Phosphoric Acid Concentration Research Articles

Extraction kinetics of cobalt and manganese with D2EHPA from lithium-ion battery recyclate

The separation of manganese from cobalt sulfate solutions is crucial in the field of spent lithium-ion battery recycling. A membrane-based microreactor is used to reveal required mass transfer characteristics as is diffusion and chemical reaction. The dependence of di-(2-ethylhexyl)phosphoric acid (D2EHPA) concentration, pH, and metal ion concentration on the extraction efficiency are investigated. A back-reaction term is introduced giving a significant influence on the effective extraction rate even at small metal complex concentrations as initial extraction rates proved to be inaccurate to describe the system. It is shown that the extraction of manganese at a pH of 3.0 is mainly diffusive while the cobalt extraction is strongly kinetically controlled. At a separating pH of 3.9 a good agreement between the model and experimental data is only given if the equilibrium back-extraction rate is considered (deviation less than 5%).

Influence of the Degumming Process Parameters on the Formation of Glyceryl Esters and 3-MCPDE in Refined Palm Oil: Optimization and Palm Oil Quality Analyses.

The presence of glyceryl esters (GE) and 3-monochloropropane-1,2-diol esters (3-MCPDE) in refined, bleached, and deodorized (RBD) palm oil is severely concerning to the palm oil consumer. In the present study, the influence of the phosphoric acid degumming process on the formation of GE and 3-MCDE and in the RBD palm oil was determined with varying the acid dose (0.03–0.06 wt%), temperature (70–100 °C), and reaction time (15–45 min). The experimental conditions of the acid degumming process were designed following the central composite design of experiments, and they were optimized using Response Surface Methodology (RSM) based on the minimal formation of GE and 3-MCDE in the RBD palm oil. The optimal experimental conditions of the acid degumming process were a reaction time of 30 min, phosphoric acid concentration of 0.06 wt%, and temperature of 90 °C. Under these experimental conditions, the minimal GE and 3-MCDE formation in RBD palm oil were determined to be 0.61 mg/kg and 0.59 mg/kg; respectively. Several analytical methods were employed to determine RBD palm oil quality, including color, phosphorus, free fatty acids (FFAs), peroxide values, and fatty acid properties. It was found that the phosphoric acid degumming of CPO effectively removed the phosphorus and hydroperoxide content without conceding the quality of palm oil.

Preparation of novel cosmetic white pigments by mechanochemical treatment of zinc oxide with phosphoric acid

ABSTRACT Zinc oxide has a photocatalytic activity, but in cosmetics it is used as a white pigment. When used in cosmetics, this photocatalytic activity causes some of the skin’s sebum to be broken down by the ultraviolet rays contained in sunlight. In this study, we attempted to mill zinc oxide with phosphoric acid to react the powder surface to zinc phosphate. Since zinc phosphate has no photocatalytic activity, the particles whose surface is replaced by zinc phosphate are expected to have little photocatalytic activity. The chemical composition, powder properties, photocatalytic activity, hue (visible light reflectance, L*a*b* value), and smoothness of the obtained powder materials were examined. A portion of the zinc oxide was reacted to zinc phosphate by milling with phosphoric acid. In some samples, the reaction to zinc phosphate was observed to be too advanced, resulting in larger particles. The photocatalytic activity of zinc oxide was successfully eliminated through milling. Although the samples in this study had sufficient whiteness, the whiteness of some of the samples decreased due to contamination by milling. The smoothness of the pigment powders produced in this study was improved by milling, especially by prolonged treatment and the use of low concentrations of phosphoric acid.

