Low Nitric Acid Concentration Research Articles

Tetradentate Ligand's Chameleon-Like Behavior Offers Recognition of Specific Lanthanides.

The surging demand for high-purity individual lanthanides necessitates the development of novel and exceptionally selective separation strategies. At the heart of these separation systems is an organic compound that, based on its structural features, selectively recognizes the lighter or heavier lanthanides in the trivalent lanthanide (Ln) series. This work emphasizes the significant implications resulting from modifying the donor group configuration within an N,O-based tetradentate ligand and the changes in the solvation environment of Ln ions in the process of separating Lns, with the unique ability to achieve peak selectivity in the light, medium, and heavy Ln regions. The structural rigidity of the bis-lactam-1,10-phenanthroline ligand enforces size-based selectivity, displaying an exceptional affinity for Lns having larger ionic radii such as La. Modifying the ligand by eliminating one preorganization element (phenanthroline → bipyridine) results in the fast formation of complexes with light Lns, but, in the span of hours, the peak selectivity shifts toward middle Ln (Sm), resulting in time-resolved separation. As expected, at low nitric acid concentrations, the neutral tetradentate ligand complexes with Ln3+ ions. However, the change in extraction mechanism is observed at high nitric acid concentrations, leading to the formation and preferential extraction of anionic heavy Ln species, [Ln(NO3)x+3]x-, that self-assemble with two ligands that have undergone protonation, forming intricate supramolecular architectures. The tetradentate ligand that is structurally balanced with restrictive and unrestrictive motifs demonstrates unique, controllable selectivity for light, middle, and heavy Lns, underscoring the pivotal role of solvation and ion interactions within the first and second coordination spheres.

Microwave-assisted acid treatment for the mineral transformation of chrysotile as an alternative for asbestos waste management

In this work, the effect of microwave-assisted acid treatments on the morphological and crystallochemical characteristics of chrysotile fibers is investigated. A low concentration of nitric acid (0.2 N) is used to remove Mg2+-species located in the octahedral sheet of its structure, thereby causing a crystallo-chemical change forming a skeleton of non-crystalline amorphous silica. This skeleton maintains an elongated morphology but characterized by rounded -not sharp-edges and porous surfaces whose physical resistance under stress is reduced when compared with the initial fibers of chrysotile, favoring a lower pathogenicity of the fibers. Thus, microwave-assisted acid treatment rise as a low-cost, fast and effective option in avoiding the dangerousness associated with asbestos waste management.

The Effect of Peptizing Agent Concentration on Processing and Properties of Alumina Based Catalyst Support

Gamma alumina (γ-Al2O3) has drawn attention as a support material for heterogeneous catalysts extensively used in the oil and gas industry due to its superior properties. Boehmite (AlOOH) is an industrially accepted and well-known precursor to produce gamma alumina-based support. The process additions such as nitric acid (HNO3) are commonly used in shaping process of alumina to control textural, mechanical and structural properties of final catalyst support. In this work, gamma alumina precursor boehmite was peptized by nitric acid at molar ratio of HNO3/AlOOH ranging from 0 to 0.054. With addition of nitric acid, extrusion paste showed higher plasticity up to 0.017 mole of HNO3/AlOOH. The addition of more than this point led to an inhomogenity of extrusion paste caused by hard and brittle structure caused by the formation of aluminum nitrate salts. Also, higher mechanical strength was observed for samples peptized with lower nitric acid concentration because of effective deagglomeration by peptization. The pore size of catalyst support pellets increased up to an acid/ boehmite molar ratio of 0.017 by peptizing of boehmite. However, beyond this point pore size decreased due to dissolution of boehmite.

Efficient Adsorption of Ammonia by Surface-Modified Activated Carbon Fiber Mesh.

