Bouncing Dynamics of Drops' Successive Off-Center Impact.

Bouncing dynamics of a trailing drop off-center impacting a leading drop with varying time intervals and Weber numbers are investigated experimentally. Whether the trailing drop impacts during the spreading or receding process of the leading drop is determined by the time interval. For a short time interval of 0.15 ≤ Δt* ≤ 0.66, the trailing drop impacts during the spreading of the leading drop, and the drops completely coalesce and rebound; for a large time interval of 0.66 < Δt* ≤ 2.21, the trailing drop impacts during the receding process, and the drops partially coalesce and rebound. Whether the trailing drop directly impacts the surface or the liquid film of the leading drop is determined by the Weber number. The trailing drop impacts the surface directly at moderate Weber numbers of 16.22 ≤ We ≤ 45.42, while it impacts the liquid film at large Weber numbers of 45.42 < We ≤ 64.88. Intriguingly, when the trailing drop impacts the surface directly or the receding liquid film, the contact time increases linearly with the time interval but independent of the Weber number; when the trailing drop impacts the spreading liquid film, the contact time suddenly increases, showing that the force of the liquid film of the leading drop inhibits the receding of the trailing drop. Finally, a theoretical model of the contact time for the drops is established, which is suitable for different impact scenarios of the successive off-center impact. This study provides a quantitative relationship to calculate the contact time of drops successively impacting a superhydrophobic surface, facilitating the design of anti-icing surfaces.

Integrated microbial electrolysis with high-alkali pretreated sludge digestion: Insight into the effect of voltage on methanogenesis and substrate metabolism.

Integrated microbial electrolysis with anaerobic digestion is proved to be an effective way to improve methanogenesis efficiency of waste activated sludge (WAS). WAS requires pretreatment for efficient improvement of acidification or methanogenesis efficiency, but excessive acidification may inhibit the methanogenesis. In order to balance these two stages, a method for efficient WAS hydrolysis and methanogenesis has been proposed in this study by high-alkaline pretreatment integrated with microbial electrolysis system. The effects of pretreatment methods and voltage on the normal temperature digestion of WAS have also been further investigated with emphasis on the effects of voltage and substrate metabolism. The results show that compared to low-alkaline pretreatment (pH = 10), high-alkaline pretreatment (pH > 14) can double the SCOD release and promote the VFAs accumulation to 5657 ± 392 mg COD/L, but inhibit the methanogenesis process. Microbial electrolysis can alleviate this inhibition effectively through the rapid consumption of VFAs and speeding up of the methanogenesis process. The optimal methane yield of the integrated system is 120.4 ± 8.4 mL/g VSS at the voltage of 0.5 V. Enzyme activities, high-throughput and gene function prediction analysis reveal that the cathode and anode maintain the activity of methanogens under high substrate concentrations. Voltage positively responded to improved methane yield from 0.3 to 0.8 V, but higher than 1.1 V is found to be unfavorable for cathodic methanogenesis and results in additional power loss. These findings provide a perspective idea for rapid and maximum biogas recovery from WAS.

Tracking the diversity and interaction of methanogens in the energy recovery process of a full-scale wastewater treatment plant.

Methanogens have been significant for the achievement of carbon neutrality in wastewater treatment plants due to their crucial roles in the anaerobic digestion of sludge. Nevertheless, the phylogenetic diversity of methanogens and their versatile metabolism have been continuously investigated, the current scientific knowledge regarding these microbes appears inadequate and requires more evaluations. This study is considered an endeavor in which functional genes sequencing was used to reveal the diversity of methanogens in the sludge process of the wastewater treatment plant. The information obtained was substantially more than that employing 16s sequencing. The methanogenic microbial resources were appropriate to sustain a self-inoculated energy recovery with a potential ability to boost methane production. A constancy was observed in 16 S rRNA gene and mcrA gene sequencing results, where the bacterial or Methanosaeta concilii dominated community of DS (digest sludge) was distinct from the inoculum sources TS (total sludge), CTS (concentrated total sludge), and HTS (hydrolysis total sludge), indicating the independent development of DS. A quantitative cross-network was constructed by coupling the absolute quantify of 16 S rRNA and mcrA sequences. The Methanobacterium petrolearium actively interacted with bacteria in the DS community rather than the dominant species (Methanosaeta concilii). Moreover, the unclassified methanogens were identified to be significantly prevalent in all communities, suggesting that unknown methanogenic taxa might be imperative in accomplishing community functions. Collectively, the findings of this research study will shed light on the comprehensive knowledge of microbial communities, especially the methanogenic microbiota. This will further enhance the exploration of the phylogenetic diversity of methanogens and their corresponding impacts in energy recovery from wastewater treatment plants.

