Low-cost Absorber Research Articles

Facile sponge-like chitosan capsules as efficient adsorbent for anionic Congo red, Reactive brilliant blue KNR, and Methyl blue dyes: Performance and mechanism

In this study, sponge-like chitosan capsules (CTS-S) were successfully prepared as efficient adsorbent through a facile and green method. The cross-linked porous structure and abundant adsorption sites of CTS-S led to stable and remarkable adsorption efficacy for the purification of wastewater containing anionic dyes in a wide pH range. The highest maximum adsorption capacity for Congo red (CR), Reactive brilliant blue KN-R (KNR), and Methyl blue (MB) were 1372.49, 881.75, and 169.04mg/g, respectively. Kinetics study suggested that KN-R and CR adsorption processes were best depicted by the PSO model, while PFO model was applicable for MB. Adsorption isotherms of CR, KNR, MB conformed to the Sips model, demonstrating that the adsorption of CR, KNR, MB onto CTS-S was monolayer and heterogeneous. Adsorption mechanism insights further verified that electrostatic forces, hydrogen bonds, and n-π stacking worked for efficient removal of CR, KNR, MB by CTS-S, which was supported by characterization results and DFT calculation. Overall, CTS-S provided a useful and promising option as low-cost and eco-friendly absorbents for the adsorption of synthetic dyes.

Design and demonstration of a simple, low-cost transparent solar absorber for glass window applications

Windows are a major source of heat loss from buildings in cold climates. Developing coatings for windows that retain high visible transparency and strongly absorbs solar energy in the near infrared region can help reduce energy consumption and cost for indoor heating. Nanophotonic structures based on metasurface and metamaterials have shown great potential for such applications. Unfortunately, most of the designs proposed so far are difficult to fabricate or expensive. In this work, we report the experimental demonstration of a low-cost alternative based on Ni/SiO2/Ni multilayer structure. The device provides a large increase in temperature under solar illumination while retaining high visible transmission. Our optical and thermal measurements reveal that the performance of the device remains stable over a long period. The combination of low cost, ease of fabrication, good optical and thermal performance, and long-term stability makes it a promising design for passive heating of windows in cold climates.

Future Parabolic Trough Collector Absorber Coating Development and Service Lifetime Estimation

This work presents a study on the optical and mechanical degradation of parabolic trough collector absorber coatings produced through the spray coating application technique of in-house developed paint. The main aim of this investigation is to prepare, cure, load, and analyze the absorber coating on the substrate under conditions that mimic the on-field thermal properties. This research incorporates predicted isothermal and cyclic loads for parabolic trough systems as stresses. Biweekly inspections of loaded, identical samples monitored the degradation process. We further used the cascade of data from optical, oxide-thickening, crack length, and pull-off force measurements in mathematical modelling to predict the service life of the parabolic trough collector. The results collected and used in modelling suggested that cyclic load in combination with iso-thermal load is responsible for coating fatigue, influencing the solar absorber optical values and resulting in lower energy transformation efficiency. Finally, easy-to-apply coatings made out of spinel-structured black pigment and durable binder could serve as a low-cost absorber coating replacement for a new generation of parabolic trough collectors, making it possible to harvest solar energy to provide medium-temperature heat to decarbonize future food, tobacco, and paint production industrial processes.

Reconfigurable Origami/Kirigami Metamaterial Absorbers Developed by Fast Inverse Design and Low-Concentration MXene Inks.