In view of the characteristics and risks of ammonia, its removal is important for industrial production and environmental safety. In this study, viscose-based activated carbon fiber (ACF) was used as a substrate and chemically modified by nitric acid impregnation to enhance the adsorption capacity of the adsorbent for ammonia. A series of modified ACF-based adsorbents were prepared and characterized using BET, FTIR, XPS, and Boehm titration. Isotherm tests (293.15 K, 303.15 K, 313.15 K) and dynamic adsorption experiments were performed. The characterization results showed that impregnation with low concentrations of nitric acid not only increased the surface acidic functional group content but also increased the specific surface area, while impregnation with high concentrations of nitric acid could be able to decrease the specific surface area. ACF-N-6 significantly increased the surface functional group content without destroying the physical structure of the activated carbon fibers. The experimental results showed that the highest adsorption of ammonia by ACFs was 14.08 mmol-L-1 (ACF-N-6) at 293 K, and the adsorption capacity was increased by 165% compared with that of ACF-raw; by fitting the adsorption isotherm and calculating the equivalent heat of adsorption and thermodynamic parameters using the Langmuir-Freundlich model, the adsorption process could be found to exist simultaneously. Regarding physical adsorption and chemical adsorption, the results of the correlation analysis showed that the ammonia adsorption performance was strongly correlated with the carboxyl group content and positively correlated with the relative humidity (RH) of the inlet gas. This study contributes to the development of an efficient ammonia adsorption system with important applications in industrial production and environmental safety.

An Integrated Model Combining Mass Transfer and Chemical Reaction for Co-Decontamination Extraction Step of PUREX Process in a Pulsed Extraction Column

ABSTRACT The accurate prediction of the extraction behaviors of various solutes in PUREX reprocessing process is crucial for the operation and implementation of the actual process. In this paper, an integrated model is developed to predict the extraction behaviors of U, Np, Pu, and HNO3 in the co-decontamination step (1A extraction step) in a pulsed extraction column. The model couples several physical and chemical processes, such as countercurrent flow, mass transfer, and chemical reaction. The mass transfer coefficients and the distribution ratios of U(VI), Pu(IV), Np(IV), Np(V), Np(VI), HNO3 and HNO2 can be obtained using this model. In particular, the redox and disproportion reactions of Np are considered in the model, and the flow direction of Np can be judged under various process conditions and the corresponding influential factors can be analyzed. The judgment is based on the yield calculated from the relative concentration profiles of Np(VI), Np(V), and Np(IV) in the two phases. For neptunium to inter 1AP step, it is necessary to select high nitric acid concentration, low nitrite concentration and especially high flow ratio. For neptunium to inter 1AW step, low nitric acid concentration, high nitrite concentration and low flow ratio are needed. Compared with the experimental data, the relative errors of the distribution ratios of various solutes are less than 30%, and the relative errors of the concentrations of U(VI) and Pu(IV) at the outlet of the organic phase are less than 10%, and our model is indicated to be reliable and applicable for co-decontamination step in the PUREX reprocessing process.

Synthesis and formation mechanism of pitch-based carbon foam for three-dimensional structural applications

Carbon foam is a three-dimensional porous, rigid, and permeable material with applications in many fields owing to its excellent electrical and thermal properties. Pitch is a promising carbon source for carbon foam production, and its modification with nitric and sulfuric acids has been widely investigated. However, the foaming phenomenon resulting from the acid treatment of pitch and the resultant formation of porous structures remain poorly understood. Herein, we clarified the mechanism by which the porous structure of pitch-derived carbon foam is formed by analyzing the components of pitch modified by nitric acid treatment and identifying essential conditions for foam production. Carbon foam was obtained by pitch modification at a high concentration of nitric acid (60 wt%), whereas no carbon foam was formed at low nitric acid concentrations (<60 wt%). Furthermore, at high nitric acid concentrations, carbon foam formation proceeded at a relatively low temperature (280 °C). The formation of carbon foam from modified pitch was attributed to the synergistic effect of the functional groups introduced onto pitch and the low-molecular-weight components resulting from cracking. This work provides new insights into pitch as a precursor and provides a straightforward method for producing carbon foam.

