Nitric Acid Extraction Research Articles

Accumulation of Particles in an Annular Centrifugal Contactor Cascade and the Effect upon the Extraction of Nitric Acid

Centrifugal contactors (CCs) are a technology candidate for the development of advanced reprocessing flowsheets. While they offer many advantages, such as process intensification, there are still uncertainties regarding their industrial deployment. The presence of particles in the process streams in particular may present a challenge to both performance and operability. Preliminary studies have been undertaken to evaluate the accumulation of particles in the contactors and the effect upon the extraction behaviour of nitric acid. Aluminium oxide (Al2O3) particles were suspended in the aqueous feed solution during the operation of a three-stage, 40 mm diameter CC cascade. The presence of insoluble solid particles in the aqueous feed, up to 7 g/L, were not observed to affect phase separation and entrainment under the experimental conditions investigated. The particles were centrifuged out of solution and accumulated as a thin cake/bed in the rotors of each stage. This work also illustrates that particles do entrain through the cascade. The predominant effect on the rate of accumulation was particle concentration in the aqueous feed solution, and increasing solids loading was observed to have an impact upon the extraction of nitric acid across the cascade.

Comprehensive investigation of pollution levels and potential bioavailable risks of 7 potentially toxic elements in Qinghai-Tibet soils by using diffusive gradients in thin-films (DGT)

ABSTRACT Seven potentially toxic elements (PTEs) including Cr, Ni, Cd, Zn, Cu, Pb and As of soil samples from Qinghai-Tibet Plateau (QTP) were measured to assess the degree of contaminations. To have a comprehensive understanding of PTEs’ risks in QTP, the single-step nitric acid extraction and diffusive gradients in thin-films (DGT) technique were employed in this study for the determination of PTEs’ total amount as well as bioavailable content, respectively. Haibei state of Qinghai province was the most contaminated sites by PTEs. Behaviors of PTEs should be highly concerned as they can produce continuous bioavailable effects to ecological systems. High DGT concentrations of Zn and Cr showed their remarkable available risks in soils. In the environment with insufficient organic matter and slight pH variations, phosphorus level was the main contributor to affect the mobility of labile PTEs, especially for Pb and Ni. Concentration ratio between DGT measurement and soil solution and correlation analysis confirmed the high bioavailability of Pb, Zn and Cr, leading to short-term mixture effects on ecological systems, while the long-term release dynamics were found for As and Cu. Results from road-side and river-side soils of QTP evidenced the short-term bioavailable risks were possibly attributed to intensive anthropogenic activities including traveling industries and vehicle driving, whereas long-term bioavailable risks was from the natural transportation and deposition.

Speciation and Organic Phase Structure in Nitric Acid Extraction with Trioctylamine.

Understanding chemical speciation and intermolecular interactions in multicomponent liquids is essential to understanding their phase and chemical equilibria, which underpin chemical separation processes, including solvent extraction. Here we report on the extraction of nitric acid from its aqueous solutions into organic solutions of trioctylamine (TOA) in toluene, investigated with spectroscopic, X-ray scattering, and computational tools to understand molecular speciation in the organic phase and its relationship with the nanoscale structure of the organic phase. Trends in acid and water extraction clearly show two and three regimes, respectively, indicating different stoichiometric relationships, but speciation of HNO3, water, and amine in these regimes is not apparent. 1H NMR of the organic phase shows that there are at least two distinct acidic protons in the organic phase while ATR-FTIR results show that the organic phase with excess acid extraction is a mixture of trioctylammonium-nitrate ion pairs (TOAH·NO3), and undissociated HNO3 molecules. Comparison with DFT-computed IR spectra show that the chain-like configurations of TOAH·NO3·HNO3·H2O are favored over TOAH·NO3·H2O·HNO3, i.e., direct interaction between the nitrate and HNO3 molecules is more favored compared to a water-mediated interaction. SAXS of the organic phases were modeled as sums of Ornstein-Zernike (O-Z) scattering and a prepeak feature in the higher Q region that corresponds to extractant packing. The extraction of undissociated HNO3 by the ion pairs leads to an increased X-ray scattering contrast in the organic phase without any significant change in the correlation length. These results show that the organic phase nanostructure is more sensitive to the concentration of TOAH·NO3 and is relatively unaffected by excess acid extraction. These findings will enable a molecular understanding of the mechanisms behind metal extraction from acidic media with basic extractants.

