Combustion characteristics and kinetic analysis of Turkish crude oils and their SARA fractions by DSC

In this study, two Turkish crude oils from southeastern part of Turkey and their saturate, aromatic, resin fractions were analyzed by differential scanning calorimetry (DSC). The experiments were performed at three different heating rates (5, 10, 15 °C min^?1) under air atmosphere. Two different reaction regions were observed from DSC curves due to the oxidative degradation of crude oil components. In the first reaction region, it was deduced that the free moisture, volatile hydrocarbons were evaporated from the crude oils, light hydrocarbons were burned, and fuel was formed. The second reaction region was the main combustion region where the fuel was burned. From DSC curves, it was observed that as the sample got heavier, the heat of the reaction increased. Saturates gave minimum heat of reaction. As the heating rate increased, shift of peak temperatures to high values and extended reaction region intervals were observed. The kinetic analysis of the crude oils and their fractions were also performed using ASTM E-698 and Borchardt and Daniels methods, respectively. Activation energy values of the crude oil samples and the fractions’ high-temperature oxidation region were close to each other and varied between 67 and 133 kJ mol^?1 in ASTM and 35 and 154 kJ mol^?1 in Borchardt and Daniels methods, respectively.     

Preparation of calix[4]arene-based sporopollenin and examination of its dichromate sorption ability

The present study describes the preparation of a new calix[4]arene-based sporopollenin material and its application for the removal of Na₂Cr₂O₇ from aqueous solution. The novel calix[4]arene-based sporopollenin material was prepared via the immobilization of dihydrazine amide derivative of p-tert-butylcalix[4]arene (3) onto the modified sporopollenin. The newly prepared calix[4]arene-based sporopollenin is characterized by using different analytical techniques such as FT-IR spectroscopy, scanning electron microscope and Elemental analysis. The batch wise sorption study was carried out to optimize various experimental parameters such as the effect of sorbent dosage, pH, temperature and Cr(VI) anion concentration. It has been found that the sorption of Cr(VI) anion on calix[4]arene-based sporopollenin was highly pH dependent and maximum sorption was achieved at pH 1.5. The sorption behavior was also evaluated by Langmuir, Freundlich and Dubinin Radushkevich isotherms. The value of correlation coefficient (R ²) showed a good agreement with Freundlich isotherm model. Result of study demonstrated that calix[4]arene-based sporopollenin proved to be highly effective for the removal of Cr(VI).     

Antimicrobial,DPPH scavenging and tyrosinase inhibitory activities of Thymus vulgaris,Helichrysum arenarium and Rosa damascena mill. ethanol extracts by using TLC bioautography and chemical screening methods

Antimicrobial, DPPH scavenging and tyrosinase inhibitory activities of Thymus vulgaris, Helichrysum arenarium and Rosa damascena Mill. ethanol extracts by using TLC bioautography and chemical screening methods. The ethanol extracts of Thymus vulgaris (Tv), Helichrysum arenarium (Ha) and Rosa damascena Mill. (Rm) (red) were screened for their antimicrobial, 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and tyrosinase inhibitory activities. The test microorganisms included bacteria of Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). Thin Layer Chromatography (TLC) - bioautography, disk diffusion and well diffusion methods were used for the antimicrobial activity assays. Rosa damascena Mill. extract was effective against E. coli and all plant extracts showed antimicrobial activity against S. aureus. The phenolic acids in the structure of the extracts were also identified by LC-MS analysis. Human blood agar well diffusion method and TLC-DPPH assays were used to identify the hemolytic and antioxidant activity of plant extracts, respectively, along with 10 compounds including phenolic acids as a standard. Among these compounds, caffeic acid (Rf = 0.68) was detected in all extracts while vanillic acid (Rf = 0.75), and gallic acid (Rf = 0.51) was found in Tv extract. Kojic acid (Rf = 0.36), on the other hand, was detected in Rm extract as a tyrosinase inhibitor. All plant extracts presented tyrosinase inhibitory activities on TLC-bioautography assay.     

Four-Component,One-Pot Synthesis of 2-Aryl-4-Thionylquinoline Derivatives and Their Aromatization

Four-component, one-pot condensation of dimedon, thiophene-2-carbaldehyde, ammonium acetate, and numerous acetophenones yielded novel 2-aryl-4-thionylquinoline derivatives. The structures were characterized by ¹H NMR, ¹³C NMR, IR, and elemental analysis.     

Synthesis and Characterization of New Chalcone Derivatives from cis-Bicyclo[3.2.0]hept-2-en-6-one

A series of chalcone derivatives (3a–k) were prepared via the reaction of cis-bicyclo[3.2.0]hept-2-en-6-one (1) with the respective arylaldehydes (2a–k) and were then characterized by Fourier transform infrared (FT-IR), ¹H NMR, ¹³C NMR, and elemental analyses.     

