Effects Of Urea Concentration Research Articles

Visualization of Fibrillated Cellulose in Polymer Composites Using a Fluorescent-Labeled Polymer Dispersant

The fibrillated cellulose embedded in the polymer matrix was visualized using confocal laser scanning microscopy (CLSM). A rhodamine-appended diblock copolymer (RhBCP) was used as a novel polymer dispersant to adsorb fibrillated celluloses and achieve fluorescent labeling and good dispersion in high-density polyethylene. The composite was produced through in situ fibrillation of wood pulp fibers during the process of melt compounding using urea as the fibrillation-accelerating agent. The length and width of the fiber, aspect ratio, and polydispersity values were determined using RhBCP and CLSM. The optimal RhBCP content to achieve good CLSM images and a high Young’s modulus was 2 wt %. The effects of urea concentration and kneading time on the fibrillation were investigated, indicating that the fiber length and aspect ratio were approximately 40 μm and 40, respectively, under optimal conditions. The maximum Young’s modulus was recorded under these conditions, and the recorded value agreed well with the value predicted by the Halpin–Tsai equation. Cellulose fibers fragmented under conditions of low urea concentration and prolonged kneading times. The method developed has the potential to analyze various cellulosic composite systems and improve their application prospects.

Experimental study on the calcium carbonate production rates and crystal size of EICP under multi-factor coupling

The production and microstructure of calcium carbonate are the fundamental indicators to evaluate the effectiveness of Enzyme-induced Carbonate Precipitation (EICP). Soybean urease is extracted, and the urease activity is controlled by the soybean powder concentration in this study. The urease reacts with the cementation solution with different concentrations of urea and calcium ions at different temperatures to determine the calcium carbonate production rates (RCC). The crystal sizes of calcium carbonate (SCC) are investigated by scanning electron microscopy (SEM) and image processing method. The RCC increase and subsequently decrease with increasing calcium ion concentration and peak at 0.75 M. A lower urea concentration is more favourable to the formation of CaCO3. Increased urease activity and temperature will lead to an increased RCC and SCC. Some crystals appear as capsules when the temperature goes up. The SCC decreases slightly with increasing calcium ion concentration under low urease activity and increases under high urease activity. The SCC increases first and subsequently decreases with increasing urea concentration under high urease activity, while the effect of urea concentration under low urease activity is not significant. XRD test results show that the calcium carbonate produced in this study is dominated by calcite crystals. The study provides additional data, a useful base to move forward toward a better understanding of the method of stabilization and its applications, for example, the treatment of different soils.

Effect of fuel concentration on structural, vibrational, morphological properties and particle stability of NiO nanoparticles

In this present research, a simple cost-effective auto-combustion method has been adopted to prepare NiO nanoparticles with nickel nitrate and urea as raw materials. Urea has been taken as a fuel to perform combustion processes with different concentrations (50%, 75%, and 100%). The effects of urea concentration on structural, optical, morphological properties, and colloidal stability of NiO nanoparticles were analyzed through various techniques (XRD, FT-IR, SEM, and Zeta Potential analyzer). The single-phase cubic structure of NiO nanoparticles was examined through an XRD profile, and it confirms that the crystallite size of the nanoparticles is in the nanoscale range. The average crystallite size of NiO nanoparticles increases with an increase in fuel concentration (18.2 nm for 50%, 27.3 nm for 75,% and 38.4 nm for 100%). Among three different fuel ratios, 50% urea has been concluded as the optimum fuel ratio to prepare fewer particles. The functional groups present in all three samples were recorded by FT-IR spectra, which confirms the metallic Ni-O presence in all the samples. The role of fuel ratio on morphology was also examined by SEM micrographs, and morphological changes under three fuel ratios were also observed. The colloidal stability of NiO nanoparticles for all three samples was analyzed by a zeta potential analyzer, and it confirms that the stability of the samples is varied with fuel ratios. Using UV–vis spectra, the optical band gap of NiO nanoparticles was calculated. The optical band gap of NiO nanoparticles decreases as particle size increases.

