Kinetics and isotherms of dazomet adsorption on natural adsorbents

The adsorption of 3,5-dimethyltetrahydro-1,3,5-thiadiazine-2-thione (dazomet) on bentonite and clinoptilolite has been studied at four temperatures (288, 293, 298 and 303 K) and two different solutions (water and water-ethyl alcohol mixture, 50% v/v). The adsorption rates at low concentrations of dazomet were found to fit the first-order kinetic equation. For each system at constant concentration, the rate constants increased with increasing temperature in aqueous solution, but these constants decreased with increasing temperature for 50% (v/v) water-ethyl alcohol mixture solution. By using the Arrhenius equation, the activation energies for each system were calculated. Thermodynamic parameters were evaluated according to Eyring's equation. The values of enthalpy of activation, deltaH*, are lower than TdeltaS*. The results indicated that the adsorption process was entropy-controlled for each system. Adsorption isotherms were determined at 288 and 303 K. These isotherms were fitted to Freundlich equation for aqueous solution at 15 °C, but adsorption from the two different solutions at 30 °C were modeled according to the Langmuir and BET isotherms

Photochemical reactions of cis-[(eta(4)-NBD)M(CO)(4)] (NBD = norbornadiene; M = Cr, Mo) olefin complex with ligand, containing S and N donor atoms

New complexes cis-[M(CO)(4)-DABRd] (M = Cr(I), Mo(II) and fac-[M(CO)(3)-SAT] (M = Cr(III), Mo(IV)) have been synthesized by the photochemical reactions of cis-[(eta(4)-NBD)M(CO)(4)] (NBD = norbornadiene; M = Cr, Mo) with 5-(4-dimethylaminobenzylidene) rhodanine (DABRd) and saticylidene-3-amino1,2,4-triazole (SAT) ligands and characterized by elemental analysis, FT-IR and H-1 NMR spectroscopy, and mass spectrometry. The spectroscopic studies show that the DABRd ligand acts as a bidentate ligand coordinating via both NH-(S)C=S sulfur donor atoms in I and II and SAT ligand behaves as a tridentate ligand coordinating via its all imine nitrogen -C=N- donor atoms in III and IV to the metal center

Kinetic studies on UV-photodegradation of some chlorophenols using TiO2 catalyst

A number of chlorophenols, namely 2-chlorophenol, 2,4,-dichlorophenol and 2,4,6-trichlorophenol, were decomposed in aqueous solution by using TiO2 as photoactivated catalyst under UV radiation emitted by a 125 W medium pressure Hg lamp in an immersion well-type quartz photoreactor. The organic-bound chlorine was converted into the environmentally harmless inorganic chloride. For catalyst doses between 0.1 and 0.5 gl(-1) the reaction mechanisms are elucidated. The corresponding rate constants were obtained by periodically measuring the remaining chlorophenol, and converted chloride in solution. A theoretical model for the degradation pathway is proposed expressing the rate as a linear function of the concentrations of chlorophenol and catalyst. Aside from the model-calculated values, the pseudo-first order rate constants for a rough approximation of chlorophenols degradation as well as the kinetic parameters of Langmuir-Hinshelwood type decomposition are compared. The photodegradation rate of chlorophenols followed the order: Cl-3.Ph > Cl-2.Ph > Cl.Ph

Spectrophotometric determination of cyclotrimethylenetrinitramine (RDX) in explosive mixtures and residues with the Berthelot reaction

