Eco-friendly, compact, and cost-efficient triboelectric nanogenerator for renewable energy harvesting and smart motion sensing

In recent years, the growth of Internet of Things devices has increased the use of sustainable energy sources. An alternative technology is offered by triboelectric nanogenerators (TENGs) that can harvest green energy and convert it into electrical energy. Herein, we assessed three different nopal powder types that were used as triboelectric layers of eco-friendly and sustainable TENGs for renewable energy harvesting from environmental vibrations and powering electronic devices. These nanogenerators were fabricated using waste and recycled materials with a compact design for easy transportation and collocation on non-homogeneous surfaces of different vibration or motion sources. In addition, these TENGs have advantages such as high output performance, stable output voltage, lightweight, low-cost materials, and a simple fabrication process. These nanogenerators use the contact-separation mode between two triboelectric layers to convert the vibration energy into electrical energy. TENG with the best output performance is based on dehydrated nopal powder, generating an output power density of 2.145 mWm-2 with a load resistance of 39.97 MΩ under 3g acceleration and 25 Hz operating frequency. The proposed TENGs have stable output voltages during 22500 operating cycles. These nanogenerators can light 116 ultra-bright blue commercial LEDs and power a digital calculator. Also, the TENGs can be used as a chess clock connected to a mobile phone app for smart motion sensing. These nanogenerators can harvest renewable vibration energy and power electronic devices, sensors, and smart motion sensing.

Polylactic acid-based plastic activated NiAl2O4 nanoparticles as highly active positive electrode materials for energy storage supercapacitor

A simple, low-cost, and environmentally benign process for synthesizing nanostructured NiO/NiAl2O4 on multiple kinds of carbon nanostructures (CNS) is presented. This method develops polylactic acid (PLA) based waste plastic materials for the producing CNS. These composites (NiO@NiAl2O4/CNS) were examined as potential electrodes in supercapacitors (SC) as they exhibit good charge/discharge reversibility and provide adequate specific capacitance values with a maximum being 1984 F/g at 0.5 A g-1. It is noteworthy that the cycling stability of this sample at 10 A g-1 maintained 101.7% of its initial capacity even after 5000 GCD cycles. An asymmetric supercapacitor (ASC) was built and analyzed, with NiO@NiAl2O4/CNS serving as the cathode and activated carbon serving as the anode of the device. The concluded device has an energy density of 58 Wh kg-1 with a power density of 986 W kg-1 and a SCs of 216.5 F/g. The results showed that the materials mentioned are a great option to use as electrode materials in applications involving the storage of energy.

Cassava bagasse as an alternative biosorbent to uptake methylene blue environmental pollutant from water

Herein, the methylene blue (MB) biosorption from the agroindustrial residue (cassava bagasse) is reported. The cassava bagasse residue presented an irregular surface, anionic character, and low specific surface area. The experiments were performed in batch mode. The biosorption behavior was investigated through the experimental variables, initial concentration of MB, pH, and temperature. The maximum biosorption capacity (170.13 mg g^-1) reached 328 K and pH 10.0. The equilibrium and kinetics were better fitted by the Sips and general order (R² ≥ 0.997 and R²_adj ≥ 0.996) models, respectively. Furthermore, the thermodynamic study revealed a spontaneous (ΔG⁰ < 0) and endothermic process. Finally, the results showed cassava bagasse is a potential material for biosorption dyes from the aqueous medium. In addition, the biosorbent has a low aggregate cost and high availability, which contributes to the destination of large amounts of waste and inspires engineering applications.

Metagenomic insights into feasibility of agricultural wastes on optimizing water quality and natural bait by regulating microbial loop

Effective screening feed substitutes for improving water quality in aquaculture systems has become a trending research topic now. In this study, three typical organic agricultural wastes, including sugar cane bagasse (SC), coconut shell powder (CS), and corn cob powder (CC), were selected to evaluate their potential roles on the optimization of water quality and natural bait compared to aquafeeds. Fish feed resulted in the highest growth rate of fish but the worst water quality. Organic detritus addition markedly improved the water quality, especially soluble reactive phosphorus (SRP, decrease of 56-61%) and ammonium (decrease of 16% in SC, 47% in CC). Specially, SC induced core microbes to mediate nutrients transformation and recycling (N₂-fixation, ammonification, nitrification, dissimilatory nitrate reduction to ammonia and organic nutrients decomposition), which facilitated the primary productivity based on their positive relationships. This further reduced the available nutrients (especially SRP) in the water and built a mutually beneficial microbial loop. In addition, SC addition increased the abundance of genes involved in amino acids biosynthesis pathways, photosynthesis, and carbon fixation. These results led to energy transfer to higher trophic levels. The addition of CC had a better effect than SC in terms of lower nitrogen levels and a higher fish growth rate (19% in CC, 5% in SC). However, low temperatures and carbon accumulation jointly drive the anaerobic decomposition, resulting in unhealthy microbial loops and low fish growth rates. In contrast to the direct consumption of fish feed, organic detritus can induce more natural bait to provide food for fish by regulating the microbial loop, as showed by the microbial community composition in the water and fish gut. To comprehensively assess water quality, natural bait, and fish growth and quality, certain organic detritus should be considered as an auxiliary material to partially replace feed for healthy and sustainable aquaculture systems.

