Biosorption of Pb(II) using Gundelia tournefortii: Kinetics,equilibrium, and thermodynamics

In this paper, the feasibility of Gundelia tournefortii was studied as a novel, high-capacity biosorbent for removing lead ions from synthetic wastewater in a batch system. The effects of various parameters such as temperature, initial concentration, initial pH, biosorbent dosage, and contact time were investigated. Based on batch results, the optimum operating conditions were found to be pH 5, biosorbent dosage of 25 mg, and temperature of 20°C in the range of lead initial concentrations from 5 to 100 mg/L. The equilibrium contact time was 60 min. The biosorption mechanism can be well described by the Langmuir isotherm with a monolayer maximum adsorption capacity of 144.928 (mg/g) at 20°C and a pseudo-second-order kinetic model. Thermodynamic studies proved that the sorption process was physical, spontaneous, feasible, random, and exothermic. In the second step, the ability of artificial neural network (ANN) to predict the adsorption capacity of Gundelia tournefortii for the removal of Pb(II) from aqueous solution was examined. The model was developed using a three-layer feed-forward back-propagation (BP) network with 5, 12, and 1 neurons in the first, second, and third layers, respectively. The Levenberg–Marquardt BP training algorithm (LMA) was found to be the best BP algorithm with a minimum mean squared error of 0.000867 and a minimum relative squared error of 0.032771. The comparison between the results of ANN and experimental data showed that ANN has a superior performance (R²= of 0.998) in the prediction of the Pb(II) removal process.     

Polyvinyl Alcohol/Alginate/Zeolite Nanohybrid for Removal of Metals

A novel polyvinyl alcohol/alginate/zeolite nanohybrid adsorbent for the adsorption of Ni(II) and Co(II) metal ions was prepared by the casting method. The prepared adsorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy as well as Barrett-Joyner-Halenda and Brunauer-Emmett-Teller analyses. The optimum adsorption conditions in terms of content of zeolite nanoparticles, adsorbent dosage, and initial pH were determined. The kinetic data for both ions were well described by the double-exponential kinetic model. The obtained Langmuir maximum adsorption capacities of Ni(II) and Co(II) metal ions were 81.51 and 79.58 mg g⁻¹, respectively. The adsorption/desorption experiments showed a good performance after 5 cycles of adsorption.     

Dielectrophoretic trapping of selenium nanorods for use in device applications

Dielectrophoretic alignment of the Selenium (Se) nanorods is reported for electrical characterization and possible applications as micro/nano devices. Selenium nanorods were successfully synthesized using a reverse microemulsion process. The produced material was investigated structurally using X-ray diffraction and transmission electron microscope. Suspensions of the Se powder in the concentration of 0.1 (g/l) were prepared in pure ethanol. Interdigitated platinum electrodes were employed for manipulation of suspended materials in the fluid. When Se particles were exposed to the platinum electrodes in two frequencies of 10 and 100 kHz, dielectrophoretic force captured suspended particles onto the interdigitated micro-electrode array. The trapped Se nanorods were aligned along the electric field lines and bridged the electrode gaps. Dielectrophoretic entrapment of Se nanorods on microelectrode was also detected by impedance measurements. The device was characterized and can potentially be used as a nanodevice.     

Microwave distillation followed by headspace single drop microextraction coupled to gas chromatography-mass spectrometry (GC–MS) for fast analysis of volatile components of Echinophora platyloba DC

To avoid the traditional and time consuming hydrodistillation, the analyses of volatile components in aerial parts of Echinophora platyloba DC was carried out by a simple microwave distillation followed by headspace single drop microextraction (MD–HS–SDME) coupled to gas chromatography–mass spectrometry (GC–MS). The headspace volatile compounds were collected after irradiation using a single drop of n-heptadecan. The extraction conditions were optimised using the relative peak areas as index. The chemical composition of the MD–HS–SDME extracts was confirmed according to their retention indexes and mass spectra. Fifty-three components were extracted and identified by using the MD–HS–SDME method. E-β-ocimene (53.81%), R-d-decalactone (12.75%), α-pinene (6.43%), n-heptanol (6.27%), β-phellanderne (2.70%) and linalool (1.89%) were the major constituents.     

