Applied Chemical Engineering (Transferred)

A two-bed pressure swing adsorption system on a commercial type of zeolite 13X adsorbent has been studied numerically over a wide range of operating conditions to helium separation from gaseous mixture. The model includes energy, mass and momentum balances. The coupled partial differential equations are solved using fully implicit forth order Rung-Kutta scheme in the simulation. The effects of adsorption step pressure, adsorption step time and feed flow rate on the helium purity and recovery were investigated. Results shown that as the adsorption step pressure increases the helium purity will be increased. In addition, the helium recovery increases, and the helium purity decreases when the feed flow rate increases. Finally, the simulation results indicated a very good agreement with some current literature experimental work.

The solubilization of polycyclic aromatic hydrocarbons (PAHs) such as naphthalene, phenanthrene and pyrene by single and mixed anionic dimeric surfactants was investigated and correlated with micellar properties of these surfactants. The surface and micellar properties of single and binary mixed combinations of anionic dimeric surfactants have been studied through surface tension as well as conductivity measurements at 300 K. The associations between their micelle properties and solubilizing efficiency towards PAHs have been quantified and discussed in terms of the molar solubilization ratio (MSR), micelle-water partition coefficient (K_m) and standard free energy of solubilization (ΔG⁰_S).The negative value of ΔG⁰_Sexhibits spontaneously the solubilization process. The MSR values increase with the order “pyrene < phenanthrene < naphthalene”. The current study provides significant information for the selection of mixed dimeric surfactants for solubilizing water-insoluble compounds.

The objective of the study was to evaluate the antioxidant response and DNA damage of heavy metals (Cd, Cu and Cr) in Elodea canadensis. Superoxide dismutase (SOD), catalase (CAT), Glutathione reductase (GR) and lipid peroxidation levels of leaves of Elodea canadensis which was exposed to different concentrations of heavy metals (Cd: 2, 5, 10, 15, 25 ppb; Cu: 200, 500, 1000, 2500 ppb and Cr: 1, 3, 10, 15, 25 ppb) in a hydroponic culture were determined spectrophotometrically. The highest induction in SOD and CAT activities were determined at highest concentration of heavy metals. The Random Amplified Polymorphic DNA Polymerase Chain Reaction (RAPD-PCR) technique was used to investigate the variation of DNA banding patterns of samples that exposed to different concentrations of heavy metals. Changing in band intensity and the gain and loss of bands were demonstrated the genotoxic effect of heavy metals. Bioaccumulation, oxidative responses and DNA damages were shown that Elodea canadensis represents a useful bioindicator.

Glauconite and kaolin are used as adsorbent materials for iron removal from synthetic solutions. Different concentrations of iron solutions have been prepared (10, 20 and 30 mg/L). Different dose of glauconite and kaolin were added (0.1, 0.55 and 1.0 g). Statistical design was used to determine the optimum conditions of iron adsorption on glauconite and kaolin. It is shown that glauconite has high adsorption for iron reaching to 95% while kaolin has lower adsorption for iron. Physical and chemical characterization of glauconite and kaolin was tested. High surface area of glauconite (19.8 m²/g) compared to kaolin (5.4 m²/g) explains its high removal efficiency. 

Pharmaceutically active compounds, emerging extensively in ecosystems as pollutants, have become an important environmental and public health issue, since they can contaminate drinking water and pose threat to wildlife and human health. Therefore, efforts should be made in order to establish proper methods for their inactivation or elimination in the environment. The photocatalytic oxidation of psychoactive drug Duloxetine (DLX) has been investigated. In the case of heterogeneous photocatalytic oxidation, the effect of TiO₂ P25 concentration (0.1–1 g L^-1), initial concentration of H₂O₂ (0.25–0.2 g L^-1) and Fe³⁺ (0.00175–0.014 g L^-1) and pH of the solution (3–10) on initial reaction rates were evaluated, while for homogeneous photocatalytic oxidation the effect of the amount of H₂O₂ (0.25–0.2 g L^-1) and Fe³⁺ (0.00175–0.014 g L^-1) were investigated. Additionally, the conversion of the heteroatoms in the molecule of DLX to inorganic ions (NO₃^-, NH₄⁺, SO₄^2-) during photocatalytic process has been observed, and phytotoxicity testing, using three plant species, was carried out in order to examine the effect of photocatalytic oxidation on the toxicity of DLX. According to the results presented in this study, both heterogeneous and homogeneous photocatalytic oxidation is an efficient methodology for DLX degradation.

This study investigated elimination of Cu⁺² and Pb₂⁺² from prepared stock solutions using MgO, nanostructured MgO sorbents. The maximum cumulative values for copper and lead were 410, 200, 494.9, and 214.6 mg g^-1, for nanostructured MgO, MgO, respectively. Freundlich and Langmuir models describe the sorption equilibrium isotherms. Freundlich model gives the best interpretation for experiment data for these ions.

The most adequate model describing the kinetic with the experimental data using MgO, nanostructured MgO was a first-order kinetic model. Nanostructured MgO probably has an efficient way to remove metal ions due to its high capability to adsorb these ions.

Atrazine is a broad spectrum herbicide of triazine family. It is a chlorine-containing molecule and it can persist in environment. Chemical and biochemical techniques are the main techniques used to decompose the chemicals. In pre-sent study, the dechlorination of atrazine (Atr) via reaction with Sn(II) ion under aqueous media at neutral pH condi-tions was studied. The observed dechlorinated metabolite was 4-Ethylamino-6-isopropylamino-[1,3,5]triazin-2-ol. Identification of dechlorinated product of Atr was performed by using spectroscopic (FTIR) and mass (ESI-MS) spectrometric analysis. The kinetics of the dechlorination of Atr was measured by using pseudo-first order kinetics. The observed reaction constants was, kobs = 6.11x10-2 (at 430 mg/ L of Atr), and kobs = 6.14 x10-2 (at 215 mg/ L of Atr). The calculated half-life (t1/2) period was, t1/2 = 0.204 d (at 430 mg/ L of Atr), and t1/2 = 0.205 d (at 215 mg/ L of Atr).

Carbon materials are continuing in progress to accomplish the requirements of energy conversion and energy storage technologies because of their plenty in nature, high surface area, outstanding electrical properties, and readily obtained from varieties of chemical and natural sources. Recently, carbon-based electrocatalysts have been developed in the quest to replacement of noble metal based catalysts for low cost energy conversion technologies, such as fuel cell, water splitting, and metal-air batteries. Herein, we will present our short overview on recently developed carbon-based electrocatalysts for energy conversion reactions such as oxygen reduction, oxygen evolution, and hydrogen evolution reactions, along with challenges and perspectives in the emerging field of metal-free electrocatalysts.