Strong HNO3 Research Articles

Sulphur/functionalized graphene composite as cathode for improved performance and life cycle of lithium-sulphur batteries

Over the past years, significant advantages have been introduced to upgrade the performance of lithium-sulfur battery (Li-S) batteries since their prototype in the 1960s. Due to high theoretical energy density and cost efficiency, Li-S batteries have obtained great attention and have made great progress in the last few years. In this work, we developed the sulfur-attached few-layer graphene composite (S/FLG), sulfur-attached functionalized few-layer graphene using acetic acid (S/FLG-COOH) and sulfur-attached functionalized few-layer graphene using strong acid H2SO4 and HNO3 (S/FLG-OH) as a cathode material with high sulfur loading. The material’s structure is confirmed through XRD. The surface morphology is confirmed through SEM and elemental composition has been obtained through EDAX. The functional groups are confirmed through FTIR. The defect level and number of layers are confirmed through Raman characterization with an excitation laser wavelength of 532 nm. The electrochemical performance of three cathodes is also identified through EIS, CV, and GCD characterization. Meanwhile, highly developed defects and edges found in the functionalization of few-layer graphene using the strong acid (H2SO4 and HNO3) which consists of a hydroxyl functional group (FLG-OH) serve as polysulfide reservoirs to mitigate the shuttle effect. Among these cathodes, S/FLG-OH shows a high specific capacitance of 157.4 F g−1 and when applied as a cathode host on a coin cell it obtained a voltage of about 2.6 V. Well-performed S/FLG-OH cathode was used to fabricate the Coin Cell. The fabricated Coin Cell with S/FLG-OH as the cathode shows a stable potential over 50 cycles.

Synthesis of phosphonic acid and amide functionalized core–shell magnetic composite and its mechanisms for synergistic adsorption of thorium from strongly acidic solution

To develop adsorbents for the preeminent extraction of thorium in strongly acidic solutions is very imperative, due to strong inorganic acids are frequently used in the fuel cycle of thorium. Herein, a robust core–shell magnetic nanocomposite Fe3O4@SiO2/P (MBA-VPA-AM) possessing phosphonic acid and amide was developed via distillation-precipitation copolymerization of N, N'-methylene diacrylamide (MBA), vinylphosphonic acid (VPA) with acrylamide (AM) employing Fe3O4 decorated by SiO2 (Fe3O4@SiO2) as magnetic core. Due to the synergistic effect of phosphonic acid and amide ligand, the sorbent could capture thorium from concentrated HNO3 media efficiently, and the maximum adsorption capacity (qmax) at 4 mol L−1 of HNO3 solution reached up to 232.5 mg g−1, superior to that of all magnetic sorbents reported previously. Furthermore, the sorbent displayed good selectivity towards thorium in the presence of competitive metal ions including La3+, Nd3+, and Ce3+. The excellent thorium sorption behavior in strong hydrogen nitrate solution was merely ascribed to the complexation of thorium with phosphonic acid ligand, and the amide ligand could not complex with thorium, evidenced by XPS, FT-IR and DFT method. However, the presence of amide ligand could enhance the hydrophilicity of the sorbent and the free movement degree of phosphonic acid ligand to a certain extent, both of which could help to promote the thorium sorption on the sorbent in strong HNO3 media. Besides, due to its core–shell structure and superparamagnetism, the sorbent not only exhibited excellent acidic resistance in strong acid medias, but could be magnetically recouped, which could avoid tedious centrifugation or filtration of traditional adsorbents. This work provides a novel strategy to develop magnetic sorbent for the preeminent entrapment of thorium from strong acid solutions.