CaP Precipitation on Titanium under UV Lighting and Effect of Urea Concentration

CaP Precipitation on Titanium under UV Lighting and Effect of Urea Concentration

Effects of temperature and urea concentration on nitrogen-rich pyrolysis: Pyrolysis behavior and product distribution in bio-oil

Nitrogen-rich pyrolysis is an important means of biomass utilization. In this paper, the effects of urea concentration and pyrolysis temperature on the composition of various nitrogen- and oxygen-containing compounds in bio-oil produced during the pyrolysis of pine powder (PP) were studied. The results showed that A-type (a benzene ring with one methoxy group) and B-type (a benzene ring with two methoxy groups) phenols were only detected in the bio-oil derived from conventional biomass pyrolysis. After nitrogen-rich pyrolysis, the total phenolic content in the bio-oil increased significantly, and all four types of phenols (A, B, C (a benzene ring featuring an alkyl group that is not a methoxy group), and D (other types of phenols)) were detected. In addition, the aldehyde and linear chain ketone contents in the bio-oil significantly decreased after nitrogen-rich pyrolysis compared to after conventional biomass pyrolysis. When the urea concentration was 10 wt%, only cyclic ketones were detected in the bio-oil. Furthermore, the content of nitrogenous heterocyclic compounds in the bio-oil significantly increased after nitrogen-rich pyrolysis when the urea concentration increased from 5 wt% to 10 wt%, with pyridine being the most abundantly produced.

Amplification of urea detection based on pH-sensitive liposomes

Abstract Background This study aimed to develop an amplification method of urea detection based on pH-sensitive liposomes. Results The urease covalently immobilized on the magnetic particles and the pH-sensitive liposomes encapsulating ferricyanide were added to the cyclic-voltammeter cell solution where urea was distributed. The conversion of urea into carbonic acid seemed to induce a pH decrease that caused a reduction in the electrostatic repulsion between the headgroups of weakly acidic 1,2-dipalmitoyl-sn-glycero-3-succinate. The reduction induced the liposomes to release potassium ferricyanide that was encapsulated inside. The effects of urea concentration and pH value were investigated. A specific concentration (0.5 mg/mL) of the urea solution was set to observe the response. The activity of urease was reversible with respect to the pH change between 7 and 5. The sensitivity of this detection was almost identical to the comparable techniques such as an enzyme-linked immunosorbent assay and a field-effect transistor. Conclusion In summary, the methodology developed in this study was feasible as a portable, rapid, and sensitive method. How to cite: Kang MK, Park J-W. Amplification of urea detection based on pH-sensitive liposomes. Electron J Biotechnol 2021;51. https://doi.org/10.1016/j.ejbt.2021.04.005

Effect of urea concentration on properties of peanut protein isolate, arachin and conarachin-based adhesives during urea-epichlorohydrin modification.

To lay a theoretical basis for the preparation of peanut protein-based adhesives and promote the sustainable development of the adhesive industry, properties of peanut protein isolate (PPI), arachin and conarachin-based adhesives modified by urea and epichlorohydrin (ECH) were investigated under different urea concentrations. When the urea concentration was 2 mol l−1, the wet shear strength of the PPI-based adhesive was 1.24 MPa with the best water resistance. With the increase of urea concentration from 0 to 4 mol l−1, the apparent viscosity of the PPI-based adhesive increased from 3.87 to 136.80 Pa s and the solid content increased from 18.11% to 31.11%. Compared with conarachin-based adhesive, the properties of arachin-based adhesive were improved more obviously during the combined modification. Scanning electron microscopy images illustrated that when the urea concentration was 2 mol l−1, the surface of the PPI-based adhesive was more compact and smoother, which was beneficial to the improvement of water resistance and related to the structure changes of arachin and conarachin components. Fourier-transform infrared spectroscopy results indicated that different urea concentrations caused the change of ester and ether bonds in the PPI-based adhesive, which was mainly related to arachin component. Thermogravimetry results suggested that when the urea concentration was 2 mol l−1, the decomposition temperature of protein skeleton in the PPI-based adhesive reached a maximum of 314°C exhibiting the highest thermal stability. The improvement of the thermal stability of conarachin was greater than that of arachin during the combined modification.

