Maximum Capability Research Articles

Effective Adsorptive Removal of Coomassie Violet Dye from Aqueous Solutions Using Green Synthesized Zinc Hydroxide Nanoparticles Prepared from Calotropis gigantea Leaf Extract

The removal of color from dye wastewater is crucial, since dyes are extremely toxic and can cause cancer in a variety of life forms. Studies must be done to use cost-effective adsorbents for the removal of color from dye effluents to protect the environment. To our knowledge, virtually no research has been done to describe the possibility of using Calotropis gigantea leaf extract zinc hydroxide nanoparticles (CG-Zn(OH)2NPs) as an adsorbent for the decolorization of Coomassie violet (CV) from the aqueous emulsion, either in batch mode or continuously. In the present batch investigation, CV dye is removed from the synthetic aqueous phase using CG-Zn(OH)2NPs as an adsorbent. The synthesized nanoparticles were characterized using various instrumental techniques such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDS) and Brunauer–Emmett–Teller (BET) surface area and pore volume, a particle size analyser, and zero-point charge. The decolorization efficacy of CV dye from an aqueous phase by the adsorbent was examined in batch mode by varying process parameters. The consequences of various experimental variables were optimized using response surface methodology (RSM) to achieve the maximum decolorization efficiency (90.74%) and equilibrium dye uptake, qe (35.12 mg g−1). The optimum pH, dye concentration, CG-Zn(OH)2NPs adsorbent dosage, and particle size were found to be 1.8, 225 mg L−1, 5 g L−1, and 78 μm, respectively for CV dye adsorption capacity at equilibrium. The adsorbent zero-point charge was found to be at pH 8.5. The Langmuir isotherm model provided a good representation of the equilibrium data in aqueous solutions, with a maximum monolayer adsorption capability (qmax) of 40.25 mg g−1 at 299 K. The dye adsorption rate follows a pseudo-second-order kinetic model at various dye concentrations, which indicated that the reaction is more chemisorption than physisorption. The negative values of ΔG and positive values of ΔH at different temperatures indicate that the adsorption process is spontaneous and endothermic, respectively. Reusability tests revealed that the prepared nanoparticles may be used for up to three runs, indicating that the novel CG-Zn(OH)2NPs seems to be a very promising adsorbent for the removal of Coomassie violet dye from wastewater.

From micro- to nano- and time-resolved x-ray computed tomography: Bio-based applications, synchrotron capabilities, and data-driven processing

X-ray computed microtomography (μCT) is an innovative and nondestructive versatile technique that has been used extensively to investigate bio-based systems in multiple application areas. Emerging progress in this field has brought countless studies using μCT characterization, revealing three-dimensional (3D) material structures and quantifying features such as defects, pores, secondary phases, filler dispersions, and internal interfaces. Recently, x-ray computed tomography (CT) beamlines coupled to synchrotron light sources have also enabled computed nanotomography (nCT) and four-dimensional (4D) characterization, allowing in situ, in vivo, and in operando characterization from the micro- to nanostructure. This increase in temporal and spatial resolutions produces a deluge of data to be processed, including real-time processing, to provide feedback during experiments. To overcome this issue, deep learning techniques have risen as a powerful tool that permits the automation of large amounts of data processing, availing the maximum beamline capabilities. In this context, this review outlines applications, synchrotron capabilities, and data-driven processing, focusing on the urgency of combining computational tools with experimental data. We bring a recent overview on this topic to researchers and professionals working not only in this and related areas but also to readers starting their contact with x-ray CT techniques and deep learning.

