Phosphoric Acid Concentration Research Articles

A pore scale model study of mass transfer and electrochemical reaction in cathode catalytic layer of high-temperature polymer electrolyte membrane fuel cells

The mass transfer and related electrochemical reactions in the catalytic layer (CL) are crucial for the performance of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), but there is a lack of understanding of the optimal phosphoric acid content and Pt/C catalyst loading in the CL. In this work, we investigate the influences of Pt/C catalyst numbers (NPt/C) and phosphoric acid film thickness (δPA) on mass transfer and electrochemical reactions of the cathode CL using a pore-scale model (300 × 300 × 300 nm3). The results reveal that larger NPt/C and δPA can impede oxygen diffusion, while lower NPt/C and δPA lead to fewer reaction active sites and lower conductivity, both of which result in lower current density. Therefore, the balance of three-phase transport is extremely important for CL. There is a 3D volcanic relationship between current density, Pt/C catalysts, and phosphoric acid film. At NPt/C = 200 (7407 per μm3) and δPA = 4 nm (the volume fractions of 37.22 % and 17.87 %), the highest current density can be achieved at a potential of 0.5 V (vs. RHE), which increased with the decrease of potential. This work is valuable for understanding the optimizing the microstructure and three-phase transport pathway of the CL to improve the performance of HT-PEMFCs.

Studies on uranium sorption from Egyptian wet-process phosphoric acid using silicone rubber modified with thiourea and methyl methacrylate composite

ABSTRACT The application of silicone rubber modified by thiourea and methyl methacrylate composite SRTM aimed at the sorption of uranium from commercial phosphoric acid is the highest objective of this examination effort. The impact of various factors on sorption efficiency for example adsorbent dose (g/ml), temperature, phosphoric acid concentration, and shaking time have remained studied. XRD, XRF, EDX, SEM, Zeta potential, BET, and FTIR analyses remained carried out to determine the properties of the produced composite. The attained results showed the sorption capacity for uranium as 25.19 mg g− 1 at the mentioned conditions; commercial phosphoric acid, 30% P2O5, 120 min, and room temperature. The investigational documents have been designated fine with pseudo-second-order kinetic scientific calculations. Balance process described by isotherm model’s Langmuir. uranium sorption thermodynamic considerations showed a spontaneous procedure and exothermic nature (ΔG (kJ/mol) = −13.8:-11.3, ∆H(kJ/mol) = −34.9, ∆S (J/mol K) = −70.9). Mechanism and reusability sorption were studied and Desorption efficiencies of about 95% for U (VI) were achieved using 1.0 M sulphuric acid solution.

Use of a natural rock material as a precursor to inhibit corrosion of Ti alloy in an aggressive phosphoric acid medium

The mechanism of interaction between magnesite mineral and phosphoric acid (0.001–0.5 M) in addition to the determination of the protective properties for Ti alloy (working electrode) in phosphoric acid both with and without an inhibitor have been investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. Results of electrochemical tests show that the corrosion resistance of titanium alloy in phosphoric acid solution only increased and hydrogen production decreased by either decreasing acid concentration or increasing immersion time associated with the thickening of the oxide film formed on the alloy surface. On adding magnesite, the corrosion resistance of Ti alloy is enhanced by increasing the phosphoric acid concentration (0.001–0.5 M) due to the formation of sparingly soluble magnesium phosphate film on the alloy surface that inhibits the effect of increasing hydrogen evolution reaction due to the pH value decreases. The increasing adsorption behavior of the magnesite inhibitor and decreasing its diffusion were deduced from EIS measurements. Thus, the addition of 3% magnesite minimizes the corrosion by forming a new protective film (Mg3(PO4)2), which differs from the traditional passive film and prevents the effect of the increase of hydrogen evolution. The surface morphology and chemical composition of the tested alloy were determined using scanning electron microscopy (SEM), Fourier transform Infra-Red spectroscopy (FTIR), X-ray diffraction (XRD), X-ray Fluorescence (XRF) and In situ Raman spectroscopy.