NITRIC ACID PROCESSING OF SERPENTENITES FROM THE KARAKALPAK DEPOSIT

Physicochemical foundations for the technology of nitrogen acid processing of serpentinite from the Karakalpak deposit with the formation of pure magnesium nitrate and magnesium-containing compound fertiliser are developed. The chemical and mineralogical composition of serpentinite from the Karakalpak deposit is studied. As determined by X-ray diffraction analysis, microscopic and thermogravimetric studies, serpentinite sample contains clinoenstatite, pyrope, spinel, magnetites and other minerals with various crystal structures. Data on the extraction of serpentinite components in nitric acid by decomposition under different conditions (temperature, duration, nitric acid concentration) are presented. The subsequent stages of nitric acid extract processing have been carried out: removal of silica residue, ammonisation of the filtrate in order to precipitate undesirable impurities to obtain magnesium nitrate. The process of evaporation and crystallization of the filtrate to obtain pure magnesium nitrate has been studied.

Assessment of metallic membrane-based counter-current micro-contactor for non-dispersive solvent extraction: Experimental studies and modelling

Non-dispersive solvent extraction (NDSX) in a micro-contactor eliminates the need of phase separator. Thus, NDSX is an approach to achieve intensification of solvent extraction process. The interface between the two phases which flow counter-currently is stabilized by metallic membrane (stainless steel mesh). However, the use of counter-current flow puts hydrodynamic limitations on stability of the interface and hence on the operation of the contactor. In this study, a theoretical model to estimate the maximum stability length and corresponding extraction is reported and validated with the experimental data of nitric acid extraction using 30% (v/v) TBP in dodecane as the solvent. The model is further used to perform parametric analysis to understand the effect of various parameters on maximum stability length and corresponding extraction. The model is also used for assessing feasibility of using metallic membrane-based counter-current micro-contactor for non-dispersive solvent extraction of uranium from nitric acid medium.

Extraction of Nitric Acid and Uranium with DEHiBA under High Loading Conditions.

The mechanism by which high concentrations (1.5 M in n-dodecane) of N,N-di-2-ethylhexyl-isobutyramide (DEHiBA) extracts HNO3 and UO2(NO3)2 is under examination. Most prior studies have examined the extractant and the mechanism at a concentration of 1.0 M in n-dodecane; however, under the higher loading conditions that can be achieved by a higher concentration of extractant, this mechanism could change. Increased extraction of both nitric acid and uranium is observed with an increased concentration of DEHiBA. The mechanisms are examined by thermodynamic modeling of distribution ratios, 15N nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy coupled with principal component analysis (PCA). Speciation diagrams produced through thermodynamic modeling have been qualitatively reproduced through PCA of the FTIR spectra. The predominant extracted species of HNO3(DEHiBA), HNO3(DEHiBA)2, and UO2(NO3)2(DEHiBA)2 are in good agreement with prior literature reports for 1.0 M DEHiBA systems. Evidence for an additional species of either UO2(NO3)2(DEHiBA) or UO2(NO3)2(DEHiBA)2(HNO3) also contributing to the extraction of uranium species is given.

Экстракционное извлечение редкоземельных металлов из растворов вскрытия фосфогипса

In the present work, a complex of investigations on the liquid extraction of REE from phosphogypsum leaching solutions was carried out, including the search for an extractant and diluent, a study of the extraction of REE and nitric acid, and the choice of conditions for the selective back-extraction of nitric acid and REE.

Technology of obtaining liquid complex fertilizers in the presence of monoethanolamine based on phosphorites of the Central Kyzylkum

The possibility of producing liquid fertilizers based on nitric acid processing of washed dried concentrate in the presence of monoethanolamine is shown. On the basis of nitric acid extract and monoethanolamine, liquid complex fertilizers with stimulating activity were obtained, composition: P2O5tot. - 10-11%, CaOtot. - 6-7%, Ntot. 12-13% and K2O-5-6%. They contribute to the acceleration of plant growth by 10- 12 days and an increase in yield by an average of 8-10% compared to the control variant. It can be concluded that they can be recommended as liquid complex fertilizers for drip application.

Особенности извлечения РЗЭ из магматических и осадочных фосфатных руд

Using the example of dependencies R(REE) = f(τ), the principal differences between the extraction of REE from phosphate raw materials of sedimentary and magmatic genesis have been revealed, consisting in the extreme and monotonous nature of kinetic curves with the exit to the plateau, respectively. The discovered features of the nitric acid extraction of REE allow us to assess the prospect of complex processing of raw materials and optimal conditions for their separation from multicomponent systems.