On-site colorimetric methods are a valuable, cost-effective tool to assess the nature and extent of contamination in remediated sites and to enable on-site screening for police criminology laboratories. The existing colorimetric method for cyclotrimethylenetrinitramine (RDX) based on a Griess reaction suffers from the non- quantitative reduction to nitrite and from the unstable character of HNO2 in acidic medium. Thus we propose a novel spectrophotometric RDX assay in explosive mixtures and residues, based on (Zn + HCI) reduction of RDX in a microwave oven, followed by neutralization of the reduction products to ammonia and low molecular-weight amines, and Berthelot reaction of these amine-compounds with phenol and hypochlorite in alkaline medium to give an intensely blue indohenol dye absorbing at 631 nm. The molar absorptivity and limit of detection (LOD) for RDX were (1.08 +/- 0.04) x 10(4) L mol(-1) cm(-1) and 0.18 mg L-1, respectively Application of the method to synthetic mixture solutions of RDX and trinitrotoluene (TNT) at varying proportions showed that there was minimal interference from TNT (which could be compensated for by dicyclohexylamine colorimetry), since the Berthelot reaction was essentially non-responsive to m-substituted anilines derived from TNT upon (Zn + HCI) reduction. The proposed method was successfully applied to military-purpose explosive mixtures of (RDX + inert matter) such as Comp, A5, Comp C4, and Hexal P30, and to (RDX +TNT) mixtures such as Comp B. The molar absorptivity of RDX was much higher than that of either ammonium or nitrate; RDX could be effectively separated from ammonium and nitrate in soil mixtures, based on solubility differences. The Berthelot method for RDX was statistically validated using Comp B mixtures against standard HPLC equipped with a Hypersil C-18 column with (40% MeOH-60% H2O) mobile phase, and against gas chromatography-thermal energy analysis (GC-TEA) system. (C) 2008 Elsevier B.V. All rights reserved

Photochemical complexation reactions of M(CO)6 (M=Cr, Mo, W) and Re(CO)5Br with rhodanine (4-thiazolidinone-2-thioxo) and 5-substituted rhodanines

The new complexes [M(CO)5-DABRd] [M=Cr; 1, Mo; 2, W; 3], [cis-Re(CO)4Br-DABRd] (4), [M(CO)5-BRd] [M=Cr; 5, Mo; 6, W; 7] and [Mo(CO)5-L] [L=Rd, 8; 2CBRd, 9; 2HNARd, 10; IBRd, 11] have been synthesized by the photochemical reactions of VIB and VIIB group metal carbonyls [M(CO)6] [M=Cr, Mo, W] and [Re(CO)5Br] with 5-(4-dimethylaminobenzylidene)rhodanine (DABRd), 5-benzylidenerhodanine (BRd), rhodanine (Rd), 5-(2-chlorobenzylidene)rhodanine (2CBRd), 5-(2- hydroxynaphtylidene)rhodanine (2HNARd), 5-(4-isopropylbenzylidene)rhodanine (IBRd) and characterized by elemental analysis, FT-IR, 1H and 13C-{1H}-NMR spectroscopy and by Mass spectrometry. The spectroscopic studies show that all rhodanine ligands act as monodentate ligands coordinating via the sulfur (CS) donor atom in (1-11).Istanbul Üniversitesi: 818/190496We thank BP (Turkey) for the provision of photochemical apparatus and Research Foundation of Ege and Dokuz Eylul University for funds. We thank TUBITAK for allocation of time at the Mass Spectra and Elemental Analyses. We thank Dr. Yurdanur Yayla for obtaining 1Hand 13C-f1Hg-NMR. spectra at Ege University. This work also supported by Research Fund of Istanbul University, Project Number: 818/190496, and Dokuz Eylul University, Project Number: 04.KB.FEN.106. -

Spectrophotometric determination of 4,6-dinitro-o-cresol (DNOC) in soil and lemon juice

