High Energy Input Research Articles

Effects of the Laser Micromelting Process Parameters on the Preparation of Micron-Sized FeCrAl Coatings on Zr Alloy Surfaces

Laser micromelting (LMM) technology allows for the remelting of pre-positioned coatings on the surface of a specimen to form a metallurgical bond with the substrate material, significantly improving the coating’s film–base bond. However, the high energy input from the laser modification process can cause severe element diffusion, rendering the coating susceptible to deformation and cracking. This can be mitigated by controlling the laser power, scanning speed, and offset of the LMM process. The temperature and stress fields of the samples in the LMM process were analyzed via finite element simulation. The effects of the LMM process parameters on the coating morphology were analyzed in conjunction with experiments. The results indicated that the laser power significantly affected the morphology of the coating after remelting, and a higher scanning speed was more likely to cause the coating to accumulate stress. Additionally, a smaller offset inhibited crack generation. At a laser power of 30 W, a scanning speed of 1200 mm/min, and a scanning spacing of 0.035 mm, the surface of the coating had no obvious defects and was relatively flat, and the adhesion and corrosion resistance were significantly improved. This study provides valuable guidance for improving the preparation of micron-sized protective coatings on Zr alloy surfaces.

Exploring metal-free ionic covalent organic framework nanosheets as efficient OER electrocatalysts via cationic-π interactions

Metal-free electrocatalysts play a crucial role in enabling practical water splitting for future clean energy production by facilitating the oxygen evolution reaction (OER). However, the preparation of such electrocatalysts presents significant challenges due to the limitations of the kinetically sluggish anodic half-cell reaction, which restricts the attainment of high energy inputs. In this study, we present a metal- and pyrolysis-free ionic covalent organic framework (COF) nanosheet, denoted as JUC-627-NS, and investigate its potential as an efficient electrocatalyst for OER by introducing cationic-π interactions. Notably, through the utilization of positively charged JUC-627-NS as cationic donors and π-conjugated graphene as electron donors for the first time, the JUC-627-NS@G-2 composite exhibits an exceptional ultralow overpotential of 275 mV at a current density of 10 mA cm−2, ranking among the top-performing metal- and pyrolysis-free electrocatalysts reported thus far. Combining theoretical calculations with in-situ infrared spectroscopy, we validate that the imidazolium salt moiety of JUC-627-NS serves as the active center of the electrocatalyst, while the robust cation-π interaction within the complex brings the reaction site closer to graphene, acting as a conductive agent. These findings highlight a novel strategy for advancing the development of metal-free OER electrocatalysts based on ionic COF materials, with promising applications in energy conversion and storage devices.

What makes people accept carbon capture and utilization products? Exploring requirements of use in the German population

Carbon Capture and Utilization (CCU) is often referred to as an important cornerstone in the context of counteracting climate change. It aims to capture CO2 from various sources and to store it in valuable products more or less permanently. While the environmental impact of this technology has already received much scientific attention, this work takes a social science perspective on the matter. Using an empirical mixed-methods approach consisting of an exploratory focus group study (N = 13) and a validating quantitative questionnaire study (N = 198), public perceptions and acceptance of CCU were assessed in Germany by identifying motivators, barriers, and usage requirements. As CCU products, clothing, cosmetics, and food packaging were under study. Potential cost savings from shortened supply chains or manufacturing steps were the biggest motivator for using CCU. However, environmental impacts resulting from the degradation and reuse of CO2 were also recognized and the conservation of fossil resources was also acknowledged. The biggest barrier, in contrast, was the concern about possible manipulation of consumers through marketing. Participants feared that CCU would be publicly portrayed as better than it actually is. In addition, a high energy input in the production of CCU products was expected and doubts were expressed about the longevity of the positive environmental impacts of CCU. General acceptance within the sample was quite high, however, the level of CCU awareness was rather low. Our results show a considerable lack of public knowledge about and information regarding the environmental impact of CCU, among other factors, despite this very topic garnering plenty of scientific attention. A need for publicly accessible information materials uniquely tailored toward potential consumer target groups was revealed.

