Purification Of Wet Process Phosphoric Acid Research Articles

Removal of Fe(III)/Al(III)/Mg(II) by phosphonic group functionalized resin in wet-process phosphoric acid: Mechanism and intrinsic selectivity.

The removal of iron ions (Fe(III)), aluminum ions (Al(III)), and magnesium ions (Mg(II)) in phosphoric acid (H3PO4) solution is vital for the production of H3PO4 and supply of phosphate fertilizer. However, the mechanism and intrinsic selectivity for removal of Fe(III), Al(III), and Mg(II) from wet-process phosphoric acid (WPA) by phosphonic group (-PO3H2) functionalized MTS9500 are still unclear. In this work, the removal mechanisms were determined via combined analysis of FT-IR, XPS, molecular dynamics (MD), and quantum chemistry (QC) simulations based on density functional theory (DFT). The metal-removal kinetics and isotherms were further studied to confirm the removal mechanisms. The results indicate that Fe(III), Al(III), and Mg(II) interact with the -PO3H2 functional groups in MTS9500 resin with sorption energies of -126.22 kJ·mol-1, -42.82 kJ·mol-1, and -12.94 kJ·mol-1, respectively. Moreover, the intrinsic selectivities of the resin for Fe(III), Al(III), and Mg(II) removal were quantified by the selectivity coefficient (Si/j). The SFe(III)/Al(III), SFe(III)/Mg(II) and SAl(III)/Mg(II)are 18.2, 55.1 and 3.02, respectively. This work replenishes sorption theory that can be used in the recycling of electronic waste treatment acid, sewage treatments, hydrometallurgy, and purification of WPA in industry.

Purification of industrial wet phosphoric acid solution by sulfide precipitation in batch and continuous modes: Performance analysis, kinetic modeling, and precipitate characterization

The purification of wet-process phosphoric acid has always been a challenge for both academic and industrial researchers. A treatment unit was developed to mitigate metallic impurities, such as cadmium, from industrial dilute wet phosphoric acid solution (25% P2O5) by NaHS precipitation in batch and continuous modes. The effects of operating parameters on the purification performance were evaluated: namely Sulfur/Cd2+ molar ratio, the presence of other metallic ions besides Cd2+, temperature, and hydraulic residence time. In the batch mode, equilibrium was attained in less than 20 min; augmenting Sulfur/Cd2+ molar ratio increased the CdS precipitation effectiveness up to 86%, but temperature increment had an adverse effect. In the continuous mode, a hydraulic residence time of 40 min was necessary to reach the same yield as in the batch mode at 25 °C. Sulfidation was found to eliminate simultaneously other metallic impurities (especially Cu and As) originally present in the wet-produced phosphoric acid. Finally, NaHS precipitation was able to reduce the concentration of cadmium from 65.95 mg Cd/kg P2O5 to 11.15 mg Cd/kg P2O5 from untreated industrial WPA solution (25% P2O5) at 25 °C, which outperforms most of the published data based on alternative treatment processes.

Optimization of operating conditions in purification of wet process phosphoric acid in a liquid-liquid extraction column

Solvent extraction is an effective method for purufucation of wet process phosphoroc acid. The aim of this study was purification of wet-process phosphoric acid using acid grade phosphorus pentoxide and minimization of fluoride and arsenic. The first step included the pre-purification which was done by discoloration of acid and clarification during which the impurities were reduced. Fluoride reduction rate of about 68% was significant at this step. In the following step, liquid-liquid extraction was used to purify the phosphoric acid from previous stage. The parameters of phase ratio, two-phase contact time and the fluid flow regime in a packed column of the fluidized bed were studied using 2-ethylhexanol as a basic solvent. The results of this part have been used as an evaluation of acid extraction yield and separation factor of impurities using an experiment designed by the Taguchi method. Arsenic, fluoride and phosphorus pentoxide concentration were measured using Inductivity Coupled Plasma (ICP) and Ion Chromatography (IC) analysis. The optimal level of parameters and their effect was obtained. By comparing the optimal and worst level in extraction step, it was found that the amount of acid extracted can vary from 23% to 73%. Furthermore, the removal rate of 49% for fluoride and 67% for arsenic in the worst conditions, can increase to the optimal conditions as much as 72% and 93%, respectively. The overal removal rate of 92% for fluoride and 96% for arsenic in two stages were achieved. Increasing of phase ratio, the time as well as increasing the flow regime created optimal conditions in the extraction section.

Purification of Wet-Process Phosphoric Acid via Donnan Dialysis with a Perfluorinated Sulfonic Acid Cation-Exchange Membrane.