OBTAINING THE SILICON-CONTAINING TITANIUM PHOSPHATE UNDER HETEROGENEOUS SYNTHESIS CONDITIONS

The authors investigated the synthesis of composite materials produced by not simply mixing the components mechanically. The materials are chemically derived on the basis that the combined action of the beneficial properties of such compositions significantly outweighs the action of each component due to synergistic effects. For this purpose, a titanosilicate precursor, TiO2∙nSiO2 (ТSP), synthesized from an accessible technogenic waste containing the mineral titanite (CaSiTiO5) was used. Researches were carried out in the heterogeneous system TiO2∙SiO2-H3PO4-H2O. And the innovative method was developed for obtaining silicon-containing titanophosphate of the composition TiOHPO4∙2H2O or TiO(H2PO4)2·2H2O, depending on the structural features of TSP, as well as on the synthesis conditions - phosphoric acid concentration and temperature. The influence of structural characteristics of titanosilicate precipitate on its chemical activity in heterogeneous synthesis of silicon-containing titanophosphate was studied. The synthesised mesaporous material is a powder with a particle size of 5-15 µm. The correlation between the phase composition of the synthesised compositions and the surface properties of their particles is shown. The sorption capacity of the obtained titanophosphates in the static mode was determined. In particular, the more titanophosphate phase is in the composition of the composition, the higher are the values of Ssp and Vpore particles and therefore their sorption capacity is higher. When comparing the sorption properties of synthesised and conventional sorbents, ion exchange resins and titanium phosphates, used for purification of liquid effluents from Sr2+, Cs+, Co2+ cations, comparable indicators were obtained. The results have shown that the use of silicon-containing titanium phosphate for the treatment of liquid effluents containing non-ferrous metal cations as well as radionuclides may be promising.

Propriedades mecânicas de concretos refratários quimicamente ligados a fosfatos

ABSTRACT The knowledge of the phase transformations and the role of different parameters in the performance of phosphate-bonded systems are of utmost importance for the refractory field. The effect of the setting agent, phosphoric acid concentration and additives on the setting time, cold crush strength, hot modulus of rupture, abrasion resistance, and thermal shock resistance of the phosphate chemically bonded refractory systems was evaluated. The setting time was shorter for mixtures containing cement (CaO) and a lower acid concentration. Mixtures with a higher acid concentration presented better mechanical, abrasion and thermal shock resistance. In spite of increasing the cold mechanical resistance and abrasion of the materials, the Budit 6H negatively impacted the hot properties. For Fabutit761, there was no liquid phase formation at intermediate temperatures and this additive increased the cold mechanical strength, but it also negatively impacted the hot mechanical strength. Compositions containing cement as a setting agent, 40°Be phosphoric acid and Fabutit761 additive as an extra source of phosphate presented a better set of properties.

Relationship between the Lactic Acid Content and Sour Taste of Broiler Broth and the Broth of Choshu-Kurokashiwa-a Japanese Jidori Chicken.

The present study aimed to determine whether lactic acid content is associated with the intensity of the sour taste of Choshu-Kurokashiwa broth. Chicken broth was prepared using breast (pectoralis major) and leg (thigh + drumstick) meat of male and female Choshu-Kurokashiwa and broilers. These broths were assessed by a screened and trained panel and analyzed for sour taste substances (lactic, citric, pyruvic, malic, succinic, acetic, phosphoric, aspartic, and glutamic acids) and pH. The sensory sour taste was significantly higher in the Choshu-Kurokashiwa breast broth than in the broiler breast broth (P>0.001), and no significant difference was observed in the leg broths among the breeds (P<0.05). Choshu-Kurokashiwa breast broth had a significantly higher lactic acid content than broiler breast broth (P<0.001). The leg meat broth of male Choshu-Kurokashiwa had a significantly lower lactic acid content than that of female Choshu-Kurokashiwa and broiler leg meat (P<0.01). The sensory sour taste score was significantly and positively correlated with lactic acid content in the breast broth (P<0.001), but not in the leg broth (P<0.1). No other organic acids were detected. Phosphoric acid and glutamic acid contents were higher in broiler broth than in Choshu-Kurokashiwa broth for both breast and leg meat (P<0.001). In the breast broth, the aspartic acid content was not significantly different (P>0.1), and in the leg broth, it was higher in broiler and female Choshu-Kurokashiwa broth than in male Choshu-Kurokashiwa broth (P<0.001). The present study suggests that high lactic acid content contributes to the sour taste of the Choshu-Kurokashiwa breast broth and demonstrated that the lactic acid content is an essential indicator for determining the sour taste of Choshu-Kurokashiwa breast meat.

Application of an Artificial Neural Network Method for the Prediction of the Tube-Side Fouling Resistance in a Shell-And-Tube Heat Exchanger

The accumulation of undesirable deposits on the heat exchange surface represents a critical issue in industrial heat exchangers. Taking experimental measurements of the fouling is relatively difficult and, often, this method does not lead to precise results. To overcome these problems, in the present study, a new approach based on an Artificial Neural Network (ANN) is used to predict the fouling resistance as a function of specific measurable variables in the phosphoric acid concentration process. These include: the phosphoric acid inlet and outlet temperatures, the steam temperature, the phosphoric acid density, the phosphoric acid volume flow rate circulating in the loop. Some statistical accuracy indices are employed simultaneously to justify the interrelation between these independent variables and the fouling resistance and to select the best training algorithm allowing the determination of the optimal number of hidden neurons. In particular, the BFGS quasi-Newton back-propagation approach is found to be the most performing of the considered training algorithms. Furthermore, the best topology ANN for the shell and tube heat exchanger is obtained with a network consisting of one hidden layer with 13 neurons using a tangent sigmoid transfer function for the hidden and output layers. This model predicts the experimental values of the fouling resistance with AARD% = 0.065, MSE = 2.168 × 10−11, RMSE = 4.656 × 10−6 and r2 = 0.994.

