Wet Phosphoric Acid Research Articles

Recovery of uranium (VI) from concentrated phosphoric acid by mixtures of new bis(1,3- dialkyloxypropan-2-yl) phosphoric acids and tri-n-octylphosphine oxide

Three new extractants, namely bis(1,3-dihexyloxypropan-2-yl) phosphoric acid, bis(1,3-dioctyloxypropan-2-yl) phosphoric acid and bis(1,3-di-2-ethylhexyloxypropan-2-yl) phosphoric acid, were synthesized and tested in mixture with tri-n-octyl phosphine oxide (TOPO) in Isane IP 185 for the recovery of uranium (VI) from 5.3molL−1 synthetic phosphoric acid and 30% wt P2O5 industrial wet phosphoric acid. The results were compared with those previously obtained with bis(1,3-dibutoxypropan-2-yl) phosphoric acid (BiDiBOPP), under similar experimental conditions. The increase of the length of the alkyloxy chains of bis(1,3-dialkyloxypropan-2-yl) phosphoric acid is responsible for an increase of the distribution coefficients of both uranium (VI) and iron (III) whereas steric hindrance effect arising from the increase of branching improves the selectivity for uranium (VI) against iron (III). A quantitative relationship between the distribution coefficients of uranium (VI) measured for the series of 7 extractants and two molecular descriptors has been developed. This opens a way for computer-guided design of new phosphoryl-containing extractants.

Sorption of iron from phosphoric acid solution using polyacrylamide grafted activated carbon

Polyacrylamide grafted activated carbon (PAAm-Ac) was prepared from chemically activated carbon of rice husk and rice straw and polyacrylamide. The prepared composite adsorbent was used for removal of iron from wet-phosphoric acid solution. Different parameters that could affect the adsorption reaction were investigated such as pH, contact time, metal ion concentration, adsorbent dose and anion concentration. The adsorption isotherms were studied to evaluate the maximum sorption capacity of adsorbent. The experimental results were found to fit with Langmuir isotherm model with maximum sorption capacity 6.15mg/g. Different kinetic models were applied upon the experimental data, and it was found to fit well with pseudo second order kinetic model with adsorption capacity of 5.29mg/g, suggesting a chemisorptions mechanism. The prepared polymeric composite adsorbent was applied for removal of iron from wet process phosphoric acid solution through batch and column experiments.

Removal of Cd(II) from Phosphoric Acid Solution by Adsorbents: Equilibrium and Kinetic Studies

The phosphoric acid obtained by wet-process is rich in impurities including heavy metals like cadmium. This work deals with the cadmium elimination from acid, by its adsorption on natural or modified clays and activated carbon, to improve its quality. The clays used in this study were effective for cadmium trapping from wet-phosphoric acid since it was reduced to approximately 80%. Moreover, our study shows that the fixation of cadmium is proportional to the temperature which however cannot exceed 313 K. On the other hand, the kinetic data, at the equilibrium, indicated that cadmium is more fixed on the inserted EDTA in the K10 montmorillonite (M). The kinetics of adsorption could be described by two models: pseudo-first- order and pseudo-second-order, which depend on temperature and the nature of adsorbent. At different temperatures used and with various adsorbents viz., K10 Montmorillonite (M), Gross kaolinite (K), Activated carbon (C), EDTA inserted in K10 montmorillonite (MD), iron oxide inserted in K10 montmorillonite (MF) and Posidonia oceanica impregnated on kaolinite (KP), the pseudo second order model was the most reliable to determine the order of kinetics of adsorption of cadmium, which is also reflected a good correlation coefficient (above 0.97). The experimental equilibrium adsorption data of Cd(II) onto different adsorbents were in agreement with the Freundlich isotherm model.

Solid-liquid extraction of Gd(III) and separation possibilities of rare earths from phosphoric acid solutions using Tulsion CH-93 and Tulsion CH-90 resins

Solid-liquid extraction of gadolinium was investigated from phosphoric acid medium using commercial amino phosphonic acid resin, Tulsion CH-93. The experimental conditions studied included equilibration time, acid concentration, mass of the resin, metal concentration, loading and elution. The percent extraction of Gd(III) was studied as a function of phosphoric acid (0.05-3 mol/L) using Tulsion CH-93 resin. The corresponding lgD vs. equilibrium pH plot gave straight line with a slope of 1.8. The percent extraction decreased with acid concentration increasing, conforming ion exchange mechanism. Under observed experimental conditions the loading capacity of Tulsion CH-93 for gadolinium was 10.6 mg/g. Among several eluants screened, the quantitative elution of Gd(III) from loaded Tulsion CH-93 was obtained with ammonium oxalate (0.15 mol/L). The extraction behavior of commonly associated metals with gadolinium was studied as a function of phosphoric acid concentration. Tulsion CH-93 resin showed selective extraction towards heavy rare earths (Lu and Yb) which could be separated from other rare earths at 3 mol/L H3PO4, similar to wet phosphoric acid (3–5 mol/L). On the other hand Gd(III) and other rare earths were studied with chelating resin Tulsion CH-90. Light rare earths were highly extracted and these could be separated from heavy rare earths and Gd.