An innovative pretreatment protocol to eliminate silver contamination-induced voltammetric interference on graphite-glass working electrode

In the last decades, a significant amount of research has been focused on the development of miniaturized and portable electrochemical sensors in the form of screen-printed electrodes (SPEs). When performing voltammetric measurements using SPEs, especially in the case of carbon-based electrodes, additional peaks can appear and overlap with analytes’ signals or otherwise interfere with results. Therefore, the development of pretreatment methods that enable the removal of interferences is of great importance for SPEs utilization, e.g. for sensor applications. Moreover, electrode pretreatment can also be used to improve electron transfer kinetics, including reversibility of the studied redox processes. In this work, we present the evaluation of different pretreatment methods using cyclic voltammetry and potentiostatic anodization, applied on an in-house graphite-glass composite working electrodes. With the use of X-ray photoelectron spectroscopy and scanning electron microscopy it was confirmed that the surface of working electrode was contaminated by sub-micrometer sized silver particles, which resulted in two interference peaks. Several strong acids, including H2SO4, HNO3, and HCl, as well as phosphate buffer solution, were evaluated as electrolytes for electrochemical pretreatment. A rapid, simple, and low-cost pretreatment protocol that enables the removal of the interference peaks, as well as improved voltammetric signals for [Fe(CN)6]3−/4− redox probe was developed. We propose the optimal pretreatment method in H2SO4 as a protocol that could be universally applied for carbon, carbon-glass, or similar types of SPEs before performing voltammetric experiments and/or further modifications of SPEs.

Selective capture of uranium and zirconium from strong HNO3 solution by ethenylphosphonic acid copolymerized polymer

The nuclear fuel rod contains mainly uranium (U) as the fuel and zirconium (Zr) as the cladding material. Improper disposition of the dissolved solution of the exhausted fuel rod releases radioactive acidic aqueous solution, which is a waste of U and Zr resources and also poses a great threat to the environment and living beings. The present work aims to selectively capture U and Zr from a 4 mol/L HNO3 aqueous solution in the presence of competing ions including La, Zn, Cd, Gd, Ce, Sr, Mn, Cu and Ba. Trimethylolpropane trimethacrylate (TMPTMA) copolymerized with ethenylphosphonic acid (EPA). TMPTMA improved the mesoporous character and adsorption ability of the adsorbent towards U and Zr. The synthesized polymer adsorbent was characterized by SEM, EDS, FT-IR, TGA, XRD, BET, XPS, and NMR to study the adsorption. The results indicated that the EPA-POP-2 adsorbent showed considerable adsorption capacity towards U(VI) (374.1 mg g−1) and Zr(IV) (217.4 mg g−1) in a strong HNO3 medium. Langmuir isotherm model fitted well to the experimental data, indicating that the monolayer adsorption process was dominating. The fitted pseudo-second-order (PSO) model represents that the adsorption mechanism is chemisorption. XPS, FT-IR, and DFT calculation results revealed that this adsorption capacity towards U and Zr was because of the P = O ligands present in the adsorbent. Van’t Hoff graph for U and Zr were also drawn to calculate the enthalpy, entropy, and Gibb’s free energy of the reaction. The reusability test showed that the adsorption capacity of synthesized adsorbent was high enough towards the U and Zr even after five consecutive cycles of adsorption and desorption.

Ionic liquid - melamine foam composites for capture of thorium under high acidity conditions

Thorium has received much attention for potential application as nuclear fuel, but its capture at high acidity still requires more research. Ionic liquids (ILs) have been used to capture and separate various metal elements, but ionic liquid-containing composites have little been studied for thorium separation under high acidity conditions. A novel ionic liquid-foam composite (SIL-M) was prepared by loading stimuli-responsive ionic liquid (SIL) onto melamine foam (MF), and applied to separate thorium under high acid conditions. Under experimental conditions, SIL-M showed maximum adsorption capacity for thorium was 269 mg g−1 with an excellent selectivity for thorium over transition metals and lanthanide metals in 1 M HNO3 (S > 2 × 103). Studies revealed that PO was complexed with thorium, which also explained the high adsorption capacity and selectivity of SIL-M for thorium under high acidity within 4 cycles. Theoretical calculations were used to reveal that the reason why SIL can maintain high separation efficiency of thorium under high acidity conditions is due to the electrostatic potential of SIL is more positive. This study explored the possibility of using ionic liquid composite materials to capture thorium under strong HNO3 media, and provided ideas for designing thorium capture materials under high acidity conditions.

