جستجوی مقالات مرتبط با کلیدواژه « concentration » در نشریات گروه « شیمی »
تکرار جستجوی کلیدواژه «concentration» در نشریات گروه «علوم پایه»-
Modeling of Groundnut Shell Mercerization Process Using a Neuro-Fuzzy Technique
Natural fiber is growing relevant in composite processing due to its low cost, lightweight, and good mechanical properties; therefore, increased natural fiber composite development is desirable. This study predicted the mercerization effect on the moisture absorption properties of groundnut shell samples using neuro-fuzzy modeling. The groundnut shells were processed, dried, and treated with NaOH varying the time and concentration of the treatment. Sensitivity analysis using the adaptive neuro-fuzzy inference system) ANFIS's exhaustive search showed that treatment time and concentration impacted the moisture absorption rate of groundnut shells. Parametric analysis via ANFIS surface plot indicated that an increase in treatment time and concentration decreased the moisture absorption rate of the samples. The characterization results from SEM(Scanning electron micrograph) and FT-IR (Fourier Transform Infrared Spectroscopy) showed that the groundnut shells were suitably mercerized. ANFIS optimum result showed that the moisture absorption rate of 1.23% was obtained at a treatment time of 4 hours and a concentration of 4 mol; pi membership function (mf) had the best coefficient of determination R2 (0.99364) and Mean Square Error (MSE, 0.011679) amongst other membership functions demonstrating a significant predictive behavior for the model. The observations from the study prove that the ANFIS technique is a practical approach for the prediction of the groundnut shell mercerization process.
Keywords: ANFIS, time of treatment, concentration, mercerization, groundnut shell} -
Mercury and its compounds are well known to have toxic effects on human body. Many research studies have reported in this field. These studies found that the prolong using of the skin whitening and lightening creams lead to accumulation of mercury in human body. As a result of that, the damage to the brain, nervous system and kidneys, can occur. In this study, the concentrations of total mercury metal in six top selling skin lightening creams sold in local markets in Benghazi, Libya were analyzed. The Cold Vapor Atomic Absorption Spectrophotometric (CV-AAS) method was used for mercury determination after suitable wet digestion process. In all analyzed samples, mercury was detected, with concentrations ranged between 0.2500 to 2.0950 ppm. The concentration of mercury in four samples exceeded the maximum permissible value for mercury in cosmetic products set by World Health Organization (WHO) and Food and Drugs Administration (FDA). The results of the present work revealed that the analyzed creams were contaminated with mercury; making risk of toxicity for consumers.Keywords: Mercury, skin lighting creams, CV-AAS, Analysis, concentration}
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In this study, the physicochemical parameters of the river Majowopa were determined. The parameters assessed are temperature, pH, turbidity, conductivity, total dissolved solids (TDS), total suspended solids (TSS), total solids (TS), total acidity, total alkalinity, chloride, nitrate, phosphate, sulphate, dissolved oxygen (DO), chemical oxygen demand (COD) and biochemical oxygen demand (BOD). The obtained result revealed that the average value of the parameters analysed are; temperature (27.99±0.51 °C), pH (6.76±0.08), turbidity (7.69±2.51 NTU), conductivity (124.90±18.42 uS/cm), TSS (18.29±2.27 mg/L), TDS (68.17±13.63 mg/L), TS (86.46±13.95 mg/L), total acidity (17.57±2.37 mg/L), total alkalinity (25.23±6.23 mg/L), chloride (27.91±1.92 mg/L), nitrate (10.14±2.28 mg/L), phosphate (7.62±1.85 mg/L), sulphate (32.72±0.87 mg/L), DO (1.60±0.55 mg/L), COD (23.79±5.45 mg/L), BOD (8.31±3.65 mg/L) and that these values are within the WHO allowed limits except for turbidity (7.69±2.51 NTU), nitrate (10.14±2.28 mg/L), phosphate (7.62±1.85 mg/L) and DO (1.60±0.55 mg/L). One-way analysis of variance (ANOVA) carried and the 95% confidence level revealed that the value of each parameter was significantly different (P<0.05) from one site to another. The variation of each parameter observed along the river was as a result of pollution from activities that take place along the river bank and the vicinity of the river.Keywords: Physico-chemical, parameter, Pollution, concentration, Permissible limit}
