oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Effectiveness of photochemical and sonochemical processes in degradation of Basic Violet 16 (BV16) dye from aqueous solutions  [cached]
Rahmani Zahra,Kermani Majid,Gholami Mitra,Jafari Ahmad
Iranian Journal of Environmental Health Science & Engineering , 2012, DOI: 10.1186/1735-2746-9-14
Abstract: In this study, degradation of Basic Violet 16 (BV16) by ultraviolet radiation (UV), ultrasonic irradiation (US), UV/H2O2 and US/H2O2 processes was investigated in a laboratory-scale batch photoreactor equipped with a 55W immersed-type low-pressure mercury vapor lamp and a sonoreactor with high frequency (130kHz) plate type transducer at 100W of acoustic power. The effects of initial dye concentration, concentration of H2O2 and solution pH and presence of Na2SO4 was studied on the sonochemical and photochemical destruction of BV16 in aqueous phase. The results indicated that in the UV/H2O2 and US/H2O2 systems, a sufficient amount of H2O2 was necessary, but a very high H2O2 concentration would inhibit the reaction rate. The optimum H2O2 concentration was achieved in the range of 17 mmol/L at dye concentration of 30 mg/L. A degradation of 99% was obtained with UV/H2O2 within 8 minutes while decolorization efficiency by using UV (23%), US (<6%) and US/H2O2(<15%) processes were negligible for this kind of dye. Pseudo-first order kinetics with respect to dyestuffs concentrations was found to fit all the experimental data.
Sonochemical degradation of the antibiotic cephalexin in aqueous solution
W Guo, H Wang, Y Shi, G Zhang
Water SA , 2010,
Abstract: The degradation of cephalexin in aqueous solution under ultrasound irradiation was investigated. Biodegradability of the solution was evaluated by the BOD5/COD ratio, which was raised from zero to 0.36 after ultrasound treatment, indicating that the ultrasound irradiation process is a successful pre-treatment step to improve the biodegradability of cephalexin solution. The influences of ultrasound power and pH value on the degradation of cephalexin were studied. It was found that the optimal ultrasound power for cephalexin degradation in the system was 200 W and the rate of cephalexin degradation was maximal in the pH range of 6.5 to 8.5. The degradation kinetics of cephalexin in aqueous solution under various operational conditions was also investigated. It was found that the degradation of cephalexin follows a pseudo-first order kinetics.
Sonochemical degradation of organophosphorus pesticide in dilute aqueous solutions
Robina FAROOQ,FENG Kai-lin,SFSHAUKAT,HUANG Jian-jun,
Robina Farooq
,FENG Kai-lin,S. F. Shaukat,HUANG Jian-jun

环境科学学报(英文版) , 2003,
Abstract: Ultrasonic irradiation was found to accelerate the rate of hydrolysis of omethoate in aqueous solution over the pH range of 2-12. Process parameters studied include pH, steady-state temperature, concentration, and the type of gases. Greater than 96% hydrolysis was observed in 30 minutes through this process and the rate of destruction increased with the help of more soluble and low thermal inert gas. So with Krypton, omethoate was found to undergo rapid destruction as compared with Argon. In the presence of ultrasound, the observed first-order rate of hydrolysis of omethoate is found to be independent of pH. The formation of transient supercritical water (SCW) appears to be an important factor in the acceleration of chemical reactions in the presence of ultrasound. A detailed chemical reaction mechanism for omethoate destruction in water was formulated. Experimental results and theoretical kinetic mechanism demonstrated that the most of the omethoate undergo destruction inside the cavitating holes. A very less effect of temperature on the degradation of omethoate within a temperature range of 20-70 degrees C proves that a small quantity of omethoate undergoes secondary destruction in the bulk liquid.
Microwave-assisted synthesis of platinum nanoparticles and their catalytic degradation of methyl violet in aqueous solution
Jolly Pal,Manas Kanti Deb,Dhananjay Kumar Deshmukh,Bhupendra Kumar Sen
Applied Nanoscience , 2013, DOI: 10.1007/s13204-012-0170-0
Abstract: A green synthesis of polyvinylpyrrolidone stabilized platinum nanoparticles (PtNPs) has been done by microwave irradiation in the presence of glucose. The formation process of the PtNPs is pursued by UV–visible spectroscopy. The morphology of the PtNPs was characterized by transmission electron microscopy and X-ray diffraction techniques. Catalytic activity of the above PtNPs has been substantiated through photodecolorization of aqueous methyl violet solution.
