Cleaner Materials最新文献

Sorbitol is one of the top twelve platform chemicals and is industrially produced via glucose hydrogenation reaction. Direct sorbitol production from cellulosic material using a low-cost catalyst is a current challenge. In this study, corn stover-derived biochar supporting dual functional catalyst (Ru/S-CCS) was prepared and extensively characterized. The Ru/S-CCS catalyst was used for direct sorbitol production from microcrystalline cellulose at various reaction temperatures (180–220 °C), times (3–18 h), H₂ pressures (1–5 MPa), and Ru contents (1–5 %). The maximum sorbitol yield (66.3 wt%) and selectivity (66.1 %) were achieved at 220 °C for 6 h under 5 MPa H₂ with 5 % Ru. Various catalyst characterization techniques revealed that the acidic characteristics and metal hydrogenation sites of the Ru/S-CCS played a vital role in direct sorbitol production from cellulose. The sorbitol yield and selectivity could be enhanced by the vigorous interactive effect of sulfonic groups and Ru metal sites. The recycling performance of the Ru/S-CCS catalyst was explored under the optimal reaction conditions. Moreover, sorbitol production from glucose, raw CS, and pretreated CS was further investigated. Overall, the results of this study show that the CS biochar used in Ru/S-CCS preparation can be a competitive material for the catalyst preparation in sorbitol production, which may subsequently be used for designing large-scale sugar alcohol production.

The development of sustainable and effective methods for extracting lignin is crucial for achieving the advantages and promoting the shift towards a more sustainable and circular bioeconomy. This study addresses the use of environmentally friendly processes, including organosolv technique, supercritical fluid (SCF), non-thermal plasma (NTP), ionic liquids (ILs), deep eutectic solvents (DES), and microwave assisted extraction (MAE) techniques for lignin extraction. Organosolv treatment offers high selectivity and purity of lignin make this process economically feasible. Using supercritical water, carbon dioxide, or ethanol to extract lignin without harmful solvents is successful and customizable. NTP technologies break down lignin, simplifying processing and increasing its value. Whereas ILs may boost lignin synthesis and change its properties via solvent design. DES-based extraction methods can efficiently and specifically extract lignin. The rapid and effective MAE method employs microwave radiation to reduce extraction times and boost yields for lignin extraction. These methods feature high selectivity, little environmental impact, and the capacity to target lignin fractions. The study describes the fundamentals, benefits, and drawbacks of each extraction process, focusing on their ability to extract lignin on a large scale and its future usage. Additionally, this review explores the most recent advancements in the application sector, as well as the challenges and potential advantages of valorizing streams derived from extraction, thereby fostering the development of environmentally friendly and sustainable solutions. This research concludes that to overcome future challenges, need to address scale concerns, cost, emissions, and efficient lignin use.

A latex blend comprising polyurethane dispersion (PUD) and carboxylated nitrile butadiene rubber (XNBR) in an 80:20 ratio was prepared in the presence of epoxide and organo-modified siloxane crosslinkers. The aim of the study was to enhance the tensile, thermal, and chemical properties of the PUD/XNBR latex blend without the incorporation of sulphur and accelerator. Studies revealed that the combined action of epoxide and organo-modified siloxane crosslinker demonstrated adequate intermolecular hydrogen bonding, thereby resulting in superior tensile strength. Differential scanning calorimetry (DSC) analysis showed alterations in chain orientation and melting enthalpy due to the introduction of two crosslinkers that impart ordered hydrogen bonding to a certain degree. The compactness of the structure of the cure molecule may be closely related to the heating enthalpy, as in the following sequence, PUD₈₀/XNBR₂₀/E₁ will have a loosely packed structure, followed by PUD₈₀/XNBR₂₀/E_0.5S_0.5 and PUD₈₀/XNBR₂₀/S_1. Chemical swelling studies revealed the impact of crosslinker combinations on hydrogen bonding (both ordered and disordered), affirming the consequential enhancement in chemical resistance. This study confirms that the attained intermolecular hydrogen bonding results in desirable mechanical and chemical resistance performance, making the latex blend suitable for glove applications.