Research on the identification of generic technology of eco-friendly materials based on text mining

The overconsumption of natural resources and the production of waste are causing severe degradation of our environment. Generic technologies (GTs) of eco-friendly materials could alleviate environmental pollution, solve resource and environment-related conflicts, and promote society's sustainable development. The identification of GTs is the first step towards GT innovation and establishing a supply of eco-friendly materials; thus, how to accurately identify GTs is an important challenge for governments and enterprises. In this paper, a new method that integrates latent Dirichlet allocation (LDA), term frequency-inverse document frequency (TF-IDF), social network analysis (SNA), and a hidden Markov model (HMM) is proposed for GT identification. The LDA model was employed to extract hidden information of eco-friendly materials. In addition, scientific linkage, betweenness centrality, technology co-occurrence rate, the number of patents, and the number of valid countries or territories designated by the patent were selected to analyse the technology topic characteristics. Then, the fundamentality, pervasiveness, and benefit characteristics of GTs were combined to identify GTs of eco-friendly materials. On this basis, HMM was employed to predict the evolution trend of GTs. The results show that sixteen technologies are GTs of eco-friendly materials. Furthermore, degradable composite materials and cellulose extraction methods will become the focus of research in the future. These studies can provide a new method for the identification of GTs of eco-friendly materials and help nations or enterprises to make effective decisions to develop GTs, minimizing the burden on the environment.

Reactive extrusion-processed native and phosphated starch-based food packaging films governed by the hierarchical structure

The aim of this research work was to investigate novel tools given by nanotechnology and green chemistry for improving the disadvantages typically associated to the starch-based films: water susceptibility and brittle mechanical behavior. With this in mind, four food packaging film systems were developed from corn starch or corn starch nanocrystals (SNCs), and modified by phosphating under reactive extrusion (REx) conditions using sodium tripolyphosphate (Na₅P₃O₁₀ - TPP) as a crosslinker. The structural, physicochemical, thermal, rheological and mechanical properties, as well as studies associated with the management of carbohydrate polymer-based plastic wastes (biodegradability and compostability) were carried out in this study. The hierarchical structure and the modification of the starch were dependent on the amylose content and degree of substitution (DS), which in turn depended on the hydrogen (H)-bonding interactions. In both cases, a higher molecular ordering of the starch chains in parallel was decisive to obtain the self-assembled thermoplastic starches. Beyond the valuable results obtained and scientifically analyzed, unfortunately none of the manufactured materials achieved to improve their performance compared to the control film (thermoplastic starch - TPS). It was even thought that the phosphated starch-based films could fertilize lettuce (Lactuca sativa) seedlings during their biodegradation, and this was not achieved either. This possibly due to the low content of phosphorus or its poor bioavailability.

Use of marble sludge waste in the manufacture of eco-friendly materials: applying the principles of the Circular Economy

The marble industry generates enormous amounts of waste every year, whose incorrect management can lead to environmental problems. The Circular Economy model can provide an effective solution to this issue, an aspect that has been addressed in this research. The suitability of a marble sludge generated in the ornamental rock industry of Andalusia (Spain) has been assessed as raw material in ceramic bricks. Mixtures containing a clayey base and 0, 2.5, 5, 7.5, and 10 wt% of marble powder have been shaped into 60 × 30 × 10-mm³ prismatic specimens and sintered at 950 °C in a muffle. The main technological properties of the bricks related to color, shrinkage, porosity, water absorption, suction, and compressive strength have been determined. The addition of marble sludge has fostered the development of a lighter color, together with a significant increase of the open porosity. This aspect has implied, on the one hand, higher water absorption and suction results and, on the other hand, a decrease of the density and the mechanical strength. The correlations obtained after applying Shapiro-Wilk normality tests and r Pearson coefficients endorse the clear relationship between the addition of marble powder and the abovementioned effects on the technological properties of the sintered bricks. All the measured properties fully meet the brick standardized requirements, which would indicate that the recycling of marble wastes could be a promising alternative to obtain eco-friendly lightweight ceramic materials.