Application of marble powder as a potential green adsorbent for miniaturized solid phase extraction of polycyclic aromatic hydrocarbons from water samples

ABSTRACT

In this study, marble powder was evaluated as a cheap, easy to prepare and efficient green sorbent for miniaturized solid phase extraction of polycyclic aromatic hydrocarbons (PAHs) and determination by high performance liquid chromatography with UV detection. Under the optimized experimental conditions, wide linear dynamic ranges were achieved in the range of 0.1–200 μg L^?1, with correlation coefficient higher than 0.996. The limits of detection and quantification for target analytes could reach 16.3–120.2 and 54.3–398 ng L^?1, respectively. The method precision based on obtained RSD values in the range of 4.9–7.9% (n = 8) was very satisfactory.     

Hydrogen recovery from ammonia purge gas by a membrane separator: A simulation study

In this study, a two‐dimensional mathematical model is proposed for modeling the hollow fiber membrane (HFM) separators for hydrogen (H₂) recovery unit implemented in the Razi Petrochemical Company (Imam Khomeini Port, Iran) to capture hydrogen from ammonia (NH₃) purge gas. In this regard, computational fluid dynamics is applied to solve the equations of momentum and mass transfer in the laminar flow conditions. Axial and radial diffusion for mass transfer inside the membrane fibers and axial diffusion within the shell side of separator were considered. The distributions of concentration, velocity, and mass transfer fluxes were achieved by the model. As the new insights, the effects of feed flow rate and feed gas concentration on mass transfer of H₂ were investigated. Moreover, fluid velocity profile and H₂ fluxes in the tube (fiber), membrane, and shell sides of the HFM separator were studied. The results of simulation were compared with the industrial data and showed that the present developed model has excellent agreement with the experimental data with a low mean deviation value of 3.5%.     

A neural network-based instrumental method for light fastness assessment with dataset validation

A novel instrumental method for the light fastness assessment has been established. The accuracy of the visual method is affected by undesirable constraints, such as the different severity and the complications due to off-tone color change of the specimens. Thus, it was desired to develop an instrumental method of the light fastness assessment. In this regard, a neural network-based instrumental method of the light fastness assessment was developed. First, a proper light fastness panel was prepared, and then the visual light fastness assessments of experienced and inexperienced observers were collected. The accuracy and repeatability of the visual assessment results from these two groups of the observers were analyzed using different statistical criteria. The statistical analysis has shown that the mean of three trials of the inexperienced observers can be combined with the mean of the results obtained by experienced. Thus, all the results from the inexperienced and experienced observers were used to prepare a valid dataset for training a neural network. Different neural network structures trained with the prepared valid dataset. Among all of the implemented structures, the most accurate neural network structure is the one with one hidden layer and a 3-7-1 structure. The root mean square error and correlation coefficients of proposed 3-7-1 NN are 0.32 and 0.975, respectively, for the test sets. According to these results and the results from the comparison of the instrumental and visual assessment of the light fastness, it was concluded that the proposed neural network can be used for the instrumental light fastness assessment.     

In situ poly(sodium acrylate)‐based nanocomposite formation by redox‐initiated solution polymerization

Polymer‐based nanocomposites have been widely investigated as a potential method to modify polymer and biopolymer properties. Poly(sodium acrylate) (PNaA)/nanosilver nanocomposites with 0.5, 1, 2, and 3 wt% nanofiller were prepared by in situ polymerization. The free radical, redox‐initiated, aqueous solution polymerization of NaOH‐neutralized acrylic acid was conducted in the presence of nanosilver. The progress of the polymerization was monitored using gravimetric conversion measurements. The addition of 0.5 wt% nanosilver to the polymerization resulted in a significant decrease in rate of polymerization The effect on rate was noticeably reduced when the experiment was repeated with nanoclay, a nonmetallic nanofiller, in lieu of nanosilver. POLYM. ENG. SCI., 55:1230–1236, 2015. © 2015 Society of Plastics Engineers     

