Acid Dissolution Process Research Articles

Direct evidence of pyrogenic aerosol iron by intrusions of continental polluted air into the Eastern China Seas

Atmospheric iron (Fe) is an important micronutrient controlling marine primary productivity, which affects marine ecosystems and biogeochemistry. However, few studies have reported the abundance of aerosol Fe and its associated mixing state and solubility in marine environments. Here, aerosol samples were collected over the Bohai Sea and the Yellow Sea near East China during a research cruise. The results show that anthropogenic Fe-containing particles accounted for 9.3% of the total observed marine particles with diameters from 0.1 to 7 μm. Almost all of the Fe-containing particles (94%) were internal mixtures of FeOx particles (i.e., Fe-rich/fly ash) and secondary aerosols (e.g., nitrate, sulfate, and organics). During their aging process, the FeOx particles grew approximately tenfold in size from 100 nm to 1 μm by acquiring a thick secondary aerosol coating after one to two days of transport. The elemental mapping on a per-particle basis showed that the secondary aerosol coating likely homogeneously contained little Fe, suggesting that the acidic coating solubilized Fe via an acid dissolution process in the marine air. Therefore, acid dissolution of metal aerosols in anthropogenic smog should be considered in studies on the biogeochemical cycle between coastal marine air and ocean productivity.

Time-Lapse In Situ 3D Imaging Analysis of Human Enamel Demineralisation Using X-ray Synchrotron Tomography.

Caries is a chronic disease that causes the alteration of the structure of dental tissues by acid dissolution (in enamel, dentine and cementum) and proteolytic degradation (dentine and cementum) and generates an important cost of care. There is a need to visualise and characterise the acid dissolution process on enamel due to its hierarchical structure leading to complex structural modifications. The process starts at the enamel surface and progresses into depth, which necessitates the study of the internal enamel structure. Artificial demineralisation is usually employed to simulate the process experimentally. In the present study, the demineralisation of human enamel was studied using surface analysis carried out with atomic force microscopy as well as 3D internal analysis using synchrotron X-ray tomography during acid exposure with repeated scans to generate a time-lapse visualisation sequence. Two-dimensional analysis from projections and virtual slices and 3D analysis of the enamel mass provided details of tissue changes at the level of the rods and inter-rod substance. In addition to the visualisation of structural modifications, the rate of dissolution was determined, which demonstrated the feasibility and usefulness of these techniques. The temporal analysis of enamel demineralisation is not limited to dissolution and can be applied to other experimental conditions for the analysis of treated enamel or remineralisation.

Understanding reactive amorphous phases of fly ash through the acidolysis

It is well understood that the reactive components of fly ash (FA) in alkali cement are mainly donated by amorphous phases. The acidolysis method is typically employed to dissolve these amorphous phases for separate analysis; however, such method is not truly convincing, especially the testing and analysis processes. This paper investigates the hydrofluoric acid (HF, 1%) dissolution process (from 0.5 h to 20 h) of two Class-F FAs with different physical and chemical characteristics. The time-dependent quantitative analysis results indicate that in addition to amorphous phases, some crystalline phases are also dissolved in 1% HF solution. Further, the chemical statistics on the dissolved amorphous phases was extracted from the scanning electron microscopy images. Amorphous aluminosilicates in FA can be quantitatively classified into six groups, of which the three reactive amorphous aluminosilicates are defined.

Measurement report: Abundance and fractional solubilities of aerosol metals in urban Hong Kong – insights into factors that control aerosol metal dissolution in an urban site in South China