Efficient separation of americium by a mixed solvent of two extractants, a diamideamine and a nitrilotriacetamide.

The Japan Atomic Energy Agency (JAEA) has proposed the Solvent Extraction from Liquid waste using Extractants of CHON-type for Transmutation (SELECT) process by solvent extraction as a new separation technology to recover minor actinides (MA) from high-level liquid waste (HLLW) produced by spent fuel reprocessing. The MA separation in the SELECT process comprises the recovery of MA and rare earths (RE) from HLLW, MA/RE separation, and Am/Cm separation. Three highly practical extractants are used in the MA separation. Furthermore, this flow configuration facilitates the preparation of nitric acid concentrations in the aqueous phase. However, the separation factor between Cm and Nd in the MA/RE separation is small (SFCm/Nd = 2.5), requiring many extraction stages for continuous extraction in a mixer settler. Therefore, this study investigated the separation of only Am from an aqueous nitric acid solution containing MA (Am and Cm) and RE using an organic phase mixed with two extractants alkyl diamideamine with 2-ethylhexyl alkyl chains (ADAAM(EH)) and hexa-n-octylnitrilotriacetamide (HONTA) used in the SELECT process. Under high-concentration nitric acid conditions, Am and La, Ce, Pr, Nd (light lanthanides) were extracted in the ADAAM(EH) + HONTA mixed solvent, whereas Cm, medium, and heavy lanthanides, and Y were partitioned in the aqueous phase. Subsequently, only light lanthanides could be back extracted from the ADAAM(EH) + HONTA mixture solvent containing Am and light lanthanides in low nitric acid concentrations. Furthermore, Am could be easily stripped with 0.2M or 5M nitric acid. This method does not require the mutual separation of Cm and Nd, which have low separation factors. Am can be efficiently separated by one extraction and two back extractions, reducing the number of steps in the SELECT process.

Efficiency of Pre-Treated Immobilized Chara Algae (C. vulgaris) for Biosorption of Copper and Lead from Aqueous Solutions

The present study evaluates the potential of chemically modified, immobilized Chara algae (C. vulgaris) to remove copper and lead from aqueous solutions. Chara algae were prepared and studied for their ability to remove heavy metal ions prepared solutions. In a batch mode, several factors affecting the adsorption process such pH, temperature, contacting period and algal dose on adsorption efficiency were studied. Results showed that the metal adsorption process takes place quickly at pH values (5.0-6.0), temperature level (25-30) oC and the order of the accumulated metal ions is Cu&gt;pb.The results showed that the handling with low concentration of nitric acid at 0.05 normality was effective in the process of desorbing metal ions. So as for regeneration of algae, 0.2 M sodium hydroxide is very effective. The regenerative algae were used for five cycles of biosorption, without losing its demineralization efficacy. FTIR absorption spectroscopic analyzes showed that all groups that present in the algae are responsible for the main biological absorption of metal ions.Adsorption process specifications are more effective when using modification processes, as the maximum adsorption of algae for both lead and copper was within a range of 6.5-10.3 mg per gram of algae when using the alkaline treatment. While the acid treatment reduced the amount of adsorbent by 4.2-5.8 mg per gram algae; The adsorption process is fast and occurs by 90% within the first 15 min. Heavy metal adsorption was observed at very low levels at pH values as low as 2.0. Algae are effective in removing lead, copper and other light metal ions from wastewater.

Separation of Americium from a Complex Matrix by Solvent Extraction Using CyMe4BTPhen in a Room Temperature Ionic Liquid Diluent

ABSTRACT The extraction performance and mechanism of 2,9-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-benzo[1,2,4]triazin-3-yl)-1,10-phenanthroline (CyMe4BTPhen) in the room temperature ionic liquid 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim][NTf2]) have been studied and are herein reported. Americium is extracted from nitric acid solutions by cation exchange and is most efficient at low (< 1 M) nitric acid concentrations as opposed to the high (4 M) concentration preferred when using most traditional molecular diluents. The kinetics are slow, taking 24 hours to achieve quantitative extraction of americium but are greatly improved, achieving the same within 8 hours, by dilution with 1-octanol. High SFAm/Eu > 3000 were achieved although decontamination factors for americium from more complex matrices were non-competitive with extraction using traditional molecular diluents. Modest improvements in decontamination factor were attained by the addition of the hydrophilic reagent N,N,N’,N’-tetraethyl diglycolamide (TEDGA).