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Iranian Journal of Chemistry and Chemical Engineering, Volume:37 Issue: 5, Sep-Oct 2018, PP 157 -165Ohmic heating is defined as a process which alternating electric current is passed through food with the primary purpose of heating it due to the electrical resistance and can be specially applied as an alternative heating method. In this research, Aloe vera gel concentrates having 0.5-2% soluble solids were ohmically heated up to 60°C by using four different voltage gradients (30–60 V/cm). The dependence of electrical conductivity on temperature, voltage gradient, and concentration were obtained. Results indicated that there was a linear relationship between temperature and electrical conductivity. The range of the electrical conductivity was 0.45 to1.20 S/m, which was dependent on the concentration and voltage gradient, although the effect of concentration was very higher than voltage gradient. The ohmic heating System Performance Coefficients (SPCs) were calculated by using the energies given to the system and taken by the Aloe vera gel samples and were in the range of 0.67- 0.89 and the highest SPC (0.89) was observed at 0.5 % and 30 V/cm.Keywords: Ohmic heating, Aloe vera gel, Concentration, Voltage gradient, Electrical conductivity, Energy Efficiency}
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Iranian Journal of Chemistry and Chemical Engineering, Volume:37 Issue: 1, Jan-Feb 2018, PP 241 -247The already initiated studies are based on size and forms of abrasive grains, but few studies have addressed the influence on the concentration of abrasive grains. This research has been done to remove some of the mysteries associated in the media "abrasives" or "chips" used in vibratory and barrel finishing, this process included within the functions and characteristics of media, its types and shapes, also the selection of the best grade for a given task. The present work provides guidance on the influence on the concentration of the particles (grain) of abrasive granules with the main parameters and technological indices of vibratory finishing treatment,in order to optimize abrasive granules and increase the productivity of the vibratory finishing taking into account media, which has certain characteristics, make it unique in its capabilities.Keywords: Particle, Concentration, Abrasive granules, Vibratory finishing}
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میکرو و نانو ذره ها در دهه های اخیر به عنوان حامل های زیست تخریب پذیر(داربست) برای تحویل و رهش کنترل شده ی عامل های درمانی گوناگونی مانند داروها، پروتئین ها، سلول ها و ژن ها، گسترش پیدا کردند. در این پژوهش، تولید میکروذره های کروی چیتوسان و بارگذاری هم زمان رتینوئیک اسید در این میکروذره های کروی بر پایه ی روش الکترواسپری هم محور به روش آماری سطح پاسخ مورد بررسی قرار گرفت. نتیجه های آزمایشگاهی نشان داد که اندازه ی ذره ها و ریخت شناسی آن ها تحت تاثیر شرایط عملیاتی، ازجمله استفاده از غلظت چیتوسان (1X)، سرعت جریان رتینوئیک اسید (2X)، نسبت چیتوسان به رتینوئیک اسید (3X) و میزان شدت نیرومحرکه الکتریکی (4X) است. بهترین میانگین قطر و توزیع اندازه ای ذره ها در غلظت چیتوسان w/v3%، شدت جریان رتینوئیک اسید mL/h1/0، نسبت چیتوسان به رتینوئیک اسید 6 و ولتاژ kV7/10 به دست آمد.پایداری میکروذره های کروی چیتوسان تولیدشده در محیط کشت برای مدت 10 روز موردبررسی واقع شد که این پایداری مناسب میکروذره های کروی امکان استفاده ی آن ها را در آزمایش های درون تنی می دهد.کلید واژگان: میکروذره های کروی, الکترواسپری هم محور, چیتوسان, انکپسوله سازی دارو, رتینوئیک اسید, روش آماری سطح پاسخ}Over decades, micro and nanoparticles were developed as biodegradable carrier or scaffolds to deliver and control a release of various therapeutic agents like drugs, proteins, cells, and genes. In the present study, production of chitosan microparticles and simultaneously, loading retinoic acid in the microspheres using coaxial electrospray method was statistically evaluated by response surface methodology. The results showed that the particle size and the morphology of produced microspheres may be controlled by changing some experimental conditions like the concentration of chitosan (X1), flow rate of the retinoic acid stream (X2), chitosan to the retinoic acid ratio (X3), and intensity of the electrical force (X4). The optimized condition to achieve a lowest particles size and narrow size distribution was found at 3%w/v chitosan, 0.1 mL/h flow rate of retinoic acid, the ratio of chitosan to retinoic acid equal to 6, and under a voltage of 10.7 kV. The stability of the produced microspheres chitosan in nutrient broth was studied for 10 days. The acceptable stability of the microspheres may allow them to be studied in vivo.Keywords: Chamomile, Nanofiltration membrane, Apigenin, Concentration, Flow rate, Percolation}