Abstract. Water-soluble metals are known to produce greater adverse human health outcomes than their water-insoluble forms. Although the concentrations of water-soluble aerosol metals are usually limited by atmospheric processes that convert water-insoluble metals to water-soluble forms, factors that control the solubilities of aerosol metals in different environments remain poorly understood. In this study, we investigated the abundance and fractional solubilities of different metals in size-fractionated aerosols collected at an urban site in Hong Kong and identified the factors that modulated metal solubilities in fine aerosols. The concentrations of total and water-soluble metals in fine and coarse aerosols were the highest during the winter and spring seasons due to the long-range transport of air masses by northerly prevailing winds from emission sources located in continental areas north of Hong Kong. The study-averaged metal fractional solubilities spanned a wide range for both fine (7.8 % to 71.2 %) and coarse (0.4 % to 47.9 %) aerosols, but higher fractional solubilities were typically observed for fine aerosols. Sulfate was found to be strongly associated with both the concentrations of water-soluble Cr, Fe, Co, Cu, Pb, and Mn and their fractional solubilities in fine aerosols, which implied that sulfate-driven acid processing likely played an important role in the dissolution of the water-insoluble forms for these six metals. Further analyses revealed that these strong associations were due to sulfate providing both the acidic environment and liquid water reaction medium needed for the acid dissolution process. Thus, the variability in the concentrations of water-soluble Cr, Fe, Co, Cu, Pb, and Mn and their fractional solubilities were driven by both the aerosol acidity levels and liquid water concentrations, which in turn were controlled by sulfate. These results highlight the roles that sulfate plays in the acid dissolution of metals in fine aerosols in Hong Kong. Our findings will likely also apply to other urban areas in South China, where sulfate is the dominant acidic and hygroscopic component in fine aerosols.

Removal of Mn(II) from hydrochloric acid leach liquors of nickel laterite ore through microbubble oxidation and acid leaching

Leach liquor obtained from atmospheric acid leaching of nickel laterite with HCl solution contain large concentrations of Mn and Mg. This paper presents a method for separating large amounts of Mn and Mg from Ni and Co chloride solution by microbubble aeration oxidation and acid leaching processes. Such methods utilize the multiple advantages of the microbubble technology, such as large specific surface area, negatively charged surface, long stagnation, high oxygen mass transfer efficiency, and the ability to generate active oxygen. The effects of aeration pore size, oxygen flow rate, reaction temperature, stirring speed, and pH were studied. Under optimal experimental conditions (bubbling O2 flow = 0.4 L/min, aeration aperture = 0.45 μm, speed of agitation = 400 rpm, temperature = 50 °C, pH = 7), the recovery efficiency of Ni and Co were 99.3% and 89.0%, and the removal efficiency of Mn and Mg were 99.5% and 97.7%, respectively. Through XRD, XPS, and FTIR, it was found that soluble Mn was first oxidized to Mn3O4 and MnO2·H2O. In the acid dissolution process, Mn3O4 reacted with dilute sulfuric acid to form MnO2, which is insoluble in dilute acid, and was thus easily separated from Ni and Co. Analysis of the mass transfer process showed that the microbubble aeration method can greatly increase the oxygen mass transfer coefficient (0.073 s−1), accelerate the dissolution of O2, and create conditions for the generation of active oxygen species.

Understanding the acid dissolution of Serpentinites (Tailings and waste rock) for use in indirect mineral carbonation

Solid carbonates can be formed by indirect mineral carbonation using the pH swing method for CO2 storage. It occurs at low temperatures and pressures in four stages: acid dissolution, purification, carbonation, and recovery. Although acid dissolution requires short reaction time that favors the extraction of reactive metals, lack of knowledge about the effects of temperature, acid concentration and particle size on metal extraction reveals that it is a critical stage of indirect mineral carbonation. In order to employ mining waste for indirect mineral carbonation, acid dissolution of serpentinites, tailings (SERP-GO) and waste rock (SERP-MG) were investigated, and their performances were compared. A Taguchi experiment design was used to assess the parameters that influence the acid dissolution process. Hydrochloric acid was used in acid dissolution for Mg and Fe extraction from both, SERP-GO and SERP-MG, and the process parameters (temperature, acid concentration, particle size and excess acid) were evaluated for 2 h of reaction. According to signal-to-noise ratio analysis of the Taguchi method, the optimized condition for Mg extraction of both samples was at 70 °C, 4 M HCl, 69 μm and twice the excess acid. The results indicated that of Mg and Fe extraction from de samples was more efficient for SERP-GO (71% and 85%) than SERP-MG (33% and 31%). Based on these findings, it was possible to have a better understanding of the factors affecting the dissolution of serpentinite tailings, to develop a more effective process for the use of mining waste in the indirect mineral carbonation process.

Nitric Acid Dissolution of Tennantite, Chalcopyrite and Sphalerite in the Presence of Fe (III) Ions and FeS2.