Recovery of Copper(II) and Silver(I) from Nitrate Leaching Solution of Industrial Dust via Solvent Extraction with LIX63

A nitrate leachate containing Cu(II), Ag(I), Ni(II), Mg(II), and Al(III) was obtained during the leaching of industrial dust, which arises during the pyrometallurgy of spent camera modules. To separate and recover Cu(II) and Ag(I) from the leaching solution, solvent extraction experiments using 5,8-diethyl-7-hydroxydodecan-6-oxime (LIX63) were conducted. LIX63 was found to selectively extract Cu(II) and Ag(I) over other metal ions (Ni(II), Mg(II), and Al(III)) at low nitric acid concentrations. The extraction efficiency of Cu(II) was more affected than that of Ag(I) by the acidity of the feed solution and the LIX63 concentration in the organic phase. Cu(II) and Ag(I) were simultaneously extracted using 2 mol/L LIX63. Cu(II) was separated from the loaded LIX63 via stripping with 4 mol/L HNO3, whereas Ag(I) was recovered via stripping with 0.1 mol/L thiourea after the removal of Cu(II). McCabe–Thiele diagrams for the extraction and stripping of Cu(II) and Ag(I) were constructed. The complete extraction of Cu(II) and Ag(I) was confirmed via counter-current extraction. Moreover, stripping simulation tests confirmed that higher than 99.99% of Cu(II) and 99.2% of Ag(I) were stripped. The purities of Cu(II) and Ag(I) in the recovered solution were 95.2% and 99.993%, respectively. A process flow chart for the recovery of Cu(II) and Ag(I) from the nitrate leachate of the target industrial dust was also provided.

Extraction of Uranium(VI) and Plutonium(IV) by New Tri Alkylcarbamides

ABSTRACT The use of tri-alkylcarbamides (TrAC) as novel extractants for the separation of uranium(VI) and plutonium(IV) by solvent extraction from spent nuclear fuels is investigated. The comparison between extraction properties of different tri-alkylcarbamides and tetra-alkylcarbamides indicates their higher ability to co-extract uranium(VI) and plutonium(IV). Moreover, tri-alkylcarbamides present very high separation factors SFU/Pu (up to 100) at lower nitric acid concentration showing that they are good candidates for U(VI)/Pu(IV) separation without redox chemistry. The addition of branched 2-ethylhexyl chains induces a decrease of distribution ratios and U/Pu separation factor. Due to the formation of intermolecular hydrogen bond between carbonyl and -NH functions, the viscosity of tri-alkylcarbamides is higher compared to tetra-alkylcarbamides. Nevertheless, the introduction of branched alkyl chains decreases the viscosity of the solvent and increases the limit organic concentration (LOC) for uranium(VI), preventing from third phase formation.

Selective uptake of thorium(IV) from nitric acid medium using two extraction chromatographic resins based on diglycolamide-calix[4]arenes: Application to thorium-uranyl separation in an actual sample