Ammonia Nitrogen Removal by Gas–Liquid Discharge Plasma: Investigating the Voltage Effect and Plasma Action Mechanisms

Atmospheric pressure gas–liquid discharge plasma has garnered considerable attention for its efficacy in wastewater contaminant removal. This study utilized atmospheric oxygen gas–liquid discharge plasma for the treatment of ammonia nitrogen wastewater. The effect of applied voltage on the treatment of ammonia nitrogen wastewater by gas–liquid discharge plasma was discussed, and the potential reaction mechanism was elucidated. As the applied voltage increased from 9 kV to 17 kV, the ammonia nitrogen removal efficiency rose from 49.45% to 99.04%, with an N2 selectivity of 87.72%. The mechanism of ammonia nitrogen degradation by gas–liquid discharge plasma under different applied voltages was deduced through electrical characteristic analysis, emission spectrum diagnosis, and further measurement of the concentration of active species in the gas–liquid two-phase system. The degradation of ammonia nitrogen by gas–liquid discharge plasma primarily relies on the generation of active species in the liquid phase after plasma–gas interactions, rather than direct plasma effects. Increasing the applied voltage leads to changes in discharge morphology, higher energy input, elevated electron excitation temperatures, enhanced collisions, a decrease in plasma electron density, and an increase in rotational temperatures. The change in the plasma state enhances the gas–liquid transfer process and increases the concentration of H2O2, O3, and, ⋅OH in the liquid phase. Ultimately, the efficient removal of ammonia nitrogen from wastewater is achieved.

Development of a novel “4E” polyethylene terephthalate bio-recycling process with the potential for industrial application: Efficient, economical, energy-saving, and eco-friendly

Recently, clean PET biodegradation has gained widespread attention in tackling white pollution. Nonetheless, the development of industrial biotechnology is still impeded by its contamination susceptibility, high energy input, and consumption of substantial freshwater resources. Thus, a novel PET biodegradation process was developed based on host screening and by-product circulation to address the aforementioned issues. The fast-growth host halophilic Vibrio natriegens (V. natriegens) was used and exhibited an increased protein expression level of 87.3% compared to E. coli. Meanwhile, the new process utilized a seawater-based medium for fermentation under non-sterile conditions, leading to energy-saving (energy reduced by 2.48-fold) and cost-reduction (cost reduced by 47.9%). Moreover, the large amount of saline wastewater from terephthalic acid purification was ingeniously reused for the cultivation of V. natriegens, thereby avoiding resource wastage and secondary pollution. Therefore, an efficient, economical, energy-saving, and eco-friendly process was designed, potentially addressing the industrial bottleneck in PET bio-recycling.

Nonsterilized Fermentation of Crude Glycerol for Polyhydroxybutyrate Production by Metabolically Engineered Vibrio natriegens.

Polyhydroxybutyrate (PHB) is an attractive biodegradable polymer that can be produced through the microbial fermentation of organic wastes or wastewater. However, its mass production has been restricted by the poor utilization of organic wastes due to the presence of inhibitory substances, slow microbial growth, and high energy input required for feedstock sterilization. Here, Vibrio natriegens, a fast-growing bacterium with a broad substrate spectrum and high tolerance to salt and toxic substances, was genetically engineered to enable efficient PHB production from nonsterilized fermentation of organic wastes. The key genes encoding the PHB biosynthesis pathway of V. natriegens were identified through base editing and overexpressed. The metabolically engineered strain showed 166-fold higher PHB content (34.95 wt %) than the wide type when using glycerol as a substrate. Enhanced PHB production was also achieved when other sugars were used as feedstock. Importantly, it outperformed the engineered Escherichia coli MG1655 in PHB productivity (0.053 g/L/h) and tolerance to toxic substances in crude glycerol, without obvious activity decline under nonsterilized fermentation conditions. Our work demonstrates the great potential of engineered V. natriegens for low-cost PHB bioproduction and lays a foundation for exploiting this strain as a next-generation model chassis microorganism in synthetic biology.