Facile synthesis of NiO nanoflakes via hydrothermal route: Effect of urea concentration

In the current investigation, NiO nanoflakes were developed using a simple and cost-effective technique known as hydrothermal method. Effect of variation of Ni precursor with concentration of urea on electrochemical properties was studied. Increased urea concentration in Ni nitrate precursor causes agglomeration of nanoparticles with morphological distortion of nanoflakes. For electrochemical experiments, samples were prepared with Ni:urea precursor ratio such as 1:2, 1:4, 1:6, 1:8, and 1:10 were used. The ratio of Ni (1):urea (2) precursor indicates the maximum capacitance value 128F g−1 in 1 M KOH electrolytes at a scan rate of at 10 mV s−1.

A novel technique to evaluate nail softening effects of different urea formulations

Urea has been incorporated into several topical ungual formulations to hydrate and soften the nail plate. In this study, we employed various characterization techniques (visual observation, scanning electron microscopy, measurement of thickness, transonychial water loss, nail electrical resistance, and mechanical study) to investigate the effect of urea concentration on the hydration of bovine hoof membranes – an in vitro model of infected human nails. We obtained inconsistent results in the thickness, transonychial water loss, nail electrical resistance, and scanning electron microscopy studies. In the mechanical study using a modified Texture Analyzer method, we reported an inverse and linear correlation between urea concentrations in the formulations and the force required to puncture the treated membrane (R 2 = 0.9582, n ≥ 8). As the urea concentration decreased from 4x to 2x, 1x, and 0x % w/w, the puncture force increased significantly from 0.47 ± 0.07 to 0.77 ± 0.07, 0.91 ± 0.09, and 1.33 ± 0.26 N, respectively (p < 0.05). Thus, urea provided a positive softening effect on the membranes and the puncture force could indicate the urea level in topical formulations. In this study, we provided a novel, efficient, and reliable tool to evaluate the hydration level and physical properties of bovine hoof membranes.

SYNTHESIS OF CELLULOSE AEROGEL FROM KAPOK FIBER FOR CLEANING THE WASTE OF LUBRICANT OIL

Cellulose aerogel is known to be superior in removal of oil pollutants and organic solvent. This research developed the synthesis of cellulose aerogel from kapok fiber, application as an adsorbent for lubricating oil waste and its reusability. Chemical delignification was carried out by immersing the kapok fibers in NaOH 6% solution at 100oC for 1h to obtained a cellulose of 65.5% (SNI-2009). The effect of urea concentration on adsorbent products was studied in the range of 8-16w%. Whereas the effect of cellulose was studied at a concentration range of 0.5-1.5w%. The gelation stage was carried out by adding cellulose in a NaOH/urea solution accompanied by stirring (1000rpm) for 15minutes. The mixture was cooled at 0 oC for 48h to form a gel. The formed gel is dried by the freeze drying method at -45°C. The cellulose aerogel from kapok fiber with a density of 0.11g/cm3 and porosity of 92.46% had an absorption capacity of up to 11.987g/g in the first cycle. The use of each aerogel cellulose sample to absorb lubricant oil waste reached a maximum of three cycles. DOI : https://doi.org/10.33005/jurnal_tekkim.v15i1.2305

Effect of urea concentration on instant refolding of Nuclear Export Protein (NEP) from Influenza-A virus H1N1: A solution NMR based investigation

Nuclear-export-protein (NEP) plays multiple-functions during influenza virus replication-cycle and shows unique pattern of conserved residues, which altogether make NEP a potential target for developing novel anti-influenza drugs. However, the mechanistic structural biology of NEP has not been fully characterized so far owing to its tendency to aggregate in solution. As structural information is important to guide rational drug-discovery process; therefore, procedural optimization efforts are going on to achieve properly folded NEP in sub-millimolar concentrations for solution-NMR investigations. As a first step in this direction, the refolding-cum-aggregation behavior of recombinant-NEP with N-terminal purification-tag (referred here as NEPN) at different urea-concentrations has been investigated here by NMR-based methods. Several attempts were made to refold denatured NEP-N through step-dialysis. However, owing to its strong tendency to aggregate, excessive precipitation was observed at sub-higher levels of urea concentration (5.0 ± 1.0 M). Finally, we used drip-dilution method with 10.5 M urea-denatured NEP-N and were able to refold NEP-N instantly. The amide 1H dispersion of 3.6 ppm (6.6–10.2 ppm) in the 15N-HSQC-spectra of instantly refolded NEP-N confirmed the folded state. This successful instant-refolding of NEP-N has been reported for the first-time and the underlying mechanism has been rationalized through establishing the complete backbone-resonance-assignments of NEP-N at 9.7 M urea-denatured state.

