Kraft Lignin-Derived Microporous Nitrogen-Doped Carbon Adsorbent for Air and Water Purification

The study presents a streamlined one-step process for producing highly porous, metal-free, N-doped activated carbon (N-AC) for CO2 capture and herbicide removal from simulated industrially polluted and real environmental systems. N-AC was prepared from kraft lignin─a carbon-rich and abundant byproduct of the pulp industry, using nitric acid as the activator and urea as the N-dopant. The reported carbonization process under a nitrogen atmosphere renders a product with a high yield of 30% even at high temperatures up to 800 °C. N-AC exhibited a substantial high N content (4-5%), the presence of aliphatic and phenolic OH groups, and a notable absence of carboxylic groups, as confirmed by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and Boehm's titration. Porosity analysis indicated that micropores constituted the majority of the pore structure, with 86% of pores having diameters less than 0.6 nm. According to BET adsorption analysis, the developed porous structure of N-AC boasted a substantial specific surface area of 1000 m2 g-1. N-AC proved to be a promising adsorbent for air and water purification. Specifically, N-AC exhibited a strong affinity for CO2, with an adsorption capacity of 1.4 mmol g-1 at 0.15 bar and 20 °C, and it demonstrated the highest selectivity over N2 from the simulated flue gas system (27.3 mmol g-1 for 15:85 v/v CO2/N2 at 20 °C) among all previously reported nitrogen-doped AC materials from kraft lignin. Moreover, N-AC displayed excellent reusability and efficient CO2 release, maintaining an adsorption capacity of 3.1 mmol g-1 (at 1 bar and 25 °C) over 10 consecutive adsorption-desorption cycles, confirming N-AC as a useful material for CO2 storage and utilization. The unique cationic nature of N-AC enhanced the adsorption of herbicides in neutral and weakly basic environments, which is relevant for real waters. It exhibited an impressive adsorption capacity for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) at 96 ± 6 mg g-1 under pH 6 and 25 °C according to the Langmuir-Freundlich model. Notably, N-AC preserves its high adsorption capacity toward 2,4-D from simulated groundwater and runoff from tomato greenhouse, while performance in real samples from Fyris river in Uppsala, Sweden, causes a decrease of only 4-5%. Owing to the one-step process, high yield, annual abundance of kraft lignin, and use of environmentally friendly activating agents, N-AC has substantial potential for large-scale industrial applications.

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

Polyurethane Recycling: Thermal Decomposition of 1,3-Diphenyl Urea to Isocyanates

Substituted urea linkages are formed during the production of polyurethane foam. To chemically recycle polyurethane toward its key monomers via depolymerization (i.e., isocyanate), it is essential to break the urea linkages to form the corresponding monomers, namely, an isocyanate and an amine. This work reports the thermal cracking of a model urea compound (1,3-diphenyl urea, DPU) into phenyl isocyanate and aniline in a flow reactor at different temperatures. Experiments were performed at 350-450 °C, with a continuous feed of a solution of 1 wt.% DPU in GVL. In the temperature range studied, high conversion levels of DPU are achieved (70-90 mol%), with high selectivity towards the desired products (close to 100 mol%) and high average mole balance (∼95 mol%) in all cases.

Engineering the Surface Chemistry and Morphology of Polymeric Carbon Nitrides Towards Greener Heterogeneous Catalysts for Biodiesel Synthesis

Biodiesel remains one of the most promising alternatives to replace fossil fuel-derived petrodiesel. Nonetheless, conventional biodiesel synthesis relies on homogeneous alkali-based catalysts that involve long and tedious purification steps , increasing biodiesel production costs. Heterogeneous catalysts have emerged as promising alternatives to circumvent these drawbacks, as they can easily be recovered and reused. Herein, polymeric carbon nitride dots and nanosheets are synthesized through a solid-phase reaction between urea and sodium citrate. Their morphology and surface chemistry are tuned by varying the precursor's ratio, and the materials are investigated as catalysts in the transesterification reaction of canola oil to biodiesel. A conversion of > 98% is achieved using a 5 wt% catalyst loading, oil to methanol ratio of 1:36 at 90 °C for 4 h, with the performance maintained over at least five reuse cycles. In addition, the effect of the transesterification reaction parameters on the reaction kinetics is evaluated, which follows a pseudo-first-order (PFO) regime. Combined with a deep understanding of the catalyst's surface, these results have allowed us to propose a reaction mechanism similar to the one observed for homogenous alkali catalysts. These carbon nitride-based nanoparticles offer a metal-free and cost-effective alternative to conventional homogeneous and metal-based heterogeneous catalysts.

