Simulation of momentum, heat and mass transfer in direct contact membrane distillation: A computational fluid dynamics approach

Hossein Hayer,Omid Bakhtiari,Toraj Mohammadi 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

Membrane distillation is one of the newest methods for water purification. In this study, the behavior ofdirect contact membrane distillation (DCMD) process under various operating conditions wasmathematically modeled using computational fluid dynamics (CFD) method. The effects of differentparameters on transmembrane flux and temperature polarization coefficient (TPC) were measured byglobal sensitivity analysis technique. The sensitivity analysis results indicated that the most affectingdesign parameters in DCMD are membrane thickness and feed temperature.

Preparation of alumina nanotubes for incorporation into CO2 permselective Pebax-based nanocomposite membranes

Nikoo Soltani,Omid Bakhtiari 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.7

Nanocomposite membranes were prepared using Pebax 1657, glycerol triacetate (GTA), and alumina nanotubes (ANTs) by solution casting method. Hydrothermally synthesized ANTs were characterized using SEM, FTIR, and XRD, and additional analysis of FESEM and DSC was also performed on the prepared membranes. ANTs loadings and employed solvent type, dimethylformamide (DMF) or ethanol/water mixture, impacts were investigated on CO2 permeability and ideal CO2/CH4 selectivity of the nanocomposite membranes. CO2 permeability of the ANTs - Pebax nanocomposite membranes was improved compared with the neat Pebax membrane. In the 4 wt% ANTs loaded nanocomposite membrane, chain packing and fractional free volume of its polymeric matrix were tuned by GTA addition (10-40 wt%) to improve the penetrants’ permeability through. The Pebax membrane loaded by 4 and 40 wt% of ANTs and GTA revealed 73.75 and -4.97% changes in its CO2 permeability and ideal CO2/CH4 selectivity, respectively. Successful ANTs functionalization by 3-aminopropyltriethoxysilane agent (FC-ANTs), for their higher compatibility with the polymeric chains, was confirmed using FTIR analysis. 2 wt% FC-ANTs loaded nanocomposite membranes' ideal selectivity prepared by using DMF and ethanol/water mixture solvents improved by 5.71 and 14.7%, respectively, while their CO2 permeability decreased by 11.95 and 11.8%.

Water desalination via novel positively charged hybrid nanofiltration membranes filled with hyperbranched polyethyleneimine modified MWCNT

Mohammad Peydayesh,Toraj Mohammadi,Omid Bakhtiari 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-

Novel positively charged hybrid nanofiltration membranes were fabricated via incorporation of hyperbranched polyethyleneimine modified multiwall carbon nanotubes into polyethersulfone matrix. The main aim of this research is induction of positive charge to negatively charged polymeric membrane by means of self-assembly of positively charged nanoparticles via phase inversion technology. The prepared membranes were evaluated in terms of morphology, surface properties, thermal and mechanical stabilities, nanofiltration performance and antifouling property. The best hybrid membrane with loading of 0.6% of nanoparticles, showed high thermal and mechanical stabilities with mean pore size, molecular weight cut off (MWCO) and isoelectric point of 0.81 nm, 600 Da and 10, respectively. Pure water flux (PWF) of the hybrid membrane compared to the neat polyethersulfone membrane was enhanced 109% and reached to 75.7 L/m2 h. Effects of pressure, temperature, feed concentration and feed pH on separation performance of the membranes were also investigated. The hybrid membrane represented superior performance for heavy metals removal in rejection order of Zn (99.06%) > Mg (97.36%) > Cd (96.72%) > Cu (95.84%) > Ca (95.25%) > Ni (94.63%) > Pb (93.39%), indicating domination of Donnan exclusion mechanism. In addition, the hybrid membrane with higher hydrophilicity and lower roughness showed improved antifouling property and life span.