Although the use of once widely applied selective herbicide, 4,6-dinitro-o-cresol (DNOC), was cancelled by US-EPA in 1987, it is still found in soil and water due to its slow degradation in the environment. Since solid phase extraction-spectrophotometry combinations are much simpler and cheaper than chromatography/MS based methods and most routine laboratories lack such sophisticated instrumentation, it is desirable to establish novel sensitive, well-established, and field-applicable spectrophotometric methods for the rapid assay of DNOC in water and soil. For this purpose, two distinct spectrophotometric methods utilizing the periodate and copper(II)-neocuproine (Nc) reagents have been developed following Zn/HCl reduction of the pesticide in a microwave oven for 15 s, and validated for DNOC determination at mg L-1 level. The LOD values were 1.6 and 0.2 mg L-1 for periodate and Cu(II)-Nc methods, respectively. Statistical comparison of the developed methods was made with the aid of high performance liquid chromatography (HPLC) equipped with a C-18 (5 mu m), 250 mm x 4.6 mm ID reversed phase column in conjunction with a UV (264 nm) detector, and a methanol (HPLC grade) +0.1% glacial acetic acid mixture mobile phase. Both spectrophotometric methods were directly applicable to soil since they were not interfered with common soil cations and anions, together with some pesticides. These methods were applied to real samples such as synthetically contaminated montmorillonite and lemon juice, and overall recovery efficiencies at the order of 95% or greater were achieved in the devised adsorption/elution procedures. An 8-hydroxyquinoline (oxine)-impregnated XAD copolymer resin stabilized with Fe(III) salt was used to preconcentrate, DNOC at a concentration factor of 20 from lemon juice contaminated with 1 mg L-1 I DNOC, and the analyte retained at pH 2.5 was eluted with 0.025 M methanolic NaOH. Both the devised spectrophotometric methods and the proposed preconcentration column with optimized sorption and desorption conditions are novel for DNOC assay in the natural environment. (c) 2006 Elsevier B.V. All rights reserved

Photochemical reactions of group VIB metal carbonyls with heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole

WOS: 000253728900009The new complexes, M(CO)(5)(Schiff base) [M = Cr; 1, Mo; 2, W; 3, Schiff base = 4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole, SAHMT, a; 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 2HNAHMT, b; 4-(3-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 3HBAHMT, c; 4-(4-hydroxybenzylidenamino)-3-hydrazino-5-mercapto-1,2,4- triazole, 4HBAHMT, d; 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole, 5BrSAHMT, e; were synthesized by photochemical reaction of metal carbonyls M(CO)(6) (M = Cr, Mo, W) with new heterocyclic Schiff bases derived from 4-amino-3-hydrazino-5-mercapto-1,2,4-triazole, a-e. The ligands and complexes have been characterized by elemental analysis, EI-mass spectrometry, FT-IR, H-1 and C-13-{H-1}-NMR spectroscopy. The spectroscopic studies show that Schiff bases, a-e, are monodentate and coordinate via azomethine N donor to the central metal atom in M(CO)(5)(Schiff base) (M = Cr, Mo, W)

TOTAL ANTIOXIDANT CAPACITY AND PHENOLIC CONTENTS OF TURKISH HAZELNUT (CORYLUS AVELLANA L.) KERNELS AND OILS

Hazelnut (Corylus avellana L.) has an important nutritional value comprising a rich variety monounsaturated fats and vitamins, with a good level of dietary fiber and a high content of minerals. In the present work, phenolics in the aqueous systems were extracted from 15 different dry Turkish hazelnut kernels without skin, cultivated in Ordu province of Turkey, with 80% (v/v) MeOH/H2O. The aqueous methanolic extracts of hazelnut kernels and of oil samples were examined for their phenolic contents (Folin-Ciocalteau), total antioxidant capacities (TAC) (CUPRAC and ABTS/persulfate) and antiradical activities (2,2-diphenyl-1-picrylhydrazyl, DPPH). The individual free phenolic constituents (mainly phenolic and hydroxycinnamic acids) found in hazelnut kernels were also identified and quantified by high-performance liquid chromatography (HPLC). Among the dry hazelnut cultivars, Mincane showed the highest TAC (TACCUPRAC: 2.98 +/- 0.37 mmol TE/g) (n = 3). This work is the first application of the CUPRAC method to Turkish hazelnut antioxidant characterization and of CUPRAC and DPPH assays to hazelnut oils. PRACTICAL APPLICATIONS Hazelnut plays a major role in human nutrition and health because of its fat, protein, carbohydrate, dietary fiber, vitamins, minerals and phenolic content. This paper presents the findings of a comprehensive investigation of phenolic contents, total antioxidant capacities (TAC) and free radical scavenging activities of 15 different dry Turkish hazelnut (Corylus avellana L.) kernels cultivated in Ordu province (in the Black Sea Region) of Turkey for the first time. The TAC and phenolic contents of Turkish hazelnuts reported in this study are believed to contribute to human nutrition and health in the selection of hazelnut-rich diets for natural antioxidant supplementation