Modeling of the extraction of uranium (VI) from concentrated phosphoric acid by synergistic mixtures of bis-(2-ethylhexyl)-phosphoric acid and tri-n-octylphosphine oxide

A thermodynamic model has been developed to describe the extraction of uranium (VI) from 5.3molL−1 phosphoric acid (a typical concentration encountered in wet phosphoric acid) by mixtures of bis-(2-ethylhexyl)-phosphoric acid (D2EHPA, also denoted hereafter HL) and tri-n-octylphosphine oxide (TOPO). A good agreement between experimental and calculated distribution coefficients of uranium (VI) was obtained by taking into account the following species in the organic phase: (HL)2TOPO, (HL)5TOPO, (HL)2(TOPO)2, UO2(HL2)2, UO2(HL2)2TOPO, and UO2L2TOPO where L is the deprotonated form of D2EHPA (HL). The speciation of uranyl, TOPO and D2EHPA in the organic phase was derived from this model as a function of the concentrations of the latter species.

Comparative Simulation of the Purification of Wet Phosphoric Acid by Tbp, Mibk and a Mixture (MIBK+TBP)

Liquid-liquid solvent extraction technology is used in several industrial processes such as petrochemical processing, pharmaceutical production, food and hydrometallurgy. It is successfully applied for the purification of Wet Phosphoric Acid (WPA) with fairly good purification performances. The purification process is basically carried out in three steps: extraction, washing and recovery, each of these steps is a liquid-liquid extraction operation. The aim was to develop a computer code that helps predicting the overall performance of the purification process for a given set of operating conditions. The adopted approach is based on determining the necessary theoretical stages for each step in the purification process using a numerical technique. Some simulation results for the WPA purification process with Tri-Butyl Phosphate (TBP) at 45°C, Methyl Isobutyl Ketone (MIBK) at 25°C and a mixture (MIBK+TBP) at 30°C are presented.

A Steady State Model for Describing the Phosphate Lattice Loss

Abstract A steady-state model for the industrial dihydrate phosphoric acid plant is developed. It is based upon material and balance equations and fundamental treatment of thermodynamics. The thermodynamic model includes the main species that are present in the aqueous phase of wet phosphoric acid process. For comparison, the electrolyte – NRTL model was used for describing the activity coefficients of the species in the aqueous solution. The model was validated by comparing its phosphate lattice loss prediction to data reported by Janikowski et al. [1] and Abutayeh and Campbell, [2] for Moroccan phosphate rock. A developed model was used to simulate the dihydrate process with the aim of quantifying the thermodynamically–controlled phosphate lattice loss. The obtained results by Electrolyte – NRTL model were in agreement with those obtained by Abutayeh and Campbell [2] that use the Edwards–Maurer– Newman–Prausnitz Pitzer model to describe the activity coefficient of the aqueous species present in the wet phosphoric acid process.

Procedure to use phosphogypsum industrial waste for mineral CO 2 sequestration

Industrial wet phosphoric acid production in Huelva (SW Spain) has led to the controversial stockpiling of waste phosphogypsum by-products, resulting in the release of significant quantities of toxic impurities in salt marshes in the Tinto river estuary. In the framework of the fight against global climate change and the effort to reduce carbon dioxide emissions, a simple and efficient procedure for CO 2 mineral sequestration is presented in this work, using phosphogypsum waste as a calcium source. Our results demonstrate the high efficiency of portlandite precipitation by phosphogypsum dissolution using an alkaline soda solution. Carbonation experiments performed at ambient pressure and temperature resulted in total conversion of the portlandite into carbonate. The fate of trace elements present in the phosphogypsum waste was also investigated, and trace impurities were found to be completely transferred to the final calcite. We believe that the procedure proposed here should be considered not only as a solution for reducing old stockpiles of phosphogypsum wastes, but also for future phosphoric acid and other gypsum-producing industrial processes, resulting in more sustainable production.