High Leach-Resistant Fire-Retardant Modified Pine Wood (Pinus sylvestris L.) by In Situ Phosphorylation and Carbamylation

The exterior application of fire-retardant (FR) timber necessitates it to have high durability because of the possibility to be exposed to rainfall. In this study, water-leaching resistance of FR wood has been imparted by grafting phosphate and carbamate groups of the water-soluble FR additives ammonium dihydrogen phosphate (ADP)/urea onto the hydroxyl groups of wood polymers via vacuum-pressure impregnation, followed by drying/heating in hot air. A darker and more reddish wood surface was observed after the modification. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance (¹³C CP-MAS NMR), and direct-excitation ³¹P MAS NMR suggested the formation of C-O-P covalent bonds and urethane chemical bridges. Scanning electron microscopy/energy-dispersive X-ray spectrometry suggested the diffusion of ADP/urea into the cell wall. The gas evolution analyzed by thermogravimetric analysis coupled with quadrupole mass spectrometry revealed a potential grafting reaction mechanism starting with the thermal decomposition of urea. Thermal behavior showed that the FR-modified wood lowered the main decomposition temperature and promoted the formation of char residues at elevated temperatures. The FR activity was preserved even after an extensive water-leaching test, confirmed by the limiting oxygen index (LOI) and cone calorimetry. The reduction of fire hazards was achieved through the increase of the LOI to above 80%, reduction of 30% of the peak heat release rate (pHRR₂), reduction of smoke production, and a longer ignition time. The modulus of elasticity of FR-modified wood increased by 40% without significantly decreasing the modulus of rupture.

Deposit formation from evaporating urea-water droplets on substrates of different wettability

HYPOTHESIS

During the evaporation of urea water solution (UWS), the wall temperature and surface properties influence the dynamics of deposit formation by affecting the internal mass transport. These effects are expected to be reflected in the resulting deposit morphology and allow different deposit regimes to be distinguished.

EXPERIMENTS

The temperature of metallic substrates is varied for three different surface treatments to analyze the wetting, evaporation behavior and the crystallization process of single UWS droplets in situ using a high-speed camera. The deposit morphology is captured by confocal microscopy and analyzed via the power spectral density method (PSD). PSD is used to extract the height of different surface features for each deposit, providing valuable information about the local crystallization history.

FINDINGS

A significant influence of the surface properties on the crystallization process as well as on the morphology of the final deposit is found. The influence of wettability is described by the resulting internal mass transport, which determine the urea distribution. PSD analysis quantified distinct trends in the scaling tendencies of the deposit aggregates under different wall conditions. The local crystal growth history extracted by PSD agrees well with proposed crystallization mechanisms, which is further supported by high-speed and SEM imaging.

From liquid to solid-state, solvent-free oxidative ammonolysis of lignins – an easy, alternative approach to generate “N-lignins”†

A new chemical modification protocol to generate N-lignins is presented, based on Indulin AT and Mg²⁺-lignosulfonate. The already known ammonoxidation reaction in liquid phase was used as a starting point and stepwise optimised towards a full solid-state approach. The “classical” liquid ammonoxidation products, the transition products from the optimization trials, as well as the “solid-state” products were comprehensively analysed and compared to the literature. The N-lignins obtained with the conventional ammonoxidation protocol showed the same properties as reported. Their molar mass distributions and the hydroxy group contents, hitherto not accessible due to solubility problems, were measured according to a recently reported protocol. N-Indulin showed an N-content up to 11 wt% and N-lignosulfonate up to 16 wt%. The transition experiments from liquid to solid-state gave insights into the influence of chemical components and reaction conditions. The use of a single chemical, the urea-hydrogen peroxide complex (UHP, “carbamide peroxide”), was sufficient to generate N-lignins with satisfying N-content. This chemical acts both as an N-source and as the oxidant. Following the optimization, a series of solid-state ammonoxidation tests were carried out. High N-contents of 10% in the case of Indulin and 11% in the case of lignosulfonate were obtained. By varying the ratio of UHP to lignin, the N-content can be controlled. Structural analysis showed that the N is organically bound to the lignin, similar to the “classical” ammonoxidation products obtained under homogeneous conditions. Overall, a new ammonoxidation protocol was developed which does not require an external gas supply nor liquids or dissolved reactants. This opens the possibility for carrying out the lignin modification in closed continuous reactor systems, such as extruders. The new, facile solid-state protocol will hopefully help N-lignins to find more consideration as a fertilizing material and in soil-improving materials.

