Potential application of biomass derived graphene for COVID-19 pandemic

Since the emergence of the novel coronavirus disease (COVID-19) pandemic, intense research has been carried out to find the effective vaccine. However, this issue remains as a global challenge. Graphene has captured various attention due to promising antimicrobial and antiviral applications, hydrophobic characteristic and superior electrical conductivity. Recently, biomass derived graphene also promises great opportunity to combat the spread COVID-19. In this paper, we demonstrated the ability and role of biomass derived graphene as superhydrophobic coating, biosensors and disinfectant in the fight against COVID-19.

Optimization of LNG Cold Energy Utilization via Power Generation, Refrigeration, and Air Separation

Natural gas is conventionally transported in its liquid form or Liquid Natural Gas (LNG). It is then transported using cryogenic insulated LNG tankers. At receiving terminals, LNG is regasified prior to distributing it through gas distribution system. Seawater has been used as the heat source, which leads to vast amount of cold energy discarded into the water. This work presents the use of LNG cold energy around Melaka Refining Company (MRC). The cold energy is utilized in power generation, propylene refrigeration cycle, and air separation plants. These systems are designed and simulated using a commercial process simulation software. Capital cost (CAPEX) function and revenues of each system are further developed as a function of LNG flowrates. These developed correlations are then used in an optimization problem to seek for the most profitable scenario. The results show that utilizing LNG for air separation unit yields the highest profit compared to power generation and refrigeration plants.

Finned spacer for efficient membrane fouling control in produced water filtration

Membrane based technologies are highly reliable for water and wastewater treatment, including for removal of total oil and grease from produced water. However, performances of the pressure driven processes are highly restricted by membrane fouling and the application of traditional air bubbling system is limited by their low shear stress due to poor contacts with the membrane surface. This study develops and assesses a novel finned spacer, placed in between vertical panel, for membrane fouling control in submerged plate-and-frame module system for real produced water filtration. Results show that permeability of the panel is enhanced by 87% from 201 to 381 L/(m² h bar). The spacer system can be operated in switching mode to accommodate two-sided panel aeration. This leads to panel permeability increment by 22% higher than the conventional vertical system. The mechanisms of finned spacer in encouraging the flow trajectory was proven by visual observation and flow simulation. The fins alter the air bubbles flow trajectory toward the membrane surface to effectively scour-off the foulant. Overall results demonstrate the efficacy of the developed spacer in projecting the air bubble trajectory toward the membrane surface and thus significantly enhances membrane panel productivity.

Two-way switch: Maximizing productivity of tilted panel in membrane bioreactor

Membrane fouling is a major challenge in membrane bioreactors (MBRs) and its effective handling is the key to improve their competitiveness. Tilting panel system offers significant improvements for fouling control but is strictly limited to one-sided panel. In this study, we assess a two-way switch tilting panel system that enables two-sided membranes and project its implications on performance and energy footprint. Results show that tilting a panel improves permeance by up to 20% to reach a plateau flux thanks to better contacts between air bubbles and the membrane surface to scour-off the foulant. A plateau permeance could be achieved at aeration rate of as low as 0.90 l min^-1, a condition untenable by vertical panel even at twice of the aeration rate. Switching at short periods (<5min) can maintain the hydraulic performance as in no-switch (static system), enables application of a two-sided switching panel. A comparison of vertical panel under 1.80 l min^-1 aeration rate with a switching panel at a half of the rate, switched at 1 min period shows ≈10% higher permeance of the later. Since periodic switching consumes a very low energy (0.55% of the total of 0.276 kWh m^-3), with reduction of aeration by 50%, the switching tilted panel offers 41% more energy efficient than a referenced full-scale MBR (0.390 kWh m^-3). Overall results are very compelling and highly attractive for significant improvements of MBR technologies.

Tackling membrane fouling in microalgae filtration using nylon 6,6 nanofiber membrane

Microalgae technology, if managed properly, has promising roles in solving food-water-energy nexus. The Achilles' heel is, however, to lower the costs associated with cultivation and harvesting. As a favorable technique, application of membrane process is strongly limited by membrane fouling. This study evaluates performance of nylon 6,6 nanofiber membrane (NFM) to a conventional polyvinylidene fluoride phase inverted membrane (PVDF PIM) for filtration of Chlorella vulgaris. Results show that nylon 6,6 NFM is superhydrophilic, has higher size of pore opening (0.22 vs 0.18 μm) and higher surface pore density (23 vs 18 pores/μm²) leading to higher permeance (1018 vs 493 L/m²hbar) and better fouling resistant. Such advantages help to outperform the filterability of PVDF PIM by showing much higher steady-state permeance (286 vs 120 L/m²hbar), with comparable biomass retention. In addition, unlike for PVDF PIM, imposing longer relaxation cycles further enhances the performance of the NFM (i.e., 178 L/m²hbar for 0.5 min and 236 L/m²hbar for 5 min). Overall findings confirm the advantages of nylon 6,6 NFM over the PVDF PIM. Such advantages can help to reduce required membrane area and specific aeration demand by enabling higher flux and lowering aeration rate. Nevertheless, developments of nylon 6,6 NFM material with respect to its intrinsic properties, mechanical strength and operational conditions of the panel can still be explored to enhance its competitiveness as a promising fouling resistant membrane material for microalgae filtration.

Tilted membrane panel: A new module concept to maximize the impact of air bubbles for membrane fouling control in microalgae harvesting

Microalgae harvesting using membrane technology is challenging because of its high fouling propensity. As an established fouling mitigation technique, efficacy of air bubbles can be improved by maximizing the impact of shear-rates in scouring foulant. In this study, it is achieved by tilting the membrane panel. We investigate the effect of tilting angle, switching period as well as aeration rate during microalgal broth filtration. Results show that higher tilting angles (up to 20°) improve permeability of up to 2.7 times of the vertical panel. In addition, operating a one-sided panel is better than a two-sided panel, in which the later involved switching mode. One-sided membrane panel only require a half of area, yet its performance is comparable with of a large-scale module. This tilted panel can lead to significant membrane cost reductions and eventually improves the competitiveness of membrane technology for microalgae harvesting application.

Aqueous room temperature synthesis of zeolitic imidazole framework 8 (ZIF-8) with various concentrations of triethylamine

The schematic illustration shows the influence of triethylamine (TEA) concentration on ZIF-8 formation.