Soraya Hosseini

Equilibrium and Kinetic St udies of Safranine Adsorption on Alkali-Treated Mango Seed Integuments

In this study , Safranine absorption onto mango seed integuments (raw and NaOH treated) has been investigated. The effects of solution pH, initial dye concentration, contact time, point zero charge and surface chemistry of the adsorbent were studied batch-wise. Safranine adsorption onto the untreated sample is influenced by the pH of the aqueous solution whereas, adsorption with the NaOH- treated sample is independent of the pH of the solution. Boehm titration showed the acidic groups of the treated sample has a higher value (0.660 mmol/g) than the untreated sample (0.375 mmol/g). Freundlich isotherm model resulted in the best data fitting for the untreated sample. However, Langmuir model indicated the best fitting with the NaOH-treated sample. The adsorption kinetics was found to obey pseudo second order kinetic model for both samples. An approximate increase of 26 % was found in the amount of dye adsorption due to the treatment with NaOH.

Kinetics, thermodynamics, and isotherm studies for the adsorption of BR2 dye onto avocado integument

AbstractAbility of avocado integuments (AI), an agricultural waste, to adsorb Basic Red 2 (BR2) was studied by batch process. Effect of parameters such as initial adsorbate solution pH, adsorbent dosage, initial adsorbate concentration, contact time, temperature, and background electrolyte on BR2 adsorption was studied. The BR2 adsorption was optimum (15.6 mg/g) at pH: 7. Acid-base titration studies showed dominance of acidic sites on AI surface. Two and three parameter isotherm models such as Langmuir, Freundlich, Toth, Redlich–Peterson, and Sips were applied to isotherm data. Studies showed Sips model applicability as revealed by linear, nonlinear isotherms, and statistical error functions. Contact times studies showed that 70% of BR2 adsorption at various concentrations on AI was achieved in 180 min. Pseudo-first-order, pseudo-second-order, and intra-particle diffusion models were applied to kinetics data. Results revealed applicability of pseudo-second-order kinetics model. Intra-particle diffusion pl...

Adsorption of a cationic dye from aqueous solution on mesoporous carbon-based honeycomb monolith

ABSTRACT A carbon-based honeycomb monolith was prepared using dip-coating method. The carbon-based monolith was then used to remove a cationic dye (methylene blue [MB]) from aqueous solution. Surface chemistry studies demonstrated that acidic functionality (0.567 mmol g−1) dominated as compared to basic functionality (0.019 mmol g−1). N2 adsorption/desorption revealed a mesoporous structure. The Brunauer-Emmett-Teller surface area was approximately 352 m2 g−1 and the mesoporous volume devoted about 67% the total pore volume. The effects of different parameters (such as initial pH, initial dye concentration, temperature, and contact time) on MB removal were investigated in batch mode. The maximum adsorption capacity is around 121.3 mg g−1 at optimum pH = 10. An increase in adsorption capacity was observed via increasing MB concentration, with equilibration time ranged between 3,200 and 4,000 min. Both the Langmuir and the Redlich-Peterson models were found to describe well the equilibrium data. Kinetic stu...

Grafting carbon nanotubes on glass fiber by dip coating technique to enhance tensile and interfacial shear strength

The effects of noncovalent bonding and mechanical interlocking of carbon nanotubes (CNT) coating on tensile and interfacial strength of glass fiber were investigated. CNT were coated over glass fiber by a simple dip coating method. Acid treated CNT were suspended in isopropanol solution containing Nafion as binding agent. To achieve uniform distribution of CNT over the glass fiber, an optimized dispersion process was developed by two parameters: CNT concentration and soaking time. CNT concentration was varied from 0.4 to 2mg/mL and soaking time was varied from 1 to 180 min. The provided micrographs demonstrated appropriate coating of CNT on glass fiber by use of CNT-Nafion mixture. The effects of CNT concentration and soaking time on coating layer were studied by performing single fiber tensile test and pull-out test. The obtained results showed that the optimum CNT concentration and soaking time were 1 mg/mL and 60 min, respectively, which led to significant improvement of tensile strength and interfacial shear stress. It was found that, at other concentrations and soaking times, CNT agglomeration or acutely curly tubes appeared over the fiber surface which caused a reduction of nanotubes interaction on the glass fiber.

An Investigation into the Optimum Carbonization Conditions for the Production of Porous Carbon from a Solid Waste

Cellulosic materials and cellulose derivatives have been long used in the synthesis of numerous materials. These include various products such as papers, cigarette filters and sanitary pads. Cigarette filters, containing 95% cellulose acetate fibers, are responsible for one of the largest solid wastes generation today. In this work, a simple one-step carbonization of cigarette filters under various operational parameters is used in order to produce porous carbon. The effects of various pyrolysis parameters including carbonization temperature, heating rate and hold time on the final porous carbon product have been investigated. Adsorption-desorption isotherms, scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX) as well as thermal gravimetric analysis (TGA) have been employed to characterize the pyrolyzed product. The optimum conditions for the production of porous carbon from cigarette filters in relation to its maximum specific surface area (637 m2/g BET surface area) is understood to be at a heating rate of 5 °C/min at 900 °C for 1 hour.