Multi-objective optimization and performance assessment of response surface methodology (RSM), artificial neural network (ANN) and adaptive neuro-fuzzy interfence system (ANFIS) for estimation of fouling in phosphoric acid/steam heat exchanger

Fouling is a common occurrence in industrial heat exchangers, leading to a decrease of the thermal efficiency. This research addresses the challenge of applying various machine learning algorithms including Response Surface Methodology (RSM), Artificial Neural Network (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS) to effectively model the fouling resistance in a heat exchanger in phosphoric acid concentration loop. Subsequently, a multi-objective optimization approach was employed to minimize the fouling resistance. Confirmatory experiments are then conducted in the phosphoric acid concentration plant using optimized variables.The findings of this study indicate that the three models accurately align with one year of operational data, achieving a remarkably high coefficient of correlation (R). Among the models utilized, RSM demonstrates the highest level of prediction accuracy, with an R of 0.9998, accompanied by the lowest mean square error (MSE) of 5.9388 10−13 and root mean squared error (RMSE) of 7.7064 10−7. The RSM optimization process identifies the optimal conditions for variables such as time, acid inlet and outlet temperature, steam temperature, acid density, and volume flow rate, which are determined to be 114.805 h; 72.214 °C; 80.407 °C; 116.784 °C; 1642.47 kg/m3; and 2308.1 m3/h, respectively. The predicted fouling resistance demonstrates a strong correlation with the actual data, with a negligible percentage difference of 2.19 %, further validating the accuracy and reliability of the RSM model.

Optimizing FeSiCr-Based Soft Magnetic Composites Using the Deionized Water as the Phosphating Solvent.

To prepare a soft magnetic powder core, the magnetic powder surface has to be insulated by phosphating treatment. Organic chemicals such as ethanol and acetone are generally used as solvents for phosphoric acid, which may cause serious environmental problems. This work proposed deionized water as the environmentally friendly phosphating solvent for FeSiCr powder. The soft magnetic composites (SMCs) were prepared using phosphoric acid for inorganic coating and modified silicon polymer for organic coating. The effect of different phosphating solvents, including deionized water, ethanol, and acetone, on the structure and magnetic properties of SMCs were investigated. It is found that the solvent affects the phosphating solution's stability and the phosphoric acid's ionization. The phosphoric acid is more stable in deionized water than in ethanol and acetone. The phosphating reaction in deionized water is also more stable in deionized water, resulting in a dense phosphate coating on the particle surface. The effects of phosphoric acid concentration and temperature on the magnetic properties of FeSiCr-based SMCs were further studied. With the increase in phosphoric acid concentration and temperature, the magnetic permeability and saturation magnetization of the powder core decrease, and the core loss decreases, followed by an increase. The optimized combination of properties was obtained for the SMCs phosphated with 0.2 wt.% phosphoric acid in deionized water at 35 °C, including a high effective permeability μe of 25.7, high quality factor Q of 80.2, low core loss Pcv of 709.5 mW/cm3 measured at 0.05 T @ 100 kHz, and high withstanding voltage of 276 V, due to the formation of uniform and dense insulating coating layers. In addition, the SMCs prepared with phosphated powder show good corrosion resistance. The anti-corrosion properties of the SMCs using deionized water as a phosphating solvent are better than those using ethanol and acetone.

Effect of phosphoric acid on leaching of monazite during low-temperature sulfuric acid cyclic leaching process

To completely recover valuable elements and reduce the amount of waste, the impact of phosphoric acid on the decomposition of rare earth, fluorine and phosphorus during cyclic leaching was studied based on the characteristics of low-temperature sulfuric acid decomposition. When a single monazite was leached using 75 wt% H2SO4 solution with phosphoric acid, the size and number of monazite particles in the washing slag gradually decrease with the increase in phosphoric acid content in the leaching solution. The monazite phase can hardly be found in the slag when the phosphoric acid content reaches 70 g/L, which indicates that phosphoric acid is favorable for monazite decomposition. The mixed rare earth concentrate was leached by 75 wt% H2SO4 containing 70 g/L phosphoric acid, the mineral compositions of the washing slag are only gypsum and unwashed rare earth sulfuric acid. After cyclic leaching of 75 wt% H2SO4, the mineral compositions of the primary leaching washing slag are mainly undecomposed monazite, rare earth sulfate and calcium sulfate. However, monazite is not found in the mineral phase of the second and third leaching washing slag. The leaching rates of rare earth and phosphorus gradually increase with the increase in cyclic leaching times. In addition, the phosphoric acid content in the leaching solution increases with the increase in the number of cyclic leaching time. However, the rising trend decreases when the phosphoric acid content reaches 50 g/L by adsorption and crystallization of phosphoric acid. A small amount of water can be used to clean the leaching residue before washing to recover the more soluble phosphorus acid according to the difference of dissolution between phosphoric acid and rare earth sulfuric acid.