An alternative ammonoxidation protocol was developed. With this new approach in “solid-state” mode, one single solid reagent is sufficient to equip lignin with different N-functionalities.

Selective Catalytic Reduction with Hydrogen for Exhaust gas after-treatment of Hydrogen Combustion Engines

In this work, two palladium-based catalysts with either ZSM-5 or Zeolite Y as support material are tested for their performance in selective catalytic reduction of NOx with hydrogen (H2-SCR). The ligh-toff measurements in synthetic exhaust gas mixtures typical for hydrogen combustion engines are supplemented by detailed catalyst characterization comprising N2 physisorption, X-ray powder diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR) and ammonia temperature programmed desorption (NH3-TPD). Introducing 10% or 20% TiO2 into the catalyst formulations reduced the surface area and the number of acidic sites for both catalysts, however, more severely for the Zeolite Y-supported catalysts. The higher reducibility of the Pd particles that was uncovered by H2-TPR resulted in an improved catalytic performance during the light-off measurements and substantially boosted NO conversion. Upon exposition to humid exhaust gas, the ZSM-5-supported catalysts showed a significant drop in performance, whereas the Zeolite Y-supported catalyst kept the high levels of conversion while shifting the selectivity from N2O more toward NH3 and N2. The 1%Pd/20%TiO2/HY catalyst subject to this work outperforms one of the most active and selective benchmark catalyst formulations, 1%Pd/5%V2O5/20%TiO2-Al2O3, making Zeolite Y a promising support material for H2-SCR catalyst formulations that allow efficient and selective NOx-removal from exhaust gases originating from hydrogen-fueled engines.

Building the uracil skeleton in primitive ponds at the origins of life: carbamoylation of aspartic acid

A large set of nucleobases and amino acids is found in meteorites, implying that several chemical reservoirs are present in the solar system. The "geochemical continuity" hypothesis explores how protometabolic paths developed from so-called "bricks" in an enzyme-free prebiotic world and how they affected the origins of life. In the living cell, the second step of synthesizing uridine and cytidine RNA monomers is a carbamoyl transfer from a carbamoyl donor to aspartic acid. Here we compare two enzyme-free scenarios: aqueous and mineral surface scenarios in a thermal range up to 250 °C. Both processes could have happened in ponds under open atmosphere on the primeval Earth. Carbamoylation of aspartic acid with cyanate in aqueous solutions at 25 °C gives high N-carbamoyl aspartic acid yields within 16 h. It is important to stress that, while various molecules could be efficient carbamoylating agents according to thermodynamics, kinetics plays a determining role in selecting prebiotically possible pathways.

Theoretical Study of the Thermal Decomposition of Urea Derivatives

An extensive theoretical study of the thermal decomposition of alkyl- and phenylureas, which are widely used in the pesticides, pharmaceuticals, and materials industries, has been carried out using electronic structure calculations and reaction rate theories. Enthalpies of formation and bond dissociation energies (BDE) of 11 urea derivatives have been calculated using different levels of theory (CBS-QB3, CCSD(T)/CBS//M06-2X/6-311++G(3df,2pd), and CBS-QM062X) according to the size of the system. Potential energy surfaces for the unimolecular decomposition pathways of these urea derivatives were also systematically computed for the first time. Several pericyclic reactions can be envisaged, as a function of the size and the nature of the N substituents, and all of these pathways were explored. Our calculations show that these compounds are solely decomposed by four-center pericyclic reactions, yielding substituted isocyanates and amines, and that initial bond fissions are not competitive. Based on the set of urea derivatives studied, a new reaction rate rule for their thermal decomposition was defined and involves the nature of the transferred H atom (primary or secondary/alkyl or benzyl) and the nature of the N-atom acceptor (primary, secondary, or tertiary). This new reaction rate rule allows us to determine the product branching ratios in the thermal decomposition of a given urea derivative and its total rate of decomposition. Applications on urea derivatives used in the chemical industry are presented and illustrate the usefulness of this new rate rule that allows to predict the previously unknown thermal decomposition kinetics of a large number of these compounds.

