Selective and highly efficient removal of uranium from radioactive effluents by activated carbon functionalized with 2-aminobenzoic acid as a new sorbent.

The purpose of this study was modification of activated carbon (AC) to prepare a new selective sorbent for removal of uranium ion. The modification was performed by introducing carboxyl groups onto AC using ammonium persulfate (APS) in sulfuric acid solution followed by functionalization with 2-aminobenzoic acid (ABA) as a selective ligand for U (VI) ion (UO22+) adsorption. The characterization of the synthetized sorbent (AC-ABA) was carried out through several methods including potentiometry, scanning electron microscopy, energy dispersive spectroscopy, x-ray diffraction and FT-IR to confirm successful functionalization of the sorbent surface with oxygen and amine groups. The sorption of U (VI) on the unmodified AC and AC-ABA was investigated as a function of contact time, sorbent content, initial uranium concentration, solution pH, and temperature using batch sorption technique. In addition, the effect of various parameters on the U (VI) sorption capacity was optimized by the response surface methodology as a potent experimental design method. The results indicated that sorption of U (VI) under the optimal conditions was significantly improved onto AC-ABA compared to AC. Kinetic studies displayed that the sorption process reached equilibrium after 100 min and followed the pseudo-second-order rate equation. The isothermal data fitted better with the Langmuir model than the Freundlich model. The maximum sorption capacity of AC-ABA for U(VI) was obtained to be 194.2 mg g-1 by the Langmuir model under optimum conditions, which demonstrates the sorption capacity has been improved by the modification process. The thermodynamic parameters (ΔH, ΔS and ΔG) indicated that sorption of uranium onto AC-ABA was an endothermic and spontaneous process. The sorption studies on radioactive effluents of the nuclear fuel plant represented high selectivity of AC-ABA for removal of uranium in the presence of other metal ions, and the selectivity coefficients significantly improved after modification of the sorbent. Application of AC-ABA for treatment of industrial effluents containing heavy and radioactive metal ions show high potential and capability of the proposed method.

Efficient removal and recovery of uranium from industrial radioactive wastewaters using functionalized activated carbon powder derived from zirconium carbide process waste.

Development of efficient sorbents for selective removing and recovery of uranium from radioactive wastewaters is highly important in nuclear fuel industries from the standpoint of resource sustainability and environmental safety issues. In this study, carbon powder waste was modified by various chemical activating agents under atmosphere of nitrogen gas at 725 °C to prepare an efficient sorbent for removal and recovery of uranium ions from radioactive wastewaters of nuclear fuel conversion facility. Activation of the carbon powder with KOH, among different activators, provided maximum porosity and surface area. The activated samples were modified by reacting with ammonium persulfate in sulfuric acid solution to generate surface functional groups. The synthetized sorbents were characterized with FT-IR, XRD, BET, and SEM-EDS techniques. The effects of solution pH, contact time, initial uranium concentration, and temperature on the sorption capacity of the sorbent with respect to U(VI) from wastewater were investigated by batch method, followed by optimizing the effect of influential parameters by experimental design using central composite design. The sorption of UO22+ ions on the sorbents follows the Langmuir isotherm and pseudo-second-order kinetic models. Maximum sorption capacity for U(VI) was 192.31 mg g-1 of the modified sorbent at 35 °C. Thermodynamic data showed that sorption of U(VI) on the sorbent was through endothermic and spontaneous processes. The sorption studies on radioactive effluents of the nuclear industry demonstrated that the modified sorbent had a favorable selectivity for uranium removal in the presence of several other metal ions.

Synthesis of ion-imprinted polymer-decorated SBA-15 as a selective and efficient system for the removal and extraction of Cu(ii) with focus on optimization by response surface methodology.

