adsorbent for the proper deletion of humic acid from aqueous media. Also, the impacts of variables including initial humic acid (HA) concentration (X1), pH (X2), adsorbent dosage (X3) and sonication time (X4) came under scrutiny using central composite design (CCD) under response surface methodology (RSM). The experiments have been designed utilising response surface methodology. In this current article, the values of 12 mg·L−1, 0.03 g, 7.0, 4.0 min were considered as the ideal values for humic acid (HA) concentration, adsorbent mass, pH value and contact time, respectively. The kinetics and isotherm studies proved the appropriateness of the second-order and Langmuir models for the kinetics and isotherm of the adsorption of humic acids (HAs) on the adsorbent. The adsorbent was proved to be recyclable more than once. Since almost 99.5% of humic acids (HAs) were deleted with ideal adsorption capacities of 105 mg·g−1 for humic acids (HAs). The use of artificial neural network model in predicting data with Levenberg–Marquardt algorithm, purelin or a linear transfer function at the output layer and tansig or a tangent sigmoid transfer function in the hidden layer with five neurons was helpful for deletion of humic acid (HAs), MSE (mean square error) of 0.33 for humic acid (HA) removal by CM-β-CD-Fe3O4NPs. The overall results confirmed that CM-β-CD-Fe3O4NPs could be a promising adsorbent material for humic acid (HA) removal from aqueous solutions.

Optimization and experimental design by response surface method for reactive extraction of glutaric acid

Abstract Glutaric acid is an attractive chemical compound which can be used for the manufacturing of polyesters, polyamides, and polyols. It can be produced by the synthesis (chemical method) and fermentation (biological method) process. Glutaric acid is presented with the lowest quantity in the fermentation broth and industrial waste streams. The separation methods of glutaric acid are difficult, costly, and non-environment friendly from fermentation broth. Reactive separation is a simple, cheapest, and environment-friendly process for the recovery of carboxylic acid. Which can be employed for the separation of glutaric acid with lower cost and environment-friendly process. In this study, response surface methodology (RSM) was used as a mathematical technique to optimize and experimental design for investigation of the reactive separation of glutaric acid from the aqueous phase. As per RSM study, 20 experiments with different independent variables such as concentration of glutaric acid, % v/v of trioctylamine, and pH for recovery of glutaric acid were performed. The optimum condition with maximum efficiency (η) 92.03% for 20% trioctylamine and pH = 3 at 0.08 mol/L of glutaric acid initial concentration were observed. The lower concentration of trioctylamine provides sufficient extraction efficiency of glutaric acid. This method can also be used for the separation from fermentation broth because a lower concentration of trioctylamine which makes this process environment-friendly. The optimization condition-defined quadratic response surface model is significant with R 2 of 0.9873. The independent variables defined the effect on the extraction efficiency of glutaric acid. This data can be used for the separation of glutaric acid from industries waste and fermentation broth.

The picric acid removal from aqueous solutions by multi‐walled carbon nanotubes/EDTA/carboxymethylcellulose nanocomposite: Central composite design optimization, kinetic, and isotherm studies

AbstractThe removal of hazardous picric acid is of great importance to making healthy and drinkable water. In this research, a nanocomposite (MWCNT‐EDTA‐CMC) based on carboxylated multiwall carbon nanotubes (MWCNT‐COOH) modified by carboxymethylcellulose (CMC) and ethylenediamintetraacetic acid (EDTA) was prepared for adsorption and removal of picric acid from aqueous solutions. MWCNT‐EDTA‐CMC was characterized by Fourier transform infrared (FT‐IR), field‐emission scanning electron microscopy (FESEM), thermal gravimetric analysis (TGA). Central composite design (CCD) was used to study the influence of pH, adsorbent dosage, and initial picric acid concentrations on the removal percentage of picric acid. At optimum conditions (pH 3.0, MWCNT‐EDTA‐CMC dosage 0.050 g, picric acid concentration 30 mg L−1), high removal efficiency (97.67%) was obtained for picric acid which was reasonably well predicted by the model. The adsorption process was demonstrated by the pseudo‐second‐order kinetic and Freundlich isotherm models for both adsorbents. In addition, the consumed MWCNT‐EDTA‐CMC could be reused up to 3th cycle of regeneration.