This paper describes the nitric acid dissolution process of natural minerals such as tennantite, chalcopyrite and sphalerite, with the addition of Fe (III) ions and FeS2. These minerals are typical for the ores of the Ural deposits. The effect of temperature, nitric acid concentration, time, additions of Fe (III) ions and FeS2 was studied. The highest dissolution degree of sulfide minerals (more than 90%) was observed at a nitric acid concentration of 6 mol/dm3, an experiment time of 60 min, a temperature of 80 °C, a concentration of Fe (III) ions of 16.5 g/dm3, and an addition of FeS2 to the total mass minerals at 1.2:1 ratio. The most significant factors in the break-down of minerals were the nitric acid concentration, the concentration of Fe (III) ions and the amount of FeS2. Simultaneous addition of Fe (III) ions and FeS2 had the greatest effect on the leaching process. It was also established that FeS2 can be an alternative catalytic surface for copper sulfide minerals during nitric acid leaching. This helps to reduce the influence of the passivation layer of elemental sulfur due to the galvanic linkage formed between the minerals, which was confirmed by SEM-EDX.

Static acid dissolution of carbonate outcrops investigated by 1H NMR and X-ray tomography

The success of oil and gas exploration in carbonate reservoirs demands better strategies. Concerning the step of acid stimulation, the understanding of the nature of the carbonate matrices and their response to the acids can contribute for improvements of this process. We report a study about the reactivity of six different carbonate rocks with aqueous solutions of hydrochloric (HCl) and acetic (HAc) acids. The reactivity of the samples was determined by measuring the mass loss of the carbonate samples during the acid dissolution process. The results demonstrate that the dolomitization of the matrices is the main factor to decrease the kinetic of dissolution. Based on visual inspection, and micro-computed tomography, it was observed that the cylindrical outcrops with low dolomitization present different patterns of morphological dissolution upon HCl or HAc. For HCl, homogenous radial dissolution is observed, producing a smooth surface, while for HAc, the radial structure is practically preserved, but the surface become very rough. Concerning the inner effect of the acids, variations on the pore distributions of the outcrops were investigated by micro-computed tomography and pore distribution were observed during the dissolution cycles with the acids. This is an indication that the reaction occurs homogeneously from the surface, with negligible dissolution of the internal pore walls, since no pressure and flow procedures were employed in this study. •Static acid dissolution of carbonate outcrops investigated by time domain Nuclear Magnetic Resonance and X-ray tomography. • Acid stimulation in carbonate improve oil exploration in carbonate reservoirs. • Kinetics of acid dissolution and morphological changes were systematic investigated. • Chemical composition of the matrices is the more relevant parameter to the rate. • The mechanism of rock dissolution is different for HCl and acetic acid.

Microstructure and dissolution of UO2 pellet after cutting by fiber laser

This study is aimed to investigate the microstructure of UO2 pellet cut by fiber laser and subsequent nitric acid solubility. A high power laser cutting system was employed to cut fuel rod which consists of stainless steel cladding and UO2 pellets. The influences of assist gas and cutting speed on the micromorphology, element distribution and phase of the cut-off surface of UO2 pellet were discussed. And the nitric acid solubility of laser cut samples was also studied. The results showed that there are defects such as shrinkage micro-pore, fragment, cave and crack on the cut-off surface of UO2 pellet, and UO2 may be converted into U3O8. However, subsequent nitric acid dissolution experiments demonstrated that the laser cut-off samples were soluble in nitric acid, and solubility and the dissolution rate were almost the same as those of the pristine UO2 pellets. This study illustrate that the laser can be employed to cut the fuel rod with the composite structure composed of stainless steel cladding and UO2 pellets with appropriate process parameters, and it has no adverse effect on subsequent nitric acid dissolution process.

Insights into the reinforcement role of peritubular dentine subjected to acid dissolution

Human dentine is a mineralised dental tissue that consists of dentinal tubules surrounded by two distinct dentinal phases: peritubular dentine (PTD) and intertubular dentine (ITD). Dental caries, which manifests itself as a consequence of demineralisation, is one of the most common chronic diseases that affect the function of human teeth. Due to the difference in the packing density of crystallites, PTD and ITD exhibit different reaction rates to acid dissolution. The present study evaluates how the effective Young's modulus degrades and how the effective stress redistributes in demineralised human dentine as a result of incremental acid dissolution process. An analytical two-layer composite model is proposed and used for the effective Young's modulus calculation. 3D numerical representative volume elements (RVEs) with different variations in PTD fraction and dentinal tubule density are established to evaluate effective stress redistribution and examine the critical factors that can affect the mechanical performance. The models are then applied on an actual dentine bulk sample. The results reveal how PTD serves as a protection to ITD thus highlight the important role that PTD plays for the structural integrity of dentine. The obtained insights are crucial for advancing the understanding of a variety of natural and therapeutic effects from the mechanical perspective, e.g. the mechanical performance assessment of human dentine subject to complex dynamic processes of de- and re-mineralisation that can occur in human dental caries and dental treatments. It will ultimately inspire the biomimetic design towards strengthening the dentine and dentine-like materials.