Investigation on thermodynamic parameters and stability of some polyelectrolyte complexes with respect to ionic strength of the medium

The effect of ionic strength of the medium on stability constant and related thermodynamic parameters (e.g. ΔH⁰ and ΔS⁰) has been studied for a typical polyelectrolyte interpolymer complexes e.g. poly (acrylic acid), poly (ethylene imine) in aqueous solution using various inorganic salts. Stability constant K, and related thermodynamic parameters have been calculated and compared for interpolymer complex in different complexation medium using Osada’s method. The comparative study indicated considerable difference in the values of these parameters which has been explained on the basis of the relative strength of electrostatic interaction in different medium.     

Relative contribution of compositional parameters to the primary and secondary oxidation of canola oil

The content of primary (PO) and secondary (SO) oxidation products of canola oil was measured, and a good correlation obtained between them (R² = 0.991). Peroxide value showed the highest contribution (53.69%) to the PO, whereas its contribution to the SO was much less significant (0.36%). Acid value contribution to the production of hydroperoxides and carbonyls was 12.75% and 29.82%, respectively. Polyene index showed a relatively low contribution to the PO (6.71%) but contributed highly to the SO (21.82%). Tocopherols were more effective to prevent the production of hydroperoxides (14.77%) than of carbonyls (4.36%). In contrast, phenolics were found to be better than tocopherols to resist off-flavours production (11.64% vs. 3.36%). Total polar compounds had a pronounced contribution to creation of off-flavours (32.00%) as well as a marked effect on the PO (8.72%).     

A new fuzzy Gaussian mixture model (FGMM) based algorithm for mammography tumor image classification

Multimedia Tools and Applications - Computer aided diagnosis systems are recently introduced to increase the accuracy of mammography interpretation. This paper introduces a new classification...     

Calculation of reactivity ratios of methacrylic acid-ethyl acrylate copolymer by on-line quantitative 1H NMR spectroscopy

The solution copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was studied by online proton nuclear magnetic resonance spectroscopy (¹H NMR) using 2,2′–azobisisobutyronitrile as an initiator in deuterated dimethyl sulfoxide at 60 °C. The chemical compositions of the copolymer and the comonomer concentrations were determined from the conversion of comonomers to copolymer by quantitative in situ NMR monitoring to estimate the reactivity ratios of the comonomers at low conversion. This is a new and easy methodology to analyze radical copolymerization. In this research, it is shown that monomer reactivity ratios can be calculated by data collected only from one initial comonomer mixture composition via online monitoring progress of the copolymerization reaction. The reactivity ratios of MAA and EA are equal to 2.360 and 0.414, respectively. This approach is used to compute the monomer reactivity ratios in a nonlinear integrated form of the copolymerization equation which is described by Mayo and Lewis terminal model. The fairly good agreement between the results and the literature data reported for the emulsion system represent the accuracy of the reactivity ratios calculated by this new approach. The calculated reactivity ratios for emulsion copolymerization are r _MAA = 2.040 and r _EA = 0.470, and the previous literature data are r _MAA = 2.580 and r _EA = 0.157.     

Application of Ozone Post-Harvest Treatment on Kabkab Date Fruits: Effect on Mortality Rate of Indian Meal Moth and Nutrition Components

Methyl bromide (MB) was used for years to treat infested stored date fruits; however, MB is due to be phased out by 2015. In this study ozone is used for disinfestations of Kabkab date against Indian meal moth in three life stage. They were exposed to four ozone concentrations (300 ± 10, 1050 ± 40, 2000 ± 40, and 4000 ± 50 ppm) during four periods (2, 4, 6, and 8 h). The findings show 2000 ppm of ozone concentration within 8 h resulted in complete mortality of larvae and adult insects and over 90% mortality of eggs. The proposed ozone treatment is a promising approach replacing application of MB for disinfestations of examined date fruits, as no remarkable changes were observed on pH of the date fruits and its chemical compositions (total phenolic content, anti-oxidant activity and free radicals).