Nashaat N. Nassar

Rapid removal and recovery of Pb(II) from wastewater by magnetic nanoadsorbents.

Iron oxide nanoadsorbents are cost-effective adsorbents that provide high adsorption capacity, rapid adsorption rate and simple separation and regeneration. In this study, Fe(3)O(4) nanoadsorbents have been employed for the removal of Pb(II) ions from aqueous solutions by a batch-adsorption technique. The effects of contact time, initial concentration of Pb(II) ions, temperature, solution pH and coexisting ions on the amount of Pb(II) adsorbed have been investigated. Pb(II) adsorption was fast, and equilibrium was achieved within 30 min. The amount of Pb(II) adsorbed increased as temperature increased, suggesting an endothermic adsorption. The optimal pH value for Pb(II) adsorption was around 5.5. Furthermore, the addition of coexisting cations such as Ca(2+), Ni(2+), Co(2+), and Cd(2+) has no remarkable influence on Pb(II) removal efficiency. The adsorption equilibrium data fitted very well to Langmuir and Freundlich adsorption isotherm models. The thermodynamics of Pb(II) adsorption onto the Fe(3)O(4) nanoadsorbents indicated that the adsorption was spontaneous, endothermic and physical in nature. The desorption and regeneration studies have proven that Fe(3)O(4) nanoadsorbents can be employed repeatedly without impacting its adsorption capacity.

Effect of surface acidity and basicity of aluminas on asphaltene adsorption and oxidation

This study investigates the effect of surface acidity and basicity of aluminas on asphaltene adsorption followed by air oxidation. Equilibrium batch adsorption experiments were conducted at 25°C with solutions of asphaltenes in toluene at concentrations ranging from 100 to 3000 g/L using three conventional alumina adsorbents with different surface acidity. Data were found to better fit to the Freundlich isotherm model showing a multilayer adsorption. Results showed that asphaltene adsorption is strongly affected by the surface acidity, and the adsorption capacities of asphaltenes onto the three aluminas followed the order acidic>basic and neutral. Asphaltenes adsorbed over aluminas were subjected to oxidation in air up to 600°C in a thermogravimetric analyzer to study the catalytic effect of aluminas with different surface acidity. A correlation was found between Freundlich affinity constant (1/n) and the catalytic activity. Basic alumina that has the lowest 1/n value, depicting strongest interactions, has the highest catalytic activity, followed by neutral and acidic aluminas, respectively.

Kinetics, Mechanistic, Equilibrium, and Thermodynamic Studies on the Adsorption of Acid Red Dye from Wastewater by γ-Fe2O3 Nanoadsorbents

The presence of dyestuffs in wastewater poses an environmental concern since these organic contaminants are toxic to aquatic and non-aquatic life. In addition, these contaminants are difficult to remove or biodegrade, which poses a challenge to the conventional wastewater treatment techniques. In this work, the adsorption of acid red dye 27 (AR27) onto γ-Fe2O3 nanoadsorbents was studied for the removal of red dye from aqueous solutions by the batch-adsorption technique. The experiments were carried out at different conditions of contact time, initial AR27 concentration, temperature, co-existing ions, and solution pH. It was found that the adsorption was a rapid process, and equilibrium was achieved in less than 4 minutes. The removal of AR27 decreased with the increase in solution pH and temperature. Furthermore, the addition of chloride and nitrate anions has no remarkable influence on AR27 removal efficiency. On the other hand, the effects of sulfate and bicarbonate anions on the removal of AR27 were significant. The adsorption equilibrium data fitted very well using Langmuir and Freundlich adsorption isotherm models. The data obtained from adsorption isotherms at different temperatures were used to calculate thermodynamic quantities of adsorption, such as standard Gibbs free energy change , enthalpy change , and entropy change . The adsorption process was found to be spontaneous, exothermic and physical in nature. The results indicate that γ-Fe2O3 nanoadsorbents could be employed for the removal of dyes from wastewater.