Solvent extraction and separation of rare-earths from phosphoric acid solutions with TOPS 99

TOPS 99, an equivalent to di-2-ethylhexyl phosphoric acid has been employed for the solvent extraction and separation of a mixture of rare-earths (four light rare-earths (LREs) La, Ce, Pr, Nd, and seven heavy rare-earths (HREs) like Tb, Dy, Y, Ho, Er, Yb and Lu) into some fractions from phosphoric acid solutions. From the acid and extractant effects, 0.1 and 1M TOPS 99 were suitable for the separation of a mixture of REs into three concentrates at 3M acid, which is similar to wet phosphoric acid solutions (WPA). McCabe–Thiele extraction isotherm predicts the separation of Yb+Lu at an aqueous-to-organic (A/O) phase ratio of 2 in three stages using 0.1M TOPS 99. Counter-current batch extraction simulation (CCES) of Yb and Lu at an A/O of 2 resulted in a raffinate containing 3.6mg/L of Yb+Lu, corresponding to an extraction efficiency of 91.9%, whereas other five HREs loss was about 6.7%. Stripping of Yb and Lu as per the predictions of McCabe–Thiele plot from loaded organic (LO) was selected at O/A phase ratio of 3 with 4M HCl and counter-current stripping simulation studies resulted 100% stripping efficiency. From the Yb+Lu raffinate, remaining five HREs were extracted about 94.4% with 1M TOPS 99 at an A/O ratio of 3 in three stages. The LRE (Pr and Nd) co extraction is 9.8%. Quantitative stripping of HREs from LO is achieved with 7M HCl at an O/A ratio of 3 in two stages. Finally, a process flowsheet was presented for the separation of rare-earths into three groups, two HRE fractions (Yb+Lu and Tb, Dy, Ho, Y, Er) and one LRE fraction from 3M phosphoric acid.

Effect of anions in commercial phosphoric acid on the extraction of uranium by DEHPA /TOPO

Extraction of uranium from commercial phosphoric acid by DEHPA/TOPO process is a well-developed process on the commercial and pilot plant scale. Commercial phosphoric acid contains certain anions such as Cl^-, F^- and SO_4^2- in varying concentrations. The presence of such anions could have a negative effect on the extraction process. This paper investigated the effect of Cl^-, F^- and SO_4^2- anions present in commercial wet phosphoric acid on the uranium extraction process. The effect of adding SiO_2 which complexes with F^- and other anions was also studied. The results obtained showed that these anions formed complexes with UO_2^2+ and therefore had a negative influence on the extraction of uranium from laboratory and commercial phosphoric acids. This effect was strong in the case of F^- followed by SO_4^2- and much less for Cl^-. Addition of SiO_2 was found to negate the effect of F^- and other anions and to exert a positive effect on uranium extraction.

Liquid–liquid extraction and separation possibilities of heavy and light rare-earths from phosphoric acid solutions with acidic organophosphorus reagents

Liquid–liquid extraction of mixture of seven heavy rare-earths (HREs) such as terbium, dysprosium, holmium, yttrium, erbium, ytterbium, and lutetium and mixture of four light rare-earths (LREs) such as lanthanum, cerium, praseodymium and neodymium has been investigated from phosphoric acid solutions. Extractants used are, Talcher organic phosphorus solvent (TOPS 99), an equivalent to di-2-ethylhexyl phosphoric acid, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (PC-88A), and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). The objective of the present study was to investigate the extraction behavior and separation possibilities among HREs and LREs and also separation of HREs as a group from LREs in 3–5 M acid, which is similar to wet phosphoric acid concentration. The parameters studied include time, H 3PO 4 concentration and extractant concentration. The percent extraction of metal decreases as the acid concentration increases with any given extractant concentration. Mechanism of metal transfer follows ion exchange type. The separation factors were evaluated based on the distribution coefficients in order to estimate the potential of the results for the separation of individual/pair of rare-earths from others and the separation of HREs from LREs. Extraction efficiency of extractants towards lanthanides from H 3PO 4 medium decreases in the series: TOPS 99 > PC 88A > Cyanex 272.