On the performance analysis of rainfall prediction using mutual information with artificial neural network

<span lang="EN-US">Monsoon rainfall prediction over a small geographic region is indeed a challenging task. This paper uses monthly means of climate variables, namely air temperature (AT), sea surface temperature (SST), and sea level pressure (SLP) over the globe, to predict monthly and seasonal summer monsoon rainfall over the state of Maharashtra, India. Mutual information correlates the temperature and pressure from a grid of 10</span><span lang="EN-US">°</span><span lang="EN-US"> longitude X 10</span><span lang="EN-US">°</span><span lang="EN-US"> latitude with Maharashtra’s monthly rainfall time series. Based on the correlations, selected features over the respective latitude and longitudes are given as inputs to an artificial neural network. It was observed that AT and SLP could predict monthly monsoon rainfall with excellent accuracy. The performance of the test dataset was evaluated through mean absolute error; root mean square error, correlation coefficient, Nash Sutcliffe model efficiency coefficient, and maximum rainfall prediction capability of the network. The individual climate variable model for AT performed better in all evaluation parameters except maximum rainfall capability, where the combined model 2 with AT, SLP and SST as predictors outperformed. The SLP-only model’s performance was comparable to the AT-only model. The combined model 1 with AT and SLP as predictors was found better than the combined model 2.</span>

Functionalization of chitosan biopolymer using two dimensional metal-organic frameworks and MXene for rapid, efficient, and selective removal of lead (II) and methyl blue from wastewater

The efficient elimination of lead (II) and methyl blue from aqueous media was a critical problem for humans. The removal of dyes and heavy metals, especially methylene blue and lead, from wastewater is essential for human health and the environment, and utilizing a suitable adsorbent to attain this goal is highly desirable. In the present study first time, chitosan biopolymer was functionalized using Two Dimensional Metal-Organic Frameworks (Ni3(HITP)2) and MXene for efficient, rapid, and selective removal of lead (II) and Methyl blue. To obtain an adsorbent (Ni3(HITP)2/MXene/CS), 1 g of chitosan (biopolymer) and Metal-Organic Frameworks were added in MXene dark-colored suspension and ultrasonically dispersed for 25 min. The batch sorption was carried out, and sorption behavior was analyzed. Batch sorption procedures were conducted to explore the sorption of Pb2+ and MB by Ni3(HITP)2/MXene/CS composite in 25 mL of aqueous solutions. The adsorbent utilized in the present experiments was 10 mg. The effect of the initial concentration of Pb2+ and MB was explored in the range of 10–400 mg L−1. Composite (Ni3(HITP)2/MXene/CS) had excellent sorption performance in the range of pH= 3–6 for lead (II) and pH= 2–9 for methyl blue. The maximum adsorption capacity for lead (II) was 448.93 mg g− 1 at 298 K, 400.59 mg g− 1 at 308 K, and 305.80 mg g− 1 at 318 K. In contrast, the maximum sorption capability for methyl blue was 424.99 mg g− 1 at 298 K, 354.03 mg g− 1 at 308 K, and 251.78 mg g− 1 at 318 K. The sorption of lead (II) and methyl blue on Ni3(HITP)2/MXene/CS composite conformed to pseudo-second-order kinetic and Langmuir model. These outcomes verified that Ni3(HITP)2/MXene/CS composite was selectivity efficient, and quick removal of Methylene blue and lead from wastewater, which is of practical importance.

Single walled carbon nanotube functionalisation in printed supercapacitor devices and shielding effect of Tin(II) Oxide

Due to this generation facing the biggest energy crisis of its lifetime, the spotlight has been shone more than ever on the rapid development of green energy and its storage. Supercapacitors are an integral technology in this renewable energy storage due to their high-power density. For an increased energy density however, one must expand the voltage window of the device and utilise electrolytes that allow for the maximum storage capability of the material. Single walled carbon nanotubes (SWCNT) were identified at the turn of the century as an excellent material for use in supercapacitor electrodes, however, at anodic potentials in sulphate-based electrolytes, they undergo irreversible oxidation which damage their electrical properties and affects long term cycling stability. Herein we provide an effective strategy to expand the voltage window of SWCNTs to 1.4 V in sulphate-based electrolytes through the small addition of tin (II) oxide (SnO), with a capacity of 102 F g-1 / 143 C g-1 at a current density of 2 A g-1. We study the effect of SnO and propose a pseudo-reversible oxidation reaction in which the SWCNTs are protected from oxidation through the formation of Sn3O4. Finally, an asymmetric device using MXene is assembled to illustrate the advantage of the expanded voltage window on energy density and cycling stability, with a capacity retention of 90% after 7,500 cycles at 10 A g-1.

