In this study, direct-contact membrane distillation (DCMD) process is simulated using computational fluid dynamics. The DCMD process is typically used to provide pure water from salt water. The system consists of a flat-sheet membrane, a feed channel with salt water as the food, and a permeate channel. The cross-current flow pattern is used in this process. The governing equations to simulate the process include the heat, mass, and momentum balance equations. The developed equations are solved numerically using the finite element scheme. To improve accuracy of the simulation results and precision of water vapor diffusion coefficient estimation in membrane pores, a composition of Poiseuille and Knudsen diffusion coefficient is applied. The simulation results are compared with experimental data obtained from the literature and a satisfactory agreement is obtained (average error less than 5%).
a b s t r ac tIn this work, the potential of the prepared polyethersulfone (PES)/NaX nanocomposite nanofibrous adsorbents for the removal of Cu 2+ , Co 2+ and Fe 2+ from aqueous solution were investigated. For this purpose, PES/polyacrylonitrile/polyvinylpyrrolidone/NaX (PES/NaX) nanocomposite nanofibers were prepared using the electrospinning process. The prepared nanocomposite nanofibers were characterized by scanning electron microscopy analysis. The effect of different parameters such as zeolite concentration, the dosage of adsorbent, pH, contact time, and the initial concentration of Cu 2+ , Co 2+ and Fe 2+ ions as well as temperature on the efficiency of adsorption were studied in a batch system. The adsorption results showed that the affinity of PES/NaX nanocomposite nanofibrous adsorbent for the removal of metal ions was on the agenda Cu 2+ > Co 2+ > Fe 2+ . The kinetic data of metal ions were analyzed by pseudo-first-order, pseudo-second-order and double-exponential kinetic models. Isotherm models namely Freundlich, Langmuir, Redlich-Peterson and Temkin were applied to explain the equilibrium data of metal ions. The maximum monolayer sorption capacities of Cu 2+ , Co 2+ and Fe 2+ were estimated to be 783.3, 654.4 and 642 (mg/g) in an equilibrium time of 60 min and temperature of 45°C. Evaluation of thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that the nature of metal ions sorption onto the PES/NaX nanocomposite nanofibrous adsorbent was feasible and endothermic. The reusability of the PES/NaX nanocomposite nanofibrous adsorbent was also evaluated after four adsorption-desorption cycles as well.
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