Urea Hydrolysis Process Research Articles

Nanoarchitecture of 2D materials: Unveiling the power trio-Ni, Co, and GNF-in eco-friendly air breathing zinc air battery through layered double hydroxides

Zinc-air batteries emerge as sustainable and efficient energy storage device towing to its potential for high energy density and environmental friendliness. Layered double hydroxide (LDH) specifically, exhibit unique properties like high surface area, stability and ion-exchange capacity, making them attractive for various applications. In this work, a simple and scalable one-pot urea hydrolysis process is adopted to synthesize NiCo-LDH supported on graphene nanofiber (GNF) sheets as a good substitute as a non-precious bifunctional catalyst. Ammonium fluoride as a structural-mediating agent is employed which offers a unique homogeneous 3D micro-sized hierarchical petal-like morphology of NiCo-OH. Electrochemical analysis shows low over potential with high durable around 15,000 potential cycles in a 0.5 M KOH solution which confirms the structural integrity and superior activity of NiCo-LDH/GNF catalyst in oxygen reduction and evolution reactions. The resulting NiCo-LDH/GNF composites demonstrate outstanding specific capacitance of 806 mAh g−1 with stable cycling performance up to 950 cycles and rate capability, making it promising alternative bifunctional electro catalyst in Zinc-air batteries.

Fabrication of magnetic α-Fe2O3/Fe3O4 heterostructure nanorods via the urea hydrolysis-calcination process and their biocompatibility with LO2 and HepG2 cells

β-FeOOH nanorods were prepared via the urea hydrolysis process with the average length of 289.1 nm and average diameter of 61.2 nm, while magnetic α-Fe2O3/Fe3O4 heterostructure nanorods were prepared via the urea calcination process with β-FeOOH nanorods as precursor, and the optimum conditions were the calcination temperature of 400 °C, the calcination time of 2 h, the β-FeOOH/urea mass ratio of 1:6. The average length, diameter, and the saturation magnetization of the heterostructure nanorods prepared under the optimum conditions were 328.8 nm, 63.4 nm and 42 emu·g−1, respectively. The Prussian blue test demonstrated that the heterostructure nanorods could be taken up by HepG2 cells, and cytotoxicity tests proved that the heterostructure nanorods had no significant effect on the viabilities of LO2 and HepG2 cells within 72 h in the range of 100–1600 μg·ml−1. Therefore, magnetic α-Fe2O3/Fe3O4 heterostructure nanorods had better biocompatibility with LO2 and HepG2 cells.

Study of microbially-induced carbonate precipitation for improving coarse-grained salty soil

The salinity of soil can result in serious potential environmental hazards such as increased collapsibility and corrosiveness. Microbially induced carbonate precipitation is an upcoming and pollution-free treatment modality that can eliminate environmental and engineering hazards of saline soil . To verify the feasibility of the method of curing saline soils, a series of tests were conducted to investigate the impact of chloride salt on urea hydrolysis, the impact of the method on engineering and mechanical properties of coarse-grained soils containing chloride salt and the deterioration mechanism of curing effect caused by salt. The study demonstrated that, even though the curing effect of the method is excellent, the negative effect of salt cannot be ignored. With increased salt concentration, the hydrolysis rate and calcium carbonate precipitation efficiency sharply decrease at first and tend to be flatter. The unconfined compressive strength and shear strength of the samples can be greatly improved through the application of the method. However, calcium carbonate content reduces with an increase in the salt content, which decreases the strength. Compared to uncured samples, the permeability coefficient of cured samples reduced from 1 to 2 orders of magnitude. On the other hand, as the dominant aperture size increases with a decrease in the calcium carbonate content, the permeability coefficient increases with an increase in the salt content. Furthermore, micro-mechanical tests, such as X-ray diffraction and scanning electron microscope tests, were conducted to analyze the mechanism by which salt degrades the reinforcement. As a guiding agent, while chloride salt can improve the proportion of calcite in calcium carbonate, it decreases the total quantity of calcium carbonate through the limiting urea hydrolysis process . A significant amount of calcium carbonate is deposited on the surface of the particles in each sample, especially the contact surface. In conclusion, even though salt has a certain deterioration effect, microbially-induced carbonate precipitation is still an effective and environment-friendly method to cure saline soil. This study can provide a theoretical basis for using this method to solidify saline soil.

Low-temperature in situ CO2 enhanced oil recovery

The new generation in situ CO2 enhanced oil recovery (ICE), which delivers CO2 by injection of a CO2 generating agent solution, was proven to offer robust recovery performances and potential cost and workflow benefits. However, the developed ICE systems are either formulated with a complex fluid recipe or a simplified version of a fluid system limited by high-temperature requirements. This work focused on removing the requirement of high reservoir temperature in our previous work while maintaining the simplicity of the single fluid injection system. Urease is studied as the catalyst for urea hydrolysis and evaluated experimentally. The denaturation behavior of urease and the reaction kinetics of the catalyzed urea hydrolysis process are tested at different urea concentrations, urease concentrations, and temperatures. Four sets of one-dimensional sand pack flowthrough experiments are conducted to verify the tertiary recovery potential of the newly developed low-temperature ICE system with different lithology. The extent of wettability alteration and the recovery mechanism for different lithologies was determined through core sample imbibition experiments and direct contact angle measurements. From the experimental results, urease-catalyzed urea hydrolysis is proven to be effective in tertiary oil recovery applications below the 50 °C reservoir temperature range with urea conversion ratio up to 68.7 %. The selected low-temperature ICE system (10 wt% urea solution with 31 U/g urease) had superior tertiary recoveries(Etr) in the flowthrough test for sandstone(Etr = 31.3 %) and carbonate(Etr = 27.5 %) than the corresponding high-temperature cases. Imbibition tests of this improved formulation with various porous media show distinct wettability reversal trends towards a more water-wet state post imbibition. This trend is associated with the produced NH3 and CO2 due to urea hydrolysis. Both oil-aged sandstone and carbonate imbibition tests show noticeable water wetness improvement. The observations of this work significantly expand the operational envelopes of the current ICE system.