Proficient matrix codes for error detection and correctionin 8-port network on chip routers

This paper verifies the applicability of the proposed code to dynamic Network on Chips that have variable faulty blocks with runtime suggesting an online error detection mechanism with adaptive routing algorithm that bypasses faulty components dynamically and the router architecture uses additional diagonal state indications for the reliable network on chip (NoC) operation. In NoC, the permanently faulty routers are disconnected to enable high runtime throughput as data packets are not lost due to self-loopback mechanism. The proposed proficient matrix codes use the capabilities of decimal matrix code technique with minimum check bits for maximum error correction capability. The proposed code is compared with existing codes such as decimal matrix codes, modified decimal matrix codes and parity matrix codes. The codes are developed in verilog hardware description language and simulated in the Xilinx ISE 14.5 tool. This proficient matrix code proves to be efficient for multiple adjacent error detection and correction with trade off in delay. Also 65% code rate is achieved with 22.73% less redundant bits that occupy less area by atleast 11.78%. The codes when used for increased data sizes like 8, 16, 32, and 64 bits, the power delay product decreased by atleast 1.74%.

Effects of COVID-19 on Kenya’s Healthcare System: Healthcare Providers’ Experiences with Maternal Health Services Utilization in Coastal Kenya

The COVID-19 pandemic overstretched health systems in developed and developing nations. Like other African nations, Kenya has a frail health system, making responding to the pandemic a problem. Recent studies during COVID-19 have shown that Kenya’s health systems were either strained to their maximum capability or worse in handling patients. Therefore, citizens were advised not to go to the hospital unless necessary. This advice applies to all, including pregnant mothers. This article utilized the anthropological description of the healthcare system, viewed as a cultural system attached to particular provisions of social institutions and forms of social connections. It is a social and cultural system in origin, structure, function, and significance. In every society, healthcare systems are forms of social reality in which they embody specific social roles and relationships between these roles. There is a dearth of information on how healthcare providers experienced the effects of COVID-19 on Kenya’s healthcare system, which this study addresses for those in Coastal Kenya. This rapid qualitative study utilized data from sixteen purposefully selected healthcare providers in charge of various departments in Kilifi County of Coastal Kenya. We utilized thematic analysis and textual description to present our findings. It emerged that there was a diversion in resources allocated for maternal health programs, health facilities were temporarily shut down due to inadequate resources and equipment for health workers, there was a lack of preparation by health workers, there was a reduced flow of pregnant mothers and missing scheduled appointments for ante- and postnatal clinics, maternal mortality increased, and mothers resorted to traditional midwives for deliveries. These findings show that maternal health services were negatively affected. Thus, the government needs to institute alternative measures for continued access to maternal health services during pandemics. We recommend expanding and supporting the existing community midwifery model (CMM). For instance, incorporating community health workers (CHWs) and other local health institutions in the community, such as traditional birth attendants (TBAs), and creating midwifery centers managed by trained midwives in communities.

Performance Evaluation of a Novel Bio-Trickling Filter for Styrene Waste Gas Treatment

In recent years, styrene waste gas has become a hot issue in the waste gas treatment industry due to its hydrophobicity and easy polymerization. This study is aimed at the problems of long empty bed residence time and low removal capacity of waste gas from styrene degradation by bio-trickling filter (BTF). A novel bio-trickling filter (NBTF) that we designed was used to explore the effects of styrene inlet concentration, empty bed residence time (EBRT), and starvation period on the performance of NBTF in the degradation of styrene waste gas. The experimental results show that the NBTF can be started in 17 days; when the inlet concentration was lower than 1750 mg/m3 and the EBRT was 59.66 s, the removal efficiency (RE) of styrene can reach 100%. When the inlet concentration was 1000 mg/m3 and the EBRT was greater than 39.77 s, styrene waste gas can also be completely degraded. The above proves that NBTF can complete the degradation of styrene waste gas with high concentration under the condition of short EBRT; in the whole operation process, the maximum elimination capability (EC) of styrene was 112.96 g/m3/h, and NBTF shows excellent degradation performance of styrene. When the starvation period was 2 days, 7 days and 15 days, respectively, NBTF can recover high degradation performance within 2 days after restart. The NBTF has good operation performance in 124 days of operation, which proves that the NBTF can effectively degrade styrene waste gas. This provides a reference basis for industrial treatment of styrene waste gas in the future.