Synthesis of core–shell magnetic nanocomposite bearing phosphonic acid ligand for uranium extraction from strong HNO3 solution

Recovery of uranium from strong acid media using magnetic nanomaterials as sorbents is vital for sustainable nuclear energy, due to their superparamagnetism and large specific surface energy. However, it remains a huge challenge to develop magnetic nanomaterials for extracting uranium from strong acid media, since magnetic nanomaterials often suffer from poor structural stability and low uranium adsorption performance in strong acid media. Herein, a novel core–shell magnetic nanocomposite Fe3O4@SiO2/P (MBA-VPA) bearing phosphonic acid was fabricated by distillation-precipitation polymerization of N, N'-methylene diacrylamide (MBA) with vinylphosphonic acid (VPA) around the surface of Fe3O4 decorated by SiO2 (Fe3O4@SiO2). By optimizing the polymerization system, high concentration of phosphonic acid with high free movement degree was led into the surface of the sorbent. Under applied conditions (c(H+) = 4 mol L−1, T = 298 K and t = 3 h), the sorbent showed a record-breaking maximum adsorption capacity (qmax) of 262.5 mg g−1 with an excellent selectivity for uranium in the presence of multi-ions. The adsorption capacity of the sorbent in strong HNO3 increased remarkably with increase of the concentration and free movement degree of phosphonic acid. By coating Fe3O4 with an inert SiO2, the sorbent exhibited excellent acidic resistance in strong HNO3. The sorbent could also be magnetically recovered within 15 s, and repeated at least six times without obvious reduction in adsorption capacity. The excellent adsorption performance in strong HNO3 media was primarily assigned to the abundant accessible PO groups, evidenced by X-ray photoelectron spectroscopy (XPS), control experiments and density functional theory (DFT). Most importantly, this work provides a new perspective for developing highly active, excellent acidic resistance, and recyclable magnetic nanomaterials for extracting uranium from strong acid media.

Separation and recovery of Th(IV) from rare earth and other cation solutions using pH-responsive ionic liquids at high acidity condition of 1 M HNO3

Thorium has received widespread attention as a potential nuclear fuel alternative, but it is still a difficult task to extract thorium from strong HNO3 media. Meanwhile, stimulus-responsive materials have received extensive attention in the field of separation due to their special properties. Herein, we designed and synthesized a new type of stimulus responsive ionic liquid (SIL) material and applied it to solve the problem of low thorium extraction efficiency in strong HNO3 media. By utilizing the pH-response performance of SIL, a SIL and thorium complex (SILTh) is found to self-assemble and precipitate out from solution upon simple adjustment of the pH. We found that the extraction efficiency of thorium can reach 99.6% under high acidity and that it can be even higher than 98.8% when the temperature changes. Under experimental conditions, SIL showed a record-breaking maximum extraction capacity for thorium (644.2 mg g−1) with an excellent selectivity for thorium over lanthanide and transition metal in 1 M HNO3 (S>1400). Studies reveal that PO is complexed with thorium, which also explains the high adsorption capacity and selectivity of SIL for thorium under high acidity. Moreover, the pH-response characteristics of SIL are reversible. The pH-responsive SIL material and the extracted thorium can be recovered, and SIL also shows an excellent recycling ability over five cycles, with extraction and recovery efficiencies for Th(IV) of 98.0% and 98.7%, respectively within five cycles, indicating that the material has a good recycling ability. This study explores the possibility of using pH-responsive materials to recover thorium in strong HNO3 media, and provides ideas for the design and synthesis of new materials for the recovery of thorium.

Polystyrene-Fe3O4-MWCNTs Nanocomposites for Toluene Removal from Water.