Synthesize of magnetite Mg-Fe mixed metal oxide nanocatalyst by urea-nitrate combustion method with optimal fuel ratio for reduction of emissions in diesel engines

Abstract In the present study, Mg0.25Fe2.75O4 nanocatalyst for reduction of emissions in diesel engine was fabricated via urea-nitrate combustion method. The effect of urea concentrations as fuel on its structural characteristics and Oxygen Storage Capacity (OSC) was thoroughly investigated. The results of various characterization analyses showed that fuel ratio significantly affects crystallinity, textural, size and morphology of particles, and thermal stability of nanocatalyst. These are mainly due to increase in combustion temperature and duration. The Mg0.25Fe2.75O4 fabricated at fuel ratio of 2.5 times of stoichiometric ratio exhibited the lowest weight loss/high crystallinity (less than 1 wt %) and lowest lattice parameter (8.346 A) which are related to well diffusion of Mg cations into ferric oxide as host. The Raman and FTIR analyses showed the existence of strong peaks correspond to formation of tetrahedral and octahedral sublattices and also the formation of spinel structure of MgFe2O4. The reduction in crystalline size, obtained with higher amount of fuel, resulted in a higher surface area (23.6 m2/g), higher pore volume (0.0950 cc/g) and proper particle size distribution (25–35 nm). These cause a better catalytic activity. Moreover, the enhanced OSC (8661 μmol H2/g) along with shifting the reduction peaks to lower temperatures, as major attributes in relation to catalytic technologies, confirmed the strong effect of fuel ratio of 2.5 on fabrication process of Mg0.25Fe2.75O4. Finally, the highest reduction in HC (33%), CO (14-17%), PM1.0 (16%), and CO2 (12%) achieved, using the optimum sample-mixed diesel fuel at 90 ppm.

Study of the effect of temperature on microbially induced carbonate precipitation

Temperature is a key factor that contributes to microbially induced calcium carbonate precipitation. At low temperatures, low enzyme activity results in a lack of calcium precipitation. In this study, Sporosarcina pasteurii and Bacillus megaterium were compared. Firstly, the optical density curves and enzyme activity curves of both bacteria were obtained during 48-h culture. Then, optical density, enzyme activity, and productive rates for calcium carbonate were measured to analyze the influence of temperature. Finally, the effect of urea concentration on carbonate precipitation was studied by changing the urea concentration that was added during inoculation. The obtained results showed that at high temperature, the growth rate of B. megaterium was close to that of S. pasteurii, while the opposite result was found at low temperature. The urease activities of B. megaterium were similar at different temperature conditions. At high temperature, B. megaterium showed lower enzyme activity, while at low temperature, it surpassed that of S. pasteurii. The same results were found for enzyme activity and for the precipitation rates of calcium carbonate. The addition of urea to the medium increased precipitation rates, and higher urea concentrations increased the obtained precipitation rates. With 20 g/L urea, the precipitation rate of B. megaterium at 15 °C matched that without urea addition at 30 °C. Therefore, adding urea to the medium at the time of inoculation can effectively overcome the low calcium precipitation at low temperature and enable subsequent low-temperature engineering applications.