Hydrogen production from urea in human urine using segregated systems

Removal of nitrogen compounds through biological processes represents the highest energy consumption in conventional centralised wastewater treatment facilities. Alternatively, segregated systems, where wastewater is treated at its source, present the potential to provide value to nitrogen-rich compounds contained in wastewater like urea. This paper demonstrates the feasibility of a novel process to recover energy from human urine based on the pre-isolation of urea to decrease the energy requirements for its thermal decomposition compared to the conventional thermal treatment when in solution, followed by its decomposition into hydrogen. Herein, urea is separated from an aqueous solution by adsorption onto activated carbon. Thermal urea desorption and decomposition into ammonia and CO₂ at 250 °C leads to full regeneration of the carbon, showing a constant adsorption capacity for at least 5 consecutive adsorption/desorption cycles. Finally, when the regeneration and urea decomposition step is coupled to an ammonia decomposition catalyst, hydrogen is produced to be used as an energy fuel. This process opens the door to a new way of circular economy by energy recovery from hydrogen-rich components in segregated wastewater streams. Preliminary energy balances show that the adoption of this energy recovery system in a city of 160,000 inhabitants would lead to a daily hydrogen production of 430 kg, with a net energy production of 2,500 kWh/day. In addition, such waste-to-energy process would lead to energy savings of 4,600 kWh/day in a conventional wastewater treatment plant reducing its energy consumption by around 35%.

Urea-Based Patches with Controlled Release for Potential Atopic Dermatitis Treatment

Skin diseases such as atopic dermatitis (AD) are widespread and affect people all over the world. Current treatments for dry and itchy skin are mostly focused on pharmaceutical solutions, while supportive therapies such as ointments bring immediate relief. Electrospun membranes are commonly used as a drug delivery system, as they have a high surface to volume area, resulting in high loading capacity. Within this study we present the manufacturing strategies of skin patches using polymer membranes with active substances for treating various skin problems. Here, we manufactured the skin patches using electrospun poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVB) fibers blended and electrosprayed with urea. The highest cumulative release of urea was obtained from the PVB patches manufactured via blend electrospinning with 5% of the urea incorporated in the fiber. The maximum concentration of released urea was acquired after 30 min, which was followed up by 6 h of constant release level. The simultaneous electrospinning and electrospraying limited the urea deposition and resulted in the lowest urea incorporation followed by the low release level. The urea-based patches, manufactured via blend electrospinning, exhibited a great potential as overnight treatment for various skin problems and their development can bring new trends to the textile-based therapies for AD.

Structure-Activity Relationship of Carbon Nitride Dots in Inhibiting Tau Aggregation

Due to the numerous failed clinical trials of anti-amyloid drugs, microtubule associated protein tau (MAPT) now stands out as one of the most promising targets for AD therapy. In this study, we report for the first time the structure-dependent MAPT aggregation inhibition of carbon nitride dots (CNDs). CNDs have exhibited great promise as a potential treatment of Alzheimer's disease (AD) by inhibiting the aggregation of MAPT. In order to elucidate its structure-activity relationship, CNDs were separated via column chromatography and five fractions with different structures were obtained that were characterized by multiple spectroscopy methods. The increase of surface hydrophilic functional groups is consistent with the increase of polarity from fraction 1 to 5. Particle sizes (1-2 nm) and zeta potentials (~-20 mV) are similar among five fractions. With the increase of polarity from fraction 1 to 5, their MAPT aggregation inhibition capacity was weakened. This suggests hydrophobic interactions between CNDs and MAPT, validated via molecular dynamics simulations. With a zebrafish blood-brain barrier (BBB) model, CNDs were observed to cross the BBB through passive diffusion. CNDs were also found to inhibit the generation of multiple reactive oxygen species, which is an important contributor to AD pathogenesis.