Reconfigurable metamaterial absorbers (MAs), consisting of tunable elements or deformable structures, are able to transform their absorbing bandwidth and amplitude in response to environmental changes. Among the options for building reconfigurable MAs, origami/kirigami structures show great potential because of their ability to combine excellent mechanical and electromagnetic (EM) properties. However, neither the trial-and-error-based design method nor the complex fabrication process can meet the requirement of developing high-performance MAs. Accordingly, this work introduces a deep-learning-based algorithm to realize the fast inverse design of origami MAs. Then, an accordion-origami coding MA is generated with reconfigurable EM responses that can be smoothly transformed between ultrabroadband absorption (5.5-20 GHz, folding angle α = 82°) and high reflection (2-20 GHz, RL > -1.5 dB, α = 0°) under y-polarized waves. However, the asymmetric coding pattern and accordion-origami deformation lead to typical polarization-sensitive absorbing performance (2-20 GHz, RL > -4 dB, α < 90°) under x-polarized waves. For the first time, a kirigami polarization rotation surface with switchable operation band is adapted to balance the absorbing performance of accordion-origami MA under orthogonal polarized waves. As a result, the stacked origami-kirigami MA maintains polarization-insensitive ultrabroadband absorption (4.4-20 GHz) at β = 0° and could be transformed into a narrowband absorber through deformation. Besides, the adapted origami/kirigami structures possess excellent mechanical properties such as low relative density, negative Poisson's ratio, and tunable specific energy absorption. Moreover, by modulating the PEDOT:PSS conductive bridges among MXene nanosheets, a series of low-concentration MXene-PEDOT:PSS inks (∼46 mg·mL-1) with adjustable square resistance (5-32.5 Ω/sq) are developed to fabricate the metamaterials via screen printing. Owing to the universal design scheme, this work supplies a promising paradigm for developing low-cost and high-performance reconfigurable EM absorbers.

(Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98/biocarbon composite: A broad band and highly efficient electromagnetic wave absorber

The combination of carbon and magnetic materials have drawn extensive attention for microwave absorption. In this study, high-performance microwave absorbing materials are prepared by direct mechanical mixing (Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98 (ZnNiCrFeO) with leaf biocarbon. After mixing with biocarbon, the magnetic materials present decent micro-wave reflection loss. Especially, the minimum reflection loss value of −41.08 dB is achieved. The excellent conductivity of biocarbon, magnetic loss of ZnNiCrFeO, and interface polarization loss (between ZnNiCrFeO and biocarbon) jointly determined the electromagnetic absorbing performance. The appropriate impedance matching as well as the synergetic effect between the biocarbon and ZnNiCrFeO magnetic material are also considered. These achievements light the way to prepare low-cost microwave absorbents with excellent electromagnetic wave absorbing performances, utilizing the leaf as precursors.

Design Of Passive Energy Absorbers For The Imares-Ucr Wave Tank.

This paper presents the results of the analysis carried out to design a low-cost passive energy absorber for the multidirectional spectral wave basin of the IMARES-UCR group. The initial analysis was conducted using a small wave flume, which facilitated the execution of tests and the comparison of data with wave dissipaters previously designed by a commercial company what are commonly employe in various wave generation laboratories worldwide. In these initial tests, reflection coefficient values where very similar to those of the compared dissipaters. Once constructed, measurements of the reflection coefficient were performed under different regular wave conditions to determine its behavior. The obtained results are presented, considered acceptable, and enable the proper operation of the wave basin.

Unveiling the microwave heating performance of biochar as microwave absorber for microwave-assisted pyrolysis technology

Microwave (MW) heating has gained significant attention in food industries and biomass-to-biofuels through pyrolysis over conventional heating. However, constraints for promoting MW heating related to the use of different MW absorbers are still a major concern that needs to be investigated. The present study was conducted to explore the MW heating performance of biochar as a low-cost MW absorber for performing pyrolysis. Experiments were performed on biochar under different biochar dosing (25 g, 37.5 g, 50 g), MW power (400 W, 700 W, 1000 W), and particle sizes (6 mm, 8 mm, 10 mm). Results showed that MW power and biochar dosing significantly impacted average heating rate (AHR) from 17.5 to 65.4 °C/min at 400 W and 1000 W at 50 g. AHR first increased, and then no significant changes were obtained, from 37.5 to 50 g. AHR was examined by full factorial design, with 94.6% fitting actual data with predicted data. The model suggested that the particle size of biochar influenced less on AHR. Furthermore, microwave absorption efficiency and biochar weight loss were investigated, and microwave absorption efficiency decreased as MW power increased, which means 17.16% of microwave absorption efficiency was achieved at 400 W rather than 700 W and 1000 W. Biochar weight loss estimated by employing mass-balance analysis, 2–10.4% change in biochar weight loss was obtained owing to higher heating rates at higher powers and biochar dosing.