Studies on the Separation and Recovery of Uranium from Phosphoric Acid Medium Using a Synergistic Mixture of (2-Ethylhexyl)phosphonic Acid Mono 2-Ethyl Hexyl Ester (PC-88A) and Tri-n-octylphosphine Oxide (TOPO)

This paper deals with studies on the extraction of uranium(VI) from phosphoric acid medium using (2-ethylhexyl)phosphonic acid mono 2-ethylhexyl ester and tri-n-octylphosphine oxide individually as well as from their synergistic mixture. Different extraction parameters were investigated. With an increase in phosphoric acid concentration in the aqueous phase, the distribution ratio (Du) was found to decrease in all the cases. Synergism was observed when a mixture of PC-88A and TOPO was used. The synergistic mixture in the mole ratio of 4:1 (1.80 M PC-88A: 0.45 M TOPO) in xylene was found to be most suitable for uranium extraction. Among the various strip liquors used, 5% (w/v) solution of (NH4)2CO3 was found to be the most suitable. Using a mixture of 1.8 M PC-88A and 0.45 M TOPO as the extractant system and 0.5 M ammonium carbonate as the stripping agent, uranium recovery was found to be better than 97% ± 3% in multiple contacts, (n = 2) from actual Davies Gray Waste while in case of wet phosphoric acid more than 52% ± 3% (n = 3) only could be recovered where n is the number of contacts.

Solid–liquid extraction of heavy rare-earths from phosphoric acid solutions using Tulsion CH-96 and T-PAR resins

Wet phosphoric acid produced industrially from natural rock phosphates generally contains uranium in appreciable amounts and rare-earths in trace concentrations. In this paper, the solid-phase extraction of mixture of seven heavy rare-earths (HREs) such as terbium (Tb), dysprosium (Dy), holmium (Ho), yttrium (Y), erbium (Er), ytterbium (Yb), and lutetium (Lu) from phosphoric acid solutions using Tulsion CH-96, a macroporous bifunctional phosphinic acid resin and T-PAR resin, a phosphoric acid resin has been investigated. The parameters studied include time, H 3PO 4 concentration, ratio of volume of aqueous phase to mass of resin, metal concentration, and temperature. Effect of H 3PO 4 concentration from 0.5 to 5 M in the aqueous phase containing 25 mg/L of each metal using Tulsion CH-96 indicated that the percent extraction of metals decreases with increase in acid concentration at any given mass of resin. Mechanism of metal transfer follows ion exchange type. The separation factors were evaluated based on the distribution coefficients in order to estimate the potential of the results for the separation of individual/pair of rare-earths from others.

Simulation of the Wet Phosphoric Acid Extraction along a Continuous Column

Simulation of the Wet Phosphoric Acid Extraction along a Continuous Column

External radiation assessment in a wet phosphoric acid production plant

The factories dedicated to the production of phosphoric acid by the so-called wet acid method are usually considered typical NORM industries, because the phosphate rock used as raw material usually contains high concentrations of 238U-series radionuclides. The magnitude and behaviour of the radionuclides involved in the production process revealed the need to determine its dosimetric impact on workers. This work aims to partially compensate this lack of knowledge through the determination of external effective dose rates at different zones in the process at a typical plant located in the southwest of Spain. To this end, two dosimetric sampling campaigns have been carried out at this phosphoric acid production plant. The first sampling was carried out when phosphate rocks originating in Morocco were processed, and the second one when phosphate rock processed came from the Kola Peninsula (Russia Federation). This differentiation was necessary because the activity concentrations are almost one order of magnitude higher in Moroccan phosphate rock than in Kola phosphate rock. The results obtained have reflected external dose rate enhancements as high as 1.4 μSv h −1 (i.e., up to thirty times the external exposition due to radionuclides in unperturbed soils) at several points in the facility, particularly where the digested rock (pulp) is filtered. However, the most problematic points are characterised by a small occupation factor. That means that the increment in the annual effective external gamma dose received by the most-exposed worker is clearly below 1 mSv (European Commission limit for the general population) under normal production. Nevertheless, special care in the design and schedule of cleaning and maintaining work in the areas with high doses should be taken in order to avoid any possibility of exceeding the previously mentioned general population limit. In addition, the results of the dosimetric campaign showed no clear correlation between 226,228Ra activity concentrations in the material fluxing during the process (the most important radionuclides from the dosimetric point of view) and the external dose rates. Furthermore, any general dependence of the origin of the rock (i.e., on their radioactive contents) on the external effective dose rate measured has not been observed. These latter findings could be a consequence of three effects: (1) a variable radiation shielding at the different points along the process, (2) a changing geometry of irradiation (from a rock pile up to a thin-layered pulp passing through a solid mass inside pipes and deposits), and (3) the existence of a “memory effect”, or background contamination in the installation equipment due to the presence of radionuclide-enriched scales and sludges in pipes and deposits.