Preparation of organic-filled compatible nanocomposite membranes for enhanced CO2 permselectivity

Zahra Rezaee,Toraj Mohammadi,Omid Bakhtiari 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.126 No.-

Ideally structured nanocomposite membranes may possess the maximum desired separation propertiesof both filler particles and the host polymer matrix. To approach this goal in this study, some nanocompositedense membranes were prepared using Pebax 1657 and polyaniline nanofiber (PANI) with closedstructural properties in their different concentrations by applying various ethanol/water solvent mixturesand the solution method casting and solvent evaporation phase inversion. The structural characteristicsof the membranes were evaluated using SEM, FTIR (ATR), and XRD analysis and then their CO2 and CH4permeabilities were measured. The structural analysis revealed that the prepared nanocomposite membraneshave defect-free structures and the amorphous PANI nanofibers were dispersed uniformly withinthe nanocomposite membranes leading to their lower crystallinities. As the nanofiber loading increasedin the continuous phase, both CO2 permeability and selectivity of the nanocomposite membranes wereincreased simultaneously and passed over the 1991 Robeson upper bound limit and approached thatof 2008. CO2 permeability and ideal CO2/CH4 selectivity of the nanocomposite membrane loaded by 10wt. % of the PANI nanofibers were increased to 121.2 Barrer and 33, respectively, revealing 64 and 40% increments.

Stabilization of [BMIM][PF6] ionic liquid membrane in structurally optimized multilayer ceramic support through aqueous DEA solution for CO2/CH4 separation

Hamid Reza Mahdavi,Mehran Arzani,Hamed Faramarzi,Omid Bakhtiari,Toraj Mohammadi 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.127 No.-

The stability of the ceramic supported liquid membranes (SLMs) is one of the most interesting researchsubjects. In this work, the SLMs’ stability for CO2/CH4 separation was investigated. Following pressing a-Al2O3 substrates at 400, 600, and 800 bar, colloidal and polymeric TiO2 intermediate and top layers werecoated. Aqueous diethanolamine (DEA) solution was used as solvent in the SLM to optimize supportstructure based on CO2/CH4 separation performance. The pressed support at 800 bar and coated withTiO2 demonstrated best performance and selected for further study. Subsequently, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) ionic liquid (IL) was immobilized inside theselected support and used as the supported ionic liquid membrane (SILM) for CO2/CH4 separation. TheSILM separation performance was evaluated under different pressures and temperatures. Temperaturewas found to has greater effect than pressure due to a decrease in IL’s viscosity and an increase in penetrantdiffusivity. At 25 C and 1 bar, SILM exhibited consistent and reliable performance as CO2 and CH4permeabilities of 244.0 and 7.4 Barrer, respectively, and CO2/CH4 selectivity of 33.0 over 6 h. The findingscontribute to understanding the implementation of multilayer ceramic SILMs for CO2/CH4 separation andhighlight its potential along with opening up new avenues.

Synthesis and gas transport performance of MIL-101/Matrimid mixed matrix membranes

Masoomeh Naseri,Toraj Mohammadi,Seyed Foad Mousavi,Omid Bakhtiari 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.29 No.-

Mixed matrix membranes (MMMs) are composites of highly selective fillers within a polymeric matrix,resulting in higher selectivity and/or flux in gas separation applications. In this work, micron sized MIL-101 crystals with potential of gas separation by adsorption were synthesized and used as filler for thepreparation of MMMs for gas separation. Gas adsorption measurements were performed for CO2, CH4and N2 using MIL-101 crystals and the results showed significant adsorption of CO2 compared with thetwo other gases at different pressures. SEM images and XRD analysis were used to characterize the fillerparticles and the synthesized membranes. MIL-101/Matrimid MMMs were synthesized with up to30 wt.% loading of filler particles. SEM images showed good dispersion of the particles in the polymericmatrix and also good adhesion between the filler particles and the polymer. Permeability measurementswere performed for pure gases of CO2, CH4 and N2 and the results showed improved CO2/CH4 and CO2/N2ideal selectivities for the MMMs compared with those for the neat Matrimid membrane. For the MMMswith 10 wt.% loading, permeability of CO2 was found as 6.95 Barrer and ideal selectivities for CO2/CH4and CO2/N2 were as 55.77 and 52.92, respectively.