The influence of sulfur addition on the hazard-type reaction of ilmenite ores with sulfuric acid

Abstract The paper presents results of thermokinetic investigation of the hazard-type reaction of Norwegian and Australian ilmenite ores with sulfuric acid, modified by the addition of elemental sulfur, to increase the process safety in industrial conditions. In the reactions of both ilmenite ores the addition of sulfur caused a reduction of the thermal power generated in the reaction and a decrease in the value of the thermokinetic parameter ΔTmax/Δτ for almost the whole range of initial concentrations of sulfuric acid. It was also found that the addition of sulfur to the reaction did not negatively affect the degree of ilmenite leaching. The interpretation of the obtained thermokinetic curves allowed to determine safe process conditions for both types of titanium raw materials.

Transcriptome Analysis of Komagataeibacter europaeus CGMCC 20445 Responses to Different Acidity Levels During Acetic Acid Fermentation.

In the industrial production of high-acidity vinegar, the initial ethanol and acetic acid concentrations are limiting factors that will affect acetic acid fermentation. In this study, Komagataeibacter europaeus CGMCC 20445 was used for acetic acid shake flask fermentation at an initial ethanol concentration of 4.3% (v/v). We conducted transcriptome analysis of K. europaeus CGMCC 20445 samples under different acidity conditions to elucidate the changes in differentially expressed genes throughout the fermentation process. We also analyzed the expression of genes associated with acid-resistance mechanisms. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis showed that the differentially expressed genes were enriched in ribosomes, citrate cycle, butanoate metabolism, oxidative phosphorylation, pentose phosphate, and the fatty acid biosynthetic pathways. In addition, this study found that K. europaeus CGMCC 20445 regulates the gene expression levels of cell envelope proteins and stress-responsive proteins to adapt to the gradual increase in acidity during acetic acid fermentation. This study improved the understanding of the acid resistance mechanism of K. europaeus and provided relevant reference information for the further genetic engineering of this bacterium.

Heat effects in the reaction of sulfuric acid with ilmenites influenced by initial temperature and acid concentration

Abstract The influence of temperature and sulfuric acid concentration on the enthalpy and the rate of heat release during the reaction of Norwegian and Australian ilmenites with sulfuric acid was determined. The experimental results obtained from calorimetric measurements were compared with theoretical calculations based on the oxide composition and the phase composition of the raw material. Experimentally determined heat of reaction for Norwegian ilmenite (900–940 kJ/kg) and Australian ilmenite (800–840 kJ/kg) showed good agreement with theoretical calculations based on the phase composition of the raw material. It was found that the enthalpy of ilmenites decomposition reaction does not depend on the concentration of sulfuric acid in the concentration range from 83% to 93%. It was also demonstrated that the temperature and concentration of sulfuric acid have a significant impact on the thermokinetics of the decomposition process, increasing the value of the average rate of temperature change.

Phytoremediation of Boron using Lemna minor from Synthetic Aqueous Solutions and Real Geothermal Water

In this study, phytoremediation performance of Lemna minor L. on boron removal from synthetic solution and real geothermal water was evaluated. Effects of initial boron concentration, initial pH, water height in cell, and initial humic acid concentration were investigated. The maximum removal efficiency was achieved as 96.7 % with the experimental run with 5 mg L-1 initial boron concentration, pH 8, and 1.5 cm water depth. Increasing the initial boron concentration from 5 to 30 mg L-1 resulted in a drastic decrease in removal efficiency to 36.6 %, due to the toxic effect of high boron content, which was clearly observed from deterioration of plant’s color and structure. SEM, FTIR, and mass balance analyses revealed that the boron removal mechanism was mainly biosorption. Geothermal water experiments indicated L. minor’s applicability with 59.5% removal efficiency, proving high potential in being used for post-treatment of geothermal waters with high boron content.

