Anaerobic membrane bioreactors for biohydrogen production: recent developments, challenges and perspectives

Biohydrogen as one of the most appealing energy vector for the future represents attractive avenue in alternative energy research. Recently, variety of biohydrogen production pathways has been suggested to improve the key features of the process. Nevertheless, researches are still needed to overcome remaining barriers to practical applications such as low yields and production rates. Considering practicality aspects, this review emphasized on anaerobic membrane bioreactors (AnMBRs) for biological hydrogen production. Recent advances and emerging issues associated with biohydrogen generation in AnMBR technology are critically discussed. Several techniques are highlighted that are aimed at overcoming these barriers. Moreover, environmental and economical potentials along with future research perspectives are addressed to drive biohydrogen technology towards practicality and economical-feasibility

Graphene oxide incorporated polyether sulfone nanocomposite antifouling ultrafiltration membranes with enhanced hydrophilicity

In this study, the polyether sulfone (PES) based membranes containing various concentrations of graphene oxide (GO), polyvinylpyrrolidone (PVP), and polyethylene glycol (PEG) were synthesized via the phase immersion method. This study aims to evaluate the effect of GO addition on the structural properties and performance of the membranes. The membranes were analyzed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transforms infrared spectroscopy (FTIR). The FTIR-ATR spectra indicated the presence of hydroxyl and carboxylic acid groups on the surface of GO-incorporated membranes, which improved their dispersion in the polymeric matrix and hydrophilicity. The SEM analysis of the GO-containing PES membranes confirmed the formation of a well-defined finger-like porous structure presenting adequate water flux (95 l.m(-2).h(-1)) and salt rejection (72%) compared to the pristine PES membranes (46 l.m(-2).h(-1) and similar to 35%, respectively). In addition, the significantly large wettability and considerably improved antibacterial characteristic (against S. aureus and E. coli strains) of the GO-PES membranes are considered impressive features.National University of Sciences and Technology (NUST) Research Directorate; HEC; NRPU [6020]6020; Higher Education Commission, Pakistan, HEC; National University of Sciences and Technology, NUS

Energy efficient harvesting of Spirulina sp. from the growth medium using a tilted panel membrane filtration

Membrane fouling is one of the main drawbacks in membrane-based microalgae harvesting. This study assessed the tilted panel to enhance filtration performance of Spirulina sp. broth. The influences of the operating parameters including the tilting angle, aeration rate and membrane materials on filtration performance and energy consumption were evaluated. Results showed that the system was effective and energy-efficient for membrane fouling control. The permeability peaked at a tilting of 45◦ thanks to combination of aeration and panel tilting. The microfiltration performed better than the ultrafiltration membrane due to the effective impact of air bubbles for foulant scouring that maximized the membrane intrinsic property. Small aeration rate of 1.0 L/min offered a high plateau permeability of 540 L/(m2⋅hr⋅bar) in which reversible fouling almost fully absent. The high permeability could be achieved under a low energy input of 0.2 kWh/m3

Microalgae-based biofuels, resource recovery and wastewater treatment: a pathway towards sustainable biorefinery

Intense utilization of natural fuel resources is threatening the global environment and societal sustainability. It triggers up the need for finding environmental-friendly and sustainable sources of energy. In this perspective, microalgae have emerged as a potential alternative. Microalgae are featured with distinct ability to provide ecological services and respond to the sustainability challenges simultaneously. Microalgae can fix atmospheric CO2, valorize waste resources and can produce a wide variety of bio-products. The promising features of microalgae pitch the idea of establishing a sustainable bio-refinery to draw multifaceted benefits and reinforce the objectives of resource efficient bio-economy. Unfortunately, in the last few years, preferential studies have been carried out to assess the potential of microalgae-based integrated bio-refinery. This review critically discussed the recent developments, opportunities, and barriers in the microalgae bio-industry and wastewater treatment. Particularly, microalgae potentials for biofuels and resources recovery are addressed towards sustainable biorefinery. Moreover, techno-economic and commercial viability of microalgae-led bio-refinery is reviewed to drive this technology towards practicality