PARAMETER-DRIVEN GENERATION OF EVALUATION PROGRAM FOR A NEUROEVOLUTION ALGORITHM ON A BINARY MULTIPLEXER EXAMPLE

Context. The problem of automated development of evaluation programs for the neuroevolution of augmenting topologies. Neuroevolution algorithms apply mechanisms of mutation, recombination, and selection to find neural networks with behavior that satisfies the conditions of a certain formally defined problem. An example of such a problem is finding a neural network that implements a certain digital logic.
 Objective. The goal of the work is the automated design and generation of an evaluation program for a sample neuroevolution problem (binary multiplexer).
 Method. The methods and tools of Glushkov’s algebra of algorithms and hyperscheme algebra are applied for the parameterdriven generation of a neuroevolution evaluation program for a binary multiplexer. Glushkov’s algebra is the basis of the algorithmic language intended for multilevel structural design and documentation of sequential and parallel algorithms and programs in a form close to a natural language. Hyperschemes are high-level parameterized specifications intended for solving a certain class of problems. Setting parameter values and subsequent interpretation of hyperschemes allows obtaining algorithms adapted to specific conditions of their use.
 Results. The facilities of hyperschemes were implemented in the developed integrated toolkit for the automated design and synthesis of programs. Based on algorithm schemes, the system generates programs in a target programming language. The advantage of the system is the possibility of describing algorithm schemes in a natural-linguistic form. An experiment was conducted consisting in the execution of the generated program for the problem of evaluating a binary multiplexer on a distributed cloud platform. The multiplexer example is included in SharpNEAT, an open-source framework that implements the genetic neuroevolution algorithm NEAT for the .NET platform. The parallel distributed implementation of the SharpNEAT was proposed in the previous work of the authors.
 Conclusions. The conducted experiments demonstrated the possibility of the developed distributed system to perform evaluations on 64 cloud clients-executors and obtain an increase in 60–100% of the maximum capabilities of a single-processor local implementation.

Fixed-time regulation of spacecraft orbit and attitude coordination with optimal actuation allocation using dual quaternion.

On-orbit service spacecraft with redundant actuators need to overcome orbital and attitude coupling when performing proximity maneuvers. In addition, transient/steady-state performance is required to fulfill the user-defined requirements. To these ends, this paper introduces a fixed-time tracking regulation and actuation allocation scheme for redundantly actuated spacecraft. The coupling effect of translational and rotational motions is described by dual quaternion. Based on this, we propose a non-singular fast terminal sliding mode controller to guarantee fixed-time tracking performance in the presence of external disturbances and system uncertainties, where the settling time is only dependent on user-defined control parameters rather than initial values. The unwinding problem caused by the redundancy of dual quaternion is handled by a novel attitude error function. Moreover, optimal quadratic programming is incorporated into null space pseudo-inverse control allocation that ensures the actuation smoothness and never violates the maximum output capability of each actuator. Numerical simulations on a spacecraft platform with symmetric thruster configuration demonstrate the validity of the proposed approach.

Novel simple algorithm for frequency planning and optimization in cellular networks

AbstractOne of the most expensive components of constructing a cellular network is frequency planning. The cost of building and maintaining a network will be reduced if a set of base stations can be established with minimal service and preparation. Planning and optimization are carried out to guarantee that the scarce frequency is used to its maximum capability. The goal of this paper is to provide an autonomous method for planning and optimizing frequency in cellular networks. The method substitutes the inefficient, inaccurate, and time-consuming manual method. The automatic technique makes work easier for radio frequency (RF) engineers and lowers operating costs. Also, this article provides an autonomous planning and optimization technique that reduces intra-system interference levels to acceptable levels within the key performance indicators (KPIs) set for any suitable cellular network.