Multiplicity of Th(IV) and U(VI) HEH[EHP] Chelates at Low Temperatures from Concentrated Nitric Acid Extractions

Organophosphorus extractants have been widely investigated for lanthanide recovery from ore and for application in the reprocessing of spent nuclear fuel, such as in Advanced TALSPEAK schemes. Determining the speciation of the extracted metal complex in the organic phase remains a significant challenge. A better understanding of the variability of HEH[EHP]-actinide complexes and the speciation of chelates for tetra- and hexavalent actinides can improve the predictability of actinide phase transfer in such biphasic systems. In this study, the extraction of Th(IV) and U(VI) from nitric acid media using HEH[EHP] in heptane is examined. The distribution ratio as a function of nitric acid concentration was quantified using UV-vis spectroscopy, and then the speciation of HEH[EHP]-metal complexes in the organic phase was investigated using Fourier transform infrared (FTIR) spectroscopy and low-temperature 31P nuclear magnetic resonance (NMR) spectroscopy. In addition to perturbation of the vibrational modes proximal to the phosphonic moiety in HEH[EHP] in the FTIR spectra, the appearance of a nitrate signal was found in the organic phase following extraction from the highest acidity conditions for U(VI). The 31P NMR spectra of the organic phase at a low temperature (-70 °C) exhibited a surprising number (n) of resonances (n ≥ 7 for Th(IV) and n ≥ 11 for U(VI)), with the distribution between these resonances changing with the initial concentration of nitric acid in the aqueous phase. These results indicate that the compositions of the inner and outer spheres of the extracted actinides in the organic phase are more diverse than initially thought.

Starch-based composite film reinforcement with modified cellulose from bamboo for sustainable packaging application

Biocomposite starch film based on modified bamboo cellulose treated with phosphoric acid were evaluated for their application as food packaging materials in food industry. In this study, the neat starch, starch with a phosphorylated cellulose–chlorine extract (St–Bam Chl-PO4 ), and starch with a phosphorylated cellulose–nitric acid extract (St–Bam HNO3-PO4 ) were mixed with glycerol using a casting process. Results showed that tensile strengths for both St–Bam Chl-PO4 and St–Bam HNO3-PO4 were increased at 1.18 and 7.74-folds as compared to the neat starch. Meanwhile, the crystallinity index of St–Bam Chl-PO4 and St–Bam HNO3-PO4 films were improved at 4.9 and 5.16-folds, respectively, without lowering the thermal stability. These indicated that the modification of hydroxyl groups from the bamboo cellulose with the phosphoryl group increased cellulose–starch compatibility. Also, St–Bam Chl-PO4 and St–Bam HNO3-PO4 films showed enhanced UV absorption, demonstrating their potential use for UV protection. This study provides new insights into the functional improvement of starch films reinforced with treated cellulose for sustainable packaging applications. • Cellulose was successfully extracted from bamboo and adhere to the starch matrix • 30% of phosphoric acid was used for surface modification of cellulose • The starch-cellulose film exhibited good mechanical and hydrophobicity property • The obtained starch cellulose film can be potentially used as packaging materials

Leaching kinetics for magnesium extraction from phosphate rock in the nitric acid method

As an indispensable part of the process of magnesium extraction from phosphate rock, the kinetics study plays a critical role in fundamental research and industrial production. According to the Arrhenius equation, the activation energy, and the frequency factor of magnesium removal from phosphate rock by a new nitric acid extraction method (nitrate-calcium-nitrate acid-magnesium nitrate) were calculated as 21.83 kJ/mol and 56.01 min−1, respectively. The results suggested that magnesium removal from phosphate rock is under mixed control. Through the derivation of the Fick's law, the kinetic equations of P2O5 loss rate and MgO removal rate were established. The process of magnesium removal from phosphate rock by the nitric acid method is described by the nuclear shrinkage model with constant particle size (η=C0+Ke-ERT[pH]∑i2αiriτ∑i2βirirθ), and the root mean square error (RMSE) is 0.12 % and 3.40 %, respectively. Simultaneously, the response surface methodology was taken to investigate the effects of pH, temperature, particle size of phosphate rock, and reaction time on the P2O5 loss ratio and MgO removal ratio, it was found that the P2O5 loss ratio could be controlled within 1.3–1.4 % with the MgO removal ratio reaching 85 %, under the optimized condition when the pH value was 2.0, the temperature was 50 °C, and the particle size of phosphate rock was 0.20–0.22 mm. This work provides an idea for the direct utilization of medium- and low-grade phosphate ore without the flotation method.