Application and Development of Selective Catalytic Reduction Technology for Marine Low-Speed Diesel Engine: Trade-Off among High Sulfur Fuel, High Thermal Efficiency, and Low Pollution Emission

In recent years, the International Maritime Organization (IMO), Europe, and the United States and other countries have set up different emission control areas (ECA) for ship exhaust pollutants to enforce more stringent pollutant emission regulations. In order to meet the current IMO Tier III emission regulations, an after-treatment device must be installed in the exhaust system of the ship power plant to reduce the ship NOx emissions. At present, selective catalytic reduction technology (SCR) is one of the main technical routes to resolve excess NOx emissions of marine diesel engines, and is the only NOx emission reduction technology recognized by the IMO that can be used for various ship engines. Compared with the conventional low-pressure SCR system, the high-pressure SCR system can be applied to low-speed marine diesel engines that burn inferior fuels, but its working conditions are relatively harsh, and it can be susceptible to operational problems such as sulfuric acid corrosion, salt blockage, and switching delay during the actual ship tests and ship applications. Therefore, it is necessary to improve the design method and matching strategy of the high-pressure SCR system to achieve a more efficient and reliable operation. This article summarizes the technical characteristics and application problems of marine diesel engine SCR systems in detail, tracks the development trend of the catalytic reaction mechanism, engine tuning, and control strategy under high sulfur exhaust gas conditions. Results showed that low temperature is an important reason for the formation of ammonium nitrate, ammonium sulfate, and other deposits. Additionally, the formed deposits will directly affect the working performance of the SCR systems. The development of SCR technology for marine low-speed engines should be the compromise solution under the requirements of high sulfur fuel, high thermal efficiency, and low pollution emissions. Under the dual restrictions of high sulfur fuel and low exhaust temperature, the low-speed diesel engine SCR systems will inevitably sacrifice part of the engine economy to obtain higher denitrification efficiency and operational reliability.

Synthesis of N-Doped Highly Graphitic Carbon Urchin-Like Hollow Structures Loaded with Single-Ni Atoms towards Efficient CO2 Electroreduction

The rational design of single-atom catalysts featuring excellent conductivity, highly accessible discrete active sites and favorable mass transfer is crucial for electrocatalysis but remains challenging. In this study, a reliable Ni-catalyzed and Ni-templated strategy is developed to synthesize a single-atom catalyst by transforming metallic Ni into single-Ni atoms anchored on hollow porous urchin-like (HPU) N-doped carbon (NC) (designated as Ni-NC(HPU)), which possesses high crystallinity and sufficient Ni-N₄ moiety (2.4 wt %). The unique hollow thorns on the surface, good conductivity and large external surface area facilitate electron/mass transfer and exposure of single-Ni sites. As a result, the Ni-NC(HPU) catalyst exhibits remarkable activity and high stability for CO₂ electroreduction. Moreover, this synthetic strategy can also be facilely extended to prepare distinct hollow porous architectures with similar components, such as the wire- and sphere-like ones.

Effects of poly(diallyldimethylammonium chloride) addition on the curing kinetics of urea-formaldehyde adhesives for particleboards

Addition of poly(diallyldimethylammonium chloride) (PDDA) on the performances of urea-formaldehyde (UF) adhesives was evaluated in this work. Three types of UF adhesives were prepared, one without PDDA addition, and two types with PDDA addition of 1 and 3 wt.% per dry UF adhesive mass. These UF adhesive systems were used for producing experimental particleboard panels. The addition of PDDA decreased the thickness swelling of the panel samples, while the internal bond of the particleboards increased significantly only at the highest PDDA content (3 wt.%). Differential scanning calorimetry (DSC) was applied to address the influence of PDDA on UF adhesive curing kinetics. DSC scans were performed in non-isothermal regimes using different heating rates (5, 10, and 20 ?C?min?1). The activation energy (Ea) of the curing reaction showed slightly lower values for the UF adhesive systems containing PDDA. However, the peak temperatures and enthalpy of reaction did not change significantly. The Kissinger-Akahira-Sunose and Friedman iso-conversional methods were applied to investigate the effects of PDDA addition on the UF adhesive curing process.

Boosting the photocatalytic hydrogen production performance of graphitic carbon nitride nanosheets by tailoring the cyano groups

Graphitic carbon nitride (g-C₃N₄) is a promising visible light responsive photocatalyst for solar hydrogen production. However, pristine g-C₃N₄ suffers from severe charge recombination, resulting in a poor photocatalytic activity. Herein, a facile KOH-assisted sealed heating process is designed to tailor the electronic structure of g-C₃N₄, leading to a significantly enhanced and stable photocatalytic hydrogen production rate of 225.1 µmol h^-1 using only 50 mg of the photocatalyst. An excellent apparent quantum efficiency of 16.82% is achieved at 420 nm. Systematic studies reveal that KOH-assisted sealed heating can generate more cyano groups onto the framework of g-C₃N₄, which can increase the charge carrier density and reduce the surface charge transfer resistance, promoting charge separation and transfer. The new findings demonstrated in this work provide a facile strategy for the design of low-cost and efficient photocatalyst for solar fuel production.