Photodegradation of cresol red by a non-iron Fenton process under UV and sunlight irradiation: Effect of the copper(II)-organic acid complex activated by H2O2

The copper(II)-organic acid complex activated by H2O2 was known to be a non-iron Fenton process. In this work, photodegradation of cresol red (CR) by a non-iron Fenton process (Cu(II)-Ox- H2O2) using Cu(II)-Oxalic acid (Ox) complex as catalyst was investigated. The results demonstrate that the combination of light and Cu(II)-Ox complex in situ generates H2O2 by producing reactive oxidants through the reaction of Cu(I) with H2O2. The second part, dedicated to the study of capacity of Cu(II)-Ox- H2O2 system to induce the degradation of CR. Kinetics experiments showed that the external supply of H2O2 to the Cu(II)-Ox system was found to further enhance the effectiveness of CR. Here, we further investigate the synergistic effect in different systems (two-component system UV/Cu(II)-Ox, and three-component system UV/Cu(II)-Ox-H2O2 with CR under the same conditions. Parameters such as pH, the initial concentrations of Cu(II), oxalic acid (Ox) and H2O2 were all investigated. Furthermore, the radical scavenging activity studies indicated that •OH was the dominant active species responsible for CR removal, and O2–• could promote CR degradation in Cu(II)-Ox-H2O2 system. These result strongly confirmed the feasibility of non-iron Fenton process (Cu(II)-Ox- H2O2) under excitation by sunlight.

Carbon dioxide bioconversion into single cell oils (lipids) in two reactors inoculated with Acetobacterium woodii and Rhodosporidium toruloides

Acetobacterium woodii was able to produce high concentrations of acetic acid, i.e., > 20 g/L, from CO2, in the presence of H2 as an energy source, which was favoured by maintaining a near-optimal pH of 7.8 in an automated bioreactor. This allows the mitigation of CO2 emissions for their conversion to acetic acid, which was then further used to produce lipids (single cell oils) by Rhodosporidium toruloides in the next assay. The yeast, grown on acetic acid, efficiently accumulated lipids in A. woodii’s medium, and further improved bioconversion would result in a highly promising process. Acetic acid inhibitory studies performed with R. toruloides, at different initial concentrations of the acid, using the fermented broth of A. woodii grown on CO2, showed that the yeast maintained a constant growth rate and substrate consumption rate up to acid concentrations of 15 g/L. Both rates remained roughly constant at higher initial acetic acid concentrations; except for a more extended lag phase observed in batch assays before the yeast entered in its exponential growth phase.

A study on the synthesis of coarse TiO2 powder with controlled particle sizes and morphology via hydrolysis

The hydrolysis of Ti(IV)-bearing acid solution to prepare titanic acid particles is a crucial step for the production of TiO2 material. The hydrolysis which takes place in HCl medium was investigated particularly with the purpose of preparing coarse particles with narrow size distributions for applications such as Ti metal powder production. The key factors that affect the hydrolysis ratio and rate, the morphology, and the size of the titanic acid particles were investigated. The results illustrated that temperature, initial free acid and equivalent TiO2 concentrations cross-influence the above-mentioned key attributes of the product particles. Near spherical rutile particles with a D50 of around 30 μm were obtained under the optimal parameters. Four stages, including incubation, acceleration, near steady-state reaction, and deceleration, were observed during the progress of the hydrolysis reaction, while the precipitate morphology evolved from irregular to smooth, and to round as a result of the nucleus agglomeration.

Experimental study on advanced treatment of landfill leachate by ultraviolet catalytic persulfate