Bioaccessibility and bioavailability evaluation of heavy metal(loid)s in ginger in vitro: Relevance to human health risk assessment

Ginger is a common spice in everyday diet. However, over time, it may absorb and accumulate heavy metal(loid)s (HMs) from the soil, posing a potential health risk to humans. In this study, we evaluated the pollution level, bioavailability, mobility evaluation, and health risk of Cr, Pb, Cd, and As in the soil–ginger system of five major ginger-producing cities in Shandong Province, China. Research indicated the concentrations of the Cr, Pb, Cd, and As in the soil were close to or even higher than background value, except Weifang. With the concentrations of Cr, Pb, Cd, and As in ginger being 0.08–0.47, 0.03–0.16, 0.002–0.03, and 0.006–0.028 mg/kg, the four HMs concentrations were within the limits of 0.1–0.5 mg/kg based on the Chinese health standard (GB2762–2017) of HMs in food. The bioavailability of HMs in soils was evaluated using diethylenetriaminepentaacetic acid (DTPA) and nitric acid (HNO3) extraction and the results showed that Pb and Cd have high bioavailability. Mobility evaluation of HMs from soil to ginger based on Pearson's correlation and the partial least squares–path method (PLS-PM) model showed that the soil's physicochemical properties influence the HMs migration process (especially Cd and Pb) in the soil–ginger system, and the PLS-PM model has good adaptability to Cd and Pb (gof > 0.5). The mean total carcinogenic risk (TCR) of bioaccessible gastric and intestinal HMs were 4.64 × 10−6 and 3.13 × 10−6, which were much lower than that of total HMs (2.60 × 10−5), indicating that existing models based on total HMs may overestimate the health risk of HMs. The bioaccessible concentrations should be considered to improve the accuracy of assessment results.

Arsenic pools in soils under native vegetation on a steatite outcrop in Brazil

Pristine soils under native vegetation can present high levels of potentially toxic elements when developed from the weathering of some unusual parent materials, especially ultramafic rocks and some metal ores. Here, we used various selective extractions in order to study the partition and potential availability of As in eight soils developed from steatite (a talc-rich rock) on an ultramafic hill in Brazil. Soils varied from shallow Entisols on the summit to Inceptisols and Oxisols on slopes and footslopes, where total As contents (determined by X-ray fluorescence) reached levels as high as 225 mg kg−1, which might raise concerns about their potential agricultural use and occupation. Despite these high values for pristine soils, water- and Mehlich-available As were nil or negligible in all soils, whereas oxalate-extractable As reached a maximum 4.2 mg kg−1, and the highest semi-total (nitric acid digestion) was 9.3 mg kg−1. However, As relative availability (compared to total As) varied widely among soils, with one Inceptisol (with a total 11–19 mg kg−1) reaching 100% of its total As extractable by nitric acid, whereas an Oxisol showed <0.1% in nitric acid extract. Generally, we can conclude that, in soils with the highest total As concentrations, most As is contained within resistant, coarse phases such as primary magnetite, chromite and others, and a minor but still considerable part is bound to secondary Fe oxides. Thus, despite the unusually high As contents for soils under pristine savannic and forest native vegetations, the different As pools assessed here apparently do not raise immediate concerns where ultramafic rocks rich in Fe oxides give rise to soils under tropical climate. However, it is theoretically possible that subsoil saturation and Fe oxide reduction release some As in ground- and surface waters, which deserves further investigation.

Trihexyl(tetradecyl)phosphonium bis-2,4,4-(trimethylpentyl)phosphinate micellar behavior in the extraction of Ag(I) from acidic nitrate media