High-throughput membrane based gas separation

Membrane technology is an attractive choice for molecular scale separations because of its inherent advantages, such as low cost, high energy efficiency, ease of processing, excellent reliability and small footprint. The commercialization of membranes for gas separations, driven to a large extent by the development of polymeric membranes, is predicted to increase significantly over the next 20 years. However, polymeric membranes are known to have a trade-off between permeability and selectivity. In addition to membrane development, the performance screening of membranes is also a critical area for membrane research. The availability of faster and more efficient techniques to screen a large variety of membranes might lead to faster developments and better optimization of membranes and membranes processes. In order to increase the pace of membrane development, a novel high throughput gas separation set up (HTGS) was designed and fabricated for the fast screening of membranes in the first part of this PhD. This equipment allows gas permeation and selectivity testing of 16 membranes simultaneously at different feed pressure and temperature. In the second part of this PhD research, mixed matrix membranes containing zeolite particles were synthesized. Modified polysulfone was covalently linked to an amine functionalized zeolite in order to improve adhesion between the polymer matrix and zeolite particles. The results showed that the covalent linkage results in the formation of defect-free membranes. Membranes showed better selectivity due to the molecular sieving effect of the zeolite particles. The effect of different operating conditions (pressure, temperature and feed composition) was also studied. The last part of this PhD deals with the investigation of gas separation properties of sulfonated poly (ether ether ketone) (S-PEEK) based membranes, directly prepared from the sulfonated monomer. This is in contrast with all earlier studies where sulfonation only took place after the polymerization, leading to different properties of the final sulfonated polymer. The effect of degree of sulfonation and of counterions on the gas separation properties of the membranes was studied. The membranes showed increased gas permeability and selectivity at higher degree of sulfonation.status: publishe

Polysulfone-ionic liquid based membranes for CO2/N-2 separation with tunable porous surface features

© 2016 Elsevier B.V. A surprisingly simple, yet effective blending method for ionic liquids (ILs) and polysulfone (PSf) is presented in this paper. Not only is the IL properly immobilised in the polymer matrix, which is crucial in high-pressure gas separation applications, but this method also produces tunable porous surfaced membranes that can be useful in several other applications. The size and distribution of the pores are dependent on the type and amount of IL incorporated into the PSf. A membrane formation mechanism is proposed to explain the presence of such a regular surface pore structure. Several commercially available ILs were tested to examine their compatibility with the polymer, and the CO2/N2 gas separation performance of the resulting membrane was screened. ATR-FTIR spectroscopy, FTIR microscopy, and SEM imaging were also employed to shed light on the observed membrane structures.status: publishe

Novel sulfonated and fluorinated PEEK membranes for CO2 separation

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Novel sulfonated and fluorinated PEEK membranes for CO2 separation

© 2016 Elsevier B.V. Polymeric membranes containing sulfonated and fluorinated poly (ether ether ketone) were prepared by solution casting method. The monomers were pre-sulfonated before the polymerization to avoid the side-effects of polymer post-sulfonation, like low degree of sulfonation and poor mechanical and thermal properties. The degree of sulfonation was varied from 20% to 40% to study its influence on the membrane performance. Pure and mixed gas permeation experiments were performed to evaluate the potential of this novel polymer in separation of CO2 from mixtures containing CH4 and N2. Increasing degree of sulfonation improved the CO2 permeability and selectivity for both gas pairs. The incorporation of fluorinated groups further enhanced the performance of membranes by simultaneous increase in gas permeability and selectivity. Diffusion and solubility measurements were also performed in order to get further insight into the role of sulfonic and fluorinated groups in membrane performance. The comparison of results with literature revealed the promising characteristics of the polymer in industrially relevant gas separations.status: publishe

Effect of zeolite surface modification with ionic liquid [APTMS] [Ac] on gas separation performance of mixed matrix membranes

© 2018 Elsevier B.V. This study focuses on using a (3-aminopropyl)trimethoxysilane and acetate ion based ionic liquid to modify zeolite 4A as a filler in a polysulfone (PSf) membrane for CO2/CH4 and CO2/N2 separation, aiming at improving the polymer-filler interaction and separation performance of the mixed matrix membrane (MMM). The ionic liquid was covalently attached onto the zeolite surface. Zeolite modification was confirmed through FTIR analysis of pristine and modified filler. N2 sorption isotherms were used to characterize the porous structure, which showed decrease in surface area and pore volume after surface modification of zeolite. The crystal structure of zeolite 4A remained unaffected after modification with ionic liquid, as shown by XRD and SEM. Moreover, the synthesized PSf-based MMMs were tested in the separation of CO2 from CH4. Experiments were conducted at different temperatures and feed conditions, and pure and mixed gas permeability/selectivity data was reported. This modification of zeolites with methoxy groups containing cation and acetate anion based ionic liquid, resulted in an improved separation performance, as the modified filler enhanced the MMMs selectivity of CO2/CH4 by 37% and for CO2/N2 by 43% at 30 wt% filler loading as compared to pristine filler MMMs. The 3-(trimethoxysilyl)propan-1-aminium acetate coating acts as a selecting film which notably improves the selectivity at marginal expense of CO2 permeance.status: publishe