Thermogravimetric Experiment of Urea at Constant Temperatures

There are still many unsolved mysteries in the thermal decomposition process of urea. This paper studied the thermal decomposition process of urea at constant temperatures by the thermal gravimetric–mass spectrometry analysis method. The results show that there are three obvious stages of mass loss during the thermal decomposition process of urea, which is closely related to the temperature. When the temperature was below 160 °C, urea decomposition almost did not occur, and molten urea evaporated slowly. When the temperature was between 180 and 200 °C, the content of biuret, one of the by-products in the thermal decomposition of urea, reached a maximum. When the temperature was higher than 200 °C, the first stage of mass loss was completed quickly, and urea and biuret rapidly broke down. When the temperature was about 240 °C, there were rarely urea and biuret in residual substance; however, the content of cyanuric acid was still rising. When the temperature was higher than 280°C, there was a second stage of mass loss. In the second stage of mass loss, when the temperature was higher than 330 °C, mass decreased rapidly, which was mainly due to the decomposition of cyanuric acid. When the temperature was higher than 380 °C, the third stage of mass loss occurred. However, when the temperature was higher than 400 °C, and after continuous heating was applied for a sufficiently long time, the residual mass was reduced to almost zero eventually.

Carbamoyl phosphate and its substitutes for the uracil synthesis in origins of life scenarios

The first step of pyrimidine synthesis along the orotate pathway is studied to test the hypothesis of geochemical continuity of protometabolic pathways at the origins of life. Carbamoyl phosphate (CP) is the first high-energy building block that intervenes in the in vivo synthesis of the uracil ring of UMP. Thus, the likelihood of its occurrence in prebiotic conditions is investigated herein. The evolution of carbamoyl phosphate in water and in ammonia aqueous solutions without enzymes was characterised using ATR-IR, ³¹P and ¹³C spectroscopies. Carbamoyl phosphate initially appears stable in water at ambient conditions before transforming to cyanate and carbamate/hydrogenocarbonate species within a matter of hours. Cyanate, less labile than CP, remains a potential carbamoylating agent. In the presence of ammonia, CP decomposition occurs more rapidly and generates urea. We conclude that CP is not a likely prebiotic reagent by itself. Alternatively, cyanate and urea may be more promising substitutes for CP, because they are both “energy-rich” (high free enthalpy molecules in aqueous solutions) and kinetically inert regarding hydrolysis. Energy-rich inorganic molecules such as trimetaphosphate or phosphoramidates were also explored for their suitability as sources of carbamoyl phosphate. Although these species did not generate CP or other carbamoylating agents, they exhibited energy transduction, specifically the formation of high-energy P–N bonds. Future efforts should aim to evaluate the role of carbamoylating agents in aspartate carbamoylation, which is the following reaction in the orotate pathway.

Chemical-free recovery of crude protein from livestock manure digestate solid by thermal hydrolysis

Protein is becoming an increasingly important resource for a variety of commercial applications. Yet, a large volume of protein is being wasted. Notably, livestock manure solids have a significant content of protein which is not only underutilized, but prone to runoff and eventual breakdown to reactive nitrogen compounds, contributing to eutrophication. It would be desirable to remove protein before it causes environmental hazards and then convert it to value-added commercial applications. We have developed a novel thermal hydrolysis process (THP) to extract crude protein from livestock manure solid, or manure digestate solid (MDS) in particular, without the use of any chemical. We demonstrate the versatility of our new process to control the molecular weight (MW) distribution of the extracted protein hydrolysate (PH). The antioxidant activity of the crude protein hydrolysate (CPH) has been examined through Oxygen Radical Absorbance Capacity Assay. The results have shown that our CPH had its antioxidant capacity against the peroxyl radical similar to that of vitamin E and exhibited almost 7 times as strong inhibition against the hydroxyl radical as vitamin E. We also evaluated the nutritional value of our PH by analyzing its amino acid composition and the MW distribution through amino acid analysis, SDS-PAGE, and MALDI-TOF mass spectroscopy. The characterizations have revealed that the PH recovered from MDS had 2.5 times as much essential amino acids as soybean meal on dry matter basis, with the MW distribution ranging from over a 100 Da to 100 KDa. Finally, the protein powder was prepared from the extracted CPH solution and its composition was analyzed.