Nanoparticle Preparation Using the Single Microemulsions Scheme

Nanoparticles serve the need for advanced materials with specific chemical, physical, and electronic properties. These proper- ties can be attained by manipulating the particle size. Consequently, size control has been recognized as a key factor for selecting a nanoparticle preparation technique. (w/o) Microemulsions, or reverse micelles, have been successfully used to prepare wide variety of nanoparticles with controlled sizes. Studies showed that adjusting microemulsion and/or operation variables provides a key to controlling nanoparticle size and polydispersity. The effect of a given variable, however, relies heavily on the reactant addition scheme. The mixing of two microemulsions scheme has been widely used in the literature, and the effect of microemulsion and operation variables on inter- micellar nucleation and growth was detailed. The single microemulsions reactant addition scheme, on the other hand, enables intramicel- lar nucleation and growth, and therefore, may lead to a different response. Moreover, studies on nanoparticle preparation using the single microemulsions scheme involved more of reactive surfactants and introduced the concept nanoparticle uptake, which pertains to the maximum colloidal concentration of nanoparticles that can be stabilized in a microemulsion system. This review looks into the mecha- nisms controlling nanoparticle formation and compares literature trends reported for the effect of microemulsion and operation variables on the nanoparticle size and polydispersity for the single microemulsions reactant addition scheme. Moreover, it sheds some light on nanoparticle uptake and its significance.

Adsorptive removal of oil spill from oil-in-fresh water emulsions by hydrophobic alumina nanoparticles functionalized with petroleum vacuum residue

Oil spills on fresh water can cause serious environmental and economic impacts onshore activities affecting those who exploit freshwater resources and grassland. Alumina nanoparticles functionalized with vacuum residue (VR) were used as a low-cost and high hydrophobic nanosorbents. The nanomaterial resulting showed high adsorption affinity and capacity of oil from oil-in-freshwater emulsion. The effects of the following variables on oil removal were investigated, namely: contact times, solution pH, initial oil concentrations, temperature, VR loadings and salinity. Kinetic studies showed that adsorption was fast and equilibrium was achieved in less than 30 min. The amount adsorbed of oil was higher for neutral system compared to acidic or basic medium. Increasing the VR loading on nanoparticle surface favored the adsorption. Results of this study showed that oil removal for all systems evaluated had better performance at pH value of 7 using nano-alumina functionalized with 4 wt% VR. Adsorption equilibrium and kinetics were evaluated using the Polanyi theory-based Dubinin-Ashtakhov (DA) model, and pseudo-first and pseudo-second order-models, respectively.

Melt Intercalation in Montmorillonite/Polystyrene Nanocomposites

Abstract Atactic polystyrene (PS) was used to study the effect of flow field (shear and/or elongational) on the intercalation of polymer/clay nanocomposites (PNC). Three grades of (PS), with different molecular weights, were compounded with an ammonium-modified montmorillonite (Cloisite 10A) in a twin-screw extruder (TSE). The compounds were subsequently fed to a single screw extruder, fitted with one of three specially designed torpedo-attachments. The attachments were designed to provide combinations of different levels of shear and elongational deformations. The resins, TSE compounds, and final PNCs were characterized for the degree of intercalation, degradation, rheological behavior, and mechanical properties. The data showed that the thermal decomposition of the quaternary ammonium intercalant caused severe damage to both PNC components: a collapse of the organoclay interlayer spacing, and the thermo-oxidative degradation of PS. In spite of these detrimental effects, the attachment employing combined elongational and shear flow resulted in generally larger gallery spacing and more improvement of the mechanical properties than the other two attachments.

Removal of oil from oil-in-saltwater emulsions by adsorption onto nano-alumina functionalized with petroleum vacuum residue

Formation water from oilfields is one of the major environmental issues related to the oil industry. This research investigated oil adsorption onto nanoparticles of hydrophobic alumina and alumina nanoparticles functionalized with a petroleum vacuum residue (VR) at 2 and 4wt% to reduce the amount of oil in oil-saltwater emulsions at different pH values (5, 7 and 9). The initial concentration of crude oil in water ranged from 100 to 500mg/L. The change in oil concentration after adsorption was determined using a UV-vis spectrophotometer. The results indicated that all of the systems performed more effectively at a pH of 7 and using Al/4VR material. The oil adsorption was higher for neutral and acid systems compared with basic ones, and it was improved by increasing the amount of VR on the surface of the alumina. Additionally, the amount of NaCl adsorbed onto nanoparticles was estimated for different mixtures. The adsorption equilibrium and kinetics were evaluated using the Dubinin-Astakhov model, the Brunauer-Emmet-Teller model, and pseudo-first- and pseudo-second-order models, with a better fitting to the Brunauer-Emmet-Teller model and pseudo-second-order model.