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گیاه بابونه از سالیان دور به علت داشتن مواد موثره مفید برای انسان در مصرف های دارویی، غذایی و آرایشی و بهداشتی استفاده می شود .هدف از تغلیظ عصاره بابونه به وسیله غشای نانو فیلتراسیون استفاده از روشی ساده، ارزان، با گزینش بهتر و بازدهی بالاتر و هم چنین خودکارسازی آسان، مقیاس و زمان فرایند کوتاه تر، هزینه های پایین تر و شرایط بهره برداری بهتر است. در این پژوهش تغلیظ عصاره بابونه به روش غشا نانوفیلتراسیون در فشار و سرعت جریان متغیر بررسی شد. عصاره (30/70)به مقدار 1000 میلی لیتر به روش خیساندن با هم زدن تهیه شد، هنگام عبور عصاره مایع اثر فشار در بازه ی 8-6 بار در سرعت جریان 10 متر بر ثانیه بررسی شد، با توجه به منحنی های شار برحسب زمان، شار عبوری از L/m2.h 6/21-4/ 14به L/m2.h8/7-02/6 کاهش یافت. در فشار 7 بار و سرعت جریان 20-10 متر بر ثانیه میزان شار از L/m2.h72-4/14 به L/m2.h9-8/7 رسید. غلظت ماده موثره آپی ژنین در فشارثابت 7 بار و سرعت جریان 20-10 متربر ثانیه از ppm 46/27 به ppm 13/10رسید. آپی ژنین که در زمره فلاونوئیدها می باشد و دارای ویژگی هایی چون ضدمیکروبی، ضد اسپاسم، ضد اضطراب و ضدسرطان است در سرعت جریان ثابت 10 متربرثانیه و فشار 8-6 بار غلظت از ppm 70/30 به ppm 86/9 کاهش یافت. کاهش غلظت و کاهش شار و افزایش بازده دفع از 88-65 درصد با دیدن تصویرهای گرفته شده از سطح غشا نانوفیلتراسیون درنتیجه ایجاد رسوب و گرفتگی و پدیده قطبش غلظتی در زمان انجام فرایند است. با بهبود پارامترهای غشا ازجمله فشار و سرعت جریان و از بین بردن رسوب و گرفتگی در سطح غشا، می توان شار عبوری را افزایش داده و بازده دفع را کاهش داد.کلید واژگان: بابونه, غشای نانوفیلتراسیون, آپی ژنین, تغلیظ, شار, خیساندن با هم زدن}Chamomile has used in pharmaceutical, food and cosmetic industry since ancient times. The purpose of Chamomile extract concentration by using the nanofiltration membranes methods is to achieve a way that will be more easy automation, more simple, cheaper, higher Efficiency, less cost, better selection, Scale and shorter process time and the better exploitation condition. Chamomile extract concentration by using the nanofiltration membranes method was investigated in variable pressure and variable flow velocity. by Improvement in Membrane parameters especially pressure and flow velocity and removing the fouling on the membrane surface, we are able to decrease the rejection efficiency and increase the flux. Effect of pressure range 6 - 8 bar was investigated when the liquid extract was passing. According to the flux curves over time, the flux was reduced from 21/6-14-4 L/m².h to 7/8-6/2 L/m².h. When the pressure was constant (7 bars) and velocity was10-20m/s the flux decreased from 72-14/4 L/m².h to 9-7/8 L/m².h, as well as the concentration of Apigenin active ingredient was reduced from 27/46 ppm to 10/13 ppm. At pressure range 6 - 8 (bar) and constant value of flow velocity(10m/s) concentration decreased from 30/ 70 to 9/86 (ppm).Concentration and flux reduction and rejection efficiency increasing that observed in images that had been taken from the surface of the nanofiltration membranes a result of creating of fouling and concentration polarization phenomenon during the process time.Keywords: Chamomile, Nanofiltration membrane, Apigenin, Concentration, Flow rate, Percolation}
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In this paper thin films of tin sulfide (SnS) were deposited on the glass substrates using spray pyrolysis method with the substrate temperatures in the range of 400600℃, keeping the other deposition parameters constant. In this work the characteristic of SnS thin films investigated. The XRD pattern and optical transmittance of thin films also are discussed. With the change in concentration of thiourea, the physical properties of the thin films are also investigated.Keywords: Tin sulfide, Spray pyrolysis, SnS thin film, Substrate temperature, Concentration}
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Graphene oxide was prepared using modified Hummers method. Stable ethylene-glycol nanofluids containing graphene oxide nanosheets were provided. Nd: YAG pulsed laser was applied to prepare reduced nanofluids. Experimental results revealed that thermal conductivity of the nanofluids is increased with increasing the concentration of graphene oxide (GO) in ethylene glycol. The enhancement ratio of 0.05% mass fraction of GO was 16.32%. Thermal conductivity improved with increasing the temperature about 14.28%. The dynamic light scattering and results of zeta potential analyses, after one week and eight months, showed the same results which demonstrated the stability of nanofluids.