Construction of ZIF-67 derived multi-interfacial composites embedded in carbonized pomelo peel for enhanced microwave absorption with 8 wt% filler loading

The development of lightweight, environmentally friendly, and cost-effective microwave absorbers with robust absorption capabilities represents a challenging yet imperative undertaking. Herein, we present a methodology wherein derived ZIF-67 (abbreviated as Co/C) embedded in carbonized pomelo peel (CPP) through a combination of pyrolysis and in-situ growth methods, demonstrates effectiveness in microwave absorption. The Density Functional Theory (DFT) provides a comprehensive analysis of the preparation and operating principles underlying the CPP@Co/C absorber. The modification of CPP with Co/C not only facilitates the creation of numerous multiple interfaces but also mitigates impedance mismatching phenomena associated with CPP. It indicates that CPP@Co/C-150 achieves a remarkable 90% wave radiation within the frequency range of 3.52–18 GHz at a mere 8 wt% loading, covering the entire C, X, and Ku bands. Furthermore, CPP@Co/C-100 exhibits a minimum reflection loss (RLmin) value of −42.5 dB at a thickness of 1.82 mm, with an effective absorption bandwidth (EAB) extending to 5.2 GHz at 2.00 mm. This represents a substantial increase of 340% and 209% compared to CPP absorbers, respectively. The exceptional absorption performance is attributed to favorable impedance matching, conductivity loss, polarization loss, and magnetic loss mechanisms. This study introduces novel strategies and benchmarks for the production of low-cost and environmental-friendly microwave absorbers with a straightforward preparation process.

Ni/Porous Carbon-Based Composite Derived from Poplar Wood with Ultrabroad Band Microwave Absorption Performance

Electromagnetic wave (EMW) absorbers and electromagnetic shielding materials have attracted much attention in recent years. In this paper, Ni/wood-based porous carbon (WPC) composite material was prepared via morphology genetic method by using nickel chloride and poplar as raw material, The experimental results show that the microwave absorbing properties of the materials are related to the pyrolysis temperature, when the pyrolysis temperature settle at 700 °C, the minimum reflection loss of WPC-Ni can reach-60.4 dB with the thickness of 2.93 mm. Moreover, the effective absorption bandwidth has been greatly broadened up to 7.3 GHz when the thickness is 2.63 mm. The reason for such excellent wave absorbing performance is that the introduction of magnetic particles Ni and WPC-Ni regular straight channels improve impedance matching, the heterogeneous interface of Ni/ wood increases the polarization loss of electromagnetic waves. It is believed that this work can provide a new idea for the preparation of low-cost and high-efficiency broadband microwave absorber.

Ge-polymer bridge waveguide for mode-locked laser pulse generation.

A Ge-polymer hybrid waveguide is sandwiched between an indium phosphide (InP) reflective gain chip and a fiber Bragg grating (FBG) to construct a laser system. The hybrid waveguide serves as a bridge between the gain chip and the fiber with tailored mode-field matching at both facets. The 50-nm amorphous Ge (α-Ge) layer shows a nonlinear absorption effect at 1550 nm. The hybrid waveguide is further verified by a femtosecond laser transmission experiment to show the pulse width compression effect. Such waveguide is then integrated inside the laser cavity as a passive saturable absorber to modulate the longitudinal modes for a pulsed output. This polymer-bridged mode-locked laser adopts an InP gain chip for compact assembly and also a FBG with a flexible length to adjust the pulse repetition rate. The mode-locked laser output around the designed 50 MHz repetition rate is demonstrated. The pulse width is measured as 147 ps, and the signal-to-noise ratio is larger than 50 dB. This work introduces a "ternary" mode-locked laser system, taking advantage of discrete photonic components bridged by a polymer-based waveguide. It also proves the feasibility of applying α-Ge films as practical and low-cost saturable absorbers in photonic devices.

Cation exchange synthesis of AgBiS2 quantum dots for highly efficient solar cells.