Motorized Robotic Closed Cervical Traction: Biomechanical Proof of Concept.

Biomechanical study. To demonstrate that robotic cervical traction can apply closed cervical traction as effectively as manual weight-and-pulley traction in extension spring and cadaveric models. Closed cervical traction is used to reduce subaxial cervical spine dislocation injuries and to distract the intervertebral space during cervical spine surgery. Weight-and-pulley cervical traction relies on cumbersome and imprecise technology without any safeguard to prevent over-traction or weights being pulled/released inadvertently. A prototype robotic traction device was designed and manufactured by the authors with real-time tensile force measurement, ±1-lbs (5 N) force application accuracy, locking/non-backdriveable linear actuators with actuator position sensing, 200-lbs (900 N) maximum force capability, up to 20° of flexion/extension manipulation, <25-lbs (111 N) device weight, and compatibility with Gardner-Wells tongs or Mayfield head clamp. The device was tested using an extension spring model and an intact fresh cadaver specimen to assess applied and desired force over time and radiographic changes in the cervical spine as traction force increased. The cadaver was tested in manual traction initially and then robotic traction in 10-lbs (50 N) increments up to 80-lbs (355 N) to compare methods. The prototype device met or exceeded all requirements. In extension spring testing, the device reached the prescribed forces of both 25-lbs (111 N) and 80-lbs (355 N) accurately and maintained the desired weight. In cadaveric testing, radiographic outcomes were equivalent between the prototype and manual weight-and-pulley traction at 80-lbs (355 N; disk space measurements within ±10% for all levels), and the device reached the desired weight within±1-lbs (5 N) of accuracy at each weight interval. This preliminary work demonstrates that motorized robotic cervical traction can safely and effectively apply controlled traction forces.

An assessment of scenarios for transuranic burning and 233U production in a small molten chloride fast reactor

Molten Chloride Fast Reactor (MCFR) attracts more and more attention owing to its significantly hard neutron spectrum and high solubility for actinide trichlorides, making it an appealing option for burning transuranic (TRU) elements discharged from pressurized water reactors (PWRs). Meanwhile, in recent years, the development of thorium fuel cycle has aroused considerable interest worldwide with the purpose of saving uranium reserves and further reducing the production of long-lived minor actinides. A small MCFR incorporating TRU burning and 233U production is proposed in this work in order to evaluate its incineration and production capabilities. By employing an in-house developed tool based on SCALE 6.1, the fuel cycle features of the small MCFR with three fuel loading scenarios, including pure TRU (scenario 1), TRU plus depleted uranium (scenario 2) and TRU plus thorium (scenario 3), are analyzed. The evolution behaviors of main nuclides, reactivity worth, neutron spectra and temperature reactivity coefficient (TRC) are discussed in detail. It is found that the MCFR can burn TRU effectively and the transmutation rates for the three scenarios are 930 kg/GWe/year, 375 kg/GWe/year and 768 kg/GWe/year, respectively, achieving a maximum capability for TRU burning of about 3.7 times the annual TRU production in a 1-GWe PWR with 50 MWd/kgU discharge burnup. Meanwhile, scenario 3 has the highest 233U production capability of about 110.3 kg per year, although it does not offer processing advantages over scenario 1 and scenario 2. The analysis of TRC indicates that the fuel salt TRC and the total core TRC are both strongly negative for all three scenarios owing to the thermal expansion of liquid fuel salt. Finally, a nuclear energy system consisting of both fast and thermal molten salt reactors is proposed and evaluated to establish a closed nuclear fuel cycle with very low radioactive wastes.