The distribution of Ag(I) between acidic aqueous phase (HNO3) and organic phases, composed of trihexyl(tetradecyl)phosphonium bis-(2,4,4-trimethylpentyl)phosphinate (Cyphos® IL 104) diluted in kerosene or kerosene/1-decanol, has been studied. In order to elucidate the interactions in solution and the chemical equilibria responsible for Ag(I) extraction by Cyphos® IL 104, ionic conductivity, dynamic viscosity, and interfacial tension measurements, determination of water and nitric acid extraction were performed, and the organic phases were characterized by infrared spectroscopy (ATR-FTIR). Ag(I) is extracted by Cyphos® IL 104 with high affinity, even under slightly acidic conditions (close to 100% at pH 5). The linear relationship between the logarithm of the distribution ratio of Ag(I) (D) and the logarithm of Cyphos® IL 104 concentration exhibits a slope greater than the stoichiometry expected (1:1), demonstrating an atypical extraction equilibrium. The change in the physicochemical properties as a function of Cyphos® IL 104 concentration permits to deduce the formation of reverse micelles or aggregates in organic phases at the critical micellar concentration CMC = 0.001 mol L-1. The ATR-FTIR characterization showed that Ag(I) was extracted by the phosphinate group of Cyphos® IL 104 with the transfer of water and nitric acid. A thorough analysis of these data indicates a similar mechanism to solvation, and the reverse micelles (or agglomerates) are involved in Ag(I) extraction.

Effectiveness of non-exchangeable potassium quantified by mild tetraphenyl‑boron extraction in estimating radiocesium transfer to soybean in Fukushima

Non-exchangeable K released from soil minerals can reduce radiocesium transfer to plants, as well as exchangeable K. We investigated the effect of non-exchangeable K on radiocesium transfer to soybean, and the non-exchangeable K extraction method most suitable for estimating the transfer risk. In Fukushima Prefecture, Japan, 106 soils were collected from 89 soybean fields during 2014–2018 to analyze non-exchangeable K contents using three methods: boiling nitric acid extraction, tetraphenyl‑boron extraction, and mild tetraphenyl‑boron extraction. The non-exchangeable K contents quantified by the former two methods were dependent on the amount of micas, which are K-bearing minerals. The non-exchangeable K content by mild tetraphenyl‑boron extraction depended on the amount of K fertilizer application and K-fixing minerals but not on micas, indicating that it reflects fertilizer K fixed by the minerals. The soil-to-plant transfer factor of radiocesium was most correlated with the non-exchangeable K content by the mild extraction (rs = −0.67). This correlation was also stronger than that between exchangeable K and the transfer factor (rs = −0.40). As non-exchangeable K content increased, the exchangeable radiocesium fraction decreased, indicating that radiocesium was fixed together with K. Additionally, multiple regression analysis indicated that non-exchangeable K by the mild extraction significantly decreased the transfer factor even if the exchangeable radiocesium fraction was kept constant. Thus, the fixed K was considered to repress radiocesium transfer to soybean through both radiocesium fixation and K supply. With the criterion of total extracted K, the sum of exchangeable and non-exchangeable K, as 65 mg K2O 100 g−1 by the mild extraction, fields with high and low transfer factors were able to be differentiated more effectively than with a current criterion of exchangeable K as 50 mg K2O 100 g−1. The results revealed that mild tetraphenyl‑boron extraction is effective for estimating radiocesium transfer to soybean.

SULFATE ADDITIVES FOR INTENSIFICATION OF THE FILTRATION OF LOW GRADE PHOSPHORITE-NITRIC ACID SUSPENSION

In the process of opening phosphate rocks and extracting the main component by acid extraction, a stage of isolation of the insoluble residue from the obtained suspensions by filtration is necessary. This will ensure an increase in the concentration of nutrients in the products of processing natural phosphorites used as model minerals. The insoluble residue on the filter baffle is a filter layer, the dense structure of which prevents the effective process of separating the liquid-solid system. In order to intensify the filtration process of nitric acid suspension based on low-quality high-siliceous phosphorite of the Polpinsky deposit, the effect of sulfate additives: sulfuric acid, ammonium sulfate and potassium sulfate on the structure of the sediment and, accordingly, the filtration time of the suspension and washing of the sediment was studied. The content of the administered additives varied in the range of 10 - 30 weight %. The results of the study of the microstructure of sediments – vertical cross–section and their surface obtained using the scanning electron microscopy method allowed us to establish that the introduction of the studied additives leads to an increase in the porosity of the layer due to the formation of large druses from single crystals of calcium sulfate dihydrate - gypsum. This improves the filtration properties of the sediment layer, reducing the filtration and washing time. It should be noted that, all other things being equal, the effectiveness of potassium sulfate additives is higher in comparison with sulfuric acid and ammonium sulfate additives. Its advantage lies not only in improving the rheological properties of suspensions, but also in the presence of potassium in the system as a nutrient component during the processing of nitric acid extract for complex fertilizers. The effective concentration of potassium sulfate in the system was experimentally established at 20 weight. %. At the same time, the maximum value of the filtration rate of the suspension is 0.537 m3/(m2∙h), which is 1.08 and 1.03 times higher compared to the filtration of suspensions containing ammonium sulfate and sulfuric acid, respectively. The revealed trend extends to the precipitation washing rate - the maximum value corresponds to 0.750 m3/(m2∙h), which exceeds the corresponding comparison samples by 1.1 and 1.15 times.