Landfill leachate is characterized by complex composition and difficult degradation. In this paper, we compared the effects of advanced treatment of ultraviolet (UV) system, persulfate (PS) system and ultraviolet/persulfate (UV/PS) system on landfill leachate. The results showed that the UV/PS system had the best removal efficiency. When the initial concentration of humic acid was 200 mg/L, the dosing of PS was 25 mmol/L, and the initial pH was 4, the maximum removal rates of UV 254 and TOC were 89.62% and 76.17%. Namely, the value of SUVA 254 decreased to 7.6603 L/(m ⋅ mg). It follows that the UV/PS system is effective in the removal of humic acid in the landfill leachate. In addition, this paper investigated the effects of temperature, initial pH and dosing ratio of chemicals on the treatment of leachate by UV/PS system. It was found that the optimal process conditions were 35 °C, pH = 4, dosing ratio = 2, and 24 h of operation. Under these conditions, the maximum removal rates of COD and TOC were 82.64% and 66.69%. The removal capacity of the system was in accordance with the pseudo-second-order kinetic equation. Therefore, this paper can provide a reference for the advanced treatment of landfill leachate. • An advanced oxidation technology for the removal of landfill leachate after biochemical treatment was presented. • Humic acid was used as a model for organic matter. The value of SUVA 254 decreased to 7.660315 L/ (m ⋅ mg) under the optimum conditions. • Under the optimal conditions, the removal rates of COD and TOC of landfill leachate after biochemical treatment reached 82.64% and 66.69%. • SR-AOPs are more efficient, economical and widely applicable compared to other technologies for deep treatment of landfill leachate.

Aerosol growth in CO2 absorption with MEA, modelling and comparison with experimental results

A new and improved aerosol model has been developed and tested against experimental data. An e-NRTL equilibrium model for MEA was extended to cover sulphuric acid containing droplets and validated against new eboulliometer data in this work.The droplet model predicts emissions without demister installed in the absorber, within ± 20% and with demister, 30-80% of the measured emissions. The model predicts well the change in emissions from NG-based to coal-based exhaust.Under conditions reported in this work, the droplet number concentration was found to have a small effect on predicted emissions because of more MEA gas-phase depletion with high droplet concentrations and slower growth. The effects counteract each other. With significant MEA depletion in the gas phase, the emissions are largely determined by the mass transfer rate from the bulk liquid.The initial droplet sulphuric acid concentration had a minor effect on the outlet droplet size distribution. The effect on MEA emissions was significant: the emissions went up with increased initial sulphuric acid concentration. The effect of sulphuric acid was stronger for low inlet gas CO2 concentration (NG) than for coal-based exhaust. The increase in emissions is believed to be caused by the increase in overall driving force for MEA between bulk liquid phase and droplets.The log-normal model does not catch small inlet droplet sizes in the range below 20-30nm. These droplet sizes hardly grow in the absorber and water wash and in the total emissions, these droplets have a negligible impact on emissions.

Benzenesulfonic acid-based hydrotropic system for achieving lignocellulose separation and utilization under mild conditions

Developing low-cost and sustainable fractionation technology is the key to achieve the maximal utilization of lignocellulosic biomass. This study reported benzenesulfonic acid (BA) as a green hydrotrope for efficient lignocellulose conversion into two fractions at atmospheric pressure: (1) a primarily cellulosic solid residue that can be utilized to produce high-value building blocks (lignocellulosic nanomaterials or sugars), and (2) the collected spent acid liquor that can be diluted with anti-solvent to easily obtain lignin nanoparticles. BA hydrotropic method exhibited greater reaction selectivity to solubilize lignin, where approximately 80% lignin were removed at only 80 °C in 20 min. The lower lignin content substrates resulted in relatively higher enzymatic hydrolysis efficiency of 80% and less entangled lignocellulosic nanofibrils (LCNF). Furthermore, the separated lignin particles size can be easily adjusted by the initial acid concentration. Overall, this work presented a promising and simple technology in achieving lignocellulose separation and utilization under mild conditions.

High resolution measurements reveal abiotic and biotic mechanisms of elevated nitric oxide emission after wetting dry soil

Wetting dry soil triggers emission of nitric oxide (NO), which can harm air quality and influence ecosystem N balance. NO released after wetting may be derived from two primary mechanisms: (1) abiotic decomposition of nitrite (NO2−) present in the dry soil and (2) biologically-mediated production of NO. The relative contributions of these mechanisms to NO emission are challenging to partition. To differentiate the two mechanisms, we made continuous observations of NO emission from a range of soils that varied in texture, pH, and exchangeable cations. We coupled NO gas exchange measurements with automated, non-destructive high-resolution sampling of inorganic N species via microdialysis. We identified two distinct phases of NO production (1) an initial phase that reached its maximum less than 30 min after rewetting; and (2) a second phase lasting up to 36 h. The magnitude of the initial phase of NO production was correlated with the initial nitrous acid concentration (calculated from NO2− concentrations and soil pH) and soil exchangeable calcium. The second phase of NO emission coincided with a peak in NO2− that preceded NO3− accumulation. Together, these results suggest that NO emissions following wetting are defined by an initial pulse of abiotic NO formation mediated by soil acidity at mineral surfaces, followed by a prolonged pulse of NO emission driven by a lag between the biological processes of ammonia oxidation and nitrite oxidation. These results can inform mechanistic models of NO emissions from soils to improve predictions of the terrestrial N cycle and atmospheric chemistry.