Hybrid multifunctional biocomposite of chitosan grafted benzaldehyde/montmorillonite/algae for effective removal of brilliant green and reactive blue 19 dyes: Optimization and adsorption mechanism

Herein, a novel hybrid multifunctional biocomposite of chitosan grafted-benzaldehyde/montmorillonite/algae (CHS-BZ/MT/AL) was designed and applied for the highly efficient removal of brilliant green (BG) and reactive blue 19 (RB19) dyes from an aquatic environment. The influence of three processing factors, including CHS-BZ/MT/AL dose (0.02–0.08 g), pH solution (4–9), contact time (5–30 min), and their interactions on the removal rate of BG and RB19 dyes, was examined using the response surface methodology integrated with Box-Behnken design (RSM-BBD). The experimental outcomes of equilibrium and kinetic investigations showed that the adsorption of BG and RB19 dyes on CHS-BZ/MT/AL obey pseudo-second-order and Langmuir models. The CHS-BZ/MT/AL possesses a maximum adsorption capability of 899.5 mg/g for BG and 213.6 mg/g for RB19. The proposed mechanism of BG and RB19 adsorption in the lighting of the CHS-BZ/MT/AL's characterization is mainly included several interactions like electrostatic forces, π-π stacking, n-π stacking, and H-bonding. The current work indicates that the synthesized CHS-BZ/MT/AL with a distinct structure and excellent adsorptive characteristics could be employed to remove hazardous cationic and anionic dyes from industrial wastewater.

Noise reduction by perforated cascades in annular ducts

One of the latest trends in noise control relating to aeroacoustics is to mimic the silent flight capability of owls. Particularly, porosity is most often applied on cascades in ducts with axial flows, such as stator structures in an aero-engine. However, current acoustic scattering models of perforated cascades are based on two-dimensional methods without including the three-dimensional effects. In this paper, we present a fully three-dimensional acoustic scattering model for perforated cascades based on the lifting surface theory in which the dominant sound source reduces to dipoles alone under the thin airfoil assumption. Accordingly, the acoustic scattering of perforated cascades with single-mode incident wave was studied and obvious noise reduction was observed. The optimum Rayleigh conductivity and the maximum noise-reducing capability of the porosity varied substantially with different incident duct modes, whilst a larger cascade chord-length could achieve more noise reduction at optimum porosity. With a background flow, the Kutta condition can greatly influence the overall distribution of the unsteady loading on vanes. Additionally, the unsteady vortex shedding at the trailing edge offers extra sound energy dissipation mechanism. Therefore, the implementation of porosity on cascades is much different to the design of a traditional acoustic liner.

Sequential quadratic programming-based non-cooperative target distributed hybrid processing optimization method

The distributed hybrid processing optimization problem of non-cooperative targets is an important research direction for future networked air-defense and anti-missile firepower systems. In this paper, the air-defense anti-missile targets defense problem is abstracted as a nonconvex constrained combinatorial optimization problem with the optimization objective of maximizing the degree of contribution of the processing scheme to non-cooperative targets, and the constraints mainly consider geographical conditions and anti-missile equipment resources. The grid discretization concept is used to partition the defense area into network nodes, and the overall defense strategy scheme is described as a nonlinear programming problem to solve the minimum defense cost within the maximum defense capability of the defense system network. In the solution of the minimum defense cost problem, the processing scheme, equipment coverage capability, constraints and node cost requirements are characterized, then a nonlinear mathematical model of the non-cooperative target distributed hybrid processing optimization problem is established, and a local optimal solution based on the sequential quadratic programming algorithm is constructed, and the optimal firepower processing scheme is given by using the sequential quadratic programming method containing non-convex quadratic equations and inequality constraints. Finally, the effectiveness of the proposed method is verified by simulation examples.