Refining the Negative Differential Resistance Effect in a TiOx-Based Memristor

The N-type negative difference resistance (NDR) is characterized by the peak/valley voltage (V_p/V_v) and the corresponding current (I_p/I_v). The N-type NDR is observed in the resistive switching (RS) memory device of Ag|TiO₂|F-doped SnO₂ at room temperature. After the TiO₂ film is equipped with a nanoporous array, the ∼1.2 V gap voltage between V_p and V_v is effectively downscaled to ∼0.5 V, and the gap current of ∼7.23 mA between I_p and I_v is improved to ∼30 mA. It demonstrates that a lower power consumption and faster switching time of the NDR can be obtained in the memristor. Compensations and synergies among the nanoscale conduction filaments (OH^-, Ag⁺, and V_o) are responsible for the refining NDR behavior in our devices. This work provides an efficient method to construct a high-performance N-type NDR effect at room temperature and gives a new horizon on the coexistence of this type of NDR effect and RS memory behaviors.

Novel nano network trigonal prismatic Ba2CoO4-deficient BaCoO3 for high-affinity sorption of radiolanthanide elements of biomedical applications: synthesis and sorption studies

Nano trigonal prismatic Ba₂CoO₄ with hierarchical structure and deficient BaCoO₃ with columnar structure have been prepared at low temperatures (400 [BC4] and 500 [BC5]) °C/3h using green method. X-ray diffraction (XRD) results demonstrate the presence of enriched Ba₂CoO₄ phase at 400 °C and multiphase structures: BaCoO₃, BaCoO_3-δ, and Co₃O₄ with a decrease in the amount of Ba₂CoO₄ at 500 °C. The prepared powders are characterized by a high specific surface area (SSA) values which are reflected to the mode of synthesis that leads to produce materials with massive active sites. The SSA of BC4 is higher than that of BC5 which can be correlated to the difference in the microstructure analysis of BC4 and BC5 as given from scanning electron microscope (SEM) and high-resolution transmission electron microscope (HRTEM) studies. Electron spin resonance (ESR) spectroscopy as an effective method for the characterization of vacancy-rich nanostructures indicates that the presence of oxygen vacancies is related mainly to BaCoO₃, BaCoO_3-δ, and Co₃O₄ phases while the effective oxygen vacancies is in BaCoO₃ and BaCoO_3-δ. The nanocrystalline structures of BC4 and BC5 as novel nano-adsorbents are the first time to be tested. Production of Gd radioisotopes through ^natGd(n,γ)^153,159,161Gd and carrier-free ¹⁶¹Tb through ¹⁶⁰Gd(n,γ,) ¹⁶¹Gd [Formula: see text] ¹⁶¹Tb are achieved at 2nd Egyptian nuclear research reactor (ETRR-2). Preliminary sorption study of Gd radioisotopes (represent the lanthanide elements) shows a promising material for the application in the separation and removal of lanthanide elements. The results demonstrated that the fast interaction and efficient sorption of lanthanides ions are based on the novel synthesized nanomaterial that can be considered for the upscale application in this field.

Simulation Study on Prediction of Urea Crystallization of a Diesel Engine Integrated after-Treatment Device

An integrated after-treatment device model was established for our target engine based on the fluid simulation software (Converge), and simulation was performed to determine the NH₃, temperature, and velocity uniformity at the front-end cross section of its SCR catalyst, urea deposition rate, liquid film mass of the mixer, and its positions under a low-load condition. Moreover, the structure of the mixer and injection pressure were optimized to improve the uniformity and reduce the liquid film mass. Our simulation results show the following facts: the liquid film is easily accumulated under a low-load condition and the structure of the mixer and the injection pressure significantly affect the urea deposition rate and uniformities and accumulation masses of the liquid film. As a result, our final optimization results indicate that the mass of the NH₃ and the NH₃ uniformity at the front-end cross section of the SCR catalyst increase by 2.83 times and 5.65%. The urea deposition rate and the cumulative mass of the liquid film fall by 4.82 and 10.4%, respectively. This study has certain theoretical guiding significance for the optimal design of this type of after-treatment devices.