Highly efficient and selective extraction of Pu(IV) using two alkyl-substituted amides of nitrilo triacetic acid from nitric acid solutions

• The extraction of U(VI), Pu(IV) and Am(III) was studied with two tripodal NTA amide ligands. • The extraction trend was Pu(IV) > >U(VI) > Am(III) with both the ligands and HONTA > HDDNTA. • The metal ion extraction was not significantly affected with U loading or absorbed gamma dose. • Stripping was facile and the encouraging reusability data promises for possible application. • Modifier content has a positive impact on water and nitric acid extraction and negative impact on metal ion extraction. Liquid-liquid extraction of the actinide ions UO 2 2+ , Pu 4+ , Am 3+ was carried out from nitric acid feed solutions using two tripodal amide extractants, viz., N,N,N’,N’,N”,N” - hexa - n -octylnitrilotriacetamide (HONTA) and N,N,N’,N’,N”,N” - hexa - n -dodecylnitrilotriacetamide (HDDNTA) in 10% isodecanol + 90% n -dodecane diluent. The metal ion extraction trend was: Pu(IV) ≫ U(VI) > Am(III) at 3 M HNO 3 , HONTA being a superior extractant than HDDNTA. Slope analysis indicated ML 2 type species for both Pu(IV) and Am(III) at 3 M HNO 3 and pH 2.0, respectively, whereas, only in case of HONTA, a ML type species was obtained with U(VI) at 3 M HNO 3 . Back extraction data suggested that a mixture of 0.5 M HNO 3 + 0.5 M oxalic acid was efficient for quantitative stripping (∼90%) of Pu(IV), whereas 1 M Na 2 CO 3 and 1 M α-HIBA gave satisfactory back extraction for U(VI) and Am(III), respectively. The ligand solutions showed reasonably good radiation stability up to an absorbed total gamma ray dose of 274 kGy. Distribution data were also obtained under U(VI) loading conditions for possible nuclear fuel cycle applications.

Extraction and separation of Pd(II) by N, N'-diethyl-N, N'-dicyclohexylmalonamide in a nitric acid system

This study indicated the extraction and separation of Pd(II) by N, N'-diethyl-N, N' -dicyclohexylmalonamide (DEDCHMA) from the aqueous nitric acid solution. The effects of extraction time, nitric acid concentration, diluent, extraction temperature, and extractant concentration on extraction distribution ratio were investigated. The extraction mechanism and the composition of the complex were further discussed based on FT-IR and slope analysis. Compared with N, N, N', N'-tetraoctyl diglycolamide (TODGA) and N, N, N', N'-tetracyclohexylmalonamide (TCHMA), the DEDCHMA showed higher extraction capacity for Pd(II), which is 46 and 15 times higher than that of TCHMA and TODGA, respectively. The stripping extraction ratio obtained in Pd(II)-loaded organic phase using thiourea or oxalic acid reached 99%. The extraction selectivity to Pd(II) and noble metals such as Ru(III), Rh(III), and some common base metals, such as Al(III), Fe(III), Ni(II), Cu(II), Zn(II), Ca(II), Mg(II), Pb(II), Sr(II), Cr(III) and CO(II), was also investigated. The results demonstrate that DEDCHMA can be used to treat and recover Pd(II) from nitrate-based wastes containing associated precious metals, such as Pd(II), Ru(III), Rh(III), and common base metal, as well as from the spent fuel reprocessing.

Obtaining Magnesium Hydroxide From Dolomite Of The Dekhkanabad Deposit

The results of a study of the effect of pH on the chemical composition and degree of precipitation of magnesium hydroxide from clarified nitric acid extracts of dolomite decomposition are presented. It was found that the main amount of magnesium is precipitated by neutralizing the clarified extract from the dolomites of the Dekhkanabad field with gaseous ammonia to pH 11-12. The filtration rate of magnesium hydroxide on dry sediment is 181.80 kg/m 2 h. All solutions have acceptable rheological properties.