Miller Compensation: Optimal Design for Operational Amplifiers with a Required Settling Time

Optimizing the settling response of an operational amplifier can be a serious design issue in today’s low-power CMOS technologies. Several design challenges emerge when improving the linear and nonlinear responses of an amplifier. In this paper, we developed a settling model for use in design and optimization of two-stage Miller-compensated amplifiers. Using this model, the closed-form relations between settling time/settling error, gain-bandwidth product, noise, power and stability have been obtained. These relations are employed to form a settling-based design routine for Miller-compensated amplifiers. Simulation results in 0.18- \(\upmu \) m CMOS validate the effectiveness of the proposed routine. In a design prototype, it predicts the settling time with an error less than 3 %. In another design example, the relationship between settling time and gain-bandwidth has been evaluated with an accuracy higher than 95 %. The proposed design routine is used to implement a 40 MS/s sample-and-hold amplifier. It achieves a settling time and signal-to-noise-plus-distortion ratio equal to 12.5 ns and 82 dB, respectively.     

The Effect of Barium Doping on the Selective Structure of Bi-2223 Phase

The partial substitution of Sr by Ba in the two nominal compositions of Bi_1.8Pb_0.4Sr_2−x Ba _x Ca_2.2Cu₃O _y [x=0.0, 0.1, 0.2, and 0.3 (A group)] and Bi_1.66Pb_0.34Sr_2−x Ba _x Ca₂Cu₃O _y [x=0.0, 0.1, 0.2, 0.3, 0.4, and 0.5 (B group)] have been investigated by resistivity, ac susceptibility measurements and by XRD and SEM analysis. In general, the nature of the temperature dependence of resistivity and susceptibility measurements indicate the presence of a superconducting transition between grains coupled by weak links. However, the XRD and SEM analyses show that the relative composition of initial elements used in Bi-(2223) is essential to the site that is selected by the Ba ions. In the A group, Ba doping up to x=0.1 will improve the phase formation of Bi-2223, and improve the superconductivity properties of the samples. In the B group, although Ba doping up to x=0.1 will enhance the phase formation of Bi-2223, it will decrease the coupling between the grain and the superconductivity properties of these systems. The presence of lower Tc phases will begin to appear for x>0.1, in both of these systems. The superconductivity properties and the phase formation of Bi-(2223) will decrease as the Ba concentration increases.     

Synthesis of TiO2 nanoparticles by a combined sol-gel ball milling method and investigation of nanoparticle size effect on their photocatalytic activities

TiO₂ nanoparticles were synthesized by a sol-gel method and the effect of ball milling of dried gel on the particle size has been investigated. The results show that the ball milling has a crucial role in preparation of nanosized TiO₂ powder. Also thermal treatment at different temperatures can control the size of prepared nanoparticles. The photocatalytic activities of TiO₂ nanoparticles with different sizes were studied by photocatalytic degradation of Congo red dye using a homemade photoreactor. The photo degradation of Congo red dye was monitored by UV-Vis absorption measurements. It was found that the nanopowders which were synthesized at 550 °C with average particle size of 55 nm show the maximum photocatalytic activities. These nanopowders which were a mixture of anatase and rutile phases did not show the same photocatalytic effect on Eriochrome black, Bromocresol green, Methyl orange and Rose Bengal dyes.     

Oleogel Fabrication Based on Sodium Caseinate,Hydroxypropyl Methylcellulose,and Beeswax: Effect of Concentration,Oleogelation Method,and Their Optimization

In the present study, the oleogel preparation with hydroxypropyl methylcellulose (HPMC) (0–2 g/100 g), sodium caseinate (CN) (0–4 g/100 g), beeswax (0–5 g/100 g), and oleogelation method (foam and emulsion template) was optimized using response surface methodology (RSM) to attain the desirable oil retaining ability, rheological, and textural characteristics. For all the chosen responses, the quadratic model was the best-fitting model with a determination coefficient of R² > 0.91. Results exhibited that the HPMC and CN concentrations were the most influential tested factors on the oil binding capacity, textural, and rheological characteristics of the oleogels due to the formation of more complex and strong network. There was a significant improvement in oil binding capacity and structure recovery of samples by beeswax addition. To produce oleogel similar to industrial shortening, the optimization method was done based on maximum oil binding capacity and thixotropic recovery and other responses were chosen equal to those of shortening values (ɳ_a = 330 Pa.s, G′ = 276,543 Pa, A value = 164,308 Pa s rad⁻¹, and firmness = 44.99 g). As regards the optimized level of structuring agents and responses (ɳ_a = 317 and 329 Pa.s, G′ = 249,782 and 260,997 Pa, A value = 180,022 and 180,373 Pa s rad⁻¹, and firmness = 44.37 and 36.98 g corresponding to Optimization 1 and Optimization 2, respectively), fabrication of oleogels with at least 90 g/100 g trans-free and low saturated oil and attributes close to industrial shortening is possible.     

Non-classical plate model for FGMs

Engineering with Computers - In this work, we developed a non-classical plate model for the analysis of the behavior of microplates prepared from functionally graded materials (FGMs). It was...