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.     

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.     

Devulcanization of waste tires using a twin‐screw extruder: The effects of processing conditions

During recent decades, for both economic and environmental reasons, recycling of waste tires that are based on SBR/NR has been widely considered. In this study the devulcanization process of the tread section of waste tires was carried out by using a twin‐screw extruder. The effects of barrel temperature and screw speed were investigated. Percent of devulcanization, sol fraction, and curing behavior of devulcanized samples were studied. After the addition of curing agents into the devulcanizates, the general behavior of the rheometry test for rubber compounds was observed. Percent of devulcanization and sol fraction depended on the screw speed and barrel temperature, respectively. The devulcanized samples were formulated with virgin rubber (15/85 wt% ratio) and re‐cured successfully. Tensile strength, elongation at break, compression set, hardness, and resilience were evaluated. It was found that the mechanical properties of the compound containing devulcanizates were slightly inferior to those of the virgin compound. J. VINYL ADDIT. TECHNOL., 2011. © 2011 Society of Plastics Engineers     

Reduction of formaldehyde emission from plywood

The aim of this work is to evaluate performances of tannin-based resins designed as adhesive in the plywood production. For this purpose, a part of phenol formaldehyde (PF) and melamine formaldehyde (MF) in the classic adhesive formulation was replaced by tannin. The physical properties of the formulated resins (rheological characterization, etc.) were measured. In order to analyze the mechanical performance of tannin-based resins, plywood panels were produced and the mechanical properties including tensile strength wood failure and three-point bending strength were investigated. The performance of these panels is comparable to those of plywood panels made by commercial PF and MF. The results showed that the plywood panels bonded with tannin–PF (PFT) and tannin–MF (MFT) resins exhibited better mechanical properties in comparison to the plywood panels made of commercials PF and MF. The introduction of small properties of tannin in PF and MF resins contribute to the improvement of the water performance of these adhesives. The formaldehyde emission levels obtained from panels bonded with tannin-based resins were lower than those obtained from panels bonded with control PF and MF. Although there are no actual reaction at all between PF, MF, and tannin, addition of tannin significantly improves the water resistance of PF and MF resins. This is a novel finding that manifests the possibility of replacing a convention PF and MF resins by tannin. Modified adhesive is one of the goals in the plywood production without changing any of their production conditions with improvement to their overall properties.     

Migration of Bisphenol-A into packaged food simulants: Development of a novel MAE-LDS-ME strategy for the investigation of storage time and temperature

In this research, migration of bisphenol A from epoxy resin into 64 food simulants including tuna fish cans, eggplant cans and cherries cans have been measured. The effective of storage time in the range 0–180 days and storage temperature at 25 and 45°C were investigated. Microwave-assisted extraction and low-density solvent based on microextraction followed by high-performance liquid chromatography has been applied to analyze migrated-BPA. The limit of detection 2.7 ng ml⁻¹ and limit of quantification 9.33 ng ml⁻¹ were obtained for the proposed method. The results confirmed that the migration of BPA has been increased with raising the storage time and temperature. Also, the migration of BPA in oily simulant was higher than acidic simulant. The migrated-BPA concentration range has been measured in the range 3.42–4165 ng ml⁻¹. The highest amount of migrated-BPA has been found for simulant of tuna fish cans at 45°C and the lowest amount of migrated-BPA has been detected for simulant of cherries cans at 25°C.     

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.     

Preparation and characterization of carboxylated styrene butadiene rubber (XSBR)/multiwall carbon nanotubes (MWCNTs) nanocomposites

This study deals with the preparation of carboxylated styrene butadiene rubber (XSBR)/multiwall carbon nanotubes (MWCNTs) nanocomposites prepared in the latex form by means of a ball mill. Two types of CNTs, i.e., non-functionalized and OH-functionalized (CNT?COH) were used. The rheological properties, FTIR spectrums, SEM micrographs and stress relaxation experiments were exploited to evaluate the resulting nanocomposites. For a given frequency, both the viscosity and storage modulus increased as the concentration of CNT was augmented with the greatest value for the nanocomposites loaded with CNT?COH. The viscosity of nanocomposites exhibited a shear thinning behavior throughout applied frequency and indicated a power law index of about n?=?0.22. Nanocomposite ATR analyses revealed the presence of physical interaction of H-bonding type between hydroxyl group of CNT?COH and carboxyl group of XSBR for XSBR?CCNTOH nanocomposites. A mechanism based on the chemistry of medium was proposed to explain the development of H-bonding. SEM micrographs confirmed the uniformity of carbon nanotubes dispersion in the resulting microstructure. A two-step innovative stress relaxation experiment was performed on the prepared nanocomposites through which the resulting microstructure of nanocomposites was further explored. The relaxation behavior of nanocomposites (both in first and second steps) were modeled and well predicted using Prony series and the parameters of generalized Maxwell equation for stress relaxation, $ \tau_{i} $ and $ g_{i} $ were computed, as well.     

Comparative and competitive adsorption of Cu(II), Cd(II) and Pb(II) onto Sepia pharaonis endoskeleton biomass from aqueous solutions

In this research, the possibility of simultaneous removal of lead, cadmium and copper divalent ions from water samples through the use of Sepia pharaonis endoskeleton powder (SPEB) as bio‐material, was investigated. The bio‐sorbent was characterised by Fourier transform infrared spectrum (FT‐IR), atomic force microscopy (AFM) and X‐ray fluorescence (XRF). The different factors affecting the bio‐sorption process were studied. Langmuir and Freundlich isotherm models were applied to analyse the experimental data. The kinetic studies showed that the pseudo‐second order model kinetics were compatible with the investigated systems. It was found that under optimal conditions, this bio‐sorbent was efficient in the uptake of these heavy metal ions from both mono and multi‐metal solutions, and high removal percentages were achieved. This study verified the potential ability of SPEB as an efficient natural adsorbent for removal of Pb(II), Cd(II) and Cu(II) ions from river, tap and mineral water samples.