In this research, multi-walled carbon nanotubes (MWCNTs) were functionalized by oxidation with strong acids HNO3, H2SO4, and H2O2. Then, magnetite/MWCNTs nanocomposites were prepared and polystyrene was added to prepare polystyrene/MWCNTs/magnetite (PS:MWCNTs:Fe) nanocomposites. The magnetic property of the prepared nano-adsorbent PS:MWCNTs:Fe was successfully checked. For characterization, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and BET surface area were used to determine the structure, morphology, chemical nature, functional groups, and surface area with pore volume of the prepared nano-adsorbents. The adsorption procedures were carried out for fresh MWCNTs, oxidized MWCNTs, MWCNTs-Fe, and PS:MWCNTs:Fe nanocomposites in batch experiments. Toluene standard was used to develop the calibration curve. The results of toluene adsorption experiments exhibited that the PS:MWCNTs:Fe nonabsorbent achieved the highest removal efficiency and adsorption capacity of toluene removal. The optimum parameters for toluene removal from water were found to be 60 min, 2 mg nano-sorbent dose, pH of 5, solution temperature of 35 °C at 50 mL volume, toluene concentration of 50 mg/L, and shaking speed of 240 rpm. The adsorption kinetic study of toluene followed the pseudo-second-order kinetics, with the best correlation (R2) value of 0.998, while the equilibrium adsorption study showed that the Langmuir isotherm was obeyed, which suggested that the adsorption is a monolayer and homogenous.

Highly efficient extraction of uranium from strong HNO3 media achieved on phosphine oxide functionalized superparamagnetic composite polymer microspheres

The magnetic adsorbent Fe3O4@SiO2/P(TRIM–VPA) developed by distillation–precipitation polymerization not only shows good adsorption efficiency for uranium in strong HNO3 media, but also has strong acid resistance in strong HNO3 solution.

Highly Energy-Efficient Vanadium Redox Flow Batteries with Thermo-Chemically Activated Graphite Felt Electrodes

The Vanadium Redox Flow Battery (VRFB) is a promising energy storage technology for large scale stationary applications that require a long cycle life of over 10 years. The specific feature of VRFB is the slower kinetics of redox reactions (V2+/V3+) on the negative electrode (NE) as compared to the kinetics of the redox reaction (VO2 + /VO2+) on the positive electrode (PE) and poor kinetic reversibility.. The commonly used electrodes for VRFBs are graphite felt electrodes (GFE). One of the main challenges facing these GFEs is their activation that enhances a rate of redox reactions due to the increase of GFE wettability and surface area. Another challenge is capability to maintain GFE activation over cycling.In this work, we report on thermal and thermo-chemical activation of GFEs which leads to the formation of functional groups (carboxyl C=O, phenolic C-O, and adsorbed O or H2O for the enhancement of the electrode wettability and active surface area. The physicochemical characterization of the activated GFEs was performed using X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The electrochemical study was conducted by cyclic voltammetry (CV) measurements in 0.2M VOSO4/2M H2SO4 at 1 mV/s and cycling tests (50 cycles, three tests for every GFE) in a commercial 9cm2 VRFB ( Standard Energy Corp.) using a charge/discharge current density of 80 mA/cm2 at 20oC and a commercial vanadium electrolyte 1.6M [V]/2M H2SO4. The increase of temperature of GFE heat treatment of GFEs from 400 to 500oC resulted in the growth of the energy efficiency (EE) of VRFBs with such electrodes from 81.3 to 87.2%, respectively, due to the increase of adsorbed oxygen or water from 1.6 to 8.72% and C-O (C-OH) groups from 0.49 to 2.09%, respectively and wettability (contact angle (CA) decreases from 78.7 to 65.1o). Analysis of CVs of the redox reaction VO2 + /VO2+ shows the decrease of the peak of potential separation ΔEp (Epa-Epc) from 0.357 to 0.345 V and the peak of current ratio (Jpa/Jpc) from 1.406 to 1.26, indicating lower polarization due to the increase of the electrode surface area, acceleration and reversibility of these redox reaction, respectively (Table 1). The proposed additional treatment of the heat treated GFE at 400oC (GFE400) in strong oxidants H2O2, H2SO4 and HNO3 for the decomposition of C=O and the enhancement of the content C-O groups and GFE wettability didnt result in the performance improvement (VRFB with GFE400+10%H2O2 - energy efficiency of 78%).The thermal treatment of GFE at 500oC demonstrated improvement of VRFB cell performance, namely growth of energy efficiency to 87.2% and VE to 90.1%, % due to the increase of wettability and active surface area of GFEs. Figure 1