Effects of magnesia and borax on the compressive strength and microstructure of phosphoric acid-activated metakaolin geopolymer

Phosphoric acid-activated geopolymer (PAG) is an environmentally friendly cementing material with broad application prospects in many fields. Currently, phosphoric acid-activated metakaolin geopolymer (PAMG) is the focus of extensive research. Most studies mainly focus on the effects of metakaolin (MK) activity, phosphoric acid (PA) concentration, mix proportion, and curing system on the compressive strength of PAMG. However, the investigation of additives is extremely limited. In this study, the effects of magnesia and borax on the mechanical properties and microstructure of PAMG were investigated. The compressive strength of PAMG reached 84.31 MPa, indicating a 57.71% increase when the magnesia content was 6%. This increase was attributed to the ability of magnesia to improve the polymerization reaction and gel formation. Furthermore, the addition of 1% borax led to a compressive strength of 87.92 MPa, representing a 64.46% improvement. The presence of borax facilitated gel formation and enhanced the gel structure through the BO bond.

Structural characterisation and reactivity measurement of chemically activated kaolinite

This study examines the structural evaluation of differently activated kaolins for potential use as supplementary cementitious materials (SCM) or as precursor for alternative cementitious materials (ACM). Chemical activation involved amorphizing the kaolinite structure using varying phosphoric acid concentrations, reaction times, and temperatures. Metakaolin obtained via thermal activation served as a comparison. Inductively Coupled Plasma – Optical Emission Spectroscopy (ICP-OES) characterization of the activating solutions revealed phosphoric acid activation leading to dealumination in kaolinite structures, with temperature emerging as the most significant parameter. X-ray diffraction (XRD) confirmed amorphization, attributed to the dealumination process causing Al loss and creating new Si–O–Si interlayered bonds, as monitored by 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) tracking the change from Q3 to Q4 environments. Furthermore, pozzolanic activity was assessed through Ca(OH)2 consumption and reaction heat release via modified Chapelle and R3 tests, respectively. Kaolinite subjected to intensive chemical activation exhibited high reactivity and increased specific surface area, indicating its potential as a pozzolanic material. Keywords: Kaolin; Chemical activation; Supplementary cementitious materials; Alternative cementitious materials; Dealumination; Pozzolanic reactivity.

Recovery of uranium from phosphate ore of Iran mine: Part II- solvent extraction of uranium from wet-process phosphoric acid

The current study in laboratory scale was aimed at developing an optimal two-stage extraction process for production of yellow cake from the phosphoric acid solution that was extracted from the Sheikh Habil phosphate rocks in central Iran. To attain an optimized extraction process, different mixtures of D2EHPA + TOPO + TBP were examined. A total extraction cycle including extraction, stripping and yellow cake precipitation was run to realistically evaluate the performances of the selected mixtures-conditions. As for optimization of the operational conditions, we exploited central composite design (CCD) method, that is a branch of the surface response methodology (RSM), and analyzed the results with standard statistical methods. The O/A (organic to aqueous ratio) = 2, 11 min extraction time, 5 wt% TOPO concentration, 10–15 wt% TBP concentration, 20 wt% D2EHPA concentration, 800 mv oxidation-reduction potential, and 25 °C temperature were obtained as optimum extraction parameters. The O/A = 15, 11 min stripping time, 50 wt% phosphoric acid concentration, 250 mv oxidation-reduction potential, and 40 °C temperature were obtained as optimum stripping parameters. Finally on the last uranium extraction from the H3PO4 strippant on the optimum conditions, the concentration of uranium was more than 4500 ppm with extraction efficiency near to 90 %. Scrubbing of organic phase was done by 2 wt% of sulfuric acid solution at 40 °C and precipitation of ammonium uranyl carbonate (AUC, (NH4)4UO2(CO3)3) was done with 2 M ammonium carbonate solution at an O/A ratio of 1/2 with efficiency more than 95 % in the uranium precipitation process.