Enhancing scalability and economic viability of lignocellulose-derived biofuels production through integrated pretreatment and methanogenesis arrest

The pursuit of affordable biofuels necessitates continuous refinement of valorization strategies, focusing on cost-effective feedstocks, accessible bioprocessing, and high-quality products. High energy input required during various stages, including pretreatment, post-pretreatment, and methanogenesis arrest, impeded the economic lignocellulose-derived biofuels production from anaerobic digestion (AD). Addressing this challenge, an upstream process integrating synergistic alkali pretreatment and arrested AD was proposed. Results demonstrated that an optimum reactor pH 10 yielded a volatile fatty acids (VFA) titer of 3.6 gCOD/L, only 23% lower than using methanogenesis inhibitor. The study further explored the interplay between initial pH, cell viability/functionality, and VFA production by assessing cell viability and cell population demographics. This integrated approach demonstrated a VFA yield of 364 gVFA/kgTSsubstrate at a cost of just USD 0.2/kgVFA, encompassing post-pretreatment and methanogenesis arrest, which underscores the viability of combining pretreatment and methanogenesis arrest for cost effective and scalable biofuels production.

A defect detection framework using three-dimensional convolutional neural network (3D-CNN) with in-situ monitoring data in laser powder bed fusion process

Laser powder bed fusion (L-PBF) is a promising additive manufacturing (AM) technology for manufacturing complex-shaped metallic parts with high density. Since L-PBF has been rapidly developed and applied in various industries, the quality assurance of the printed part using the process became a topic of primary importance. In this respect, in-situ monitoring techniques have received increased attention in recent years for aiding the quality control of L-PBF process and the certification of the products. This study proposes a novel defect detection framework with a three-dimensional convolutional neural network (3D-CNN) and in-situ monitoring of light intensity for detecting both the lack-of-fusion and keyhole-induced defects. The proposed 3D-CNN model works with a 3D moving window to perform the local inspection using the measured light intensities in three-dimensional space to classify the type of defect. Furthermore, the model predicts the local volume fraction to provide insights into the degree of defect. To perform the classification and regression with a single 3D-CNN, the joint classification and regression approach was adopted to train the model using the results obtained with micro-computed tomography as the ground truth. In order to build the training dataset, the samples with artificial defects were fabricated in different process regimes with energy densities ranging from 19.84J/mm3 to 110.12J/mm3. After the training process, the proposed model was evaluated with the test specimens which contain randomized defects generated due to the excessively low and high energy input. The results showed that the proposed 3D-CNN-based defect detection framework can detect pores greater than 80μm induced by both lack-of-fusion and keyhole mode melting. The sensitivity of the proposed framework was evaluated, showing the true positive rate of 75.69% and 70.47% for lack-of-fusion and keyhole defects with a void volume larger than 0.0003mm3. The prediction of local volume fraction with R2 score of 0.91 was also achieved with the proposed 3D-CNN approach.

Drought impacts on river water temperature: A process‐based understanding from temperate climates

AbstractHigh river water temperature (Tw) extremes have been widely reported during drought conditions as extreme low‐flows often coincide with high atmospheric energy inputs. This has significant implications for freshwater ecosystem health and sustainable river management practices globally. However, the extent to which different meteorological and hydrological processes interact during droughts to govern Tw dynamics, and how this varies between environmental contexts, remains poorly understood. Here, we review the mechanisms controlling Tw dynamics during droughts across temperate, maritime environments, using the United Kingdom as a detailed case study. We evidence that Tw spikes have widely occurred during extreme low‐flow events observed within droughts, but such trends have been inconsistent due to varying hydroclimatic conditions and river basin controls. To better understand this, we re‐conceptualize the mechanisms governing drought‐induced Tw dynamics operating across three ‘process sets’: (i) ‘energy flux dynamics’ as non‐advective controls on Tw; (ii) the role of ‘reach‐scale habitat conditions’ in mediating non‐advective controls on Tw, including hydraulic properties (e.g., residence time) and physical conditions (e.g., riparian vegetation coverages, wetted perimeters); (iii) ‘water source contributions’ (surface water and groundwater) as advective heat and water flow controls. We review natural and anthropogenic influences affecting Tw controls within each process set and discuss how such mechanisms are likely to change under drought conditions. More systematic research (spanning various river environments and drought severities) is required to test such concepts, with existing scientific knowledge on drought‐induced Tw dynamics being largely gleaned from studies examining non‐extreme low‐flow conditions or with broader focuses (e.g., annual thermal dynamics). We conclude by highlighting critical future research questions that need to be answered to better model Tw dynamics during future droughts and for unmonitored sites. Such scientific advances would more effectively inform how high Tw extremes could be better managed through evidence‐based mitigation and adaptation strategies.