Silver bismuth sulfide (AgBiS2) nanocrystals have emerged as a promising eco-friendly, low-cost solar cell absorber material. Their direct synthesis often relies on the hot-injection method, requiring the application of high temperatures and vacuum for prolonged times. Here, we demonstrate an alternative synthetic approach via a cation exchange reaction. In the first-step, bis(stearoyl)sulfide is used as an air-stable sulfur precursor for the synthesis of small, monodisperse Ag2S nanocrystals at room-temperature. In a second step, bismuth cations are incorporated into the nanocrystal lattice to form ternary AgBiS2 nanocrystals, without altering their size and shape. When implemented into photovoltaic devices, AgBiS2 nanocrystals obtained by cation exchange reach power conversion efficiencies of up to 7.35%, demonstrating the efficacy of the new synthetic approach for the formation of high-quality, ternary semiconducting nanocrystals.

Exploring the potential of standalone and tandem solar cells with Sb2S3 and Sb2Se3 absorbers: a simulation study

Thin-film antimony chalcogenide binary compounds are potential candidates for efficient and low-cost photovoltaic absorbers. This study investigates the performance of Sb2S3 and Sb2Se3 as photovoltaic absorbers, aiming to optimize their efficiency. The standalone Sb2S3 and Sb2Se3 sub-cells are analyzed using SCAPS-1D simulations, and then a tandem structure with Sb2S3 as the top-cell absorber and Sb2Se3 as the bottom-cell absorber is designed, using the filtered spectrum and the current matching technique. The optimal configuration for maximum efficiency is achieved by adjusting the thickness of the absorber layer. The results show that antimony chalcogenide binary compounds have great potential as photovoltaic absorbers, enabling the development of efficient and low-cost solar cells. A remarkable conversion efficiency of 22.2% is achieved for the optimized tandem cell structure, with absorber thicknesses of 420 nm and 1020 nm for the top and bottom sub-cells respectively. This study presents a promising approach towards high-performance tandem solar cells.

Mid-Infrared (MIR) Complex Refractive Index Spectra of Polycrystalline Copper-Nitride Films by IR-VASE Ellipsometry and Their FIB-SEM Porosity

Copper-nitride (Cu3N) semiconductor material is attracting much attention as a potential, next-generation thin-film solar light absorber in solar cells. In this communication, polycrystalline covalent Cu3N thin films were prepared using reactive-RF-magnetron-sputtering deposition, at room temperature, onto glass and silicon substrates. The very-broadband optical properties of the Cu3N thin film layers were studied by UV-MIR (0.2–40 μm) ellipsometry and optical transmission, to be able to achieve the goal of a low-cost absorber material to replace the conventional silicon. The reactive-RF-sputtered Cu3N films were also investigated by focused ion beam scanning electron microscopy and both FTIR and Raman spectroscopies. The less dense layer was found to have a value of the static refractive index of 2.304, and the denser film had a value of 2.496. The iso-absorption gap, E04, varied between approximately 1.3 and 1.8 eV and could be considered suitable as a solar light absorber.

Synergistic Desulfurization Performance of Industrial Waste Red Mud: A Comprehensive Experimental and Computational Study for COS Removal and CO(g) Production

The desulfurization process is crucial to produce high-purity hydrogen from natural gas because the gas contains sulfur compounds, which triggers the corrosion of tanks and pipes, and deactivates hydrogen fuel cell catalysts. This study evaluated experimentally and computationally the desulfurization performance of industrial waste red mud. The experimental results show that red mud has an outstanding performance in COS desulfurization, in which the sulfur capacity was larger than that for Fe2O3 by 146–156 %. The experimentally observed high performance originated from the synergetic effects between the main active phase of Fe2O3 and another element (Ti). Interestingly, the red mud provides the catalytic behavior producing CO(g) with deposited solid sulfur during the desulfurization reaction. Computational analysis proposed that the Ca/Fe2O3 phase plays a critical role in the catalytic behavior of COS decomposition. Adsorbed CO and S weakly bind on the Ca/Fe2O3 surface compared to the other phases. Based on the results, red mud has a strong potential to be a desulfurization absorber and COS decomposition catalyst. In addition, these findings provided initial insights into the development of the new low-cost sulfur absorber (Ti substituted Fe2O3) and COS decomposition catalyst (Ca substituted Fe2O3), producing the value-added product of CO(g) from COS(g).