Nitrogen-doped carbon nanotubes as an anode for a highly robust potassium-ion hybrid capacitor

Potassium ion hybrid capacitors (KIHCs) have drawn growing interest owing to their outstanding energy density, power density and excellent cycling stability. However, the large ionic radius of potassium triggers a huge volume change during continuous K⁺ insertion/extraction processes, restricting the development of KIHCs. Here, we report N-doped carbon nanotubes (NCNTs) for high-performance K⁺ storage. The NCNTs possess a hierarchical structure and N functional groups and not only offer sufficient space to relieve the volume expansion, but also provide highly efficient channels to transport electrons and ions. As a result, the NCNTs anode presents a high specific capacity and an excellent cycling stability with an average decay rate of 0.0238% per cycle (the lowest value among the reported carbon-based anodes for K-ions batteries) during 3600 continuous cycles. A potassium ion hybrid capacitor (KIHC) was also designed with the NCNT anode and a commercial active carbon cathode and achieved both a high energy/power density (117.1 W h kg^-1/1713.4 W kg^-1) and a long cycle life (2000 cycles at 1 A g^-1). Moreover, the in situ Raman and ex situ element mapping characterization demonstrate the outstanding electrochemical reversibility of the NCNTs. This work provides a superior strategy to design low-cost anode materials with excellent K⁺ storage electrochemistry.

Biuret-A Crucial Reaction Intermediate for Understanding Urea Pyrolysis To Form Carbon Nitrides: Crystal-Structure Elucidation and In Situ Diffractometric, Vibrational and Thermal Characterisation

The crystal structure of biuret was elucidated by means of XRD analysis of single crystals grown through slow evaporation from a solution in ethanol. It crystallises in its own structure type in space group C2/c (a=15.4135(8) Å, b=6.6042(3) Å, c=9.3055(4) Å, Z=8). Biuret decomposition was studied in situ by means of temperature-programmed powder XRD and FTIR spectroscopy, to identify a co-crystalline biuret-cyanuric acid phase as a previously unrecognised reaction intermediate. Extensive thermogravimetric studies of varying crucible geometry, heating rate and initial sample mass reveal that the concentration of reactive gases at the interface to the condensed sample residues is a crucial parameter for the prevailing decomposition pathway. Taking these findings into consideration, a study on the optimisation of carbon nitride synthesis from urea on the gram scale, with standard solid-state laboratory techniques, is presented. Finally, a serendipitously encountered self-coating of the crucible inner walls by graphite during repeated synthetic cycles, which prove to be highly beneficial for the obtained yields, is reported.

Ammonia Recovery from Hydrolyzed Human Urine by Forward Osmosis with Acidified Draw Solution

Forward osmosis (FO) is a low-pressure membrane process that can selectively separate low molecular weight neutral compounds such as ammonia from urine. However, an understanding of how un-ionized ammonia transfers is vital for maximizing ammonia recovery. Therefore, this research aimed to determine the transport behavior of low molecular weight neutral nitrogen compounds in order to maximize ammonia recovery from real hydrolyzed human urine by FO. Using urea as a model, batch FO experiments concluded that low molecular weight neutral compound transfer is dependent on concentration equilibrium between the feed and draw solutions due to its ability to freely move across the FO membrane. Therefore, 50% recovery is the theoretical maximum that could be achieved. However, novel strategic pH manipulation between the feed and the draw solution allowed for up to 86% recovery of ammonia by keeping the draw solution pH < 6.5 and the feed solution pH > 11, overcoming the 50% recovery barrier. An economic analysis showed that ammonia recovery by FO has the potential to be more economically favorable compared to ammonia air stripping or ion exchange if the proper draw solute is chosen.

On the influence of water on urea condensation reactions: a theoretical study

The influence of water molecules on the kinetics of urea condensation reactions was studied with high-level quantum chemical methods and statistical rate theory. The study focuses on the production of biuret, triuret, and cyanuric acid from urea because of their relevance as unwanted byproducts in the urea-based selective catalytic reduction (urea-SCR) exhaust after treatment of Diesel engines. In order to characterize the potential energy surfaces and molecular reaction pathways, calculations with explicitly-correlated coupled-cluster methods were performed. It turned out that the reactions proceed via pre-reactive complexes and the inclusion of one or two water molecules into the condensation mechanisms leads to a decrease of the energy barriers. This effect is particularly pronounced in the production of biuret. Due to the pre-reactive equilibria, the rates of the overall reactions can increase or decrease by incorporating water into the mechanism, depending on the temperature and water concentration. Under the conditions of urea-SCR, the studied reactions are too slow to contribute to the observed byproduct formation.