Comparative removal of phenols and its chlorinated derivatives by carbon-coated monolith: equilibrium, kinetics and regeneration studies

AbstractThe adsorptive performance of phenol, 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) onto carbon-coated monolith (CCM) was comparatively evaluated by batch mode. Experiments were carried out by varying pH, contact time, initial adsorbate concentration and reaction temperature. Regeneration performance of CCM was also assessed. The studies showed optimum 2,4-DCP adsorption, followed by 4-CP and phenol at pH 5. The adsorption equilibration time for phenol, 4CP, 2 and 4-DCP were 600, 470 and 400 min, respectively. The equilibrium adsorption capacities were increased 13.1–37.6 mg/g for 50–250 mg/L (phenol), 51.9–93.7 mg/g for 250–450 mg/L (4-CP) and 84.3–117.5 mg/g for 400–600 mg/L (2,4-DCP), respectively. The adsorption at different temperatures was monolayer as depicted by linear and non-linear isotherm models. Kinetic studies showed better applicability of pseudo-second-order kinetics model. The adsorption increases with increase in reaction temperature from 30 to 50°C showing endothermic a...

Lead removal from aqueous solution using non-modified and nitric acid-modified charred carbon from the pyrolysis of used cigarette filters

AbstractThe efficiency of lead removal from aqueous solution using non-modified and nitric acid-modified charred carbon has been investigated. The charred carbon was obtained through the direct pyrolysis of used cigarette filters, one of the world’s largest solid wastes. The effects of lead solution’s pH, adsorbent dosage, initial lead concentration, and contact time on lead uptake from water by the two carbons were studied. It was revealed that the maximum lead uptake from water was at optimum pH values of 5 and 4 for non-modified and surface modified carbons, respectively. However, the effect of adsorbent dosage was almost identical for both carbons with an optimum value of 0.1 g. The equilibrium was reached after almost 24 h of contact time for both types of carbons. The adsorption data were fitted by the Freundlich and Langmuir adsorption isotherm models. The adsorption for both carbons was best explained by Freundlich adsorption isotherm. The kinetics of the adsorption were also investigated. Pseudo-...

Synthesis, characterization, and performance evaluation of multilayered photoanodes by introducing mesoporous carbon and TiO 2 for humic acid adsorption

Nanostructured photoanodes were prepared via a novel combination of titanium dioxide (TiO2) nanoparticles and mesoporous carbon (C). Four different photoanodes were synthesized by sol–gel spin coating onto a glassy substrate of fluorine-doped tin oxide. The photocatalytic activities of TiO2, TiO2/C/TiO2, TiO2/C/C/TiO2, and TiO2/C/TiO2/C/TiO2 photoanodes were evaluated by exposing the synthesized photoanodes to UV–visible light. The photocurrent density observed in these photoanodes confirmed that an additional layer of mesoporous carbon could successfully increase the photocurrent density. The highest photocurrent density of ~1.022 mA cm−2 at 1 V/saturated calomel electrode was achieved with TiO2/C/C/TiO2 under an illumination intensity of 100 mW cm−2 from a solar simulator. The highest value of surface roughness was measured for a TiO2/C/C/TiO2 combination owing to the presence of two continuous layers of mesoporous carbon. The resulting films had a thickness ranging from 1.605 µm to 5.165 µm after the calcination process. The presence of double-layer mesoporous carbon resulted in a 20% increase in the photocurrent density compared with the TiO2/C/TiO2 combination when only a single mesoporous carbon layer was employed. The improved performance of these photoanodes can be attributed to the enhanced porosity and increased void space due to the presence of mesoporous carbon. For the first time, it has been demonstrated here that the photoelectrochemical performance of TiO2 can be improved by integrating several layers of mesoporous carbon. Comparison of the rate of removal of humic acid by the prepared photoanodes showed that the highest performance from TiO2/C/C/TiO2 was due to the highest photocurrent density generated. Therefore, this study showed that optimizing the sequence of mesoporous carbon layers can be a viable and inexpensive method for enhanced humic acid removal.

Production and applications of electric-arc-furnace slag as solid waste in environmental technologies: a review

Slag, a by-product of steelmaking industries, has invaluable potentials for various environmental applications. Slag is generally produced in different types of furnaces working under various operating conditions and contains alumina, calcium oxide, silica and so on. Physical and chemical properties of a typical slag dictate the distinct methods of slag solidification including air cooling, steam introduction and injection of additives. Owing to this uniquely-widespread range of properties, slags are being increasingly considered attractive materials in a broad range of applications. They are widely used in transportation industry, construction, and cement manufacturing as well as wastewater and water treatment. This makes slag an important substitute for natural resources, leading to significant minimization in natural resource utilization. This paper walks through a comprehensive essay of steelmaking slag retained in a wide range of furnaces, their modifications and their applications alike.

Thermochemical Properties of Glass Wool/Maerogel Composites

Aerogel blankets are composites of silica aerogel particles dispersed in a reinforcing fiber matrix that turns the brittle aerogel into durable and flexible insulating materials. In this study, silica aerogel was loaded on glass wool with different concentrations (0–18.6%) and morphological and thermal characteristics of the aerogel blankets were studied. Rate of modified blanket decomposition was slower at temperatures between 250°C and 650°C due to the retardant effect of the silica aerogel. The average diameter of the fiber for either original glass wool or modified glass wool materials was approximately 20 μm and samples had porous, interconnected particles with dendritic-like structure.