Cr(VI) removal from the aqueous solutions by the samples of polyanyline doped with phosphoric acid

Samples of polyaniline (PAn) were synthesized by oxidative polycondensation of aniline in the presence ammonium peroxydisulfate in the aqueous solutions of phosphoric acid (PA) of different concentrations (0.16–3.30 M). Produced polyaniline was in the form of the emeraldine salt of phosphoric acid (PAn–PA). The prepared samples were used to study in the static conditions of their adsorption properties with regard to Cr(VI) from the aqueous solutions of different concentrations, namely 50, 100, 150, 200 and 300 mg/L, accordingly to the following technique: the 10 ml of the K 2 Cr 2 O 7 solution with appropriate concentration has been added to the portion of adsorbent sample, recorded time and at certain intervals took samples with a volume of 500 μl. These selected samples have been placed into the quartz cuvette with 2 mm thick and has been photometered. The amount of adsorpted substance was determined by the calibration plot. The adsorption experiments were carried out under the temperature 20±1°С. It is shown that the percentage of Cr(VI) removal by PAn samples reaches 94–99 %. It was found that the sorption capacity of all PAn–PA samples increases with increasing phosphoric acid concentration in the reaction mixture during synthesis. Analysis of the IR-FT spectra of PAn–PA samples shown that the partial oxidation of the emeraldine salt to pernigraniline takes place in the result of Cr(VI) adsorption. It was demonstrated that this process can be described sufficiently good by Langmuir or Freundlich adsorption isotherms, while the kinetics of process is in good agreement with model of pseudo second order. As a result of research, the possibility of the using of PAn samples, where polymer is doped with phosphoric acid during synthesis, for sorption of Cr(VI) from aqueous solutions without their additional acidification, has been determined. Keywords : polyaniline, Cr(VI) sorption, kinetics.

In-situ, facile and green preparation of nanoscale silver supported on activated carbon: Disinfection properties and removal of inorganic DBPs from drinking water

Activated carbon (AC) was prepared from date palm leaves by phosphoric acid activation. The factors affecting the carbon percentage yield such as phosphoric acid concentration, synthesis temperature, and heating time were studied. The prepared AC was studied by chemical analysis of the functional groups on its surface. The prepared AC was decorated with silver nanoparticles (Ag NPs) by in-situ reduction of adsorbed silver ion. Silver ions were introduced on carbon surface by adsorption and ion exchange. Characterization of the prepared AC was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), infra-red spectroscopy (IR), and thermogravimetric analysis (TGA). Results showed that silver ions are impregnated and reduced to Ago NPs with sizes between 30 and 50 nm on the surface of AC. The disinfection properties of Ag-loaded AC were tested for EscherichiaColi and Staphylococci bacteria. The removal of some inorganic disinfection by products (DBPs) including iodate, chlorate, chlorite, and bromate were tested. The results showed that the prepared AC-Ag is effective for antibacterial disinfection and inorganic anions removal applications.

Phosphoric acid involved laser induced microporous graphene via proton conducting polybenzimidazole for high-performance micro-supercapacitors

Functional electrodes with unique ion storage and rapid ion migration properties through microstructure and chemical-doping modulation are always crucial for rapid charging devices such as micro-supercapacitors (MSCs). In this work, proton exchange membrane named phosphoric acid (PA) doped polybenzimidazole membrane (PA-PBI) is studied as a unique precursor for assembling laser induced graphene (LIG) based electrodes (PA-PBI-LIG) in MSCs, toward the enhancement of energy storage performance via simultaneous heteroatoms doping, microporous structure improving and proton-conducting substrate introducing. By tuning PA concentration, the microporous structures perform adjustable specific surface area from 20.2 to 384.46 m2 g−1, thereby enhancing changeable capacitance from 2.44 mF cm−2 to 149 mF cm−2, with highest specific energy density of 20.7 μWh cm−2. To understand the mechanism, PA and the initiated free radicals are proposed to motivate microporous formation and heteroatoms doping during laser fabrication via unique laser absorption properties of PA. Additionally, PA-PBI substrates work synergistically on ions migration with microporous graphene, potentially promoting energy storage efficiency especially in the acid-based electrolyte. Overall, the raised PA-PBI-LIG electrodes simultaneously promote microporous, heteroatomic and multilayered graphene with proton conducting substrate, which show great potentials in micro energy storage devices.