Bipolar membrane electrodialysis for mixed salt water treatment: Evaluation of parameters on process performance

In the present study, bipolar membrane electrodialysis (BMED) process was employed as an alternative separation method to the distillation unit in the Solvay process for the synthetic soda ash production. The applicability of BMED was investigated by evaluating the effects of system parameters on process performance. Desalination ratio, salt based acid and base conversion ratio, flux, product purity, and energy consumption were defined as the process performance criteria for the BMED systems. Initial salt concentration, applied current and voltage, and initial acid and base concentrations were chosen as system parameters. The results of the study revealed that current/voltage and initial salt concentration are the most effective factors affecting all performance criteria. When all system parameters were considered, BMED provides the desalination ratio in between 90% and 98%, the acid and base conversion ratio of salt in between 60% and 80%, and the energy consumption in the range of 1.54–2.33 kWh/kg acid. Furthermore, the desalinated water can be reused as process water and the distillation unit waste problem can be resolved by the utilization of BMED system.

Photocatalytic degradation of humic acid using a novel visible-light active α-Fe2O3/NiS2 composite photocatalyst

The effects of α-Fe2O3/NiS2 composite for the humic acid removal were systematically studied and compared with the synthesized α-Fe2O3 and NiS2. The obtained mesoporous composite has a stacked plate-like surface, active at a visible light region with a bandgap of 2.49 eV, and has a lower rate of recombination compared to the α-Fe2O3 but higher than the NiS2. The highest humic acid removal (93.7%) was achieved by the α-Fe2O3/NiS2 composite followed by the α-Fe2O3 (88.7%) and NiS2 (86.4%) at optimum conditions of 0.1 g L−1 catalyst loading, pH 5, and 30 mg L−1 initial humic acid concentration. The mineralization achieved 96.8% and the catalyst was stable up to the fourth cycle. These encouraging results were due to the better adsorption capacity of the composite, being active in visible light, and quenching of the photoluminescence that led to effective separation of subsequent reduction in the rate of recombination of the charged carriers.

Investigation of the effects of ionic liquid as diluent in separation of lactic acid from aqueous media by reactive extraction

The fact that fossil fuels will be depleted in near future and the increase of environmental awareness in humans causes biotechnology to seek new and develop existing processes constantly. That is why researchers have turned to work in this field in recent years. In this study, the separation of lactic acid, an industrially important organic acid, from aqueous solutions by reactive extraction method where tripropylamine (TPA) has been used as an extractant and hydrophobic ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) as a diluent was investigated. Six different traditional organic solvents (n-pentane, toluene, 2-octanone 1-octanol, methyl isobutyl ketone (MIBK), dimethyl phthalate (DMP)) have been chosen to compare the efficiency of the selected ionic liquid. The batch physical and reactive extraction experiment results were presented as distribution coefficient (D), loading factor (Z), and extraction efficiency (E). All experiments were performed at 298.15 K with an initial lactic acid concentration of 1.28 mol·L-1 (10.275% w/w). In reactive extraction experiments, the effect of different TPA concentrations (0.35–1.4 mol·L-1) on extraction efficiency was investigated. While the extraction efficiency in physical extraction varied between 5.55 and 14.06%, ionic liquid has the highest extraction efficiency. In the reactive extraction results, it was seen that the ionic liquid has 99.61% extraction efficiency at 1.40 mol·L-1 TPA concentration. According to this result, the use of (TPA + 1-butyl-3-methylimidazolium hexafluorophosphate) organic mixtures is a suitable alternative to separate lactic acid from aqueous solutions.