Plant extracts as an eco-friendly approach to remove paraquat from aqueous solution

Nowadays, water pollution by herbicides is known as a global concern. Paraquat (PQ) (1-1-methyl-4,4-bi-pyridinium-dichloride) is a chip with high performance, which is being widely used herbicide to remove weeds from agricultural and natural ecosystems. PQ can contaminate water sources due to its high solubility in water. Human death by poisoning effects of PQ has been reported in several countries. Therefore, the side effects of PQ are a global challenge. This study aimed to investigate the bioremediation of PQ by plant extracts, as a low-cost, nontoxic, and natural absorbent to remove PQ from aqueous solutions in different conditions. In this regard, the extracts of common purslane (portulaca oleracea), florist kalanchoe (kalanchoe blossfeldiana), and jade plant (crassula portulaca) were used as adsorbents. For this purpose, the effect of various parameters such as contact time, initial concentration of PQ solution, temperature, pH, and amount of extract was investigated. The results of present study showed that P. oleracea extract and C. portulaca extracts have higher adsorption efficiency than k. blossfeldiana extract. The highest PQ removal was obtained by P. oleracea extract (79.04%) and C. portulaca extract (78.72%) at pH = 11, the adsorbent content of 0.2 mg L−1, and the lowest absorption of PQ (50.6%) was obtained by K. blossfeldiana extract. The highest PQ removal by plant extract was observed at 30 min for P. oleracea and C. portulaca, and at 15 min for k. blossfeldiana extract. Moreover, surface absorption capacity increased with increasing plant extract concentration, decreasing PQ concentration and decreased with increasing temperature. Finally, it can be concluded that plant extract can help to remove PQ from the aqueous solution.

High-efficient removal and adsorption mechanism of organic dyes in wastewater by KOH-activated biochar from phenol-formaldehyde resin modified wood

The treatment of wastewater contaminated with organic dyes has become an intricate challenge in water pollution control. Currently, sophisticated chemical modifications and synthetic methods are frequently needed to enhance the adsorption capacity of biochar for removing dyes during the treatment process. In order to develop a facile, low-cost and efficient biochar absorbent, an activated biochar (KOH/PF-WB) was successfully synthesized from phenol-formaldehyde (PF) resin modified wood via pyrolysis and potassium hydroxide (KOH) activation. Based on the joint effect of PF resin and wood, KOH/PF-WB-700–2 exhibited a remarkable porous structure and abundant oxygen-containing functional groups, which resulted in a substantially high specific surface area (SBET = 2301.61 m2/g) and total pore volume (Vtotal = 1.205 cm3/g). Additionally, the PF resin modification led to increased disorder and more defect sites of activated wood biochar. As a result, KOH/PF-WB-700–2 demonstrated superior adsorption capacity for congo red (3472.22 mg/g) and methylene blue (1112.35 mg/g) dyes compared to some reported adsorbents. The adsorption process could be better described by the pseudo-second-order kinetic model and Langmuir isotherm model, while the overall process was spontaneous and feasible. The primary adsorption mechanism involved pore filling through the modulation of PF resin, along with the cooperative effects of electrostatic attraction, hydrogen bonding and π-π interaction. This finding provides a viable strategy for the waste PF-modified wood cyclic application, and offer technical support for the prospect of KOH/PF-WB for the removal of organic dyes.

Mechanisms of CaO particle gelation by laser ablation of CaO powder dispersed in alcohol

Our earlier study showed that CaO particle gel, with loosened agglomerations of CaO particles, was generated by laser ablation of CaO powder dispersed in ethanol. We also demonstrated that porous CaO, a candidate of a low-cost and non-toxic CO2 absorbent, was obtained by simply drying the gel. For the present study, we conducted further investigation of the gelation mechanism to utilize this phenomenon as a simple and alternative preparation method of porous CaO. First, we observed the relation between the agglomeration tendency, including gelation and non-gelation, and the electrostatic interaction of CaO particles in different alcohols (methanol, ethanol, 1-propanol), because we have assumed electrostatic interaction among CaO particles as the most important factor affecting the gelation. Results showed that the agglomeration tendency of CaO particles increased with the decreasing zeta potential of CaO particles in these alcohols, which is consistent with the assumption. However, no decreased electrostatic repulsion caused by laser ablation was observed, suggesting the presence of another important factor affecting the gelation. As a possible factor, the CaO particle size composition was inferred: the colloid should contain both large particles and small particles. Interestingly, this assumption was validated by the fact that the gel was formed by mixing a raw colloid and a colloid prepared using laser ablation.