Evaluation of recycle pathways for out-of-specification uranium microspheres from the internal gelation process

During the production of uranium oxide microspheres with carbon using internal gelation, a small fraction of microspheres will not meet the required size or sphericity specification. The uranium microspheres with carbon can be rejected after they have been air-dried or converted into uranium carbide and uranium oxide (UCO) kernels. The next step for the rejected spheres was an air oxidation for carbon removal. The air-dried spheres became triuranium octoxide (U3O8) spheres, which were sometimes ground into powder. The UCO kernels became U3O8 powder during the air oxidation. The next recycle step was nitric acid dissolution of the U3O8 spheres or powders to produce acid-deficient uranyl nitrate (ADUN) solutions, which were used to make new uranium oxide microspheres with carbon and subsequently UCO kernels. The kinetics of the acid dissolution process were compared, and the impurity levels in the different ADUN solutions were determined. X-ray diffraction results for the UCO kernels from the initial and recycled ADUN solutions indicate that changes in the impurity levels can impact the uranium carbide to uranium dicarbide ratio in the UCO kernels.

Recovery of Mn-Zn ferrite from waste batteries and development of rGO/Mn-Zn ferrite nanocomposite for water purification

Inpresent paper the recovery of Mn-Zn ferrite nano-particles from waste batteries by using acid dissolution and ferrite process were studied. The recovered Mn-Zn ferrite nano-particles were decorated on rGO by using facile solvothermal method. The prepared material were characterized by X-ray powder diffraction (XRD) to study particle size and crystallinity, the morphology of the particles were analyzed by using Scanning Electron Microscopy (SEM), functional group were observed using Fourier Transform Infrared Spectrometer (FTIR) and band gap energy were examined by UV-Visible spectrometer. Graphene oxide used toeliminatethe pollutantspresent in the wastewater. The developed material used as an adsorbent for the removal of ionic dye in acid orange 88. The Mn-Zn ferrite nano-particles decorated with rGO showed a superior photocatalytic activity compared to that of Mn-Zn ferrite nano-particles.

The Effect of Atmospheric Acid Processing on the Global Deposition of Bioavailable Phosphorus From Dust

AbstractThe role of dust as a source of bioavailable phosphorus (Bio‐P) is quantified using a new parameterization for apatite dissolution in combination with global soil data maps and a global aerosol transport model. Mineral dust provides 31.2 Gg‐P/year of Bio‐P to the oceans, with 14.3 Gg‐P/year from labile P present in the dust, and an additional 16.9 Gg‐P/year from acid dissolution of apatite in the atmosphere, representing an increase of 120%. The North Atlantic, northwest Pacific, and Mediterranean Sea are identified as important sites of Bio‐P deposition from mineral dust. The acid dissolution process increases the fraction of total‐P that is bioavailable from ~10% globally from the labile pool to 18% in the Atlantic Ocean, 42% in the Pacific Ocean, and 20% in the Indian Ocean, with an ocean global mean value of 22%. Strong seasonal variations, especially in the North Pacific, northwest Atlantic, and Indian Ocean, are driven by large‐scale meteorology and pollution sources from industrial and biomass‐burning regions. Globally constant values of total‐P content and bioavailable fraction used previously do not capture the simulated variability. We find particular sensitivity to the representation of particle‐to‐particle variability of apatite, which supplies Bio‐P through acid‐dissolution, and calcium carbonate, which helps to buffer the dissolution process. A modest 10% external mixing results in an increase of Bio‐P deposition by 18%. The total Bio‐P calculated here (31.2 Gg‐P/year) represents a minimum compared to previous estimates due to the relatively low total‐P in the global soil map used.

