Papers by Keyword: Urea

Abstract: Due to the importance of environmentally friendly solvents, deep eutectic solvents (DES) have gained the attention of many. They have physical properties almost similar to ionic liquids, but DES is less toxic. In this study, several DESs have been produced using urea as a hydrogen bond donor (HBD). These DESs include choline chloride - urea, betaine - urea and magnesium chloride hexahydrate - urea. Infrared analysis results indicate the presence of hydrogen bonding between the hydrogen bond acceptor (HBA) and HBD, confirming the formation of DES. The absorption of these hydrogen bonds occurs in the range of 3600 - 2800 cm^-1, causing the absorption bands to broaden. The DESs produced can be used in various extraction and separation processes.

Abstract: Present study, activated carbon was precarbonised and chemically activated to prepare activated charcoal from different lignins , and their adsorption properties had been investigated. The influences of carbon source selection with urea modification on the CO₂ adsorption performance of the materials were investigated. The selectivity, warmth of adsorption and cyclic steadiness of the materials had been in addition tested. The urea-modified porous carbon materials were prepared using dealkylated lignin (LCC), calcium lignosulfonate (CLS) and sodium lignosulfonate (SLS) as carbon precursors, KOH as activator and urea as nitrogen dopant. The CO₂ adsorption values of the LCC-0.5N samples had been 5.52 mmol/g and 3.90 mmol/g at 1 bar, 273 K and 298 K, respectively, and were obtained in 10 successive adsorption-desorption cycles. The CO₂ adsorption ability remained stable and greater than 110 mg/g after 10 consecutive adsorption-desorption cycles.

Abstract: The presence of N-dopant in Reduced Graphene Oxide has contributed to the change of their optical band gap. In this research, this mechanism has been implemented to synthesize nitrogen-doped graphenic carbon (NGC) proposed as an n-type semiconducting layer. The graphenic-based carbon (GC) was derived from coconut shells by a green synthesis method. The two sources of nitrogen dopants were prepared from ammonia water (NH₄OH) and urea (CH₄N₂O). Synthesis of NGC was conducted from GC and a particular dopant with a ratio of 1:20 and 1:40 by wet mixing. Then the NGC solution was deposited onto a 1x1 cm² glass substrate using a nanospray method to form a layer. X-ray diffraction (XRD) of NGC film has indicated an amorphous characteristic of the film. According to Energy Dispersive X-ray (EDX) spectroscopy, the presence of nitrogen as a doping material in the GC was successfully demonstrated. The SEM cross-section image has performed the NGC layer on the substrate. Absorbance analysis from UV-Vis spectroscopy also explains the occurrence of electronic transitions, both in the form of a solution and a layer of NGC material. The further analysis explained that the optical band gap of the NGC material ranged from 1.66 – 1.86 eV, which exhibits the semiconductor characteristic of the NGC material.

Abstract: The oxide-ruthenium electrode is used for the analysis of oxygen-containing biologically active organic substances. This electrode can be recommended for the analysis of formic acid in dilute solutions (no more than 2 ml in 100 ml of solution). Due to the presence of two display potentials, the reliability of the determination of formic acid in solution is quite high. For the determination of nitrogen-containing compounds (urea), oxide-ruthenium electrodes are unsuitable. The obvious differences in the polarization curves of magnesium orotate tautomers indicate that the structural differences of tautomers persist in aqueous solutions. An electrochemical method using a ruthenium oxide electrode can be recommended for the analysis of the isomeric state of organic compounds containing OH and COOH groups. The electrochemical method has clearly shown that the difference in the structural state of magnesium orotate tautomers persists in solutions.

Abstract: The quality of gel - based silicon, which forms an insulating content to prevent water and sand in oil and gas wells, have been improved. Based on the reaction between the liquid glass and hydrochloric acid, the optimal concentration of the initial reagents for the formation of the gel process was determined. The rheology, initial and final setting time of the silicon based gel, and the temperature dependencies of the gel forming process were also studied by adding 0.1-1.0% (mass ratio) of urea as cross-linking to the Na2SiO3/HCl solution. At the same time, the impact of the obtained gel of the permeability of the rock pores was determined and the filtration characteristics were studied. It has been determined that with 0.1-0.8% mass concentration of the urea added to the Na2SiO3/HCl solution, the setting time of the gel could be regulated according to the well-layer regime. The resulting silicone-based gel can be used as an injection solution that can set in 3-22 hours in oil and gas wells between the temperature of 20-80 °C.