Application of ATR-FTIR spectroscopy and chemometrics for the forensic discrimination of aged peripheral and menstrual bloodstains

Accurately distinguishing between peripheral and menstrual bloodstains at crime scenes is a major challenge in forensic practice. The time since deposition (TSD) of bloodstains at the crime scene also plays an essential role in determining the postmortem interval or injury time. In this study, we used attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy combined with chemometric methods to differentiate peripheral and menstrual bloodstains considering the TSD and menstrual phase.The results of the principal component analysis (PCA) model showed that the fresh peripheral and menstrual bloodstains were relatively easy to distinguish, while the aged samples (2 W, 4 W, and 6 W TSD) caused a certain level of spectral signature convergence in the spectral features. Subsequently, the partial least squares discriminant analysis (PLS-DA) model and the genetic algorithm combined with PLS-DA (GA-PLSDA) model were constructed considering the TSD.The accuracy of internal cross-validation and external validation of the PLS-DA model demonstrated internal and external classification abilities of 88.3 % and 90.0 % accuracy, respectively. Additionally, the results of GA-PLSDA model showed that the accuracy of external and internal validation was 89.2 % and 90.0 %, respectively.The PCA, PLS-DA, and GA-PLSDA models showed that the critical differences between peripheral and menstrual bloodstains were in protein, phosphoric acid and glucose content. This preliminary study suggests that ATR-FTIR spectroscopy combined with chemometrics may be a potential method to distinguish between peripheral and menstrual bloodstains using complex conditions and provides support for further studies.

Influence of Physical and Chemical Activation of Coconut Shell Applied to Reduce Free Fatty Acids of Used Cooking Oil in Biodiesel Plant

This research was conducted to compare the characteristics of activated carbon that synthesized via different methods, physical and chemical activation. It was applied to reduce Free Fatty Acids (FFA) in used cooking oil which will be used in the manufacture of biodiesel. Physical activation was carried out by heating dried coconut shell in a tube furnace at 900°C in N2 gas flowing, by varied the holding time; 2 hours, 3 hours, and 4 hours. Meanwhile, chemical activation was conducted using phosphoric acid solution with various concentrations: 9%, 10%, and 11%. The BET (Brunauer-Emmett-Teller) test was processed to determine the surface area of ​​the activated carbon. The FFA test was conducted to determine the FFA content in treated used cooking oil. The activated carbon with chemical activation has a surface area of ​​260.57 m2/gram, 323.55 m2/gram, and 162.21 m2/gram at concentrations of phosphoric acid 9%, 10%, and 11%, respectively. Meanwhile, for physical activation, the surface area were 278.58 m2/gram, 448.368 m2/gram, and 444.74 m2/gram with variations in heating holding time of 2 hours, 3 hours, and 4 hours, respectively. The lowest levels of FFA are found in cooking oil with a phosphoric acid concentration of 11%, which is 1.505%. The higher the concentration of chemical activator, the greater the adsorption power of an activated carbon. The lowest levels of fatty acids are found in cooking oil with a holding time of 4 hours, which is 1.805%. FFA (Free Faty Acid) test results show that the longer the heating holding time, the better the activated carbon will be.

Preparation and properties of geopolymer containing phosphoric acid-activated fly ash and mechanically-milled kaolinite: Experiments and density function theory

The environmental pollution resulted from the stacking of solid wastes, and the 250 kg CO2 emission caused by calcined a ton of kaolinite have become an urgent problem to be solved. In this study, a novel phosphoric acid-activated geopolymer was developed, which was composed of fly ash (FA), mechanically activated-kaolinite (MAK). The influences of phosphoric acid concentration, mechanical grinding duration, and curing temperature were investigated. Microstructural properties of FAMAK geopolymers were examined through a serious of tests. Furthermore, the Gibbs free energy and nano-scale structure characteristics of acid-activated hydration products were calculated for the first time by using density functional theory. The results show that the optimal mass ratio of FA to MAK is 7:3 with 8 mol/L phosphoric acid, which led to the maximum compressive strength of 36.6 MPa at 56-day. Besides, the optimal grinding time is 3 h and temperature is 40 °C. Moreover, the content of silicon promotes the polymerization reaction. The valence and bonding of aluminum are primarily affected by its coordination number. The key outcomes in this study provides a low-carbon cementitious materials, which can achieve the double benefits of carbon reduction and the utilization of solid wastes.