Ion-imprinted polymer-decorated SBA-15 (SBA-15-IIP) for the adsorption of copper was synthesized and characterized using different techniques, including FT-IR, XRD, TG/DTA, SEM, BET, and TEM. It was used as a green, efficient and rapid sorbent for the removal of Cu(ii) from aqueous solution. The effect of several parameters on the removal percentage of copper was studied using the central composite design. The equilibrium data were investigated using the Langmuir and Freundlich isotherm models, and found to be well-fitted by the Langmuir model with the maximum adsorption capacity of 322.58 mg g-1. The adsorption kinetics was investigated using four models, and found to be well-fitted by the pseudo-second-order model. Also, the recyclability of SBA-15-IIP was studied, and the results after 6 cycles demonstrated that SBA-15-IIP was a promising sorbent for the removal of Cu(ii) from aqueous solution. Subsequently, SBA-15-IIP was used as an efficient and selective sorbent for the extraction of Cu(ii). Various parameters affecting the extraction efficiency of the analyte were investigated and optimized using the Box-Behnken design. The optimized methodology presented good linearity between 0.2 and 100 µg L-1 (R2 > 0.9946) and a detection limit of 0.05 µg L-1. The method had an enhancement factor of 220 and relative standard deviation (RSD) of 3.1% and 4.5% for intra-day and inter-day, respectively.

Decolorization of crystal violet from aqueous solutions by a novel adsorbent chitosan/nanodiopside using response surface methodology and artificial neural network-genetic algorithm.

A novel adsorbent of chitosan/nanodiopside nanocomposite (CS-NDIO) was synthesized as a green composite for the removal of crystal violet (CV) and characterized by techniques like XRD, FT-IR, BET, and FESEM analysis. The influence of parameters like molar ratios of CS to NDIO, initial pH of the solution, dosage of adsorbent, initial concentration of CV and contact time was investigated and evaluated by central composite design (CCD; 5 levels and 4 factors). Also, Hybrid model of (ANN) model with genetic algorithm (GA) optimization was applied to the experimental data get through CCD. The optimized molar ratio of CS-NDIO was found: 20/80. Optimal parameter choice for maximum CV adsorption process using CCD and ANN-GA were as follows: pH = 7.50 and 7.499, adsorbent mass: 0.0077 and 0.0077 g, CV concentration: 20.000 and 20.002 mg/L, and contact time: 25.00 and 25.00 min, respectively. The evaluation adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (qmax: 104.66 mg g-1 and R2: 0.9937) and pseudo-second order kinetics mechanism (R2: 0.9978). Thermodynamic parameters (R2: 0.9180, ΔH°: -74.93 kJ mol-1, ΔG°: -12.89 kJ mol-1, and ΔS°: 0.93 kJ mol-1 K-1) were calculated and indicating adsorption to be an exothermic and spontaneous process.

Efficient removal of crystal violet from aqueous solutions with Centaurea stem as a novel biodegradable bioadsorbent using response surface methodology and simulated annealing: Kinetic, isotherm and thermodynamic studies.

The novel green bioadsorbent, Centaurea stem, was utilized for crystal violet removal from aqueous solutions. SEM and FT-IR were used for characterization of Centaurea stem. The effects of the pH, time, temperature, bioadsorbent amount, and initial dye concentration were investigated. Response surface methodology was used to depict the experimental design and the optimized data of pH 12.57, time 19.661, temperature 38.94 °C, amount of bioadsorbent 12.218 mg, and initial dye concentration 36.62 mg L-1 were achieved. Moreover, artificial neural network (ANN) and simulated annealing (SA) were applied for prediction and optimization of the process respectively. The SA acquired optimum conditions of 10.114, 7.892 min, 25.127 °C, 64.405 mg L-1, 14.54 mg for pH, time, temperature, initial dye concentration, and bioadsorbent amount, respectively which were more close to the experimental results and indicated higher ability of SA-ANN in prediction and optimization of the process. The adsorption isotherms confirm the experimental data were appropriately fitted to the Langmuir model with high adsorption capacity of 476.190 mg g-1. The thermodynamic parameters were evaluated. The positive ΔH° and ΔS° values described endothermic nature of adsorption. The adsorption of crystal violet followed the pseudo-second order kinetic model.

A study of donor-acceptor in the charge transfer molecular complexes of some thiacrown ethers with dihalogen molecules by DFT method.

The molecular complexes of 1,3,5-trithiane, (TT), tetrathia-8-crown-4, (TT8C4), and trithia-9-crown-3 , (TT9C3) with dihalogens in the ground state were investigated in the gas and dicholoromethane phases using B3LYP method and 6-31G** and 6-31+G** bases sets. In both TT and TT8C4 complexes, it is predicted that charge transfer takes place from the dihalogen to the thiacrown ether molecule; the magnitude trend of the total CT was ICl > IBr > I2, and Cl2 > Br2 > I2, respectively. There was not such a trend with TT9C3. The frequency analysis showed that all complexes in the excited state were unstable. The analysis of natural bond orbitals and comparison of the calculated thermodynamic quantities of the complexes between the gas phase and tetrachloromethane solution confirmed the results.