This work reports the application of an electromembrane process, Donnan dialysis (DD), for the purification of so-called wet-process phosphoric acid (WPA). Nitric acid is used as the stripping solution to remove metallic cations (mostly Fe3+, Al3+, and Mg2+) that are harmful to the further processing of WPA. The paper first presents a set of experimental data on the measurements of the metallic cation fluxes through a perfluorinated sulfonic acid cation-exchange membrane. Not only WPA, but also synthetic phosphoric acid solutions with mixed metallic cations (MPA) and with a single metallic cation (SPA) were studied. This confrontation confirms (1) that the order of metallic cations fluxes is Mg2+ > Al3+ > Fe3+; (2) that, compared with MPA, the purification effect of WPA causes only negligible change; (3) that, by comparing the DD processes with SPA and MPA solutions, the reason for the low transmembrane fluxes of Fe3+ and Al3+ could be explained by the large ionic charge and large hydrated ion radius. Furthermore, by analyzing the ion composition of membranes equilibrated in SPA solutions, we conclude that the forms of cations in the membrane are most likely Fe3+, Al3+, and Mg2+.

Investigation of the Process of Purification of Wet-Process Phosphoric Acid and Production of Concentrated Phosphoric Fertilizers Based on it

Fluoride compounds have the most harmful effects on the environment. The main source of fluoride in the soil is phosphorus-containing fertilizers. Purification of wet-process phosphoric acid (WPPA) from fluorine will significantly reduce its content in phosphorous-containing fertilizers and improve the quality of the resulting products. The aim of the study is to reduce the content of fluorine and sulfates in the wet-process phosphoric acid by introducing calcium carbonate, dolomite or phosphorite into the finished extraction pulp before filtration and obtaining high-quality calcium and magnesium-containing phosphate fertilizers based on it. Phosphates were determined by differential photometric, fluorine – ionometric, calcium, magnesium, aluminum, and iron-complexometric, and sulfates-by weight methods. For the first time, scientifically-based data were obtained on the simultaneous reduction of the content of fluorine and sulfates in WPPA from phosphorites of Central Kyzylkum and the production of calcium-magnesium phosphate fertilizers based on it. Optimal technological parameters of the process of simultaneous defluorination and desulfatation of WPPA from Central Kyzylkum phosphorites with calcium carbonate, dolomite and washed burnt phosphoconcentrate (WСPC) were found by introducing them into the second section of the extractor, into the finished extraction pulp in the amount of 100% for sulfate binding and 100-150% for fluorine binding, as well as obtaining high-quality products based on purified WPPA. The degree of transition of fluorine to the gas phase and phosphogypsum at a rate of 100-150% of calcium oxide for fluorine binding is 86.2-89.4% and its content in the wet-process phosphoric acid decreases from 1.18% to 0.22-0.29%. At the same time, the SO3 content in the acid decreases from 1.21% to 0.24-0.26%. The filtration rate of the sulfate-phosphate pulp varies slightly and is 807.6-812.6 kg/m2·h by dry residue.

PROBLEMS AND PROSPECTS OF PRODUCTION AND QUALIFICATION OF PHOSPHORIC ACID

The qualification of phosphoric acid is carried out depending on the use of phosphates of various deposits and the necessary quality of the final products. An acquisition of phosphoric acid of the required quality should be carried out taking into account three aspects: resource-energy, ecology and complex processing. Solving the problems of one aspect entails solving the problems of the other aspects. The rational use of natural resources and the reduction of environmental pollution is the determining factor in the choice of technological regimes for complex processing of raw materials with a reduction in the volume of waste of all kinds or transferring them into forms easily recyclable or specially stored. The absence of economically sound technologies for processing phosphogypsum determines its preferential warehousing. The second component that requires recycling is fluorine. In this regard, the purification of phosphoric acid from fluorine should use technologies that realize the trapping of fluorine compounds released into the gas phase. This is relevant from the point of view of the complexity of processing raw materials with the extraction of rare-earth elements. The use of mechanochemical activation makes it possible to achieve a nanoscale level. To a lesser extent, this aspect relates to the stage of sulfuric acid decomposition, proceeding with the participation of three phases: solid, liquid and gas. In turn, the surface structure of the gas-liquid layer plays the role of an energy barrier for evaporation. To establish the basic energy patterns of concentration and defluorination n the disc apparatus and to optimize the process, a thermophysical model was developed in which the range of effective parameters was determined by the joint solution of a number of equations for the desired ingredients in the phosphoric acid concentration range of 52-65%. The solution of the problem of complex purification of wet-process phosphoric acid can be carried out by adsorption methods that allow to remove to some extent almost all impurities.For citation:Smirnov N.N., Smirnova D.N., Ilyin A.P., Kochetkov S.P. Problems and prospects of production and qualification of phosphoric acid. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 7. P. 48-56.

Liquid–Liquid Equilibrium Data of Extraction with Tri-n-butyl Phosphate on Phosphoric Acid Containing Sodium Sulfate or Potassium Sulfate

Wet-process phosphoric acid is developed with the lack of a quality mineral. More and more research focuses on the purification of wet-process phosphoric acid with solvent extraction method. Liquid–liquid equilibrium data are of important significance in the industrial reality. In this work, equilibria data have been obtained for the two quaternary systems phosphoric acid–sodium sulfate–water–tri-n-butyl phosphate and phosphoric acid–potassium sulfate–water–tri-n-butyl phosphate, which contain concentrations of components and densities and viscosities of the equilibrium phases, and also the varieties of distribution coefficient of phosphoric acid are analyzed. In different systems (phosphoric acid solution with sodium sulfate or potassium sulfate at 303.2 K), the distribution coefficient of phosphoric acid with sodium was found to be higher than that of potassium ion, which demonstrates that the extraction of phosphoric acid with sodium is greater than that with potassium ion. In addition, NRTL model and ...

