Dipak Rana

Bio: Dipak Rana is an academic researcher from University of Ottawa. The author has contributed to research in topics: Membrane & Contact angle. The author has an hindex of 54, co-authored 270 publications receiving 9283 citations.

Insight Studies on Metal-Organic Framework Nanofibrous Membrane Adsorption and Activation for Heavy Metal Ions Removal from Aqueous Solution.

Abstract: Electrospun nanofiber composite membranes containing water-stable metal-organic frameworks (MOFs) particles (Zr-based MOF-808) supported on polyacrylonitrile (PAN) nanofiber synthesized via co-electrospinning have been prepared. MOF particles were dispersed in the organic polymer, and their subsequent presence was inferred by scanning electron microscopy. Membrane performance in heavy metal ion adsorption in batch filtration was evaluated on the basis of Cd2+ and Zn2+ ions sequestration. The adsorption capacities of the pristine MOF and the MOF composite membrane revealed that MOF particles in the membrane could be accessed for adsorption in the hydrophilic PAN membranes. The maximum adsorption capacities were 225.05 and 287.06 mg g–1 for Cd2+ and Zn2+, respectively. Conventional thermal activation of pristine MOF and composite membrane revealed a crystal downsizing, while “hydractivation” produced an expanded MOF with enhanced adsorption potentials. The PAN/MOF-808 “hydractivated” composite membrane coul...

Preparation and characterization of highly hydrophobic poly(vinylidene fluoride) – Clay nanocomposite nanofiber membranes (PVDF–clay NNMs) for desalination using direct contact membrane distillation

Abstract: Electrospun nanofiber membranes consisting of poly(vinylidene fluoride) (PVDF) blended with clay nanocomposites were prepared and tested in this paper for direct contact membrane distillation (DCMD) applications. Various compositions of PVDF–clay nanocomposite nanofiber membranes (NNMs) were prepared and characterized by water contact angle, Fourier transform infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy and investigated for DCMD. The incorporation of clay nanocomposites increase the hydrophobicity of the membranes, which increase as the concentration of clay nanocomposite increases in the mixture. The highest water contact angle achieved was 154.20 ± 3.04°. The melting point of the PVDF–clay electrospun nanofiber membrane increases with the increasing concentration of clay indicating that the clay particles influence the crystallization process of the nanocomposite membrane. The PVDF–clay NNMs showed improved performance in DCMD applications and provide a way to prevent pore wetting in DCMD process.

Metal–organic frameworks supported on nanofibers to remove heavy metals

Abstract: Fe(III) and Zr(IV) based metal–organic frameworks (MOFs) were enmeshed in polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF) electro-spun nanofibers to produce nanofibrous MOF membranes (NMOM) The pristine MOFs showed high adsorption capacity for lead ions and mercury ions from aqueous solution The Fe(III) based MOFs with PAN based NMOM exhibited a high flux of 348 L m−2 h−1 with a permeance of 870 L m−1 h−1 bar−1 At room temperature, the NMOM could treat 395 mL of 100 ppb Pb(II) solution, while maintaining a drinking water standard of <10 ppb of permeate Pb(II) concentration Due to the high compatibility between MOF and PVDF nanofibers, MOF was not detected in the permeate even after four cycles of filtration and desorption experiments and more than 90% of the NMM adsorption capacity was retained The excellent filtration performance and re-generability of the membrane coupled with the hydro-stability of the MOFs suggests that the NMOMs have potential for water treatment through the process of membrane adsorption

Strategies for effective oral insulin delivery with modified chitosan nanoparticles: A review

Abstract: Over the last few decades, various natural polymers have been applied to the problem of oral insulin delivery using advanced nanotechnology. Parenteral administration of insulin is widely accepted, but administration via the oral route could overcome the poor patient compliance with repeated injection. Polymers from natural as well as synthetic sources have recently been used in the synthesis of insulin delivery vehicles suitable for oral administration. The biopolymer chitosan has been widely studied in oral insulin delivery due to its favorable properties such as biocompatibility, biodegradability, non-immunogenicity and non-toxicity. This review focuses on progress in the synthesis of chitosan and modified chitosan nanoparticles for efficient oral insulin delivery, with an emphasis on the biological efficacy of the nanoparticles. Obstacles to oral delivery and possible remedies are also brought into focus. Modifications to protect insulin from the harsh acidic environment of the gastro-intestinal (GI) tract are described. Chemical barriers such as the acidic gastric pH and the presence of proteolytic enzymes in the stomach and intestine limit the effective absorption of external insulin within the GI tract. Absorption of insulin is physically hindered by the absorption barrier consisting of a single layer of columnar epithelial cells joined at the apical surface by a tight junction complex. The presence of negative charges in the junction complex leads to segregation of the apical layer from the basolateral compartment of the epithelial cells, making the intestinal environment selective for particles based on size and charge. Nanoparticles are able to overcome these barriers and deliver insulin. While this technology still has some drawbacks, chitosan and modified chitosan nanoparticles are highly promising agents for oral insulin delivery.