КИНЕТИКА СЕЛЕКТИВНОГО ГИДРАЗИНОЛИЗА МАЛЕИНОВОЙ КИСЛОТЫ НА КИСЛОТНОМ КАТАЛИЗАТОРЕ

For the first time, kinetics and the mechanism of the reaction of hydrazinolysis of maleic acid in the presence of cation exchanger resin KU-2-8 in H-form have been studied. The experiments were carried out in a static system in a thermostat glass reactor. It was found that cation exchanger shows high catalytic activity in the studied process - maleic acid conversion was 93%, and maleic hydrazide yield was 90%. The conversion selectivity of maleic acid to maleic hydrazide was 97,8%. The reaction rate was determined from the accumulation of maleic hydrazide. The apparent reaction rate constant (k) was calculated from the second-order reaction rate equation. The effect of initial concentrations of maleic acid and hydrazine hydrate, the temperature on the reaction rate was studied. The first order of maleic acid and hydrazine hydrate is determined. Activation energy of the process found from the Arrhenius dependence is 32,1 kJ/mol. On the basis of kinetic and IR spectroscopic methods, a probable reaction mechanism involving polymer-bound hydrogen ions is proposed.

Modelling and Simulation of Biobutanol Fermentation by Clostridium saccharoperbutylacetonicum N1-4

Biobutanol exhibits high octane number, non-hygroscopic, non-corrosive and can be mixed with gasoline without engine modification. Furthermore, the use of biobutanol as a fuel can reduce the negative impact of environmental due to the use of fossil-based fuel. Therefore, research on the development of biobutanol is still very much needed, including research on modelling and simulation of biobutanol production by fermentation. With modelling and simulation, we can predict various biobutanol production behaviour. This paper deals with the modelling and simulation of the production of biobutanol from glucose in batch bioreactor using Clostridium saccharoperbutylacetonicum N1-4. C. saccharoperbutylacetonicum N1-4 exhibits a good growth ability on simple or complex sugars, such as glucose, sucrose, or starch. This study concerned with the kinetics models of biobutanol production as developed by Shinto based on the C. acetobutylicum metabolic pathway which consists of the glycolysis, acidogenesis and solventogenesis pathways with several simplification of reactions. In this study, modelling was carried out by adapting the rate parameter value of k13 indicating the rate constant of cell death. The adapted models were applied to determine the effect of the initial concentration of glucose and organic acids on the production of butanol and compared to the experimental data from previous research. Model simulations were performed by using MATLAB® software. The butanol yield was affected by the initial glucose concentration. The highest butanol yield of 77% was obtained at a glucose concentration of 22 g/L. The simulation results exhibit that the biobutanol yield decreases when the glucose concentration is higher than 22 g/L. These results are consistent with previous experimental data. The simulation results also show the effect of the concentration of acetic acid in the fermentation medium and can be optimized. From the simulation results, the presence of 7.5 g/L acetic acid can increase the biobutanol production by 20%. However, previous experimental data showed that a concentration of 2.5 g/L acetic acid was preferred. The simulation results also show the effect of the addition of butyric acid and lactic acid on the production of biobutanol.

Reductive leaching of indium from the neutral leaching residue using oxalic acid in sulfuric acid solution

The present study evaluates the reductive leaching of indium from indium-bearing zinc ferrite using oxalic acid as a reducer in sulfuric acid solution. The effect of main factors affecting the process rate, including the oxalic-acid-to-sulfuric-acid ratio, stirring rate, grain size, temperature, and the initial concentration of synergic acid, was precisely evaluated. The results confirmed the acceptable efficiency of dissolving indium in the presence of oxalic acid. The shrinking-core model with a chemical-reaction-controlled step can correctly describe the kinetics of indium dissolution. On the basis of an apparent activation energy of 44.55 kJ/mol and a reaction order with respect to the acid concentration of 1.14, the presence of oxalic acid was found to reduce the sensitivity to temperature changes and to increase the effect of changes in acid concentration. Finally, the equation of the kinetic model based on the factors under study is presented.