Degradation kinetics of benzyl nicotinate in aqueous solution  [cached]
Mbah C
Indian Journal of Pharmaceutical Sciences , 2010,
Abstract: The degradation of benzyl nicotinate in aqueous solution over a pH range of 2.0-10.0 at 50±0.2 o was studied. The degradation was determined by high performance liquid chromatography. The degradation was observed to follow apparent first-order rate kinetics and the rate constant for the decomposition at 25 o was estimated by extrapolation. The reaction was shown to be hydroxide ion catalyzed and the Arrhenius plots showed the temperature dependence of benzyl nicotinate degradation. A significant increase in the stability of benzyl nicotinate was observed when glycerol or polyethylene glycol 400 was incorporated into the aqueous solution.
Kinetics of Light Induced Degradation of Aqueous Solution of Chloramphenicol
S.O. Okeniyi,J.A. Kolawole,M.T. Odunola,O.A. Babatunde,J.T. Bamgbose
Research Journal of Applied Sciences , 2012,
Abstract: Aqueous solution of chloramphenicol, plain and ophthalmic preparations were exposed to sunlight, ultraviolet radiation at 365 mm wavelength and red light for varying length of time. The kinetics of decomposition was studied using TLC techniques and U.V. Spectrophotometric methods of analysis of chloramphenicol and decomposing products. The rate of decomposition followed first rate reaction and the K value obtained were 3.386 x 10-2 h-1, .149 x 10-2 h-1 and 0.0659 x 10-2 h-1 in sunlight, ultraviolet radiation and red-light, respectively. The respective half-life (t ) of the decomposition was 20.47 h, 2.0 h and 1051.59 h. The average K value for the ophthalmic chloramphenicol preparations were 3.291 x 10-2 h-1 and 3.540 x 10-1 h-1 in sunlight and ultraviolet radiation respectively. The stability of chloramphenicol aqueous solution is established in the presence of red light.
The Sonochemical-degradation Mechanism of Toluene in Aqueous Solution
功率超声场作用下水溶液中甲苯的降解机理

Bian Huasong,Zhang Danian,Zhao Yixian,Jin Zhiqing,Hua Bin,
卞华松
,张大年,赵一先,金至清,华彬

环境科学 , 2001,
Abstract: The sonochemical degradation of toluene in the airproof aqueous solution was studied, and the mechanism and course of degradation was explored. It was found that the sonication time had great effect on the removal rate of toluene, and the degradation followed a pseudo-first-order kinetic law, and 90%-95% of toluene was removed only after being irradiated for 40 min, types of dissolved gas and pH also had some effects. After aqueous solution was analyzed pH and scanned UV-wavelength and identified components with SMPE-GC-MS, results confirmed that radical-oxidation controlled the sonochemical-oxidation of toluene, and main middle-products included benzaldehyde, bibenzyl, dibutyl phthalate, et al., final products were carbon dioxide and water.
Equilibrium and Kinetics Study of Adsorption of Crystal Violet onto the Peel of Cucumis sativa Fruit from Aqueous Solution
T. Smitha,S. Thirumalisamy,S. Manonmani
Journal of Chemistry , 2012, DOI: 10.1155/2012/457632
Abstract: The use of low-cost, locally available, high efficiency and eco-friendly adsorbents has been investigated as an ideal alternative to the current expensive methods of removing dyes from wastewater. This study investigates the potential use of the peel of Cucumis sativa fruit for the removal of crystal violet (CV) dye from simulated wastewater. The effects of different system variables, adsorbent dosage, initial dye concentration, pH and contact time were investigated and optimal experimental conditions were ascertained. The results showed that as the amount of the adsorbent increased, the percentage of dye removal increased accordingly. Optimum pH value for dye adsorption was determined as 7.0. The adsorption of crystal violet followed pseudo-second order rate equation and fit well Langmuir and Freundlich equations. The maximum removal of CV was obtained at pH 7 as 92.15% for adsorbent dose of 0.2 g/50 mL and 25 mg L-1 initial dye concentration at room temperature. The maximum adsorption capacity obtained from Langmuir equation was 34.24 mg g-1. Furthermore, adsorption kinetics of (CV) was studied and the rate of adsorption was found to conform to pseudo-second order kinetics with a good correlation (R2 > 0.9739). The peel of Cucumis sativa fruit can be attractive options for dye removal from diluted industrial effluents since test reaction made on simulated dyeing wastewater show better removal percentage of (CV).