The significant increase in the number of vehicles, traffic speed, and load has significantly reduced the lifespan of pavements and increased maintenance costs. Therefore, the incorporation of polymers into bituminous binders is imperative to enhance pavement quality and performance. Nowadays, polymer-modified asphalt binders (PMBs) play a crucial role in pavement engineering. This polymer absorbs asphalt molecules to form a network connecting the entire binder, giving it better viscoelasticity than the base asphalt. Although polymers do enhance the properties of asphalt to some extent, there are still certain limitations hindering the future development of polymer-modified asphalt, such as high costs, low resistance to aging, and poor storage stability. Additionally, there is limited literature available that reviews the advantages and disadvantages of various polymer modifiers. The aim of this paper is to conduct a systematic review that evaluates the benefits and drawbacks of different polymer types in modifying asphalt materials. This comprehensive synthesis study thoroughly examines the historical evolution of polymer modified binders (PMBs) for asphalt pavement, including selection criteria for polymers used in asphalt modification, current state-of-the-art knowledge regarding the internal structure and morphology of PMBs, evaluation methodologies for PMB properties, binder specifications specific to PMBs, recommendations based on findings, and future research. This review will not only merit research from an academic perspective, but also provide guidance for pavement engineering.

3D Printing Concrete (3DPC) represents an innovative advancement in construction, enabling the creation of intricate and custom structures while simultaneously reducing material waste and expediting construction schedules. This comprehensive review delves into the latest advancements in 3DPC technology and its capacity to reshape the building and construction sectors. The paper explores recent progress in 3DPC printing systems, methodologies, materials, and applications. It places particular emphasis on the diverse parameters and concrete mix proportions that wield substantial influence over the 3DPC process. Furthermore, this study delves into the utilization of waste materials as Supplementary Cementitious Materials, i.e., nano clay, nano-silica, and ground granulated blast-furnace slag, to enhance the properties of 3DPC. This discussion extends to the consideration of 3DPC as a low-carbon concrete, outlining both its advantages and the challenges associated with its practical implementation. Additionally, the paper presents case studies of large-scale 3DPC applications and structures, discussing their economic and environmental outcomes, particularly when incorporating waste materials into 3DPC applications. Through this comprehensive analysis, the paper highlights the potential of 3DPC to revolutionize construction practices and anticipates further advancements in this dynamic field.

A novel method for the recycling of end-of-life mattresses foam, using an AIR-LAY process which employs a bi-component fiber as a binder for the polyurethane foam, have been developed and optimized. This method permits to obtain materials with the same density of the starting foam (25 kg/m³) and with a significantly lower density with respect to that obtainable with the rebonding process (above 70 kg/m³) that uses isocyanates to bond the foam particles. The obtained recycled foams have been tested by mechanical compression and recovery tests showing that compression values of 3.7 KPa, similar to that of the mattress foam (3.0 KPa), can be achieved using 20 % of bi-component fibers as binders and a density of 35 kg/m³. On the contrary, only 3 times stiffer and denser materials can be obtained using the rebonding technology, thus making them not suitable for application in mattresses. On the basis of the results of the optimization tests a set of mattresses containing a layer of the recycled foams have been prepared. The results of the tests on the prepared mattresses have shown that they have the same compression behavior, recovery time and durability (after 30,000 cycles of compression) of a standard mattress without the recycled layer, thus proving that a fully circular approach in the recycling of the foam of the mattresses is possible using the AIR-LAY process.

The Cu₂O/Cu emerges as a promising candidate for photocatalytic application owing to its efficient photon absorption in the visible light spectrum. However, the susceptibility of Cu₂O-based photocatalysts to self-decomposition diminishes their effectiveness. This study introduces CoNi as co-catalyst to enhance the durability of Cu₂O/Cu photocatalyst. Electrodeposition was employed to decorate the Cu₂O/Cu crystal surface with Co, Ni and CoNi. The deposition potential of CoNi was optimized to produce a high-performance photocatalyst. The utilization of CoNi co-catalyst resulted in significant enhancements in photoelectrochemical properties under light irradiation when compared to using a single Co or Ni co-catalyst, suggesting a synergistic effect between Co and Ni within the system. The enhancement is evidenced by a noteworthy increase in the photocurrent of the photocatalyst, rising from 10.24 mA/cm² to 20.81 mA/cm². In addition, the decoration of CoNi resulted in a reduction of the charge transfer resistance from 4.2 kΩ to 0.7 kΩ, while simultaneously increasing the electrochemically active surface area of the photocatalyst from 15.49 cm² to 157.69 cm². The observed modifications lead to a substantial improvement in the photocatalytic efficiency, resulting in an impressive 88 % degradation of methylene blue, which is 3.4 times higher than achieved in the absence of the co-catalyst. Moreover, there was a significant improvement in the photostability of the photocatalyst, with an increase from 16.81 % to 50.55 %. These findings demonstrate the significance of CoNi co-catalyst decoration in producing a highly active and durable photocatalyst, making it a promising candidate for efficient synthetic dyes degradation.