The effects of urea concentration on microstructures of ZnCo2O4 and its supercapacitor performance

The effects of urea concentration on microstructures of ZnCo2O4 during hydrothermal process and their supercapacitors performance were investigated. The sphere ZnCo2O4 oxide with nanostructure arrays was formed after hydrothermal process containing low urea concentration. The slim and curved ZnCo2O4 nanowires were formed on Ni foam due to medium urea concentration, while sharp and separated ZnCo2O4 nanostructure arrays were formed on Ni foam due to high urea concentration. The sharp and separated ZnCo2O4 nanostructure arrays on Ni foam showed the best electrochemical performance. ZnCo2O4 nanostructure arrays obtained were composed of interconnected ZnCo2O4 nanoparticles. The gaps between ZnCo2O4 nanoparticles promoted penetration of the electrolyte, which induced the high supercapacitive performance. The sharp and separated ZnCo2O4 nanostructure arrays on Ni foam had the lowest charge transfer resistance, which improved supercapacitive performance. In addition, the strong and separated ZnCo2O4 nanowires improved significantly cycle life during the charge-discharge process due to good strain accommodation of the unique structure.

Effect of Urea Concentration on the Viscosity and Thermal Stability of Aqueous NaOH/Urea Cellulose Solutions

Aqueous solutions of sodium hydroxide (NaOH) and urea are a known and versatile solvent for cellulose. The dissolution of cellulose occurs at subambient temperatures through the formation of a cellulose-NaOH-urea “inclusion complex” (IC). NaOH and urea form a hydrate layer around the cellulose chains preventing chain agglomeration. Urea is known to stabilize the solution but its direct role is unknown. Using viscometry and quartz crystal microbalance with dissipation monitoring (QCM-D) it could be shown that the addition of urea reduced the solutions viscosity of the tested solutions by almost 40% and also increased the gelation temperature from approximately 40°C to 90°C. Both effects could also be observed in the presence of additional cellulose powder serving as a physical cross-linker. Using Fourier transform infrared (FTIR) spectroscopy during heating, it could be shown that a direct interaction occurs between urea and the cellulose molecules, reducing their ability to form hydrogen bonds with neighbouring chains.

The effect of urea on microstructures of Ni3S2 on nickel foam and its hydrogen evolution reaction

The effects of urea concentration on microstructures of Ni3S2formed on nickel foam and its hydrogen evolution reaction were investigated. The Ni3S2 nanosheets with porous structure were formed on nickel foam during hydrothermal process due to low urea concentration. While high urea concentration facilitated the forming of Ni3S2 nanotube arrays. The resulting Ni3S2 nanotube arrays exhibited higher catalytic activity than Ni3S2nanosheets for hydrogen evolution reaction. This was mainly attributed to a fact that Ni3S2 nanotube arrays facilitated diffusion of electrolyte for hydrogen evolution reaction.

(Science for Solving Society’s Problems Challenge Grant Winner) Electrochemical Disinfection of Wastewater Using Urea Electrolysis

Wastewater treatment to recover useable water for human consumption and industrial application will always be an important area of research. In recent years, the high cost and energy intensive operation of the water and wastewater treatment facilities have caught everyone attention. Approximately 3-4 % of the United States energy consumption has been allocated for operating the drinking water and wastewater systems (1). There is a need to convert or upgrade the existing water and wastewater treatment plants into energy efficient and sustainable facilities. The United States Environmental Protection Agency (U.S. EPA) report on water and wastewater treatment facilities proposed various measures to achieve sustainable wastewater treatment plant, which included use of efficient disinfection equipment to enable faster and effective removal of disease causing microorganisms from the wastewater (2). Urea electrolysis is an established process where urea is electrochemically oxidized to nitrogen, carbon dioxide, and hydrogen (3-5). Nickel, an inexpensive metal in comparison to platinum group metals, is the best catalyst for anode where the oxidation of urea takes place in alkaline media (Eq. 1). On the cathode electrode, water is reduced to hydrogen gas as shown in equation 2. Therefore, the overall electrochemical reaction for urea electrolysis (Eq. 3) is conversion of urea to nitrogen, carbon dioxide, and hydrogen, a high-value product. Current disinfection methods employed for treating wastewater are chlorination, ultra-violet irradiation, and ozonation. These methods are expensive due to high-energy consuming equipment and they can generate chemicals that are carcinogenic in nature. In the present study, an attempt is made to electrochemically disinfect simulated wastewater containing urea and E. coli using the urea electrolysis process. Benefit of using urea electrolysis for destroying or killing microorganisms are disinfection of wastewater, chemical conversion of urea to basic compounds, and synthesis of high-value product (H2) for possible energy recovery application. The electrochemical cell for this study utilizes nickel, as both anode and cathode electrode, and the electrolyte will be simulated urea solution containing E. coli. The effect of urea concentration, E. coli count, current density, pH of the solution, and flow condition will be investigated. The destructive capabilities of the current and fluctuations of localized pH on electrode surface during urea electrolysis over E. coli population will be analyzed for the above-mentioned parameters. References U.S. EPA, State and Local Climate and Energy Program: Water / Wastewater, www.epa.gov/statelocalclimate/local/topics/water.htmlU.S. EPA, Local Government Climate and Energy Strategy Guides: Energy Efficiency in Water and Wastewater Facilities, EPA-430-R-09-038 (2013).B. K. Boggs, R. L. King and G. G. Botte, Chemical Communications, 32, 4859 (2009).V. Vedharathinam and G. G. Botte, Electrochimica Acta, 81, 292 (2012).D. Wang and G. G. Botte, ECS Electrochemistry Letters, 3, H29 (2014). Figure 1