Abstract: The high mobility of urea as a nitrogen nutrient in the soil leads to inefficient absorption by plants. Hence efforts to design a slow-release fertilizer (SRF) are significant. This paper reports the incorporation of urea fertilizer with carbon or zeolite in a bioplastic made of carboxymethyl cellulose as the matrix. The bioplastics were made by mixing the zeolite or activated carbon suspensions into a sodium carboxymethyl cellulose (Na-CMC) gel. Glycerol was then added as a plasticizer. Six variations of bioplastics were prepared, namely CMC-urea 0.5 and 1.0, CMC-urea-zeolite, CMC-urea-zeolite-glycerol, CMC-urea-activated carbon, and CMC-urea-activated carbon-glycerol. The weight ratio of CMC and urea fertilizer was kept constant at 2:1 since the resulted bioplastics showed higher texture transparency and homogeneity than those of bioplastics with a weight ratio of CMC to urea 1:1. The addition of zeolite increased the tensile strength of the bioplastics by about two times. While, the glycerol addition improved the elongation at break. The release of urea from the bioplastics was slower for bioplastics with zeolite than with activated carbon. The composite bioplastics may serve as a slow-release urea for agriculture.

Abstract: This study investigated the effect of degree of availability (d.o.a) of nitrogen and time on increasing the surface hardness of AISI H13 steel using pack nitriding. Urea (46 % N) and ZA (21% N) were selected as a nitrogen source. In this study, hardening was carried out at a temperature of 1030°C then held for 3 hours and continued to quenching with 19 bar nitrogen. Nitriding process used the in-pack process by which the specimens were buried in the urea and ZA powder charged into a nitriding box. Pack nitriding was performed in a vacuum furnace at 600°C for 2, 4 and 6 hours. The surface of nitride-steels was characterized using microhardness tester, SEM/EDS and XRD. After nitriding process, the hardness of AISI H13 steels was increased up to 1648 HV, with the highest hardness achieved by nitriding process of 6 hours and 0.4 d.o.a, in urea media. The nitrogen was dissolved to the steel and induced precipitation of Fe₃N, Fe₂N, and αFe. From the calculation based on Arrhenius equation, the activation energy (Q) of 0.4 and 0.3 d.o.a were 1.381 kCal/mol and 1.455 kCal/mol, respectively.

Abstract: Urea is high solubility nitrogen fertilizer. There is major nitrogen pollution in ecosystem. Slow-release nitrogen fertilizer the way to decrease nitrogen form agriculture. Slow-release nitrogen fertilizer the way to decrease nitrogen in agriculture. Slow-release formulations of nitrogen fertilizer were developed based on alginate-gelatin by using calcium chloride as the cross-linker in the egg-box model as hydrogels. Water-retaining ratio, loading behavior, and the release kinetics were examined. The release kinetic rates were investigated by Zero-order kinetic, First-order kinetic, Higuchi, Korsmeyer-Peppas, Weibull, and Hixson-Crowell models. The results showed that the S1G0.5 sample (alginate 1 g and gelatin 0.5 g) was the optimum condition for application as urea slow-release fertilizers because it was a minimal release kinetic rate for 12 hrs. These results indicate that the alginate-gelatin hydrogel can be a slow-release nutrient to plant an environmentally friendly fertilizer.

Abstract: A novel redox couple of metallic nickel (Ni) catalyst can become a great candidate of non-enzymatic detection. By taking advantage of fast electron transfer, Ni redox couples can be tailored as pseudo-enzyme in urea measurement. In this study, Ni catalyst on nitrogen doped carbon (Ni-NC) was synthesized and characterized morphological, elemental, and electrocatalytic properties in comparison to different configuration of pure nickel (Ni), Ni with carbon (Ni-C), and bare carbon electrode, assessed by cyclic voltammetry and differential pulse voltammetry. By examining various Ni redox couples in rapid electron transfer process, the prominent anodic and cathodic peaks of Ni²⁺/Ni³⁺ were applicable to detect urea in the detection range of 1-20 mM, with an excellent sensitivity and relative standard deviation of 1.634 μA.mM^-1 (R² of 0.989) and 4.89%, respectively. Therefore, Ni-NC can find practical applications for material sensing device toward non-enzymatic urea measurement.

Abstract: In this study, commercially available bare stainless steel 304 was investigated as a working electrode in urea electrooxidation in alkaline solution using different electrochemical techniques like cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The electrode stability was also investigated by the constant potential electrolysis test. Different concentrations of KOH (0.5-4 M) were employed to study the electrooxidation of urea solution with concentration of 0.33 M. An anodic peak current density of 34.82mA/cm² was obtained at 473 mV versus Ag/AgCl reference electrode in urea solution at KOH concentration of 4 M. Stainless steel properties such as corrosion resistance, low cost in addition to its catalytic activity make it an ideal anodic electrocatalyst for electrooxidation of urea-rich wastewater.