Printed electronics specifically printed strain sensor is emerging as a way forward for wearable application because of its flexibility and sustainability. Many efforts have been made to ensure the eco-friendliness of synthesized carbon-based ink to reduce the electronic waste. Carbon based fillers such as carbon nanotube have been widely used because of high electrical conductivity and excellent mechanical properties. However, the production of carbon-based fillers towards the environment still needs to be attended due to the involvement of hazardous fossil-based precursors that may harm the environment. Besides, the involvement of binders such as polyvinyl chloride (PVC), synthetic solvents and additives in the synthesis of the carbon-based conductive ink can impact serious health and environmental issues. Hence, the usage of natural precursors for green synthesis of carbon and the incorporation of biopolymer binder which are environmentally friendly and renewable need to be considered as an alternative to produce eco-friendly conductive ink. This review article presents the progress in green synthesis of the carbon-based filler, recyclability of the ink and material selection for the ink composition from biopolymer binder, solvent and additives that are eco-friendly. The performances of the carbon-based conductive ink are discussed in terms of the percolation theory and tunneling effect that form the conductive pathway in microscopic level in stretching and relaxing phenomena for printed strain sensor applications. The rheological properties of the printed ink such as viscosity, surface tension and adhesion properties to the chosen substrate also plays crucial role depending on the chosen printing technique of the printed strain sensor. The highlight of this paper is it also correlates the performance of the printed strain sensor in terms of its sensitivity using different eco-friendly carbon-based conductive ink with different printing techniques.

Worldwide every year massive amount of coal fly ash is being generated as by product in the power plants which creates economic, environmental and most importantly health problems. Usually coal fly ash is used in cement production worldwide. At present, in Bangladesh, about 95 % of fly ash remains still unutilized. The alkali activation of fly ash has become a top research topic as it is possible to synthesize low cost and ecologically sound mesoporous zeolite type materials. In the present work, to the best of our knowledge, for the first time in Bangladesh, synthesis and characterization of crystalline mesoporous (H3 type hysteresis) aluminosilicate consisting of Na-P1 zeolite with a high BET specific surface area and a high pore volume from coal fly ash based on hydrothermal alkali activation technique have been successfully done. This product has versatile applications like catalysis, gas separation, water softening, water purification, gas sensing etc. The variable of alkali concentration was studied which has the notable influence on the development of the framework of the pores. The untreated coal fly ash (CFA) and the synthesized modified fly ashes (MFAs) were tested by WDS-XRF, XRD, N₂ physisorption, FE-SEM, FT-IR, XPS, EDAX-mapping, particle size analysis and other technologies. The BET specific surface area, total pore volume and average pore diameter of the CFA were only 3 m²/g, 0.01 cc/g and 6.3 nm respectively based on nitrogen gas physisorption technique, whereas, after alkali activation at a specific temperature and time, and then curing, significant and promising increased values of the said parameters of 45 m²/g, 0.11 cc/g and 9.8 nm were obtained respectively. In methylene blue dye adsorption experiment, MFA showed higher adsorption capacity (23.87 mg/g).

Concrete is versatile but prone to cracking, which weakens its strength and durability. Self-healing concrete can automatically repair cracks, thereby preventing their occurrence. Previous studies have focused on improving self-healing efficiency in concrete to regulate cracks and minimize their effects. Unfortunately, the initial cost of self-healing concrete concerning calcite precipitation by bacterial actions is high. The current study implemented cost-reduction measures by synthesizing calcium lactate from waste eggshells and lactic acid using a more affordable bacterial growth medium made of yeast extract and molasses. To make self-healing concrete specimens, a mixture of OPC, sand, gravel, water, calcium lactate, and Bacillus subtilis bacterial solution was mixed directly at a concentration of (9.84 x 10⁶ and 4.56 x 10⁸) cells/mL. The study found that the workability of bacterial concrete exceeds that of conventional concrete, attributed to the addition of calcium lactate, which acts as a retarding agent and improves the mix's fluidity. Over a 28-day curing period, bacterial concrete with a dosage of 20 mL at a concentration of 9.84 x 10⁶ cells/mL enhanced compressive strength by 14.37 % and reduced water absorption by 23.05 %. This may be due to the calcite precipitation by bacteria that fills voids and micro-cracks inside the concrete matrix. The study also discovered that cracks smaller than 0.5 mm were fully healed within 14 days due to calcite formation produced by bacterial activity. Images from scanning electron microscopes and X-ray diffraction verified the existence of calcite in these cracks. Additionally, the current study highlighted cost reductions in waste eggshell-based self-healing bacterial concrete compared to other study-related findings. Overall, the study emphasizes the advantages of using bacterial self-healing concrete: eco-friendly, cost-effective, enhances workability, strength, and durability, and can autonomously repair cracks without human intervention.