Scavenging H2S(g) from oil phases by means of ultradispersed sorbents

Ultradispersed catalysts significantly enhance rates of reaction and mass transfer by virtue of their extended and easy accessible surface. These attractive features were exploited in this study to effectively capture H(2)S((g)) from an oil phase by ultradispersed sorbents. Sorption of H(2)S((g)) from oil phases finds application for scavenging H(2)S((g)) forming during heavy oil extraction and upgrading. This preliminary investigation simulated heavy oil by (w/o) microemulsions having 1-methyl-naphthalene; a high boiling point hydrocarbon, as the continuous phase. H(2)S((g)) was bubbled through the microemulsions which contained the ultradispersed sorbents. The type and origin of sorbent were investigated by comparing in situ prepared FeOOH and commercial alpha-Fe(2)O(3) nanoparticles as well as aqueous FeCl(3) and NaOH solutions dispersed in the (w/o) microemulsions. The in situ prepared FeOOH nanoparticles captured H(2)S((g)) in a chemically inactive form and displayed the highest sorption rate and capacity. Temperature retarded the performance of FeOOH particles, while mixing had no significant effect.

Maghemite nanosorbcats for methylene blue adsorption and subsequent catalytic thermo-oxidative decomposition: Computational modeling and thermodynamics studies.

In this study methylene blue (MB) has been investigated for its adsorption and subsequent catalytic thermo-oxidative decomposition on surface of maghemite (γ-Fe2O3) nanoparticles. The experimental adsorption isotherm fit well to the Freundlich model, indicating multi-sites adsorption. Computational modeling of the interaction between the MB molecule and γ-Fe2O3 nanoparticle surface was carried out to get more insights into its adsorption behavior. Adsorption energies of MB molecules on the surface indicated that there are different adsorption sites on the surface of γ-Fe2O3 confirming the findings regarding the adsorption isotherm. The catalytic activity of the γ-Fe2O3 nanoparticles toward MB thermo-oxidative decomposition has been confirmed by subjecting the adsorbed MB to a thermo oxidation process up to 600 °C in a thermogravimetric analyzer. The experimental results showed a catalytic activity for post adsorption oxidation. The oxidation kinetics were studied using the Ozawa-Flyn-Wall (OFW) corrected method. The most probable mechanism functions were fifth and third orders for virgin MB and MB adsorbed onto γ-Fe2O3 nanoparticles, respectively. Moreover, the results of thermodynamic transition state parameters, namely changes in Gibbs free energy of activation (ΔG(‡)), enthalpy of activation (ΔH(‡)), and entropy of activation (ΔS(‡)), emphasized the catalytic activity of γ-Fe2O3 nanoparticles toward MB oxidation.

Comparative study on thermal cracking of Athabasca bitumen

In this study, three commonly used isoconversional methods, namely: Ozawa–Flynn–Wall (OFW), Kissinger–Akahira–Sunose (KAS), and the advanced non-linear integral method of Vyazovkin (NLN) were employed for the first time for calculating the activation energy for thermal cracking of Athabasca bitumen under inert conditions. Thermal cracking of Athabasca bitumen was carried out at nonisothermal conditions at different heating rates under nitrogen atmosphere using thermogravimetic analyzer (TG). One isothermal TG experiment was conducted for model prediction. Differences in the values of activation energy determined from the three methods selected have been demonstrated. These differences were mainly attributed to the approximations used for the temperature integral employed in the integral methods. Nonetheless, all the methods tested in this study provided satisfactory isothermal predictions. The study showed that, among the three methods tested, the NLN method provided more accurate results. This is because NLN is approximation free and uses small time segments for the temperature integral.