Effect of Purification from Sulfates on Phase Composition of Sodium Tripolyphosphate Obtained from Wet-Process Phosphoric Acid Derived from Kola Apatite

The effect of purification of wet-process phosphoric acid (WPA), obtained from Kola apatite in one of the Polish plants, on sodium tripolyphosphate (STPP is a key constituent of detergents) formation and polymorphic transformation was investigated. Phase composition of the product, prepared by neutralisation of phosphoric acid with NaOH up to a molar ratio of Na/P = 5/3, water evaporation from the solution, and heating of the dry residue obtained, depends on the presence of SO 4 2 − -ions in the acid and on the temperature of heating (250–550°C). When crude WPA, having 2 wt. % of SO 4 2 − , was used, the formation of STPP was suppressed up to a temperature of 400°C, at which the low-temperature modification Na 5 P 3 O 10 -II was observed. Transformation of Na 5 P 3 O 10 -II (Form-II) → Na 5 P 3 O 10 -I (Form-I), that was expected to occur in the range of 450–500°C, was also suppressed. To obtain Form-I heating at a temperature of 550°C was required. After WPA was purified down to 0.1 wt. % of SO 4 2 − using CaHPO 4 ·2H 2 O (with Ca 2 + /SO 4 2 − = 1) the low-temperature Form-II was not observed at any temperature of heating. The high-temperature modification (Form-I), that appeared at temperature as low as 300°C, remained stable while heated up to 550°C.

Density of organic phases in the extraction system tributyl phosphate-phosphoric acid

Data on the density of phosphoric acid solutions in crude TPB and TBP-based commercial extractant for purification of wet-process phosphoric acid are tabulated over the phosphoric acid concentration range 0.62–27.74 wt% (recalculated to P2O5).

Purification of Wet-Process Phosphoric Acid by Hydrogen Peroxide Oxidation, Activated Carbon Adsorption and Electrooxidation

In this work, three technologies are studied for the purification of phosphoric acid produced by the wet process: chemical oxidation with hydrogen peroxide, adsorption onto activated carbon, and electrochemical oxidation by boron-doped diamond anodes. The treatment of wet-process phosphoric acid by chemical oxidation with H2O2 as oxidizing agent can remove 75 % of the initial TOC as maximum, indicating that this wet-process phosphoric acid contains an important amount of organics that cannot be oxidized by hydrogen peroxide under the operation conditions used. High temperatures and hydrogen peroxide/TOC ratios close to 150 g H2O2/g TOC allow obtaining the best chemical oxidation results. The adsorption onto activated carbon can remove between 40 and 60 % of the initial TOC as maximum. Adsorption times of 2 hours and activated carbon/WPA ratios close to 12 g AC/Kg WTP assure both steady state and maximum adsorption of organics. The electrochemical process is the only technique by which complete mineralization of WPA organics can be achieved. Operating at 60 mA cm–2 and at room temperature, high current efficiencies are achieved which only seem to decrease by mass transport limitations.

Interaction of Tri-n-butyl phosphate, water, and phosphoric acid in purification of wet-process phosphoric acid

The material balance of water, phosphoric acid, and tri-n-butyl phosphate in the real process of purification of wet-process phosphoric acid by TBP extraction was studied. A process mechanism was suggested.

Identification of impurities accumulated in the extractant in the course of purification of wet-process phosphoric acid with tri-n-butyl phosphate

Impurities accumulated in the extractant in the course of operation of the plant for purification of wet-process phosphoric acid, obtained from apatite concentrate, by extraction with tri-n-butyl phosphate are identified by IR and mass spectra.

Extraction of Mineral Acids with Neutral Organophosphorus Extractants

Extraction of HNO3, HCl, H2SO4, H3PO4, H3AsO4, HF, and H2C2O4 with triisoamyl phosphate (TiAP), diisooctyl methylphosphonate (DiOMP), isoamyldialkyl(C7-C9)phosphine oxide (DRPO), and cyclohexyldialkyl(C7-C9)phosphine oxide (DRPO-1Ts) was studied, and the extraction isotherms were obtained. The solvation numbers of certain acids and extractants were determined by dilution and saturation methods. Purification of wet-process phosphoric acid to remove arsenic was studied. Distribution of Cu, Zn, Ni, Co, Fe, and Mn microamounts in the oxalic acid-neutral organophosphorus compound (NOPC) extraction systems was measured, and the feasibility of purification of oxalic acid to remove these metals to a 10-7% content was demonstrated.