Effect of biochar modified with magnetite nanoparticles and HNO3 for efficient removal of Cr(VI) from contaminated water: A batch and column scale study

Chromium (Cr) poses serious consequences on human and animal health due to its potential carcinogenicity. The present study aims at preparing a novel biochar derived from Chenopodium quinoa crop residues (QBC), its activation with magnetite nanoparticles (QBC/MNPs) and strong acid HNO3 (QBC/Acid) to evaluate their batch and column scale potential to remove Cr (VI) from polluted water. The QBC, QBC/MNPs and QBC/Acid were characterized with SEM, FTIR, EDX, XRD as well as point of zero charge (PZC) to get an insight into their adsorption mechanism. The impact of different process parameters including dose of the adsorbent (1–4 g/L), contact time (0–180 min), initial concentration of Cr (25–200 mg/L) as well as solution pH (2–8) was evaluated on the Cr (VI) removal from contaminated water. The results revealed that QBC/MNPs proved more effective (73.35–93.62-%) for the Cr (VI) removal with 77.35 mg/g adsorption capacity as compared with QBC/Acid (55.85–79.8%) and QBC (48.85–75.28-%) when Cr concentration was changed from 200 to 25 mg/L. The isothermal experimental results follow the Freundlich adsorption model rather than Langmuir, Temkin and Dubinin-Radushkevich adsorption isotherm models. While kinetic adsorption results were well demonstrated by pseudo second order kinetic model. Column scale experiments conducted at steady state exhibited excellent retention of Cr (VI) by QBC, QBC/MNPs and QBC/Acid at 50 and 100 mg Cr/L. The results showed that this novel biochar (QBC) and its modified forms (QBC/Acid and QBC/MNPs) are applicable with excellent reusability and stability under acidic conditions for the practical treatment of Cr (VI) contaminated water.

Highly Efficient Removal of Thorium in Strong HNO3 Media Using a Novel Polymer Adsorbent Bearing a Phosphonic Acid Ligand: A Combined Experimental and Density Functional Theory Study.

It is an important task to develop the technologies for the extraction of thorium from strong HNO3 media with high efficiency. In this work, solvothermal polymerization of trimethylolpropane trimethacrylate (TRIM) and vinylphosphonic acid (VPA) has been used to synthesize a novel polymer material P (TRIM-VPA) bearing a phosphonic acid ligand for thorium entrapment in strong HNO3 media. Under the current experiment condition, the polymer adsorbents showed a record-breaking maximum adsorption capacity for thorium (403.2 mg g-1) with an excellent selectivity for thorium over Gd(III), Nd(III), Ce(III), Sr(III), Sm(III), and La(III) in 4 mol L-1 HNO3 media at 298 K. The content of P═O ligands existing on P (TRIM-VPA) has an obvious influence on the adsorption capacities for thorium. Increasing the content of P═O ligands would result in higher adsorption capacity of thorium. The isothermal data fitted well the Langmuir model, and the sorption kinetics fitted the pseudo-second-order model. The adsorption behavior was not only spontaneous but also endothermic in reality. Both XPS and FTIR studies revealed that the adsorption interaction for thorium extraction was acquired only via the coordination of P═O groups anchored on P (TRIM-VPA) with thorium. Moreover, P (TRIM-VPA) still had high adsorption capacity after five sorption-desorption cycles in 4 M HNO3 media. DFT calculation suggested that a 1:2 ratio of Th(IV) with the P═O group on the same graft chain validated the experimental findings. Thus, the solvothermal polymerization method might be a promising way for the synthesis of the adsorbents for the highly efficient extraction of thorium from strong HNO3 media.

Ion-Imprinted Mesoporous Silica for Selective Removal of Uranium from Highly Acidic and Radioactive Effluent.