Monitoring of the Physical and Chemical Properties of a Gasoline Engine Oil during Its Usage.

Physicochemical properties of a mineral-based gasoline engine oil have been monitored at 0, 500, 1000, 2000, 3500, 6000, 8500, and 11500 kilometer of operation. Tracing has been performed by inductively coupled plasma and some other techniques. At each series of measurements, the concentrations of twenty four elements as well as physical properties such as: viscosity at 40 and 100°C; viscosity index; flash point; pour point; specific gravity; color; total acid and base numbers; water content have been determined. The results are indicative of the decreasing trend in concentration of additive elements and increasing in concentration for wear elements. Different trends have been observed for various physical properties. The possible reasons for variations in physical and chemical properties have been discussed.

Using molecular structure for reliable predicting enthalpy of melting of nitroaromatic energetic compounds.

In this work, a reliable simple method has been introduced for predicting enthalpy of melting of nitroaromatic energetic compounds through their molecular structures. This method can be used for a wide range of nitroaromatics including halogenated nitroaromatic compounds. The contribution of hydrogen bonding and polar groups as well as structural parameters can be used to improve the predicted values on the basis of the number of carbon, nitrogen and oxygen atoms. The predicted results show that this method gives reliable prediction of standard enthalpy of melting with respect to the best available methods for different nitroaromatic compounds including high explosives with complex molecular structures.

Reliable prediction of electric spark sensitivity of nitramines: a general correlation with detonation pressure.

For nitramines, a general correlation has been introduced to predict electric spark sensitivity through detonation pressure. New method uses maximum obtainable detonation pressure as a fundamental relation so that it can be corrected for some nitramines which have some specific molecular structure. There is no need to use crystal density and heat of formation of nitramine explosives for predicting detonation pressure and electric spark sensitivity. The predicted electric spark sensitivities are compared with calculated results on the basis of quantum mechanical computations for some nitramines that latter can be applied. The root mean square (rms) deviations from experiment for new method and the predicted results of complicated quantum mechanical method are 1.18 and 3.49J, respectively.

Nanoparticles of zinc sulfide doped with manganese, nickel and copper as nanophotocatalyst in the degradation of organic dyes.

Nanoparticles of zinc sulfide as undoped and doped with manganese, nickel and copper were used as photocatalyst in the photodegradation of methylene blue and safranin as color pollutants. Photoreactivity of doped zinc sulfide was varied with dopant, mole fraction of dopant to zinc ion, pH of solution, dosage of photocatalyst and concentration of dye. The characterization of nanoparticles was studied using X-ray powder diffraction (XRD) patterns and UV-vis spectra. The maximum degradation efficiency was obtained in the presence of Zn(0.98)Mn(0.02)S, Zn(0.94)Ni(0.06)S and Zn(0.90)Cu(0.10)S as nanophotocatalyst. The effect of dosage of photocatalyst was studied in the range of 20-250 mg/L. It was seen that 150.0 mg/L of photocatacyst is an optimum value for the dosage of photocatalyst. The most degradation efficiency was obtained in alkaline pH of 11.0 with study of photodegradation in pH amplitude of 2-12. The degradation efficiency was decreased in dye concentrations above of 5.0 mg/L for methylene blue and safranin dyes. In the best conditions, the degradation efficiency was obtained 87.3-95.6 and 85.4-93.2 for methylene blue and safranin, respectively.

Highly sensitive sensor for picomolar detection of insulin at physiological pH, using GC electrode modified with guanine and electrodeposited nickel oxide nanoparticles.