Removal of Metal Ions in Phosphoric Acid by Electro-Electrodialysis with Cross-Linked Anion-Exchange Membranes.

There are numerous metallic impurities in wet phosphoric acid, which causes striking negative effects on industrial phosphoric acid production. In this study, the purification behavior of metallic impurities (Fe, Mg, Ca) from a wet phosphoric acid solution employing the electro-electrodialysis (EED) technology was investigated. The cross-linked polysulfone anion-exchange membranes (AEMs) for EED were prepared using N,N,N′,N′-tetramethyl-1,6-hexanediamine (TMHDA) to achieve simultaneous cross-linking and quaternization without any cross-linkers or catalysts. The performance of the resulting membranes can be determined using quaternization reagents. When the molar ratio of trimethylamine/TMHDA/chloromethylated polysulfone is 3:1:1, the cross-linked membrane CQAPSU-3-1 exhibits lower water swelling and membrane area resistance than the non-cross-linked membrane. The low membrane area resistance of CQAPSU-3-1 with long alkyl chains is obtained due to the hydrophilic–hydrophobic microphase separation structure formed by TMHDA. EED experiments with different initial phosphoric acid concentrations of 0.52 and 1.07 M were conducted to evaluate the phosphoric acid purification of different AEMs. The results show that the EED experiments were more suitable for the purification of wet phosphoric acid solution at low concentrations. It was found that the phosphoric acid concentration in the anode compartment could be increased from 0.52 to 1.04 M. Through optimization, with an initial acid concentration of 0.52 M, CQAPSU-3-1 exhibits an enhanced metallic impurity removal ratio of higher than 72.0%, the current efficiency of more than 90%, and energy consumption of 0.48 kWh/kg. Therefore, CQAPSU-3-1 exhibits much higher purification efficiency than other membranes at a low initial phosphoric acid concentration, suggesting its potential in phosphoric acid purification application.

Effect of acid treatments on thermal properties of bacterial cellulose produced from cassava liquid waste

Bacterial cellulose, BC is a natural compound that produced by bacteria Acetobacter xylinum in static or agitated cultures. BC has excellent properties such as excellent mechanical properties, high crystallinity, high purity, high water holding capacity and high permeability for water vapour and gases. Based on this unique and extraordinary properties, BC has the potential to be used in a wide range of applications, including food packaging, biomedical products, electronics, and energy. Nata de cassava (NdC) is a type of BC produced from cassava liquid waste that is fermented with the help of bacteria Acetobacter xylinum in static culture. The acid treatment using various concentration of phosphoric acid, H3PO4 (20 – 60 mmol) on the NdC samples was done to improve the BC thermal stability. This research aims to study the effects of acid treatments on the thermal properties of NdC. FTIR has confirmed the successful of acid treatments on the samples, while thermogravimetric analysis (TGA) was carried out to determine thermal stability of the NdC membrane. Thermal decomposition occurs primarily in two stages: the first occurs at a rapid rate of decomposition, while the second occurs more slowly. The last step shows that by increasing the acid concentration, resulted in increase of membrane residue where the higher (60 mmol) concentration of phosphorous-contained membrane exhibited a low degradation, reduced by 72.69% of its mass at 600 °C, in comparison to pure NdC which reduced by 91.39% of its mass. The main reason in improvement of char residue is that the treatment of cellulose with H3PO4 has released the ester form so that the phosphorous radicals (PO and POO) can be easily released during the thermal decomposition of this compound. It indicates that by treating the NdC samples with H3PO4 resulted in less weight degradation and improve the thermal stability of bacterial cellulose. In conclusion, the acid treatment on the NdC has successfully improved the thermal properties, thus it has potential to be applied as a conducting membrane in fuel cell application.