Removal of Methyl Violet 2B from Aqueous Solution Using Casuarina equisetifolia Needle  [PDF]
Muhammad Khairud Dahri,Muhammad Raziq Rahimi Kooh,Linda B. L. Lim
ISRN Environmental Chemistry , 2013, DOI: 10.1155/2013/619819
Abstract: One of the major contaminants of water bodies is dye pollutants that come from textile, paper, and leather industries. In this study, Casuarina equisetifolia needle (CEN) is used to remove methyl violet 2B (MV) from aqueous solutions. Batch experiments were done to investigate the contact time, effect of pH, initial dye concentrations, and temperature. Langmuir and Freundlich isotherm models were used to describe the interaction between the adsorbate and adsorbent. The sorption mechanism was described using Lagergren 1st order, pseudo 2nd order, and Weber-Morris intraparticle diffusion models. FTIR spectroscopy was used to analyze the functional groups of CEN before and after sorption with MV. Optimal conditions were found to be at room temperature with 2?h contact time and no pH adjustment was needed. Experimental data was best fitted onto Langmuir model with maximum adsorption capacity of 164.99?mg/g, while pseudo 2nd order best described the experimental data for the kinetics study. Thermodynamic parameters such as change in Gibbs free energy ( ), enthalpy ( ), and entropy ( ) were also investigated. 1. Introduction Synthetic dyes are inexpensive and widely used in textile industry, food, and cosmetics as well as dyeing plastic, rubber, leather, and paper materials [1, 2]. Discharging industrial wastewater containing such dyes to aquatic environment can contaminate surface water bodies and groundwater. This can result in serious damage to the aquatic flora and fauna as dyes may be toxic and mutagenic [3, 4]. Damages can be extended to the soil through leachant and irrigated water. Common methods used by the industry to treat the wastewater include adsorption, filtration, reverse osmosis, photodegradation, biodegradation, ion-exchange method, coagulation, and chemical treatments by reduction, oxidation, and neutralization [2, 5, 6]. Biosorption is a preferred method due to the usage of low-cost materials, low energy usage, and high efficiency [2]. Material that can be regenerated and reused is considered as an added advantage. In biosorption process, dye molecule is adsorbed onto the biomass through physical or chemical adsorption and thus avoids the formation of degraded dye products which may be more harmful than the dye itself. Biosorption via “renewable biomass” is a key advantage over nonrenewable adsorbents such as clay, peat, zeolite, lignite, and some forms of activated carbons [7]. Methyl violet 2B (MV), is a basic dye, with high brilliant and intensity and is highly used in the industry. Molecular structure of MV is shown in Figure 1.
Stability Characterization, Kinetics and Mechanism of Degradation of Dantrolene in Aqueous Solution: Effect of pH and Temperature  [PDF]
Saeed R. Khan, Mobin Tawakkul, Vilayat A. Sayeed, Patrick Faustino, Mansoor A. Khan
Pharmacology & Pharmacy (PP) , 2012, DOI: 10.4236/pp.2012.33037
Abstract: The mechanism of degradation of dantrolene in aqueous buffer solutions was studied at various pH values in the range of pH 1.2-9.5 and at temperatures ranging from 25℃ to 75℃ to determine the optimum pH and temperature requirements for its stability and eventual product performance over the human gastrointestinal pH range. Dantrolene was analyzed by reversed phase ultra-performance liquid chromatographic (UPLC). Chromatographic separation was achieved on a Waters Acquity UPLC system using a Waters BEH C18 analytical column and Waters BEH C18 guard column. The compounds were eluted with a linear acetonitrile gradient (25%-75%) over three minutes with a buffer composition of 2.0 mM of sodium acetate at pH 4.5 for degradation studies. The flow rate was maintained at 0.5 mL/min. Column temperature was maintained at 35℃. Injection volume was 4 μL and the degradation products were detected by a photodiode array (PDA) detector at 375 nm. Degradation products, including compound B and C were analyzed by mass spectroscopy (MS) and nuclear magnetic resonance spectroscopy (NMR) and the degradation pathways were proposed. Degradation of dantrolene followed pseudo first–order kinetics and a V-shaped pH-rate profile over the pH range 1.2-9.5. The maximum stability was observed at pH 7.4 and 37℃. Although the focus of this paper was on the mechanism of hydrolysis of dantrolene, the poor aqueous solubility of dantrolene, the developed understanding can be utilized to improve the quality of the formulation and the risk associated with the extravasation of dantrolene sodium solution in its current form.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.