Determination of total arsenic in soil and arsenic-resistant bacteria from selected ground water in Kandal Province, Cambodia

Cambodia has geological environments conducive to generation of high-arsenic groundwater and people are at high risk of chronic arsenic exposure. The aims of this study are to investigate the concentration of total arsenic and to isolate and identify arsenic-resistant bacteria from selected locations in Kandal Province, Cambodia. The INAA technique was used to measure the concentration of total arsenic in soils. The arsenic concentrations in soils were above permissible 5 mg/kg, ranging from 5.34 to 27.81 mg/kg. Bacteria resistant to arsenic from two arsenic-contaminated wells in Preak Russey were isolated by enrichment method in nutrient broth (NB). Colonies isolated from NB was then grown on minimal salt media (MSM) added with arsenic at increasing concentrations of 10, 20, 30, 50, 100 and 250 ppm. Two isolates that can tolerate 750 ppm of arsenic were identified as Enterobacter agglomerans and Acinetobacter lwoffii based on a series of biochemical, physiological and morphological analysis. Optimum growth of both isolates ranged from pH 6.6 to 7.0 and 30–35 °C. E. agglomerans and A. lwoffii were able to remove 66.4 and 64.1 % of arsenic, respectively at the initial concentration of 750 ppm, within 72 h of incubation. Using energy dispersive X-ray technique, the percentage of arsenic absorbed by E. agglomerans and A. lwoffii was 0.09 and 0.15 %, respectively. This study suggested that arsenic-resistant E. agglomerans and A. lwoffii removed arsenic from media due to their ability to absorb arsenic.     

Alternate Method for the Synthesis of Six-Membered Carbocycles with Five Stereocenters: 1,2,3,4,6-Pentasubstituted-4-hydroxy-cyclohexanes

A series of novel 1,2,3,4,6-pentasubstituted-4-hydroxy-cyclohexanes (3a–u) were synthesized from the reaction of aromatic ketones with aromatic aldehydes under mild reaction conditions in good yields. The stereochemistry of the synthesized compounds was established using 1D and 2D-NMR spectra.     

Comparative Study of Biosorption of Heavy Metals Using Living Green Algae Scenedesmus quadricauda and Neochloris pseudoalveolaris: Equilibrium and Kinetics

The biosorption of several heavy metals such as cobalt(II), chromium(III), lead(II), cadmium(II), nickel(II), and manganese(II) from aqueous systems on living microalgae cultures, Scenedesmus quadricauda and Neochloris pseudoalveolaris were studied under laboratories conditions. The kinetic and statistical parameters were calculated by using the data obtained from batch cultivation and well fitted a pseudo-first-order rate equation. The initial metal concentrations in solution were about 5–40 mg · L^?1. According to the pseudo-second-order model, the biosorption capacities of Scenedesmus quadricauda for Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions were found in the ranges of 2.14–52.48, 1.98–81.98, 8.05–4.26, 7.81–24.96, 2.17–55.71, and 3.54–75.20 mg g^?1, respectively. Kinetic studies revealed that the metal uptake capacity of each living green algae was rather fast. It was also observed that the biosorption kinetic rate decreased with increasing concentration for both microalgae. The application of diffusion-controlled models to the experimental results indicated that the contribution of intraparticle diffusion to the overall sorption kinetics was not very important. Results showed that Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions could effectively be absorbed by using living microalga cultures from aqueous solutions.     

Adsorption of Cd(II) Ions onto Activated Carbon Prepared from Hazelnut Husks

In this study, a batch adsorption of Cd(II) ions onto activated carbon (AC) produced from hazelnut husks were investigated. The factors controlling the adsorption process such as initial pH, agitation time, dosage and initial concentration have been examined. The AC was showed a high affinity to Cd(II) ions at pH values between 5.0 and 7.0. The equilibrium time was found to be 300 minutes. Cd(II) adsorption equilibrium was analyzed with both Langmuir and Freundlich isotherm equations and it was found that Langmuir equations fitted well with the experimental data. Maximum Cd(II) adsorption capacity of AC was calculated to be 20.9 mg g^?1. Cd(II) adsorption kinetics described well with the pseudo second order model. The activated carbon prepared from hazelnut husks is efficient sorbent material for the removal of Cd(II) ions from aqueous solutions.     

Selective back-extraction and preconcentration of zinc(II) from metal-1,3,5-triketone extracts prior to its determination by flame atomic absorption spectrometry

A simple back-extraction method was developed for the separation and preconcentration of trace levels of zinc from different matrices. Ethyl-2-(4-methoxybenzoyl)-3-(4-methoxyphenyl)-3-oxopropanoylcarbamate (EMPC) was used as a new complexing agent for the extraction of zinc(II) from the aqueous sample phase to the methyl isobutyl ketone (MIBK) phase as Zn(EMPC)₂ complexes. The Zn(II) can be selectively stripped with 1?mL of 0.5?mol?L^?1 HCl from Mⁿ⁺(EMPC)_n complexes [Ag(I), Al(III), Cd(II), Cr(III), Cu(II), Fe(II), Fe(III), Mn(II), Ni(II), Pb(II) and Pd(II)] which dissolved in MIBK phase. Some experimental parameters, which are important for the whole extraction process, including pH, sample volume, shaking time, amount of the EMPC reagent, amount of MIBK, ionic strength, and type of back-extractant were investigated. The recovery for Zn(II) was greater than 95%. The detection limit of the method was found to be 0.2?µg?L ^{? 1} and the relative standard deviation as 6.4%. The concentrations of Zn(II) in the certified reference materials (LGC6019 river water and NIST-1547 peach leaves) by the presented method were in good agreement with the certified values. The proposed method was succesfully applied to the determination of zinc in some natural waters, rice, hair, soil, and tea samples.