Application of interface material and effects of oxygen gradient on the performance of single-chamber sediment microbial fuel cells (SSMFCs).

Single-chamber sediment microbial fuel cells (SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study. Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032mW/m2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28µm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants.

Molecular Dynamics Simulations on Coalescence and Non-coalescence of Conducting Droplets.

When an electric field with various strengths is applied to two adjacent conducting droplets, the droplets may completely coalesce, partially coalesce, or bounce off one another. To reveal an atom-scale mechanism of coalescence or non-coalescence, dynamic behaviors of two conducting nanodroplets at a homogeneous electric field are studied via molecular dynamics simulations in this work. The results show that there is a critical field strength and a critical cone angle above which the two droplets partially coalesce or bounce off. Charge transfer between the two droplets is observed when the droplets are brought into contact. The partial coalescence and the bounce-off of the two droplets at strong field strengths are found to be due to the high charge transfer rate, which leads to the breakup of the coalescing droplet at different locations.

Perspective of material evolution Induced by sinusoidal reflex charging in lithium-ion batteries.

Background: Lithium-ion batteries are globally prominent and extensively employed alternative energy sources with decisive applications. In depth understanding of influences of various charging and discharging cycles on electrode materials and life span of these batteries is critical as cycle-life and safety of lithium-ion batteries are closely related crystallinity of electrode materials. This study is a detailed investigation endeavor in observing the degree of damage to electrode materials under multiple charging and discharging cycles. Method: ology: A constant current-sinusoidal reflex charging method (CC-Sinusoidal) was implemented to charge commercial cathode Lithium cobalt oxide (LiCoO2) electrodes and anode graphite electrodes in comparison to the conventional charging method of constant current-constant voltage (CC-CV). After 100, 300, and 500 cycles of charging and discharging, EIS, SEM, XRD, and Raman spectroscopies were used to compare the degree of electrode damage caused by different charging methods. Significant outcomes: The structure of positive LiCoO2 electrode of the battery was observed to be stable, with no significant change in both the charging methods after 500 cycles. The use of CC-CV charging method had caused severe damages to graphite electrode with generation of solid electrolyte interface (SEI) films. The CC-Sinusoidal charging method had maintained the electrode material in a relatively ideal state.

Evaluation of the effect of biofilm formation on the reductive transformation of triclosan in cathode-modified electrolytic systems.

The performance of electrochemical reduction is often enhanced by electrode modification techniques. However, there is a risk of microbial colonization on the electrode surface to form biofilms in the treatment of actual wastewater with modified electrodes. In this work, the effects of biofilm formation on modified electrodes with reduced graphene oxide (rGO), platinum/carbon (Pt/C), and carbon nanotube (CNT) were investigated in triclosan (TCS) degradation. With biofilm formation, the TCS degradation efficiencies of carbon cloth (CC), rGO@CC, Pt/C@CC, and CNT@CC decayed to 54.53 %, 59.77 %, 69.19 %, and 53.97 %, respectively, compared to the raw electrodes. Confocal laser scanning microscopy and microbial community analysis revealed that the difference in biofilm thickness and activity were the major influencing factors on the discrepant TCS degradation rather than the microbial community structure. The electrochemical performance tests showed that the biofilm formation increased the ohmic resistance by an order of magnitude in rGO@CC, Pt/C@CC, and CNT@CC, and the charge transfer resistance was increased by 2.45, 3.78, and 7.75 times, respectively. The dechlorination and hydrolysis governed the TCS degradation pathway in all electrolysis systems, and the toxicity of electrochemical reductive products was significantly decreased according to the Toxicity Estimation Software Tool analysis. This study presented a systematic assessment of the biofilm formation on modified electrodes in TCS reduction, and the undisputed experimental outcomes were obtained to enrich the knowledge of implementing modified electrodes for practical applications.

Laser-scribed Graphene Electrodes Functionalized with Nafion/Fe3O4 Nanohybrids for the Ultrasensitive Detection of Neurotoxin Drug Clioquinol.