It is strategically important to recycle uranium from radioactive liquid wastes for future uranium supply of nuclear energy. However, it is still a challenge to adsorb uranium selectively from highly acidic and radioactive waste. In this paper, we report a novel strategy for effective uranium removal from highly acidic and radioactive media by surface ion-imprinted mesoporous silica sorbent. The sorbent was successfully synthesized by a co-condensation method with uranyl as the template ion and diethylphosphatoethyltriethoxysilane as the functional ligands. The pseudo-second-order model and Langmuir model showed better correlation with the sorption kinetic and isotherm data, and the sorption equilibrium could be reached within 40 min, the maximum adsorption capacity from Langmuir model was 80 mg/g in 1 mol/L nitric acid (HNO3) solution at 298.15 K. The sorbent showed faster kinetics and higher selectivity toward uranium over other ions compared with nonimprinted mesoporous and other previous sorbents. Furthermore, the ion-imprinted materials exhibited remarkable radioresistance stability and could be regenerated efficiently after five cycles. This work may provide a new approach for highly efficient sorption of uranium from strong HNO3 and radioactive media.

Highly selective adsorption of uranium in strong HNO3 media achieved on a phosphonic acid functionalized nanoporous polymer

The competition between uranium and other metal ions is one of the greatest challenges for recovery of uranium in strong HNO3 media.

HgNO3 sensitivity of AlGaN/GaN field effect transistors functionalized with phytochelating peptides

This study examined the conductance sensitivity of AlGaN/GaN field effect transistors in response to varying Hg/HNO3 solutions. FET surfaces were covalently functionalized with phytochelatin-5 peptides in order to detect Hg in solution. Results showed a resilience of peptide-AlGaN/GaN bonds in the presence of strong HNO3 aliquots, with significant degradation in FET ID signal. However, devices showed strong and varied response to Hg concentrations of 1, 10, 100, and 1000 ppm. The gathered statistically significant results indicate that peptide terminated AlGaN/GaN devices are capable of differentiating between Hg solutions and demonstrate device sensitivity.

Magnetic solid-phase extraction of strontium using core–shell structured magnetic microspheres impregnated with crown ether receptors: a response surface optimization

A new kind of core–shell structured magnetic microspheres impregnated with di-tert-butyl cyclohexano-18-crown-6 (DtBuCH18C6) receptors in the encapsulation layer was developed in this study, and was utilized for selective removal of strontium in strong HNO3 solutions via magnetic solid-phase extraction (MSPE). The magnetic microspheres, labelled as Fe3O4@SiO2@DtBuCH18C6, exhibited good magnetism (M s = 52.2 emu g−1), fast response under applied magnetic field and easy redispersion ability due to the superparamagnetic nature. Adsorption behaviors and mechanism were comprehensively studied, showing that the adsorption of Sr(II) by Fe3O4@SiO2@DtBuCH18C6 was most likely to be a monolayer chemisorption process via forming complexation between the crown ether receptors and Sr(II) (i.e. Langmuir model). More importantly, central composite design based on response surface methodology was utilized for optimizing the operational conditions of the adsorption process. A quadratic model was obtained to describe the relationship between adsorption capacity and the independent factors such as initial Sr(II) concentration, HNO3 concentration etc. The simulated model well predicted the optimum HNO3 concentration (~1.7 mol L−1) to achieve the best Sr(II) adsorption capacity. On this basis, a conceptual MSPE process was proposed for an effective separation of strontium in simulated high level liquid wastes.

Removal of cadmium and lead from heavy metals loaded PVA–SA immobilized Lentinus edodes