The electrochemical behavior of insulin at glassy carbon (GC) electrode modified with nickel oxide nanoparticles and guanine was investigated. Cyclic voltammetry technique has been used for electrodeposition of nickel oxide nanoparticles (NiOx) and immobilization of guanine on the surface GC electrode. In comparison to glassy carbon electrode modified with nickel oxide nanoparticles and bare GC electrode modified with adsorbed guanine, the guanine/nickel oxide nanoparticles/modified GC electrode exhibited excellent catalytic activity for the oxidation of insulin in physiological pH solutions at reduced overpotential. The modified electrode was applied for insulin detection using cyclic voltammetry or hydrodynamic amperometry techniques. It was found that the calibration curve was linear up to 4muM with a detection limit of 22pM and sensitivity of 100.9pA/pM under the optimized condition for hydrodynamic amperometry using a rotating disk modified electrode. In comparison to other electrochemical insulin sensors, this sensor shows many advantages such as simple preparation method without using any special electron transfer mediator or specific reagent, high sensitivity, excellent catalytic activity at physiological pH values, short response time, long-term stability and remarkable antifouling property toward insulin and its oxidation product. Additionally, it is promising for the monitoring of insulin in chromatographic effluents.

Predicting activation energy of thermolysis of polynitro arenes through molecular structure.

The paper presents a new method for activation energy or the Arrhenius parameter E(a) of the thermolysis in the condensed state for different polynitro arenes as an important class of energetic molecules. The methodology assumes that E(a) of a polynitro arene with general formula C(a)H(b)N(c)O(d) can be expressed as a function of optimized elemental composition as well as the contribution of specific molecular structural parameters. The new method can predict E(a) of the thermolysis under conditions of Soviet Manometric Method (SMM), which can be related to the other convenient methods. The new correlation has the root mean square (rms) and the average deviations of 13.79 and 11.94kJ/mol, respectively, for 20 polynitro arenes with different molecular structures. The proposed new method can also be used to predict E(a) of three polynitro arenes, i.e. 2,2',2'',4,4',4'',6,6',6''-nonanitro-1,1':3',1''-terphenyl (NONA), 3,3'-diamino-2,2',4,4',6,6'-hexanitro-1,1'-biphenyl-3,3'-diamine (DIPAM) and N,N-bis(2,4-dinitrophenyl)-2,4,6-trinitroaniline (NTFA), which have complex molecular structures.

Novel correlation for predicting impact sensitivity of nitroheterocyclic energetic molecules.

A novel correlation is introduced for predicting impact sensitivity of a variety nitroheterocyclic molecular types, such as nitropyridines, nitroimidazoles, nitropyrazoles, nitrofurazanes, nitrotriazoles and nitropyrimidines. This approach is based on elemental composition and two structural parameters of C(a)H(b)N(c)O(d) nitroheterocyclic energetic compounds. The results for mentioned compounds are compared with complex neural networks computations which use compositional and topological descriptors. Root mean square (rms) of deviation of different nitroheterocyclic molecules including nitropyridines, nitroimidazoles, nitropyrazoles, nitrofurazanes, nitrotriazoles and nitropyrimidines are 58 and 71cm for new correlation and neural networks computations methods, respectively.

Prediction of shock sensitivity of explosives based on small-scale gap test.

A new method is described to predict shock sensitivity of C(a)H(b)N(c)O(d) explosives without using any experimental data. It can determine shock sensitivity based on small-scale gap test as the pressure required to initiate material pressed to 90%, 95% and 98% of theoretical maximum density. Three essential parameters would be needed in the new scheme which contain a+b/2-d, the existence of alpha-C-H linkage in nitroaromatic compounds or NNO(2) functional group and difference of the number of amino and nitro groups attached to aromatic ring. Predicted shock sensitivities in some well-known explosives have a root mean square (rms) deviation of 3.97, 4.02 and 5.89kbar of experiment to initiate pressure of material pressed to 90%, 95% and 98% of theoretical maximum density, respectively.

The simplest method for calculating energy output and Gurney velocity of explosives.

Two correlations are introduced for calculating Gurney velocity as a useful parameter for thermochemical estimation of explosive energy output. For CaHbNcOd explosives, only the chemical composition of high explosive as well as its condensed or estimated gas phase heat of formation, which later is calculated by group additivity rules, is needed for calculating Gurney velocity. The introduced simple correlations in the present work may be applied to any explosive that contains the elements of carbon, hydrogen, nitrogen and oxygen with no difficulties at any loading density. There is no need to use any assumed decomposition reaction in present work. Gurney velocity are calculated for different pure and explosive formulations and compared with measured Gurney velocity at specified loading density. The results show that the agreement is good for present method as compared to previous correlations.