Two novel extraction chromatography resins (ECRs) containing two diglycolamide (DGA) -functionalized calix[4]arenes with n-propyl and isopentyl substituents at the amide nitrogen atom, termed as ECR-1 and ECR-2, respectively, were evaluated for the uptake of Th(IV) from nitric acid feed solutions. While both the resins were having a quite high Th(IV) uptake ability (Kd >3000 at 3 M HNO3), the uptake was relatively lower with the resin containing the isopentyl DGA, which appeared magnified at lower nitric acid concentrations. Kinetic modeling of the sorption data suggested fitting to the pseudo-second order model pointing to a chemical reaction during the uptake of the metal ion. Sorption isotherm studies were carried out showing a good fitting to the Langmuir and D-R isotherm models, suggesting the uptake conforming to monolayer sorption and a chemisorption model. Glass columns with a bed volume of ca. 2.5 mL containing ca. 0.5 g lots of the ECRs were used for studies to assess the possibility of actual applications of the ECRs. Breakthrough profiles obtained with feed containing 0.7 g/L Th(NO3)3 solution resulted in breakthrough volumes of 8 and 5 mL, respectively, for the ECR-1 and ECR-2 resins. Near quantitative elution of the loaded metal ion was possible using a solution of oxalic acid and nitric acid. A method for the separation of Th-234 from natural uranium was demonstrated for the possible application of ECR-1.

Study on the Behavior and Removal of Cadmium and Zinc Using Taraxacum officinale and Gazania under the Application of Biodegradable Chelating Agents

The removal of cadmium (Cd) and zinc (Zn) from soil by phytoremediation was investigated using Taraxacum officinale and Gazania. A plant environmental control system was used to cultivate the plants. The effects of different biodegradable chelating agents (i.e., EDDS, HIDS, and GLDA), relative humidity, and other competitive metals on the adsorption of Cd and Zn were also studied. In addition, the approach for metal recovery was explored by extraction of metals from plants after phytoremediation using Gazania. The concentrations of Cd and Zn were determined by inductively coupled plasma mass spectrometry (ICP-MS). In addition, one-way analysis of variance (ANOVA) tests were performed.to determine significant differences between the experimental treatments adopted in this work. Consequently, the following main conclusions were obtained: (1) In the case of Taraxacum officinale, Cd and Zn could be removed even under the presence of other heavy metals. (2) By adding a chelating agent, the amount absorbed by the shoot generally increased. (3) In the case of Gazania, the concentration of Cd was higher in root than that in shoot, whereas the concentration of Zn was higher in the shoot than that in the root. (4) Taraxacum officinale was more suitable for phytoremediation of Cd than Gazania. (5) Cd and Zn could be extracted from plants by adding a low concentration of nitric acid. (6) The one-way ANOVA tests showed no statistically significant differences among the experimental treatments.

CYANEX 925 As Potential Extractant For the Extraction and Separation of Zirconium (IV) And Niobium (V) From nitric acid Solution

The potential use of CYANEX 925 in kerosene for the extraction and separation of Zirconium (IV) and Niobium (V) from nitric acid solution is explored. The effects of the different parameters affecting the extraction process as extractant, metal, nitric acid and nitrate concentrations as well as temperature were separately investigated. Stripping investigations on the recovery of Zr(IV) and Nb(V) from their loaded organic solutions were also carried out. The obtained results indicate that the extracted metal species are Zr(NO‌3)‌‌4.CYANEX 925 and Nb(OH)2(NO‌3)3.CYANEX 925 for Zr(IV) and Nb(V), respectively. The difference in the extraction and stripping behavior of the investigated metals indicated that a good separation between Zr(IV) and Nb(V) could be obtained when carrying out the extraction from low nitric acid concentration at low temperature or when using 1M sulphuric acid for stripping 99% of Zr(IV) with nearly no stripping of Nb(V) from the loaded organic solution. The obtained results indicate that CYANEX 925 is a promising extractant for high extraction and separation of Zr(IV) and Nb(V) from nitric acid solution compared with other organophosphorus extractants.