Preparation of thin-film-composite polyamide membranes for desalination using novel hydrophilic surface modifying macromolecules

Abstract: A new concept for the preparation of thin-film-composite (TFC) reverse osmosis (RO) membrane by interfacial polymerization on porous polysulfone (PS) support using novel additives is reported. Hydrophilic surface modifying macromolecules (LSMM) were synthesized both ex situ by conventional method (cLSMM), and in situ within the organic solvent of the TFC system (iLSMM). The effects of these LSMMs on the fouling of the TFC RO membranes used in the desalination processes were studied. FTIR results indicated that both cLSMM and iLSMM were present in the active layer of the TFC membranes. SEM micrographs depicted that heterogeneity of the surface increases for TFC membranes compared to the control PS membrane, and that higher concentrations of LSMM provided smoother surface. AFM characteristic data presented that the surface roughness of the skin surface increases for TFC membranes compared to the control. The RO performance results showed that the addition of the cLSMM significantly decreased the salt rejection of the membrane and slightly reduced the flux, while in the case of the iLSMM, salt rejection was improved but the flux declined at different rates for different iLSMM concentrations. The membrane prepared by the iLSMM exhibited less flux decay over an extended operational period.

Electrospinning and Electrospun Nanofibers: Methods, Materials, and Applications

Abstract: Electrospinning is a versatile and viable technique for generating ultrathin fibers. Remarkable progress has been made with regard to the development of electrospinning methods and engineering of electrospun nanofibers to suit or enable various applications. We aim to provide a comprehensive overview of electrospinning, including the principle, methods, materials, and applications. We begin with a brief introduction to the early history of electrospinning, followed by discussion of its principle and typical apparatus. We then discuss its renaissance over the past two decades as a powerful technology for the production of nanofibers with diversified compositions, structures, and properties. Afterward, we discuss the applications of electrospun nanofibers, including their use as "smart" mats, filtration membranes, catalytic supports, energy harvesting/conversion/storage components, and photonic and electronic devices, as well as biomedical scaffolds. We highlight the most relevant and recent advances related to the applications of electrospun nanofibers by focusing on the most representative examples. We also offer perspectives on the challenges, opportunities, and new directions for future development. At the end, we discuss approaches to the scale-up production of electrospun nanofibers and briefly discuss various types of commercial products based on electrospun nanofibers that have found widespread use in our everyday life.

Advanced functional polymer membranes

Abstract: A review. This feature article provides a comprehensive overview on the development of polymeric membranes having advanced or novel functions in the various membrane sepn. processes for liq. and gaseous mixts. (gas sepn., reverse osmosis, pervaporation, nanofiltration, ultrafiltration, microfiltration) and in other important applications of membranes such as biomaterials, catalysis (including fuel cell systems) or lab-on-chip technologies.

A review of reverse osmosis membrane materials for desalination—Development to date and future potential

Abstract: Reverse osmosis (RO) is currently the most important desalination technology and it is experiencing significant growth. The objective of this paper is to review the historical and current development of RO membrane materials which are the key determinants of separation performance and water productivity, and hence to define performance targets for those who are developing new RO membrane materials. The chemistry, synthesis mechanism(s) and desalination performance of various RO membranes are discussed from the point of view of membrane materials science. The review starts with the first generation of asymmetric polymeric membranes and finishes with current proposals for nano-structured membrane materials. The paper provides an overview of RO performance in relation to membrane materials and methods of synthesis. To date polymeric membranes have dominated the RO desalination industry. From the late 1950s to the 1980s the research effort focussed on the search for optimum polymeric membrane materials. In subsequent decades the performance of RO membranes has been optimised via control of membrane formation reactions, and the use of poly-condensation catalysts and additives. The performance of state-of-the-art RO membranes has been highlighted. Nevertheless, the advances in membrane permselectivity in the past decade has been relatively slow, and membrane fouling remains a severe problem. The emergence of nano-technology in membrane materials science could offer an attractive alternative to polymeric materials. Hence nano-structured membranes are discussed in this review including zeolite membranes, thin film nano-composite membranes, carbon nano-tube membranes, and biomimetic membranes. It is proposed that these novel materials represent the most likely opportunities for enhanced RO desalination performance in the future, but that a number of challenges remain with regard to their practical implementation.

Nanofiltration membranes review: Recent advances and future prospects

Abstract: Nanofiltration (NF) membranes have come a long way since it was first introduced during the late 80's. With properties in between those of ultrafiltration (UF) and reverse osmosis (RO), NF membranes have been used in many interesting applications especially in water and wastewater treatment and desalination. Other applications include those in pharmaceutical and biotechnology, food and non-aqueous types of application. This review will comprehensively look at the recent advances in NF membranes research. Significant development has taken place in terms of the fundamental understanding of the transport mechanism in NF membranes. This has been translated into predictive modeling based on the modified extended Nernst–Planck equation. Similarly various methods have been used to fabricate improved NF membranes especially through interfacial polymerization incorporating nanoparticles and other additives, UV grafting/photografting, electron beam irradiation, plasma treatment and layer-by-layer modification. New applications were also explored in many industries. However fouling is still a prevalent issue that may hinder successful application of NF membranes. Efforts towards NF fouling prevention and mitigation have also been reported. The review ends with several recommendations on the future prospect of NF membranes research and development.