Micromorphology control of the lignin-based activated carbon and the study on the pyrolysis and adsorption kinetics

The waste corncob-based lignin (AL) treated by alkali was applied as feedstock to prepared activated carbon (AC) for the methylene blue (MB) adsorption. To explore the pyrolysis mechanism of ALs, the pyrolysis kinetics were discussed by the methods of Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) equations at different heating rates, which are widely applied in the determination of dynamic parameters with reduction of the errors of multi-step dynamics. In the process of preparing lignin-based activated carbon (LC), the relationship between pyrolysis condition and structure of LCs was systematically investigated. The maximum specific surface area of LCs reached 1215.83 m2/g with high the mesoporous proportion (77.3%) at optimal activation conditions including activation temperature (550 °C), activation duration (120 min) and phosphoric acid concentration (50%). For the adsorption of methylene blue (MB) solution, the fitted kinetic model was in accordance with the pseudo-second-order kinetic model. The adsorption capacity of MB could achieve as high as 493.28 mg/g (± 5 mg/g), and the highest removal rate of MB could reach 99.0% (± 0.2%) during the secondary adsorption process. This work offers a prospective proposal to provide theoretical reference for producing LC based on pyrolysis of alkaline lignin, and utilize the LC as potential adsorbent in the dyeing wastewater treatment.

The phosphating effect on the properties of FeSiCr alloy powder

The surface passivation is an effective technique to improve the magnetic properties of iron-based powder cores. The phosphating effect on the magnetic properties and rust resistance of FeSiCr alloy powder was explored. The FeSiCr alloy powder was treated by different phosphoric acid content, and prepared to magnetic powder cores. The FeSiCr powder particles were analyzed by FTIR spectra, SEM, EDS, XRD and XPS in detail. It was found out that, the particle surface was covered uniformly by the phosphating film, which was mainly composed of FeHPO4, FePO4 and CrPO4. Magnetic analysis results were demonstrated that, with the increase of phosphoric acid content, magnetic permeability and saturation magnetic induction were gradually decreased, the core losses were slightly increased at low frequencies. Experimental results from salt spray were shown that the rust resistance of FeSiCr magnetic powder core was greatly improved once a certain phosphoric acid content was reached.

PREPARATION AND CHARACTERIZATION OF PORE STRUCTURE BY PHOSPHORIC ACID ACTIVATED CARBON FROM UNUSED WOOD OF CITRUS SHRUB

Present study aimed to prepared large surface area activated carbon from unused wood of citrus with 45%w/w concentration of phosphoric acid as activating agent after maintaining optimum condition related to activation time of 25- minute, activation temperature at 550˚C and impregnation ratio 4:1 during chemical activation process by means of two stage process. The effect of optimum condition related to activation parameter was studied, the surface and pore structure of activated carbon was characterized by nitrogen adsorption isotherm method. The pore and surface properties of the resultant carbon including Langmuir surface area, BET surface area, pore size distribution, micropore volume and average pore radius were identified by nitrogen adsorption isotherm data using the BET, DFT, DA and BJH method. BET surface area, Langmuir surface area, micropore volume and average pore radius were obtained as high as 649m2/g, 3015m2/g, 0.34cc/g and 1.34 nm respectively which exhibit resultant carbon has high surface area and with welldeveloped micropores.

Physicochemical and Sorptive Properties of a Phosphorylated Mercerized Cotton Fabric.

A process of phosphorylation for a mercerized cotton kersey fabric was investigated. After wet oxidation, the phosphorus content in each sample was determined by spectrophotometric analysis. The range was 0.179 to 0.950 mmol g–1. A significant decrease in the tensile strength of samples resulted from an increase of phosphoric acid concentration in the phosphorylating solution. The mercerization has a positive impact on the process of phosphorylation, as the phosphorus content was found to be three times higher in the samples that underwent mercerization. The sorption properties of phosphorylated cotton fabric were studied using the Cu2+ sorption process as a reference. The value of the static exchange capacity for the phosphorylated fabric was determined to reach its maximum when the concentration of the H3PO4 in the phosphorylating solution was 1.40 M, and was found to be 1.48 ± 0.11 mmol g–1 with the phosphorus content equal to 0.898 ± 0.090 mmol g–1. The sorption of Cu2+ by a single phosphorus-containing group occurred for samples with phosphorus content not exceeding 0.80 mmol g–1. The preliminary studies of micro-quantities of 241Am, 233U, and 239Pu radionuclide sorption from aqueous solutions with phosphorylated textile demonstrated the high efficiency.

