The complexation reaction between salen (Bis(salicylidene)ethylenediamine) and Cu(II) cations in methanol (MeOH), 2-propanol (2-PrOH), acetonitrile (AN), tetrahydrofuran (THF), and chloroform (CHCl3) as nonaqueous solvents at 25º C has been investigated. The stoichiometry and formation constants of complexes have been determined spectrophotometrically and conductometrically by method of continuous variations and mole ration method. The stoichiometry of Cu(II)-salen complexes in all solvents were 1:1 (ML) type using the two methods. By method of continuous variation, chloroform 2-propanol methanol ~ acetonitrile ~ tetrahydrofuran. However, by mole ratio method, the order of stability was as follows: chloroform ~ tetrahydrofuran 2-propanol methanol ~ acetonitrile. The resulting average of pKf values in each solvent using the two spectrophotometric methods was as follows: 7.40, 6.89, 6.8, 6.22, and 6.18 for chloroform, 2-propanol, tetrahydrofuran, acetonitrile, and methanol, respectively. The Cu(II) cation formed a more stable complex with salen in chloroform. However, the less stable complex was in methanol.
In this study, the level of selected organophosphorus and organochlorine pesticide residues from water samples of Gilgle Gibe (I) hydroelectric dam reservoir and its potential tributaries, Jimma zone, Ethiopia, was determined by gas chromatography-electron capture detector (GC-ECD). Low density based dispersive liquid-liquid microextraction (LD-DLLME) using toluene (as extractant) and acetonitrile (as disperser) was used for extraction of pesticide residues from the samples. Calibration curves constructed at six concentration points have good linearity with coefficient of determination (r2) ranging from 0.995 - 0.999. The limits of detection (LOD) and quantification (LOQ) of the method which were determined as 3 and 10 times the signal-to-noise ratio were ranging from 0.0001 - 2.5810 µg/L and 0.0005 - 8.6050 µg/L, respectively. The efficiency of the method was also evaluated using recovery studies by spiking the water samples with known concentrations of the analytes. The obtained recoveries were ranging from 67 - 105% with relative standard deviations of 0.79 - 12.5%. The findings revealed that the studied water samples contain significant amount of the target pesticides, but endrin was not detected in any of the water sample. Methidathion was also detected only in Nada Qalla and Nada Gudda river water samples. The detected residual concentrations of the target pesticides were above the maximum residue limits, except DDT in acute toxic level. The finding indicated that the studied water samples contain considerable amount of the studied residual pesticides that can influence the health of aquatic organisms and other consumers.
This work describes the synthesis of a novel magnetic graphene oxide composite for removal of Cr(VI) ions. The synthesized nanosorbent were characterized with various techniques such as FT-IR, X-ray diffraction (XRD), scanning electron microscopy (SEM), elemental analysis and vibrating sample magnetometry (VSM). This material is illustrated to represent a viable sorbent for the removal of Cr(VI) ions. A Box-Behnken design was applied to optimize the parameters affecting the removal of Cr(VI). Three variables including sorption time, amount of the magnetic sorbent and sample pH were optimized in the removal process. Besides, the recovery of the sorbent was studied. Equilibrium isotherms were studied, and three models were applied to analyze the equilibrium adsorption data. The results revealed that the adsorption process obeyed the Langmuir model. Kinetic studies indicated the adsorption process followed a pseudo-second-order model. Maximum sorption capacity of the sorbent for Cr(VI) ions was 250 mg g-1.
Abstract In this paper, Qeera wastewater containing stream, found in Bakkee-Jamaa district of Nekemte town, was assessed for selected metals and physico-chemical properties. The metals were determined by flame atomic absorption spectrophotometry (FAAS). Additional water samples collected from Dangi spring water, which is found about 10 km far away from the town, and Chalalaqi waste water containing stream were also assessed for reference. Analysis of concentration of Pb, Cd, Cr, Ca, and Ni metals were carried out using FAAS. For metal analysis good linearity were obtained with coefficient of determination (R2) 0.998 or better. The LOD for the metals were in the range of 0.003 to 0.018 mg L−1 and LOQ, 0.010 to 0.06 mg L−1. Recovery studies ranged from 92 % to 104 % for the metals. The study shows that Ca, Cd and Ni are quantified in all the three water bodies. Overall, the level of the metals studied is higher in the urban area streams than that of Dangi spring in the rural area. The average concentrations (in mg/L) of Ca, Cd and Ni were found to be 9.56., 0.22 and 0.38, respectively. When compared with international guide lines for the quality of irrigation water, Cd and Ni are above permissible levels and show significant pollution of the water. The data obtained from the study of selected physico-chemical properties (EC, TDS, pH, TSS and Cl¯) of the water samples were found to be within the recommended level except TSS.
Oxazine derivatives are significant class of heterocycle compounds, which has involved much synthetic attention due to their extensive variety of pharmacological activities. Oxazine is a heterocyclic compound can be formally derived from benzene, and its reduction products, by suitable substitution of carbon (and hydrogen) atoms by nitrogen and oxygen. In the last few years oxazine derivatives have proved to be valuable synthetic intermediates and also possess important biological activities like sedative, analgesic, antipyretic, anticonvulsant, antitubercular, antitumour, antimalarial and antimicrobial. In these days, progress of drug resistance is a most important difficulty and to overcome this situation, it is necessary to synthesize new classes of compounds. The aim of the article is to review the generalization of the collected data about the synthesis of oxazine derivatives and their activities. We expect that this effort will be a specific interest for researchers concerned with oxazine derivatives.
In this study 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) interaction with carbon nanocone(NC) and nanocone Sheet (NCS) was evaluated by density functional theory. The calculated thermodynamic parameters including Gibbs free energy changes and Enthalpy alterations showed the interaction of TATB with the both nanostructures are exothermic, spontaneous, experimentally possible and irreversible. The specific heat capacity values proved the heat sensitivity of TATB decline after its adsorption on the surface of carbon nanocone and nanocone sheet. The effect of temperature on this process was also investigated and the results indicated 300 K is the optimum temperature for the interaction of TATB with the nanostructures. The frontier molecular orbital analysis was also employed and the findings indicated the reactivity and energetic traits of TATB have enhanced significantly after its interaction with carbon nanocone and nanocone sheet. Indeed, both of the nanostructures cause a substantial improvement in energetic features and a tangible decrease in the heat sensitivity.