Altering the structure and properties of iron oxide nanoparticles and graphene oxide/iron oxide composites by urea

Iron oxide (Fe2O3) nanoparticles were grown on graphene oxide (GO) using a simple microwave-assisted method. The effects of urea concentration on Fe2O3 nanoparticles and GO/Fe2O3 composite were examined. The as-prepared samples were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The Fe2O3 nanoparticles were uniformly developed on GO sheets. The results showed that urea affects both Fe2O3 morphology and particle size. In the absence of urea, the Fe2O3 nanostructures exhibited a rod-like morphology. However, increasing urea concentration altered the morphology and decreased the particle size. The Raman results of GO/Fe2O3 showed that the intensity ratio of D band to G band (ID/IG) was decreased by addition of urea, indicating that urea can preserve the GO sheets during synthesis of the composite from exposing more defects. The surface area and thermal stability of GO/Fe2O3 and Fe2O3 were compared using the Brunauer–Emmett–Teller method and thermal gravimetric analysis, respectively. The results showed that the increased concentration of urea induced a larger surface area with more active sites in the Fe2O3 nanoparticles. However, the increase in urea concentration led to decreased thermal stability of the Fe2O3 nanoparticles. The magnetic properties of Fe2O3 nanoparticles were characterized by a vibrating sample magnetometer and results revealed that the magnetic properties of Fe2O3 nanoparticles are affected by the morphology.

Concentration of injetion solution and its effects on soil and on yield of fertirrigated banana cv. Terra Maranhão

The Fertigation is the combined application of water and nutrients to a crop. It can be adapted to all types of agricultural crops. The objective of this study was to evaluate the effect of urea concentration in irrigation water on electrical conductivity of the soil solution and saturation extract along the first cycle of banana cv. Terra Maranhão. The experiment followed a completely randomized design with six treatments and ten replications. Treatments regarded for using three urea concentrations (1.0; 2.5 and 4.0 g L-1) in irrigation water applied by two micro irrigation systems (microsprinkler and drip). Results showed that there was a linear elevation of electrical conductivity of saturation extract and soil solution with the increase on concentration of urea in the injection solution. Urea should be used under concentrations up to 2.5 g L-1 in irrigation water without causing increase on electric conductivity of soil solution and saturation extract, considering 1.1 dS m-1 as the tolerated value for the crop. Nitrate in the soil solution increased significantly with the increase of urea concentration in the injection solution. The maximum concentration of nitrate in the soil occurred for 4,0 g L-1 concentration of the injection solution.

The Experiment on Soil Water Characteristic Curve Considering the Effect of Urea Concentration

A new soil water characteristic curve (SWCC) experiment contemplating urea concentration is presented in the paper. We focus on the impact of the SWCC considering urea concentration test method for materials selection and introduction, experimental results, and finally, we have conducted some experiments of SWCC and obtained some valuable data which could affect urea concentration. By using linear fitting, an exponential function between water content and suction and urea concentration is established.