Printable and low-cost perfect terahertz absorber realized by a laser-induced graphene metasurface.

Terahertz (THz) absorbers are highly desired with the rapid development of THz technology. Although metasurface-based absorbers can realize perfect absorption, their fabrication often requires complicated micro-nano-processing with a high cost. In this paper, fast printable and low-cost metasurface absorbers based on a laser-induced graphene (LIG) technique are proposed. Experimental results demonstrate that these two metasurfaces can achieve maximum absorptions of 99.3% and 99.9% at their resonant frequencies in an incident angle range of ±55°. Fabrication of a metasurface with a size of 1 × 1 cm costs only 11 s. The absorbers may be applied in THz dichroism and communications.

Low-cost and broadband microwave absorption materials derived from carbonized papers

Low-cost microwave absorption materials with broad bandwidth are highly attractive in practical applications. Herein, three kinds of low-cost biomass papers, that are printer paper, toilet paper and newspaper, have been utilized to fabricate microwave absorbers by a facile one-step carbonization method. These three kinds of carbonized papers show potentials in microwave absorption, where the carbonized toilet paper (CTP) exhibits the best performance. It is found that the fibers in CTP exhibits a helix-like morphology with loose and porous state, which would be beneficial to induce the unique cross-polarization loss for the chiral materials and multiple scatting of microwave. Besides, a hybrid structure of polycrystalline-amorphous carbon is formed in the fibers by controlling the carbonization temperature, which would increase the interfacial polarization and tune the conductivity that leads to a good impedance matching. Consequently, the minimum reflection loss of CTP reaches −47 dB at 18.0 GHz with a thickness of only 2.0 mm. Meanwhile, CTP also exhibits as wide as 7.2 GHz effective absorption bandwidth at a thickness of 2.5 mm. This study provides a useful guidance for recycling the biomass materials to design and prepare low-cost and broadband microwave absorbers.

A Novel Vermiculite/TiO2 Composite: Synergistic Mechanism of Enhanced Photocatalysis towards Organic Pollutant Removal.

There has been increasing concern over water pollution, which poses a threat to human life and health. Absorption by low-cost absorbents is considered to be a cost-effective and efficient route. However, the non-reusability of absorbents greatly limits their applications. In this study, a novel vermiculite/TiO2 composite combining the inexpensive absorbent with the commonly used photocatalyst was firstly synthesized via the sol-gel method. On the one hand, the organic pollutants are absorbed by vermiculite and then decomposed through the photocatalysis process, enabling the next round of absorption and creating an absorption-decomposition reusable cycle. On the other hand, the modulation effect of optical and electronic structure on the prepared TiO2 photocatalyst by the vermiculite incorporation could significantly improve the photocatalytic activity and eventually enhance the aforementioned cyclic degradation capacity. The layer-structured vermiculite (Vt) supports a uniform coverage of TiO2 at an optimized ratio, providing an optimal adsorption environment and contact area between the photocatalyst and methylene blue (MB) molecules. Vt/TiO2 heterojunction is formed with Si-O-Ti bonding, at which electrons transfer from Vt to TiO2, enriching electron density in TiO2 and favoring its photocatalytic activity. Furthermore, the incorporation of Vt increases the light absorption of TiO2 in the visible range by narrowing the optical band gap to 1.98 eV, which could promote the generation of photo-excited carriers. In addition, PL measurements revealed that the carrier recombination is substantially suppressed, and the charge separation and migration are greatly enhanced by a factor of 3. As a result, the decomposition rate of MB is substantially increased 5.3-fold, which is ascribed to the synergistic effects of the elevated photocatalysis and the large absorption capacity governed by the chemisorption mechanism of the intra-particle diffusion. These results pave the way for composite design towards efficient, economical, and pragmatic water pollution treatment.