Micellar mediated selective leaching of manganese nodule in high temperature sulfuric acid medium

The present study evaluates the possibility of selective leaching of manganese from complex, manganese and iron oxy-hydroxide based sea bed nodule utilising micelles in high temperature acid dissolution process. Application of surfactants during acid leaching of manganese nodules are described based on results from leaching studies. The factors that affected the sulfuric acid leaching of the manganese nodules in the presence of various surfactants were investigated. The effect of anionic (SDS-Sodium Dodecyl Sulphate), cationic (CTAB-Cetyl Trimethyl Ammonium Bromide) and nonionic (Triton-X 100) surfactant on the various metals extraction with respect to sulfuric acid concentration, temperature, type of surfactants and surfactant concentration is reported. Among them, CTAB showed highest improvement in the recovery of Cu, Ni, Co, Zn and Mn. Iron, aluminium, and silica were removed effectively through the present approach of high temperature sulfuric acid leaching route assisted by surfactant. Increasing the temperature of the medium has significant impact in the selective leaching of Mn, Cu, Ni and Co. The optimum conditions established for maximum metal extraction are: pulp density 10%, time 2h, temperature 160°C, sulfuric acid 5.0% (v/v) and at critical micellar concentration of CTAB. Under these conditions, recovery of Mn was 99% along with the (˃99%) recovery of Cu, Co, and Ni. The leached residues were analysed and their phase and morphologies were included herein. The present process may find application of separation of manganese from iron and aluminium at high temperature during various hydrometallurgical treatment of manganese based ores.

Extraction and characterization of alumina nanopowders from aluminum dross by acid dissolution process

A significant amount of aluminum dross is available as a waste in foundry industries in Bangladesh. In this study, alumina was extracted from aluminum dross collected from two foundry industries situated in Dhamrai and Manikgang, near the capital city, Dhaka. Aluminum dross samples were found to approximately contain 75wt% Al2O3 and 12wt% SiO2. An acid dissolution process was used to recover the alumina value from the dross. The effects of various parameters, e.g., temperature, acid concentration, and leaching time, on the extraction of alumina were studied to optimize the dissolution process. First, Al(OH)3 was produced in the form of a gel. Calcination of the Al(OH)3 gel at 1000°C, 1200°C, and 1400°C for 2 h produced γ-Al2O3, (α+γ)-Al2O3, and α-alumina powder, respectively. Thermal characterization of the Al(OH)3 gel was performed by thermogravimetric/differential thermal analysis (TG/DTA) and differential scanning calorimetry (DSC). The phases and crystallite size of the alumina were determined by X-ray diffraction analysis. The dimensions of the alumina were found to be on the nano level. The chemical compositions of the aluminum dross and alumina were determined by X-ray fluorescence (XRF) spectroscopy. The microstructure and morphology of the alumina were studied with scanning electron microscopy. The purity of the alumina extracted in this study was found to be 99.0%. Thus, it is expected that the obtained alumina powders can be potentially utilized as biomaterials.

Solubility and thermodynamic functions of cefazolin acid in pure and mixed solvents at (278.15–308.15) K

Solvent screening is of great importance in the design and optimization of drug crystallization. In this paper, the solubility data of cefazolin acid in five pure solvents and one binary solvent mixtures (N, N-dimethylformamide+2-propanol) were experimentally measured in temperature range from (278.15–308.15)K by using UV spectrometer method. The melting temperature of cefazolin acid was estimated by three-level group contribution method. All the experimental solubility data were correlated by the modified Apelblat model and the λh equation. The experimental solubility data in binary solvent mixtures were also correlated by the nearly ideal binary solvent CNIBS/Redlich–Kister model. In addition, based on the modified van’t Hoff equation, the thermodynamic properties of cefazolin acid dissolution process were also calculated and discussed.