The analysis of pharmaceutical active ingredients plays an important role in quality control and clinical trials because they have a significant physiological effect on the human body even at low concentrations. Herein, a flexible three-electrode system using laser-scribed graphene (LSG) technology, which consists of Nafion/Fe3O4 nanohybrids immobilized on LSG as the working electrode and LSG counter and reference electrodes on a single polyimide film, is presented. A Nafion/Fe3O4/LSG electrode is constructed by drop coating a solution of Nafion/Fe3O4, which is electrostatically self-assembled between positively charged Fe3O4 and negatively charged Nafion on the LSG electrode and is used for the first time to determine a neurotoxicity drug (clioquinol; CQL) in biological samples. Owing to their porous 3D structure, an enriched surface area at the active edges and polar groups (OH, COOH, and -SO3H) in Nafion/Fe3O4/LSG electrodes resulted in excellent wettability to facilitate electrolyte diffusion, which gave ∼twofold enhancement in electrocatalytic activity over LSG electrodes. The experimental parameters affecting the analytical performance were investigated. The quantification of clioquinol on the Nafion/Fe3O4/LSG electrode surface was examined using differential pulse voltammetry and chronoamperometry techniques. The fabricated sensor displays preferable sensitivity (17.4 µA µM-1 cm-2), a wide linear range (1 nM to 100 µM), a very low detection limit (0.73 nM), and acceptable selectivity toward quantitative analysis of CQL. Furthermore, the reliability of the sensor was checked by CQL detection in spiked human blood serum and urine samples, and satisfactory recoveries were obtained.

Electrochemical polarization analysis for optimization of external operation parameters in zinc fuel cells.

Zinc-air flow fuel cells utilizing zinc particles as fuel possess the potential to evolve as efficient distributed grid generators. In this research study, electrochemical impedance analysis was employed to determine the optimum design and operational parameters for the feasible maneuver and enhanced energy generation from zinc fuel cells. Polarization resistance (R p), ohmic resistance (R s), and mass transfer resistance (R m) were used as the indicators for determination of the optimum parameters of fuel cell performance. Experimental conditions optimized from previous studies like potassium hydroxide electrolyte with temperature of 25 °C and concentration of 40 wt% zinc powder quantity of 20 g, electrode reaction surface area of 48 cm2 were followed in the fuel cells used in the present study. Parameters like collector plate material, air flow velocity and cell operating temperature were augmented and finally were all implemented in the fuel cell and operated. Plain nickel or nickel-plated copper were both advantageous as collector plate materials whereas an air flow velocity ranging from 1-3 m s-1 and a cell operating temperature of 25 °C to 45 °C were beneficial for the stability and performance of the zinc fuel cells. Finally, based on the optimized parameters obtained from the above experiments, performance tests of zinc fuel cells were investigated. The maximum power produced was 16.5 W, along with a corresponding voltage of 0.8 V, maximum current density of 430 mA cm-2 and peak power density of 364.6 mW cm-2. Thus it can be concluded that the fuel cells designed and operated in this study were capable for feasible and efficient future applications.

Highly heterogeneous interior structure of biofilm wastewater for enhanced pollutant removals.

Biofilm processes are widely used in wastewater treatment. The biofilm has highly heterogeneous interior structure, which can significantly affect the transport processes and the biological reactions over the biofilm. This study for the first time detailed the complicated velocity and concentration fields of substrate in a real biofilm structure. With a real biofilm interior being profiled and meshed to numerical solutions, the flow-through mode has significant distortion of inflow velocity fields and concentration distributions, which lead to enhanced biological reactions at regimes nearby major pores. Conversely, the crossflow mode depends weakly on the biofilm interior structure. The uniform biofilm model fails to describe the real biofilm processes. Future research needs based on real biofilm structures were discussed.

Novel bufferless photosynthetic microbial fuel cell (PMFCs) for enhanced electrochemical performance.

Photosynthetic microbial fuel cells (PMFCs) are novel bioelectrochemical transducers that employ microalgae to generate oxygen, organic metabolites and electrons. Conventional PMFCs employ non-eco-friendly membranes, catalysts and phosphate buffer solution. Eliminating the membrane, buffer and catalyst can make the MFC a practical possibility. Therefore, single chambered (SPMFC) were constructed and operated at different recirculation flow rates (0, 40 and 240 ml/min) under bufferless conditions. Furthermore, maximum power density of 4.06 mW/m2, current density of 46.34 mA/m2 and open circuit potential of 0.43 V and low internal resistance of 611.8â€¯Ω were obtained at 40 ml/min. Based on the results it was decided that SPMFC was better for operation at 40 ml/min. Therefore, these findings provided progressive insights for future pilot and industrial scale studies of PMFCs.