Effect of Electrolyte Anions on the Activity of Iridium Oxide Catalysts for Water Electrolysis

Developing environmentally friendly and renewable energy sources is essential due to the environmental and energy security issues caused by traditional combustion of fossil fuel-based energy sources. Therefore, as a clean and sustainable energy carrier, hydrogen has attracted great attention in recent years. In this regard, water electrolysis utilizing renewable energy sources to produce hydrogen is considered one of the most promising technologies. It is believed elucidation of the reaction mechanism of highly active iridium oxides is promising for the further development of cost-efficient PEM water electrolysis catalysts. The properties of the MEA could be affected by many parameters such as the catalysts, operating temperature, and pressure1,2. Another important factor is the cation impurities that can be found in the circulating water, which could severely degrade the MEA performance during the operation of a PEM water electrolyze. However, there are less reports on anion impurities such as SO4 2- and PO4 3-. Therefore, in this study, the relationship between electrolyte anions and OER activity was investigated for IrOx catalysts with different crystal structure. By using operando X-ray absorption spectroscopy (XAS), we investigated the electronic state of Ir and O under operation potential.IrOx with different degree of crystallinity (SA3.5 and SA58) were provided by Tanaka Kikinzoku Kogyo K.K., Chemical & Refining Company and named after their BET surface areas. These two samples were then tested for electrochemical properties in different concentrations of phosphoric acid and perchloric acid, respectively. The electrochemical measurements were performed using a standard three-electrode cell connected to an MPG-205-NUC system (Bio-Logic). The cyclic voltammograms (CV) were scanned from 0.1 V to 1.2 V vs. RHE at 50 mV s-1. The electrochemical activities of the catalysts were subsequently investigated using linear sweep voltammetry (LSV) in the range of 1.1 to 1.7 V vs RHE at 10 mV s−1. operando XAS were collected using a home-made flow-type cell, where Pt wire and RHE worked as counter and reference electrodes, respectively. The catalyst ink was coated onto an Nafion membrane to prepare both the X-ray window and working electrode. The electrolyte was circulated at the flow rate of 100 mL min-1.The catalytic performance of IrOx was investigated at different types and content of electrolyte under H3PO4 and HClO4. Figure 1 shows the CVs of SA3.5 and SA58 under different types and content of electrolyte. In the presence of phosphate anions, SA3.5 showed a tendency to decrease Ir redox between 0.6 and 1.1 V with increasing electrolyte concentration. On the other hand, there were no obvious changes in SA58. It was found that IrOx catalysts have an great effect of specific adsorption of anions and low symmetry of monoclinic phase catalysts (SA 3.5) are more susceptible to anion poisoning. Figure 2 shows the result of examining the poisoning mechanism using soft X-ray XAS. O K-edge results present the formation of µ2-O (O-O) bond at around 528.7 eV, which was previously observed by Nong, H. N. et. al. through operando O-K edge measurements during OER process3. The peak intensity at 528.7 eV of the amorphous samples was in the same order as the OER activities. According to potential dependence change of the pre-edge peak, under the presence of phosphate anions, the hole formation to Ir-O hybrid orbitals was suppressed in SA3.5. This result indicates that the anion adsorbs to the active site, poisoning the catalyst surface and inhibiting the reaction. Acknowledgements This work is based on results obtained from a project (JPNP14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO) of Japan. References Zhang, Y.; Zhu, X.; Zhang, G.; Shi, P.; Wang, A.-L.; et al. J. Mater. Chem. A: 2021, 9, 5890-5914.Chen, Z.; Duan, X.; Wei, W.; Wang, S.; Ni, B.-J.; et al. Nano Energy: 2020, 78, 105270.Nong, H. N.; Falling, L. J.; Bergmann, A.; et al. Nature 2020, 587 (7834), 408-413. Figure 1