Evaluation of sample dissolution method for Sm-Nd isotopic analysis of scheelite

Sm-Nd isotope systematics of scheelite is becoming a powerful geochronometer for dating the Au and W ore deposits. However, Sm-Nd isotopic analysis of scheelite is relatively difficult due to the formation of large amounts of tungstic acid (H2WO4) precipitates during the conventional acid decomposition of scheelite. In this study, both the low temperature attack and Teflon bomb acid dissolution methods for Sm-Nd isotope analysis of scheelite have been thoroughly investigated. It has been shown that, for both low temperature attack and Teflon bomb methods, although a large amount of tungstic acid precipitate remains during the 2.5 M HCl acidification process prior to cation exchange separation, only less than 10% of the Sm and Nd remains in the tungstic acid precipitate. On the other hand, it has been found that, for isotope dilution analysis, the spike-sample isotopic equilibration was only completely achieved for the Teflon bomb method and not completely achieved for the low temperature attack method, indicating that the low temperature attack method has possibly not liberated all the rare earth elements (REEs) from the scheelite crystal structure. Consequently, for high precision scheelite Sm-Nd dating purposes, the complex Teflon bomb rather than the simple low temperature attack method should be used in order to completely digest scheelite samples; alternatively, since it has been found that the tungstic acid precipitate formed during the acid dissolution process can be completely dissolved by self-purified low-blank 30% NaOH, a simple low temperature attack method combined with low-blank 30% NaOH dissolution of the remaining tungstic acid precipitate can also possibly be used to completely dissolve the scheelite sample for Sm-Nd isotopic analysis.

Recovery of nickel from spent catalyst from palm oil hydrogenation process using acidic solutions

In this study, recovery of nickel from spent catalyst from palm oil hydrogenation process is carried out via extractive leaching process using sulfuric and hydrochloric acids. The effects of acid concentration, solid-liquid ratio, temperature and digestion time on the recovery (acid dissolution) process are investigated. It is found that sulfuric acid is the better leaching solution as compared to hydrochloric acid for recovery (dissolution) of nickel from the spent catalyst. Results from speciation modelling using VMINTEQ further imply that nickel can form sulfate complexes which are more stable than chloride complexes at concentrations higher than 1 M. The optimum conditions for maximum recovery at 85% are achieved at 67% sulfuric acid concentration, digestion time of 140 min, solid-to-liquid ratio of 1:14 and reaction temperature of 80 °C. At solution temperatures higher than 80 °C, the percentage nickel extraction is reduced. The optimization study presented here is useful for spent catalyst generators in the palm oil industry intending to recover valuable metals which may assist in reducing palm oil processing costs.

A model developed for acid dissolution thermodynamics of a Turkish bentonite

A model was proposed to calculate some thermodynamic parameters for the acid dissolution process of a bentonite containing a calcium-rich smectite as clay mineral along with quartz, opal and feldspar as impurities. The bentonite sample was treated with H2SO4 by applying dry method in the temperature range 50–150°C for 24 h. The acid content in the dry bentonite-sulphuric acid mixture was 45 mass%. The total content (x) of Al2O3, Fe2O3 and MgO remained in the undissolved sample after treatment was taken as an equilibrium parameter. An apparent equilibrium constant, K a, was calculated for each temperature by assuming K a=(x m−x)/x where x m is the total oxide content of the natural bentonite. Also, an apparent change in Gibbs free energy, ΔG a o , was calculated for each temperature by using the K a value. The graphs of lnK a vs. 1/T and ΔG a o vs. T were drawn and then the real change in both the enthalpy, ΔH o and the entropy, ΔS o, values were calculated from the slopes of the straight lines, respectively. Inversely, real ΔG o and K values were calculated from the real ΔH o and ΔS o values through ΔG o = −RT ln K = ΔH o − TΔS o equation. The best ΔH o and ΔS o fittings to this relation were found to be 65687 J mol−1 and 164 J mol−1K−1, respectively.

Calorimetric study of dissolution kinetics of phosphorite in diluted acetic acid

In this report, we present a thermodynamic and kinetic study of the selective dissolution of calcite from low-grade phosphate ores (Epirus area, Greece) by dilute acetic acid at isothermal conditions. A twin calorimeter with two identical membrane vessels, for the acid dissolution process, and for the reference was used. The curves of rate vs. time of the phosphorite dissolution for various temperatures show that the maximum (.qmax) was increased, whereas the time (tpeak) to achieve the corresponding .qmax values was decreased, as the experimental temperature was increased. The dissolution enthalpy was increased from 13.1 to 16.7 kJ mol−1, as the experimental temperature was increased from 10.0 to 28.0°C. The chemical analysis of the supernatant solutions shows that the main process was the calcite dissolution. The reaction model with general form, ln(1/(1-X))=ktm, was found to fitted the experimental data regardless of the experimental temperature. These results were assigned in the presence of two different kinds of particles in the phosphorite. The activation energy of the dissolution process was found 69.7 kJ mol−1. The SEM micrographs of acid dissolution samples showed two different textures after acid dissolution.