Ahmad Arabi Shamsabadi

A review on chitosan-based adsorptive membranes.

Membrane adsorbents have emerged as powerful and attractive tools for the removal of hazardous materials such as dyes and heavy metal ions, mainly in trace amounts, from water resources. Among membrane adsorbents, those prepared from or modified with chitosan biopolymer and its derivatives are cases of interest because of chitosan advantages including biocompatibility, biodegradability, nontoxicity, reactivity, film and fiber forming capacity and favorable hydrophilicity. This review is oriented to provide a framework for better insight into fabrication methods and applications of chitosan-based adsorptive membranes. Critical aspects including thermokinetic analyses of adsorption and regeneration capacity of the membrane adsorbents have been also overviewed. Future of chitosan-based adsorptive membranes might include efforts for the improvement of mechanical stability and reusability and also most targeted application of appropriate copolymers as well as nanostructures in preparing high performance adsorptive membranes.

Facilitated transport of CO2 through novel imidazole-containing chitosan derivative/PES membranes

In the present study, a new imidazole alkyl derivative of chitosan (Im-CS) is synthesized and characterized by FT-IR and 1H-NMR spectroscopy. This derivative was blended in various ratios with polyethersulfone (PES) to fabricate newly integrally skinned PES membranes. Scanning Electron Microscopy (SEM) was used to study the changes in the membrane morphologies. The prepared membranes were used for the separation of CO2 from CH4. Our findings indicated that by adding a small amount of Im-CS, membrane performance was improved significantly. In addition, the effect of feed pressure and feed temperature on the performance of the prepared membranes was investigated in this study.

Mitigation of Thin-Film Composite Membrane Biofouling via Immobilizing Nano-Sized Biocidal Reservoirs in the Membrane Active Layer

This work investigates the use of a silver-based metal-organic framework (MOF) for mitigating biofouling in forward-osmosis thin-film composite (TFC) membranes. This is the first study of the use of MOFs for biofouling control in membranes. MOF nanocrystals were immobilized in the active layer of the membranes via dispersion in the organic solution used for interfacial polymerization. Field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) characterization results showed the presence of the MOF nanocrystals in the active layer of the membranes. The immobilization improved the membrane active layer in terms of hydrophilicity and transport properties without adversely affecting the selectivity. It imparted antibacterial activity to the membranes; the number of live bacteria attached to the membrane surface was over 90% less than that of control membranes. Additionally, the MOF nanocrystals provided biocidal activity that lasted for 6 months. The immobilization improved biofouling resistance in the membranes, whose flux had a decline of 8% after 24 h of operation in biofouling experiments, while that of the control membranes had a greater decline of ∼21%. The better biofouling resistance is due to simultaneous improvement of antiadhesive and antimicrobial properties of the membranes. Fluorescence microscopy and FE-SEM indicated simultaneous improvement in antiadhesive and antimicrobial properties of the TFN membranes, resulting in limited biofilm formation.

Efficient CO2-removal using novel mixed-matrix membranes with modified TiO2 nanoparticles

Modified TiO2 nanoparticles were successfully embedded into Pebax-1657 as a polymer matrix. The resulting mixed-matrix membranes are highly efficient for CO2 removal especially at high pressures. Nanofiller grafting with 3-aminopropyl-diethoxymethylsilane (silane agent) and surface modification with carboxymethyl chitosan led to Pebax-modified-TiO2 composite membranes with 50–60% increase in CO2 permeability and 30–33% in CO2/N2 selectivity compared to the pristine Pebax. The performance of the nanocomposite membranes is favorably above the 2008 Robeson upper bound. Stability analyses of the prepared membranes showed acceptable durability of the membranes in permeation experiments. Characterization techniques such as FT-IR, DSC, TGA, and SEM showed the compatibility of the nanoparticles and the polymer, better thermal stability of the nanocomposite membranes, and satisfactory dispersion of nanofillers into the polymer.

Separation of manganese from aqueous solution using an emulsion liquid membrane

The present study deals with the carrier-facilitated transport of manganese from this acidic leach solution in an emulsion liquid membrane system. The ELM consists of MDEHPA as the extractant, industrial solvent as the inert diluent, non-ionic polyethylene glycol as a surfactant and sulfuric acid as the stripping solution. The main parameters influencing the ELM stability and the extraction of manganese are the pH of the acidic leach solution, mixing speed, concentrations of the stripping solution, extractant and surfactant, phase ratio and treatment ratio. With respect to the parameters mentioned, the optimum conditions for the process were determined. The results demonstrated the possibility of 93% extraction of manganese by ELM from the acidic leach solutions at optimum operational conditions.