Balancing proton and mass transfers in cathode catalyst layer of high-temperature proton exchange membrane fuel cell via gradient porous structure design

The porous structure within the cathode catalyst layers (CLs) plays a crucial role in facilitating phosphoric acid (PA) invasion and oxygen diffusion, which was essential for establishing the triple-phase boundaries (TPBs) in high-temperature proton exchange membrane fuel cells (HT-PEMFCs).In this work, a gradient porous structure is deliberately constructed within the cathode CL by carefully controlling the microstructures of the double CLs. The effects of pore diameter distribution in the cathode CL and PA content in the membrane electrode assembly (MEA) on the single cell performance of HT-PEMFC are systematically investigated. By incorporating an appropriate amount of PA in the MEA, along with the optimized gradient porous structure, the inner pores effectively stored acid and prevented its outward diffusion. Simultaneously, the pores in the outer CL provided additional pathways for oxygen transfer. Consequently, the optimized gradient porous structure enhanced the peak power density of H2/Air fuel cells to 0.510 W cm−2 at a Pt loading of 0.5 mgPt cm−2, a notable improvement compared to 0.396 W cm−2 of the traditional single CL. The mechanism analysis further reveals that the cathode CL with gradient porous structure can successfully balance proton transfer and mass transfer, hence reducing the polarizations in fuel cell.

Research on wet etching techniques for very long-wavelength InAs/GaSb superlattices

Manufacturing high-quality very long-wavelength infrared detectors (VLWIR) on GaSb substrate is significant for advancing the superlattices application in the field of infrared detection. In this study, superlattices with excellent surface and crystal quality were obtained. Based on it, we delved into the wet chemical etching fabrication for very long-wavelength InAs/GaSb superlattices. The impact of varying concentrations of different components on surface etching results along the growth direction was examined through univariate experiments. The analysis revealed that the concentration and ratios of phosphoric acid and hydrogen peroxide notably dictated both the etching rate and surface roughness. The surface chemistry of GaSb and InAs bulk materials treated with various etching solution components was investigated using X-ray photoelectron spectroscopy (XPS). The objective of this study is to provide a comprehensive understanding of the effects caused by different components in wet etching, thereby enhancing the understanding of the wet etching process for InAs/GaSb materials.

Pressed Phosphate Materials Using Dispersed Rocks

The possibility of contact hardening of dispersed rocks after their acid activation by phosphoric acid is shown. The parameters of pressing, content and concentration of phosphoric acid, as well as the values of temperatures during thermal treatment are given. It is established that the obtained pressed phosphate materials (analogs of geopolymers) have high acid resistance, alkali resistance and heat resistance.

Poly(triphenylene-piperidine) membranes reinforced by carboxy intrinsic microporous polymers towards high output power at low phosphoric acid levels for HT-PEMFC

To address the inferior mechanical properties associated with high phosphoric acid (PA) content, a rigid microporous polymer containing carboxyl groups (cPIM) was incorporated into poly (triphenylene-piperidine) (PTP) matrix to prepare composite membranes (PTP-xcPIM) for high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Compared to the original membrane (PTP/PA), the PTP-xcPIM/PA reinforced membranes exhibited improved mechanical properties (13–17 MPa) and higher proton conductivity (>90 mS cm−1@180 °C) at a similar PA content. After assembling into a single HT-PEMFC, the reinforced composite membrane could achieve a high output power of over 1000 mW cm−2. The addition of the microporous layer to the composite membranes significantly increased the PA retention due to its siphoning effect on PA. Especially, PTP-10cPIM/PA retained 57.64% of PA after 100 h at 60 °C and 50%RH, while PTP/PA retained only 52.11% in the same harsh environment. These phenomena imply that the strategy of introducing rigid microporous polymers containing functional groups can lead to the simultaneous enhancement on the PA retention capacity and proton conductivity at low PA doping levels, and effectively avoid the “trade-off” effect between the mechanical properties and the output performance.