Electrochemical and spectrochemical analysis of U(VI) reduction in nitric acid solutions

Abstract The reduction behaviors of U(VI) ions in nitric acid media were investigated electrochemically by cyclic voltammetrys (CVs) and square wave voltammetrys (SWVs). The electrochemical redox reactions of uranium between different oxidation states was found to proceed quasi-reversibly at 295 K. At low nitric acid concentrations and in the absence of additional chemical reductant, the reduction of U(VI) was found to be diffusion controlled. The diffusion coefficient of U(VI) was determined to be 3.30–8.83 × 10−6 cm s−1 and the activation energy for the diffusion of U(VI) was calculated as 23 kJ mol−1 by cyclic voltammetry at different temperatures. The reduction of U(VI) at relatively high nitric acid concentrations was further studied by chemical reduction (hydroxylamine, N,N-diethylhydroxylamine and acetaldoxime), potentiostatic/galvanostatic electrolysis, as well as the two ways combined (electrolysis in the presence of chemical reductants). No obvious reduction of U(VI) was observed by absorption spectroscopy when only electrolysis or chemical reductants were used. In contrast, U(VI) could be obviously reduced to U(IV) by electrolysis in the presence of chemical reductants. Moreover, hydroxylamine was found to be the best choice among the three chemical reductants used as holding reductant to ensure efficient reduction of U(VI) by electrolysis. Temperature has mixed effect on the electrolytic reduction rate as evaluated by absorption spectra.

Bifunctional Amidophosphonate Molecules for Uranium Extraction in Nitrate Acidic Media

ABSTRACT Bifunctional amidophosphonate derivatives, already known as efficient ligands in uranium extraction from phosphoric media, have been evaluated and compared to the conventional tri-n-butyl phosphate (TBP) for uranium extraction from nitrate medium. The efficiency of U extraction and its selectivity towards competing elements such as Th, Zr, Mo, Fe, and V was evaluated with various ligand structures. It was found that extractant molecules containing a monosaponified phosphonate moiety instead of phosphonate moieties are less effective and selective. Furthermore, it was observed that the alkylation of the methylene bridge linking the two functional groups prevents the formation of precipitates during the uranium loading. Effects of acidity as well as ligand concentration were also investigated in order to estimate the loading capacity of the molecules. More detailed stoichiometry and transfer energy were further determined by the slope analysis method and a thermodynamic study. The possible uranium recovery from the organic phase has moreover been demonstrated thanks to stripping steps at low nitric acid concentration.

Modeling of the Competition between Uranyl Nitrate and Nitric Acid upon Extraction with Tri-n-butyl Phosphate.

Uranium is a strategic element and plays an important role in energy resources. A H2O–HNO3–UO2(NO3)2–TBP (tri-n-butyl phosphate)–diluent system is commonly used for uranium separation and purification in liquid–liquid extraction. Uranyl nitrate is promoted by the existence of nitrate at low HNO3 concentrations but is inhibited at high HNO3 concentrations. Considering the competitive extraction between HNO3 and UO2(NO3)2, a generic extraction model is developed. The activities of components in the aqueous phase were estimated using Pitzer models. The thermodynamic equilibrium constants and Pitzer parameters were regressed by experimental data. The resulting model was able to successfully predict uranyl nitrate, nitric acid, and water extraction over a large range of conditions (U, 0–1.8 mol/L; HNO3, 0–10 mol/L; TBP, 5–100 vol %) within average absolute relative deviations of 11.2, 15.7, and 23.8%, respectively. The predicted results show that water and nitric acid were extracted as di-solvates HNO3·(TBP)2·H2O and (TBP)2·2H2O at low nitric acid concentrations, with the formation of mono-solvates HNO3·TBP and HNO3·TBP·H2O as the acid concentration increased. Uranyl nitrate was shown to be rejected from the organic phase as the formation of HNO3·TBP and HNO3·TBP·H2O in acid was extracted at high acid concentrations.

Evolution of Acid-Dependent Am3+ and Eu3+ Organic Coordination Environment: Effects on the Extraction Efficiency.