Mathematical Modeling of CO2/CH4 Separation by Hollow Fiber Membrane Module Using Finite Difference Method

Removal of CO 2 in landfill gas recovery processes and fractured wells as well as its application in enhanced oil recovery and its environmental aspects are of interest. Also separation of CO 2 from CH 4 in Ethylene Oxide plant is an environmental policy of Marun Petrochemical Company. In the present work, a shell-fed hollow fiber module was modeled mathematically for CO 2 separation from CH 4 . Finite difference method was used for solving the equations. Comparison between co-current and counter-current flow patterns showed that for all conditions, counter current pattern had better efficiency for CO 2 /CH 4 separation. Influence of operating parameters such as feed pressure, permeate pressure, feed flow rate, fiber length and CO 2 concentration of feed on separation efficiency of CO 2 /CH 4 mixture was investigated. Also the effect of feed and permeate pressures on required membrane area showed that the membrane area increases by increasing permeate pressure and decreases by increasing feed pressure. The modeling offers valuable data about feasibility study and economical evaluation of a gas separation unit operation as a helpful unit in the industry.

Simultaneous Improvement of Antimicrobial, Antifouling, and Transport Properties of Forward Osmosis Membranes with Immobilized Highly-Compatible Polyrhodanine Nanoparticles

This work shows that incorporating highly compatible polyrhodanine nanoparticles (PRh-NPs) into a polyamide (PA) active layer allows for fabricating forward osmosis (FO) thin-film composite (TFC)-PRh membranes that have simultaneously improved antimicrobial, antifouling, and transport properties. To the best of our knowledge, this is the first reported study of its kind to this date. The presence of the PRh-NPs on the surface of the TFC-PRh membranes active layers is evaluated using FT-IR spectroscopy, SEM, and XPS. The microscopic interactions and their impact on the compatibility of the PRh-NPs with the PA chains were studied using molecular dynamics simulations. When tested in forward osmosis, the TFC-PRh-0.01 membrane (with 0.01 wt % PRh) shows significantly improved permeability and selectivity because of the small size and the high compatibility of the PRh-NPs with PA chains. For example, the TFC-PRh-0.01 membrane exhibits a FO water flux of 41 l/(m2·h), higher than a water flux of 34 l/(m2·h) for the pristine TFC membrane, when 1.5 molar NaCl was used as draw solution in the active-layer feed-solution mode. Moreover, the reverse solute flux of the TFC-PRh-0.01 membrane decreases to about 115 mmol/(m2·h) representing a 52% improvement in the reverse solute flux of this membrane in comparison to the pristine TFC membrane. The surfaces of the TFC-PRh membranes were found to be smoother and more hydrophilic than those of the pristine TFC membrane, providing improved antifouling properties confirmed by a flux decline of about 38% for the TFC-PRh-0.01 membranes against a flux decline of about 50% for the pristine TFC membrane when evaluated with a sodium alginate solution. The antimicrobial traits of the TFC-PRh-0.01 membrane evaluated using colony-forming units and fluorescence imaging indicate that the PRh-NPs hinder cell deposition on the TFC-PRh-0.01 membrane surface effectively, limiting biofilm formation.

Crystal structure of 5,7,12,14-tetra­hydro-5,14:7,12-bis­([1,2]benzeno)­penta­cene-6,13-dione

5,7,12,14-Tetrahydro-5,14:7,12-bis([1,2]benzeno)pentacene-6,13-dione, used as a precursor in the synthesis of polymers of intrinsic microporosity (PIM) membranes, recrystallizes from DMF.

Mixed Matrix Membranes for CO2 Separations

Abstract The membrane technology has great potential for practical CO2 removal. To realize the potential, efforts have been made to fabricate membranes with satisfactory separation efficiency and durability. Mixed matrix membranes (MMMs), which contain nanomaterials dispersed in polymer matrices, have appealing CO2 separation performances. They usually have facile processability and are inexpensive to manufacture. However, developing a completely defect-free polymer/filler interface is still a challenge. To overcome the membrane performance limitations and the fabrication challenges, numerous nanomaterials have been synthesized and applied for fabricating MMMs. This chapter reviews and puts in perspective advances made in fabricating novel MMMs containing nanomaterials such as nonporous nanoparticles, metal and metal oxides, zeolites, carbon-based nanomaterials, organic frameworks (metal and covalent), and sheetlike two-dimensional nanomaterials. Effects of defects at the interfaces of polymers and nanomaterials, and the addition of adhesion agents are discussed. Several nanomaterial modification techniques used for alleviating the MMM manufacturing problems are also covered.