Study of the Effect of Magnesium Sulfate and Ammonium Nitrate on the Chemical Activity of Solutions of Phosphoric Acid

The present study aimed to study the effect of magnesium sulfate and ammonium nitrate on the chemical activity of phosphoric acid solutions. The results of studies on increasing the chemical activity of extractive phosphoric acid from Central Kyzylkum and Karatau phosphorites due to the concentration of the first hydrogen ions and the pH of the medium are presented. It has been shown that introducing magnesium sulfate heptahydrate into the acid reduces the concentration of the first hydrogen ions. Adding an amount of ammonium nitrate increases the concentration of the first hydrogen ions even higher than in the acid without magnesium. It has been established that the solubility of magnesium hydrophosphate increases with an increase in the content of P2O5 phosphoric acid, dihydrogen phosphate decreases as a result of dissociation with the formation of a hydrophosphate ion, and phosphoric acid dissociates with the formation of a dihydrophosphate ion, which binds with hydrogen ions, forming a dihydrophosphate ion.

Selectivity and competitive mechanism of cation exchange resin for Fe, Mg, and Al ions in phosphoric acid

AbstractThe presence of iron, magnesium, and aluminum elements as the primary impurities in wet‐process phosphoric acid (WPA) adversely affects the industrial phosphoric acid and subsequent phosphorus chemical products. This study aims to investigate the selectivity and competition mechanism of Sinco‐430 cation exchange resin for Fe, Mg, and Al ions in phosphoric acid solution. By studying the effects of different process conditions on the removal efficiency, the suitable conditions for the static removal of metal ions from Fe‐Mg, Al‐Mg, and Fe‐Al binary systems were determined: solid–liquid mass ratio (S/L) of 0.3, phosphoric acid concentration of 27.61 wt.%, system temperature of 50°C, and rotational speeds of 200, 400, and 200 rpm, respectively. By calculating the selectivity coefficients of the resin for metal ions under different experimental conditions and mutual replacement experiments, the semi‐empirical formulas for the selectivity coefficients were derived and order of selectivity was determined as follows: Mg2+ > Fe2+ > Al3+. Visual MINTEQ 3.1 software and density functional theory (DFT) calculations demonstrated that at low pH, the main forms of Fe, Mg, and Al present in phosphoric acid were FeH2PO4+, Mg2+, and AlH2PO42+, respectively. This finding explained the differences in selectivity of the resin for Fe, Mg, and Al. The dynamic removal of metal ions from phosphoric acid was investigated. The order of metal ion selectivity of the resin by the dynamic method is the same as that of the static method, and the dynamic exchange behaviour was most consistent with the Yan model.

Adsorption of Methyl Red on porous activated carbon from agriculture waste: Characterization and response surface methodology optimization

Activated carbon is an internationally recognized adsorbent substance that removes contaminants from industrial discharges. In this study, we evaluate the capacity of Activated carbon produced by the chemical carbonization of Rosemary root, considered agricultural waste, by using phosphoric acid as an activator to adsorb Methyl Red (MR) from aqueous solutions. To identify the optimum conditions for the carbonization process, the effects of several factors on the removal of methyl red were examined. These parameters included carbonization time, temperature, phosphoric acid concentration, and contact time, with the help of experimental design. We found that 550 °C is the optimal temperature for carbonization of rosemary root, and the concentration of H3PO4 was discovered to be 5.5 mol/l. What about the times we determined for contact time and carbonization time, which were 30 min and 120 min, respectively. The resulting Activated Carbon of Rosemary Root (ACRR) material was then characterized using XRD, FTIR, Boehm titration, SEM/EDX, RAMAN, and Zeta potential. A batch system is used to perform our adsorption. In addition to pH effects, initial MR concentration, contact time, and masse effect were examined, and all the results were confirmed via experimental design using full factorial. In the present study, 15 mg of the adsorbent exhibited an adsorption capacity of 154.53 mg/g at pH 3.25 and a temperature of 328.15 k at a concentration of dye 50 mg/l. The adsorption results of methyl red onto ACRR powder showed that the adsorption process was best correlated with Freundlich isotherm and pseudo-second-order kinetic. According to the thermodynamic study, the system is exothermic. In order to understand the activated sites presented on MR and the mechanism of adsorption, density functional theory (DFT) using the B3LYP/6-311G base was used. Furthermore, the experimental results agree with the results of the computational model.