Global Phosphorus Flows in the Industrial Economy From a Production Perspective

SummaryHuman activity has quadrupled the mobilization of phosphorus (P), a nonrenewable resource that is not fully recycled biologically or industrially. P is accumulated in both water and solid waste due to fertilizer application and industrial, agricultural, and animal P consumption. This paper characterizes the industrial flows, which, although smaller than the agricultural and animal flows, are an important phosphorus source contributing to the pollution of surface waters. We present the quantification of the network of flows as constrained by mass balances of the global annual metabolism of phosphorus, based on global consumption for 2004, all of which eventually ends up as waste and in the soil and water systems. We find that on a yearly basis, 18.9 million metric tons (MMT) of P is produced, of which close to 75% goes to fertilizer and the rest to industrial and others uses. Phosphoric acid is the precursor for many of the intermediate and end uses of phosphate compounds described in this study and accounts for almost 80% of all P consumed. Eventually, all of the P goes to waste: 18.5 MMT ends up in the soil as solid waste, and 1.32 MMT is emissions to air and water. Besides quantifying P flows through our economy, we also consider some possible measures that could be taken to increase the degree of recovery and optimization of this resource and others that are closely related, such as the recovery of sulfur from gypsum and wastewater (sludge), and fluorine from wet phosphoric acid production.

Extraction of cadmium (II) from phosphoric acid media using the di(2-ethylhexyl)dithiophosphoric acid (D 2EHDTPA): Feasibility of a continuous extraction-stripping process

The extraction of cadmium from phosphoric media has been studied. The D 2EHDTPA was used as extractant and dodecane as diluent. No third phase was observed in the investigated conditions. A continuous micro-pilot scale mixer-settler was successfully tested for both extraction and stripping. More than 99% extraction rate was obtained in steady-state conditions with a flow rate ratio Aqueous/Organic equal to 1.1. Continuous stripping was performed using HCl 4 M. More than 96% of the cadmium was stripped in one continuous mixer-settler stage for flow rate ratio equal to 0.7. Results were in good agreement with the predicted values based on the McCabe–Thiele method. Experimental mixer-settler stages behave as ideal ones (Murphree efficiency > 98%). An optimal flow sheet is proposed to purify the Wet Phosphoric Acid (WPA) and to recover a relatively concentrated cadmium solution (1 g L − 1 ). Two ideal stages operating at phase ratio A/S equal to 5/1 are required for the extraction step leading to a very depleted raffinate (< 0.2 µg L − 1 ). For the stripping step, six stages are required (S/A = 5/1). The recovered organic phase contains less than 2 µg L − 1 and could be recycled in the extraction step.

Reduction of fluoride and sulfate ions in Syrian phosphoric acid by extraction with tertiary amins

General Fertilizer Company GFC Homs produces a lot of wet phosphoric acid, but it is unsuitable for food or pharmaceutical uses. Reduction of fluoride and sulfate ions contents in wet phosphoric acid by liquid - liquid extraction with tertiary aliphatic amins was studied. The effect of solvent concentration and temperature on the extraction was studied. The effect of diluent on the extraction yield and raffinate acid specifications was also studied.

Counter current extraction of phosphoric acid: food grade acid production

Extraction, scrubbing and stripping of phosphoric acid from the Syrian wet-phosphoric acid was carried out using Micro-pilot plant of mixer-settler type of 8 l/h capacity. Tributyl phosphate (TBP)/di-isopropyl ether (DIPE) in kerosene was used as extractant. Extraction and stripping equilibrium curves were evaluated. The number of extraction and stripping stages to achieve the convenient and feasible yield was determined. Detailed flow sheet was suggested for the proposed continuous process. Data obtained include useful information for the design of phosphoric acid extraction plant. The produced phosphoric acid was characterized using different analytical techniques.

Application of the TOF-SIMS and SEM-EDS methods to assess the influence of dusting from a phosphate waste deposal place based on hair analysis

Application of the TOF-SIMS and SEM-EDS methods to assess the influence of dusting from a phosphate waste deposal place based on hair analysis In this work, scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) and the time-of-flight secondary ion mass spectrometry (TOF-SIMS) were used to study the particles present on the hair surface of the inhabitants of Wislinka (people environmentally exposed due to the closeness of a dump) in order to obtain the information about the possible influence of dusting from a phosphate waste deposal place. Additionally, the morphology and the composition of fresh phosphogypsum were analyzed. Waste phosphogypsum is formed in the process of a wet phosphoric acid production and there is still a problem with its storage. A thorough understanding of the composition and chemistry of phosphogypsum seems to be necessary to evaluate its environmental impact comprehensively. The results obtained from these two techniques turned out to be complementary and revealed the information expected.