This study, relates to results of Cd(II) and Pb(II) adsorption and removal efficiency from polyvinyl alcohol–Na-alginate (PVA–SA) immobilizing cells of Shi-take mushroom (Lentinus edodes) by H2SO4, HNO3, HCl, Na2CO3, NaHCO3, and NH4Cl solutions. Of these desorbing agents, H2SO4, HNO3, and HCl had strong desorbing potential, while HCl and HNO3 did better. The bio-sorbent particles, after desorption by both H2SO4 and HNO3 were found to be corroded. H2SO4 solution was most severe and it caused formation of amorphous matter at the surface that wrapped bio-sorbent particles and caused their round-shape coagulation. This membranes formed, further blocked desorption of Cd(II)/Pb(II). After desorption by HNO3, the particles were broken down due to strong oxidative power of the acid itself; while no obvious surface corrosion happened after desorption of the bio-sorbent particles when HCl was used as desorption agent. Since HCl solution had a weak influence on the bio-sorbent’s surface features, this acid was used as desorbing agent. An optimal time at equilibrium for Pb(II) desorption by 1 mol/L HCl was 90 min and for Cd(II) by 0.1 mol/L HCl was 60 min, with maximum efficiency of 90% and 81%, respectively. The pseudo-second-order model well-fitted to Cd(II)/Pb(II) desorption rates and the correlation coefficients (R2) were 0.9989 and 0.9969, respectively. From trial to trial as regeneration of bio-sorbent continued, its absorptive potential gradually weakened. Nevertheless, after three regeneration trials, the absorptive potential of reused bio-sorbent still reached 69% for Cd(II) and 85% for Pb(II), and what was displayed is that the immobilizing technology with the abandoned stipe of Shi-take mushroom can be feasible in practical application. After Pb(II) bio-sorption, the surface of bio-sorbent became rich in Pb(II) and energy spectra confirmed that the crystals found in scanning electron microscope (SEM) analysis were Pb(II) salts. On the other side, the spectral peak from Cd(II) was not as clear as from Pb(II). After desorption phase of Pb(II) and Cd(II), there were no spectral peaks from these heavy metals at the surface of the regenerated bio-sorbent.

The Application of Modified Multi-Wall Carbon Nano-Tube Particles in PCM as the Nucleating Agent

Paraffin waxes as the phase change materials (PCM) usually tend to become supercooled in their crystallization processes, which limits their applications. As a solution, the modified multi-wall carbon nanotube (MWCNT) particles were dispersed in PCM as the nucleating agent to effectively reduce the super cooling, oxidized by strong acids H2SO4 and HNO3 to increase the compatibility with the organic liquid. In this study, the n-hexadecane-1-decanol slurry with modified MWCNT in different concentration was prepared and analyzed. Thermal analysis by differential scanning calorimeter (DSC) indicated that the super cooling of PCM was significantly decreased. The effective ranges of nucleating agent concentration were summarized which provided a promising way of improving the performance of system energy efficiency in building cooling and heating applications.

SYNTHESIS OF MESOIONIC 3-ARYL(HETARYL)-1,2,3,4-OXATRIAZOL-5-ONES BASED ON N-ARYL- AND N-HETARYLHYDRAZONES OF BROMONITROFORMALDEHYDE

Dehydrobromination of N-arylhydrazones of bromonitroformaldehyde (at 20°C) in the presence of alkali and ammonium salts of strong mineral acids, HNO3, silica gel, and Al2O3 forms mesoionic 3-aryl-1,2,3,4-oxatriazol-5-ones (3-arylazasydnones). The effect of the electronic properties of the aryl substituent on the course of the reaction is evaluated. This evaluation is used to develop a general method for preparing 3-arylazasydnones with various substituents including novel 3-hetarylazasydnone derivatives of pyrazole, 1,2,4-triazole and pyridine. Aromatic electronic effects (s I , s R , s m , s p ) of the mesionic 1,2,3,4-oxatriazol-5-on-3-yl moiety are determined by 19F NMR. A scheme is proposed for the dehydrobromination of the bromonitroformaldehyde N-arylhydrazones that includes the intermediate N-aryl-C-(nitro)nitrilimines, ArN – – N=C + NO 2 , with subsequent isomerization of the latter into 3-arylazasydnones. Authors: S. A. Shevelev, I. L. Dalinger, V. I. Gulevskaya, T. I. Cherkasova, V. M. Vinogradov, B. I. Ugrak, and A. M. Starosotnikov. English Translation in Chemistry of Heterocyclic Compounds , 1999, 35 (3), pp 363-373 http://link.springer.com/article/10.1007/BF02259369

Novel mesoporous silicas bearing phosphine oxide ligands with different alkyl chains for the binding of uranium in strong HNO3 media

A new class of mesoporous silicas functionalized with varieties of alkylphosphine oxide ligands was developed via the post-derivatization of a vinyl-anchored precursor. The mesoporous silicas showed effective adsorption towards uranium in strong HNO3 solutions, which is of importance for the uranium recovery in radioactive liquid waste (RLW).