A facile strategy to construct layered membranes with high and stable proton conductivity based on sulfonated graphene oxide

Spin coating as an easy-operation strategy to construct layered membranes has been widely mentioned in the fields of microelectronics, energy storage, and conversion, etc. In this research, the successful construction of proton exchange membranes (PEMs) bearing layered structure consisting of sulfonated graphene oxide (SGO) nanosheets and polyvinyl chloride (PVC) with the spin coating method has been demonstrated by the identification of the multilayered dispersion of components and compact structure. The hydrophilic SGO nanosheets could increase the hydrophilicity of composite membranes since they bore a large number of polar oxygen functional groups. Phosphoric acid (PA) can be combined through the formed intermolecular hydrogen bonds between PA molecules and SGO nanosheets. The content of PA in PEMs can be adjusted by controlling the concentration of PA solutions, immersion temperature, and duration time. A comparative study with the membrane from the solution casting method has been performed, expecting to understand the influence of layered structure on membrane performance. It was found that the well-ordered distribution of SGO nanosheets facilitated proton conduction, demonstrating from the proton conductivity of 3.63 × 10−2 S/cm at 150°C. The fine proton conductivity stability, for instance, the result of 2.71 × 10−2 S/cm at 140°C lasting 1000-hour supported the component stability and mechanical strength. The research revealed that the spin coating technique could provide a facile and effective strategy to construct well-ordered membrane electrolytes for the application of high- temperature proton exchange membrane fuel cells.

Effect of Organic Fertilizer on Tomato Growth and Production under Soil-less System

Soil-less system constitutes an efficient approach for the cultivation of tomato; however, organic liquid amendments are very limited under such systems. The current experiment aimed to evaluate the effects of Kurojiru (K), an organic liquid fertilizer and fulvic acid (FA) on the growth and production of tomato, Solanum lycopersicum L. cv. ‘Momotaro’. Recently, it is desirable to reduce the environmental impact and fertilizer cost by lowering the concentration of inorganic components in the culture medium. Therefore, we explored the effect of adding these organic fertilizers on the yield and quality of tomatoes by gradually reducing the phosphoric acid concentration in the culture medium (87, 58 and 29 mmol・pot-1・week-1). The whole experiment was conducted for 20 weeks (from seeding until harvesting). The plant biomass, tomato fruit weight and chlorophyll content were measured. The fresh weight (FW) of both root and shoot indicated a progress response according to phosphorus concentration in liquid media, in FA treatments. Total fresh weight was significantly higher in the treatment with K+FA than in the control. Additionally, the yield responded to the all treatments within the 58 mmol P. Especially, in this level of P the relative fruit weight was higher only under K application. The chlorophyll content responded K+FA treatment under a low P content (29 mmol), and to all of those in 58 mmol. These results indicate that Kurojiru has some positive effects on tomato growth in soil-less systems.

Effects on the crystallite growth behavior of LaPO4 nanopowders and its mechanical properties

The effects of pH of the reaction solution and the concentration of phosphoric acid on the crystal growth behavior of LaPO4 crystallites were investigated and the mechanical properties of rare-earth phosphates were compared. As a result, the concentration of phosphoric acid of 10% was beneficial to the crystal growth of LaPO4 nanocrystalline. When the pH value of the reaction solution was 2, the size of LaPO4 crystallites increased gradually with the increasing reaction temperature, and the smallest crystallite size of 43.27 nm was obtained after heat-treatment at 1000 °C. Simultaneously, the activation energy for crystal growth of LaPO4 nanocrystalline was relatively lower (26.82 kJ mol−1). With the decreasing radii of rare-earth ions, the hardness, Young's modulus and fracture toughness of the bulk rare-earth phosphates exhibited a reduced tendency, resulted from the increase of porosity under the same preparation process.

Composition and Properties of Triple Superphosphate Obtained from Oyster Shells and Various Concentrations of Phosphoric Acid.

Triple superphosphates [TSPs, Ca(H2PO4)2·H2O] were produced by exothermic reactions of oyster shells and different concentrations of phosphoric acid (10, 20, 30, 40, 50, 60, and 70% w/w) in a molar ratio of 1:2. The percentage yields, P2O5 and CaO contents, metal impurities, and thermal behaviors of all the as-prepared products are dependent on the concentrations of phosphoric acid added during the production processes, which confirm to get the best optimum of 60% w/w phosphoric acid. All the as-prepared products were characterized by several characterization methods [X-ray fluorescence, thermal gravimetric/derivative thermal gravimetric analysis, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy], verifying that all the obtained compounds are TSP that can be used as fertilizers without metal toxic contaminants. From the successful results, the method for TSP production can be applied in the fertilizer industry based on starting waste materials of oyster shells that can replace the use of unsustainable phosphate or calcium minerals obtained from nonliving things.