Roles of Metal Oxide Nanostructure-Based Substrates in Sustainable Electrochemical Water Splitting: Recent Development and Future Perspective

Increasing energy demand to find everlasting and eco-friendly resources is now mainly dependent on green hydrogen production technology. Water electrolysis has been regarded as a clean route for green H2 production with zero carbon emission, but different bottlenecks in the development of electrodes impeded its realization. Recently, transition metal oxides (TMO) have gained tremendous attention as suitable cathodes and anodes due to their sustainability under harsh conditions, high redox features, maximum supportive capability, easy modulation in valence states, and enhanced electrical conductivity. In this review, we have highlighted the role of transition metal oxides as active and supported sites for electrochemical water splitting. We have proposed different perspectives for the rational design of TMO-based electrode materials, i.e., electronic state modulation, modification of the surface structure to control the aerophobicity and hydrophilicity, acceleration of the charge and mass transport, and stability of the electrocatalyst in harsh environments. We have systemically discussed the insights into the relationship among catalytic activity, certain specified challenges, research directions, and perspectives of electrocatalysis of the OER and HER.

An energy-efficient CMOS interface circuit with maximum power point tracking and power management capabilities for self-powered sensor node applications using 50/60 Hz transmission line magnetic field harvesters

An energy-efficient CMOS interface circuit with maximum power point tracking and power management capabilities for self-powered sensor node applications using 50/60 Hz transmission line magnetic field harvesters

Soft-assembled, bio-gel electrolytic double layer capacitor system for sustainable energy storage

ABSTRACT Carrageenan is an attractive bio-derived polymer electrolyte due to its high ionic conductivity, cyclic stability, and cost-effectiveness in copolymerizing with other biocompatible polymers such as polyvinyl alcohol (PVA). This paper discusses the physical and chemical characterizations of the bio-electrolyte(s): PVA, carrageenan, and PVA-carrageenan copolymer blend. We also describe a fabrication method to create a soft-printed, thin-film, bio-gel electrolytic double-layer capacitor (bio-EDLC) using a PVA-carrageenan polymer blend. The addition of PVA to carrageenan provided structural and mechanical stability to the biopolymer, as confirmed by the hydrogen bonds detected using attenuated Fourier-transform infrared spectroscopy analysis. The assembled bio-EDLCs were analyzed for their electrical properties including their internal charge transfer mechanism, electrical breakdown, specific capacitance, power density, and energy density. It was determined that the bio-EDLC offers specific capacitance of 84 F/g and power density of 4.15E-02 W/kg and has a breakdown voltage of ~1.1 V. Furthermore, preliminary optimization was performed on the bio-EDLC with a drop casting of reduced graphene oxide at the electrode/electrolyte interface to create surface micro-roughness resulting in a bio-EDLC system which demonstrated superior electrical characteristics with an overall specific capacitance of up to 118 F/g, breakdown voltage of ~1.3 V, and improved maximum charging capability to 80%.

Synthesis of iron-magnetite nanocomposites for hexavalent chromium sorption

Owing to multiple industrial applications of chromium compounds, developing chronic and highly water soluble chromium adsorption methods has gained attention. Nano-iron-magnetite nanocomposite (IM-NCs) was successfully synthesized from Eucalyptus globulus leaf extract for chromium adsorption from an aqueous solution. The occurrence of the black solution was the first physical indication of the formation of zero-valent iron. The X-ray diffraction pattern analysis confirmed the formation of the Fe/Fe3O4 nanocomposite. The FT-IR spectrum indicated the presence of Fe-O stretch, probably due to the development of iron oxides, which confirmed the oxidation of parts of the zero-valent iron to magnetite. The SEM image showed the agglomerated morphology of nanoparticles (NPs). The EDX analysis showed the existence of the expected elemental compositions of Fe and O. The UV–vis spectra showed peaks at 450 and 550 nm with a broader absorption band ranging from 350 to 650 nm, probably resulting from the octahedral ferric ions and magnetite. The BET and TEM/HRTEM image analyses yielded specific surface areas and an approximate crystallite size of 14 m2 g−1 and 19 nm, respectively. The Langmuir adsorption isotherm fitted the experimental data more than the Freundlich isotherm model. The well-fitted pseudo-second-order (PSO) model compared with the pseudo-first-order (PFO) model describes the chemisorption nature of the adsorption process. The negative free energy value confirms the spontaneity of the adsorption process. The maximum adsorption capability of the materials was 19 mg/g.