Solar-driven photocatalysis for recycling and upcycling plastics

The widespread use of plastics in modern societies generates huge amounts of plastic waste. With a view toward sustainability, researchers are now seeking strategies for recycling and upcycling plastic waste to valuable products. There is currently a significant amount of research on thermal catalytic recycling of plastics. These studies are mostly limited by high energy input, and the economic efficiency of the reaction process is not ideal. Photocatalysis and photothermal catalysis show superiority in terms of energy compared to traditional thermal catalysis. Recent researches about photocatalysis and photothermal catalysis to achieve chemical recycling and upcycling of plastics are reviewed, especially for the concept and application of three types of photothermal catalytic processes. Considering the most important efficiency, energy, and separation issues in plastic recycling, photothermal catalysis has a huge potential in the future field of plastic chemical recycling and upcycling.

Thermo-mechanical analysis of functionally graded nickel/titanium alloys under different process parameters of directed energy deposition

The build-up of residual stress and porosity plays an important role in the mechanical properties of as-built parts during directed energy deposition (DED). However, the thermo-mechanical behavior of functionally graded nickel/titanium alloys (FGNTAs) in the DED process remains unclear. In this study, a computationally efficient thermo-mechanical coupled model of DED-printed FGNTAs with different porosities is developed. The temperature-dependent effective material properties of FGNTAs are first determined based on the rule of mixture. Subsequently, the temperature, residual stress, and deformation fields within as-built FGNTAs are predicted using the differential quadrature method. The predicted results show excellent agreement with the predictions and experimental data in the literature. Furthermore, the effect of key parameters on the thermo-mechanical responses of DED-printed FGNTAs is investigated, including energy density, porosity distributions, part dimensions, temperature settings, and structural modes. The results show that the residual stress and vertical deflection increase with the higher energy input, length-to-width ratio, and evener porosity distributions, while decreasing with larger porosity, preheating as well environment temperatures, external loads, and power index. These results can provide a useful guideline for the design and manufacturing of high-quality FGNTAs during DED.

Application of instantaneous power draw analysis to investigate the impact of microwave heating on kimberlite ore crushing

Traditional crushing methods rely on a limited number of existing natural cracks as the source of crack propagation to break ore particles. Microwave-assisted crushing, on the other hand, facilitates the crushing process by inducing intergranular and transgranular cracks in ore particles. This not only reduces the energy consumption of the crusher but also improves the production rate of the process. In this study, microwave-assisted crushing of kimberlite ore is investigated ingeniously by examining the change in power draw trends to understand better the roles of larger cracks and smaller cracks induced by microwave treatment. An innovative calculation method is proposed to enable continuous monitoring of power draw instead of average power consumption. This method establishes a quantitative standard for exploring ore crushing capacity and the mechanisms of rock samples. From this study, the cumulative specific crushing energy and crushing time reduction in microwave-treated samples can be attributed to three distinct mechanisms. Firstly, the preferential generation of comparatively bigger cracks on large particles improves the breakage rate within the accumulating zone. Secondly, the generation of sufficient comparatively smaller cracks on large particles contributes to a lower peak net power amplitude. Lastly, the well-distributed generation of cracks across all particle sizes results in a shorter declining zone and an overall improvement in crushing time. The most significant reduction in both crushing energy and crushing rate is observed with the high microwave energy input. However, even at lower microwave energy inputs, substantial reductions in specific crushing energy and crushing time can still be achieved. This study demonstrates that the proposed method can be applied to other comminution systems, whether with or without microwave assistance.

Hydrodynamics intensification and interface control in the flotation conditioning process using fractal impellers

Flotation conditioning, an essential part affecting the function of flotation reagent and flotation performance, has gradually become a key field for the process enhancement of flotation. A fractal impeller device was proposed in this paper for use in pre-flotation pulp conditioning. The flow field characteristics and relevant effects on the liquid–solid mixing performance were investigated by the numerical simulation of computational fluid dynamics. The outcome of particle surface modification was assessed by studying changes in the contact angle and zeta potential of diaspore particles. These results showed that the increase of turbulent kinetic energy induced by the fractal impeller improved the dispersion of mineral particles. Meanwhile, the strong turbulence and high shear induced by the fractal impeller provided favorable conditions for collector adsorption and particle modification, leading to the increase in contact angle under relatively higher energy input. This work introduced a kind of novel fractal impellers used in the flotation conditioning to strengthen the flotation separation of minerals.