Keywords: Graphene Oxide, Ethylene, glycol, Thermal Conductivity, Reduce, Concentration} -
The effect of chloride ions concentration on the semiconducting behaviors of 1050 and 6061 Al alloys in 0.003 M NaOH has been investigated by using potentiodynamic polarization, cyclic potentiodynamic polarization and Mott-Schottky analysis. Potentiodynamic and cyclic potentiodynamic polarization curves indicate that chloride ionsconcentration narrowed passivation region for both Al alloys. Also, these polarization curves revealed that increasing chloride ions concentration leads to decrease the pitting potential of both Al alloys. Mott–Schottky analysis demonstrated that the passive films formed on both Al alloys in 0.003 M NaOH with and without NaCl addition show n-type semiconducting behaviors in nature. For both alloys, the passive films formed in chloride-free solution are most stable, and that formed in chloride-containing solution are unstable. Also, the Mott– Schottky results showed that the donor density evaluated from the Mott–Schottky plots increases with increasing chloride ions concentration.Keywords: Al alloy, Chloride, Concentration, Passive film, Mott–Schottky}
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A new anti-corrosion compound, Melamine Formaldehyde (MF), was formulated by the addition of proper amount of formaldehyde to melamine under specific conditions. This compound was mixed with a novel nano powder, which was extracted from corn cob ash containing SiO2 particles, in order to improve its corrosion inhibition efficiency. This inhibitor provides a high level of protection for steel subjected to saline environments. The synthesized inhibitor works immediately with forming a dense protective layer and after adding the nano powder, its inhibition efficiency is improved. The electrochemical standard corrosion tests and the surface examination, using Scanning Electron Microscope (SEM) of steel specimen immersed in 3.5%Wt NaCl solutions with and without any inhibitor at room temperature, were carried out to investigate the inhibition behavior of the synthesized inhibitor. All of the results, which include the corrosion and electrochemical testing data, show that the tested corrosion inhibitor is generally effective and its efficiency gets better by adding the ceramic powder.Keywords: Corrosion inhibitors, Electrolyte, Concentration, Chemical nature, Film forming corrosion inhibitor, Corn cob ash}
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Structural, Optical and Electrical Properties of SilverNanoparticlesDeposited by Spin Coating MethodIn this study, silver nanoparticles were synthesized by chemical reduction method at different concentrations of Ag colloid in the range of 500-16000 ppm. Nanoparticles were deposited by spin coating method on pre-etched glass and Si substrates. Structural, optical and electrical properties of the samples were studied using Scanning Electron Microscopy equipped with EDAX, UV-Vis spectrophotometry and four-point probe. Particles size was determined according SEM results and was compared for two different substrates.Keywords: Chemical reduction, Concentration, Ag Nanoparticles, Spin coating}
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In this research new adsorbents were prepared by modification of surfactant-coated -alumina with three ligands; 1-(2-pyridylazo)-2-naphtol (PAN), dithizone (HDZ) and dimetyl golyoxime (DMG). The adsorbents were used for removal and pre-concentration of Pb+2, Cd+2, Ni+2, Cu+2, Co+2. Aqueous solutions of the metal ions were passed through a column filled with the adsorbent and the retained cations were eluted with nitric acid. Recoveries greater than 96% were obtained for most studied cations. The selectivity of the adsorbent was examined in the presence of different interfering cations. The results showed that the synthesized adsorbents posseses good capacity and selectivity for the most studied cations. The reusability test of the adsorbent showed its capability after five adsorption–elution cycles.Keywords: Pre, concentration, alumina, Surfactant, coated alumina, Ligand modification}
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