Coordination of trivalent lanthanide and actinide metal ions by lipophilic diglycolamides and phosphonic acids has been proposed for their separation through extraction from aqueous nitric acid solutions. However, the nature of M3+ coordination complexes in these combined solvent systems is not well understood, resulting in low predictability of their behavior. This work demonstrates that a combination of N,N,N',N'-tetrakis(2-ethylhexyl)diglycolamide (T2EHDGA) and weakly acidic 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) in n-dodecane exhibits a complicated extraction mechanism for Eu3+ and Am3+, which continuously evolves as a function of the aqueous phase acidity. At low aqueous phase nitric acid concentrations, M3+ ions are primarily extracted via exchange of the phosphonic acid proton and coordination with HEH[EHP]. At high aqueous phase nitric acid concentrations, HEH[EHP] remains protonated, and M3+ ions are transported to the organic phase by the coextraction of nitrate anions from the aqueous phase, thus forming complex species with T2EHDGA. At moderate acid regimes, both ligands participate in the coordination of M3+ ions and show a synergistic relationship resulting in considerable enhancement of M3+ transport into the combined solvent system over the simple sum of the individual extractants. The observed synergism is caused by differences in organic phase M3+ speciation and has a significant impact on the performance of the organic solvent. Distribution studies with Eu3+ indicate that nominally two or three T2EHDGA ligands participate in metal extraction in the presence of phosphonic acid, while nominally three diglycolamide ligands participate in the presence or absence of phosphonic acid. While synergistic behavior has been observed in many solvent-extraction processes, this system demonstrates a clear correlation between the continuously changing organic speciation of M3+ and its transport into the organic solvent. This paper reports the spectroscopic characterization of the organic phase M3+ species by IR, X-ray absorption, and visible spectroscopies. Spectroscopic evidence indicates a mixed-ligand complex, i.e., a ternary complex at the moderate acid regime, where the greatest degree of synergism is observed. Differences in synergistic extraction of Am3+ and Eu3+ at the low acid regime were observed, indicating their dissimilar extraction behavior.

Steam cracking of green diesel (C12) to BTX and olefins over silane-treated hierarchical BEA

Commercial BEA zeolite was modified under the radiation of microwave labstation with different modification strategies. Catalytic properties and textural properties were manipulated by desilication using sodium hydroxide or tetrapropyl ammonium hydroxide solution. It was found that sodium hydroxide can lead to very fragile textural properties and low catalytic activity. While tetrapropyl ammonium hydroxide is highly recommended for the improvement of textural properties, especially at long desilication time. Parent and desilicated samples were further modified by octadecyltrichlorosilane (OTS) in order to add the silane functionality to the zeolitic materials. This addition led to minimizing the textural properties of the silane-treated BEA zeolites and consequentially led to a reduction in the catalytic activity. Recovering and improving the catalytic activity and textural properties were then performed by calcining the silane-treated catalyst to combust the long-chain alkyl groups, which facilitate the formation of silica layer. Another modification strategy was found that the desilicated BEA sample can enhance the catalytic activity and catalytic stability when it treated with a low concentration of nitric acid after desilication. This modification strategy led to improving the catalytic conversion from 29% to 76%.

Selective sorption of 134Cs and 60Co radioisotopes using synthetic nanocopper ferrocyanide-SiO2 materials

New Nanocopper ferrocyanide-silica nanoparticles (SiO2-CuFe-CN) NPs were synthesized by co-condensation (one-pot) procedure; the prepared composite were characterized using FTIR, XRD, EDS and SEM. The sorption affinity of nanocopper ferrocyanide-SiO2 materials towards 134Cs and 60Co radioisotopes from aqueous and nitrate medium were extensively studied. The factors affecting the sorption process such as mixing time, pH, metal ion concentrations and temperature were conducted. The experimental isotherm data were found to fit with both Langmuir and Freundlich isotherms. The thermodynamic parameters were evaluated. The results obtained proved that (SiO2-CuFe-CN) NPs is a promising material for the remediation of low level radioactive waste solutions contains 134Cs, 60Co, 99Mo and 90Sr of relatively low nitric acid concentration. The results obtained in the application section reveals that (SiO2-CuFe-CN) NPs gives high selective sorption of 99Mo radioisotope over other radioisotopes from 0.01 M HNO3.