The Energy and Environmental Evaluation of Maize, Hemp and Faba Bean Multi-Crops

Agriculture uses a lot of fuel, fertilizers, pesticides and other substances, while emitting large amounts of GHGs. It is important to optimize these inputs and outputs. One such way is by increasing crop biodiversity. For this reason, single crops and mixtures of maize, hemp and faba bean as binary and ternary crops were investigated at the Experimental Station of Vytautas Magnus University, Lithuania. The results showed that consumption of diesel fuel was 31–46% higher than in single and 22–35% higher than in binary cultivations was found in a ternary crop. This had influence on the highest energy input of near twice higher than in maize and hemp single crops and maize+hemp binary crop, but similar with binary crops with faba bean. Despite this, the productivity of the ternary crop and, at the same time, the energy output were 2–5 times higher than in other treatments. This compensated for higher energy inputs and the energy efficiency ratio. In the ternary crop, energy productivity was from 1.1 to 2.8 times higher and net energy was 1.9–5.3 times higher than in other tested cultivations. The highest total GHG emissions were obtained in binary maize+hemp and maize+faba bean cultivations (1729.84 and 2067.33 CO2eq ha−1). Ternary cultivation with the highest energy inputs initiated average GHG emissions of 1541.90 kg ha−1 CO2eq. For higher efficiency, the ternary crop could be sown and harvested in one machine pass. Faba beans should be included in ternary crops, as their biomass makes up a significant part of the total biomass produced. We recommend reviewing the intercropped faba bean seeding rates, as faba bean seeds have a high energy input equivalent.

Microstructure and Elevated Temperature Flexure Testing of Tungsten Produced by Electron Beam Additive Manufacturing

Due to their superior high-temperature thermomechanical capabilities, sputter erosion durability, and excellent resistance to hydrogen isotopes, tungsten materials have garnered significant interest in fusion nuclear applications. However, low room-temperature ductility and complex machining strategies present significant challenges for traditional fabrication. Electron beam powder bed fusion (EB-PBF) shows promise in manufacturing pure tungsten via high thermal energy input, elevated build temperature, and a tightly controlled high-vacuum environment. This work explores the process, structure, and property relationship of pure tungsten fabricated by EB-PBF, where 99.8% relative density was achieved with reduced cracking by isolating the build substrate and optimizing the print parameter suite. Optical and electron imaging revealed that the microstructure contained equiaxed grains along the build direction, with subgrains present in all inspected grains. Flexural testing at ambient and elevated temperatures demonstrated high ductility at 900°C and flexural strength of 470 MPa at room temperature of additively manufactured tungsten.

Impact of Thickness on Direct Ammonia Decomposition in Solid Oxide Fuel Cells, Numerical and Experimental Research

The growing share of renewable energy sources (RES) in the energy mix and the desire to reduce greenhouse gas and pollutant emissions are driving widespread technological progress. One of the main areas is the development of hydrogen technologies, as manifested, for example, in the emerging hydrogen strategies of countries around the world. However, the widespread use of H2 is limited by the high energy input required for storage. This makes ammonia a promising carbon-free hydrogen carrier. Its application is being considered, e.g. in power systems for deep-sea transportation. Ammonia can be used like a fuel in energy systems, but often requires proper processing or decomposition into hydrogen and nitrogen in the presence of a catalyst. These activities increase financial or technological inputs which can complicate energy systems and reduce their efficiency or energy density. Power plants based on solid-oxide fuel cells (SOFCs) have the ability to process NH3 as fuel whether in external or internal cracking mode. However due to the nickel-based anode and operating temperatures above 600°C, SOFCs can directly use NH3 as a fuel - direct-ammonia SOFCs (DA-SOFCs). Lowering the operating temperature of the cells and reducing their thickness brings with it a wider opportunity for SOFC-based systems e.g. decrease energy density, and reduction of used materials. An additional advantage of direct ammonia conversion in SOFC cells is the endothermic nature of the reaction, allowing for a reduction in the amount of cooling air supplied to the system. In this study, the performance of cells with different anode thickness was compared under similar operating conditions for direct ammonia-fueled solid oxide fuel cells (SOFCs). The experimental results were reproduced in the open source computational fluid dynamics (CFD) software, Open Fuel Cell, in which the source term responsible for internal cracking was introduced. Then calculations were made to determine the distribution of ammonia and temperature in the functional part. It was determined that in the case of counter-current flow of fuel and oxidizer, thinner cells show a smaller temperature gradient. Lowering the operating temperature and cell thickness does not lead to incomplete conversion of ammonia in the cell. Post-mortem analysis of the cells used in the experiment showed no negative effect of ammonia on the functional layers of the cells.

Energy balance and life cycle assessments in producing microalgae biodiesel via a continuous microalgal-bacterial photobioreactor loaded with wastewater

Life cycle assessments of microalgal cultivation systems are often conducted to evaluate the sustainability and feasibility factors of the entire production chain. Unlike widely reported conventional microalgal cultivation systems, the present work adopted a microalgal-bacterial cultivation approach which was upscaled into a pilot-scale continuous photobioreactor for microalgal biomass production into biodiesel from wastewater resources. A multiple cradle-to-cradle system ranging from microalgal biomass-to-lipid-to-biodiesel was evaluated to provide insights into the energy demand of each processes making up the microalgae-to-biodiesel value chain system. Energy feasibility studies revealed positive NER values (4.95–8.38) for producing microalgal biomass but deficit values for microalgal-to-biodiesel (0.14–0.23), stemming from the high energy input requirements in the downstream processes for converting biomass into lipid and biodiesel accounting to 88–90% of the cumulative energy demand. Although the energy balance for microalgae-to-biodiesel is in the deficits, it is comparable with other reported biodiesel production case studies (0.12–0.40). Nevertheless, the approach to using microalgal-bacterial cultivation system has improved the overall energy efficiency especially in the upstream processes compared to conventional microalgal cultivation systems. Energy life cycle assessments with other microalgal based biofuel systems also proposed effective measures in increasing the energy feasibility either by utilizing the residual biomass and less energy demanding downstream extraction processes from microalgal biomass. The microalgal-bacterial cultivation system is anticipated to offer both environmental and economic prospects for upscaling by effectively exploiting the low-cost nutrients from wastewaters via bioconversion into valuable microalgal biomass and biodiesel.

Modular Functionalization of Metal‐Organic Frameworks for Nitrogen Recovery from Fresh Urine**

AbstractNitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy‐extensive Haber‐Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source‐separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal–organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF‐808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75 % total nitrogen reduction and 45 % nitrogen recovery with a 30‐minute treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Modular Functionalization of Metal-Organic Frameworks for Nitrogen Recovery from Fresh Urine.

Nitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy-extensive Haber-Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source-separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal-organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF-808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75 % total nitrogen reduction and 45 % nitrogen recovery with a 30-minute treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Tribochemically Controlled Atom Transfer Radical Polymerization Enabled by Contact Electrification.

Traditional mechanochemically controlled reversible-deactivation radical polymerization (RDRP) utilizes ultrasound or ball milling to regenerate activators, which induce side reactions because of the high-energy and high-frequency stimuli. Here, we propose a facile approach for tribochemically controlled atom transfer radical polymerization (tribo-ATRP) that relies on contact-electro-catalysis (CEC) between titanium oxide (TiO2 ) particles and CuBr2 /tris(2-pyridylmethylamine (TPMA), without any high-energy input. Under the friction induced by stirring, the TiO2 particles are electrified, continuously reducing CuBr2 /TPMA into CuBr/TPMA, thereby conversing alkyl halides into active radicals to start ATRP. In addition, the effect of friction on the reaction was elucidated by theoretical simulation. The results indicated that increasing the frequency could reduce the energy barrier for the electron transfer from TiO2 particles to CuBr2 /TPMA. In this study, the design of tribo-ATRP was successfully achieved, enabling CEC (ca. 10 Hz) access to a variety of polymers with predetermined molecular weights, low dispersity, and high chain-end fidelity.