Rapid soil rewetting promotes limited N2O emissions and suppresses NH3 volatilization under urea addition

The alternation of dry and wet is an important environmental factor affecting the emission of nitrous oxide from soil. However, the consistent or opposite effects on NH3 and N2O emissions caused by adding exogenous urea in this process have not been fully considered. Here, we controlled the initial (slow drying) and final (adding water) water-filled pore space (WFPS) at 70%, 60%, or 50% through microculture experiment to simulate a process of slow drying-fertilization and rapid wetting of the soil from rice harvest to dryland crop fertilization. Through measuring soil chemical properties and the abundance and composition of related microbial communities during drying process, we studied the pathways of influence of drying and rewetting on the emission of N2O and NH3 after urea application. During the progressive drying process (WFPS decreasing from 70% to 60% and 50%), soil N2O and NH3 emissions decreased by 49.77%–72.13% and 17.89%–42.19%, respectively. After rapid rewetting (WFPS increasing from 60% to 70%, 50%–60% and 70%), N2O emissions showed a slight increase, while NH3 volatilization continued to decrease. Soil NH4+-N and DOC contents both decreased during progressive drying, while the soil NO3−-N content was enhanced. The drying process changed the community structure of ureC and amoA-b and reduced their abundance but had no effect on amoA-a, nirK or nirS. Correlation analysis indicated that the reductions in NH4+-N content and the abundances of ureC and amoA-b were the main factors suppressing N2O and NH3 emissions. We believe that drying process limits the related microbial activity and substrate supply during ammonia oxidation process in terms of N2O emissions, while in terms of NH3 volatilization, it reduces the related microbial activity of urea hydrolysis process and increases the ammonium adsorption to the soil.

Performance Analysis of a Waste-to-Energy System Integrated with the Steam–Water Cycle and Urea Hydrolysis Process of a Coal-Fired Power Unit

An innovative hybrid energy system consisting of a waste-to-energy unit and a coal-fired power unit is designed to enhance the energy recovery of waste and decrease the investment costs of waste-to-energy unit. In this integrated design, partial cold reheat steam of the coal-fired unit is heated by the waste-to-energy boiler’s superheater. The heat required for partial preheated air of waste-to-energy unit and its feedwater are supplied by the feedwater of CFPU. In addition, an additional evaporator is deployed in the waste-to-energy boiler, of which the outlet stream is utilized to provide the heat source for the urea hydrolysis unit of coal-fired power plant. The stand-alone and proposed designs are analyzed and compared through thermodynamic and economic methods. Results indicate that the net total energy efficiency increases from 41.84% to 42.12%, and the net total exergy efficiency rises from 41.19% to 41.46% after system integration. Moreover, the energy efficiency and exergy efficiency of waste-to-energy system are enhanced by 10.48% and 9.92%, respectively. The dynamic payback period of new waste-to-energy system is cut down from 11.39 years to 5.48 years, and an additional net present value of $14.42 million is got than before.

Characterization of bio-adsorptive removal performance of strontium through ureolysis-mediated bio-mineralization

The adsorptive removal performance of strontium (Sr) through bio-mineralization metabolism under various parameters was evaluated in this study. The primary mechanism of bio-mineralization used in this study was the urea hydrolysis process through bacterial enzymatic catalysis. Bacillus sp, which was isolated from river sediment, was used as a ureolytic bacteria. Various environmental conditions were set as different initial concentrations of Sr (10, 50, 100, 200, and 500 mg/L), and various ratios of Mg/Ca (4, 2, 1, 0.5, and 0.25). The concentrations of Sr2+, Ca2+, and Mg2+ in the solution of the batch experiment were measured to identify the bio-mineralization performance and the removal rate of Sr. In addition, the main Sr removal mechanism of ureolytic bacteria was identified. As a result, for Sr removal of bacteria, the bio-mineralization mechanism was more predominant than the adsorption of Sr. The rapid growth and high nucleation site production were observed when the initial concentration of Sr2+ increased and the Mg/Ca ratio was lowered, resulting in high biomineralization performance and Sr removal rate. The main phases of carbonate minerals formed in the presence of Sr, Ca, and Mg were SrCO3 and SrCa(CO3)2. Mg2+ could retard the bacterial growth and participate in the formation of carbonate minerals, when a large amount of Mg2+ was present. Furthermore, the desorption rate of Sr2+ from bacterial pastes containing the carbonate minerals increased as the concentration of HCl increased, although the carbonate minerals were in a stable state.

Evaluation of MICP treatment through EC and pH tests in urea hydrolysis process

Microbially induced calcite precipitation (MICP) using ureolytic bacteria has been investigated to improve the engineering properties of soil. Urease, produced by ureolytic bacteria, can hydrolyse urea to drive the biogeochemical reaction in MICP. The goal of this study was to use changes in electrical conductivity (EC) and pH values from the urea hydrolysis test as an indicator to monitor the ureolytic activities of bacteria before the MICP process and using this indicator to maintain a consistent MICP treatment. Laboratory experiments were conducted to establish the relationship between the EC and pH values and unconfined compression strength (UCS) of MICP-treated soil. The EC and pH values of the mixed solution were measured after adding bacterial suspension into urea solution. Then, the bacterial suspension was mixed with a sand sample and cementation medium to drive the MICP process. The results showed that, once the bacterial suspension was mixed with urea, the EC and pH values of the mixed solution increased immediately due to urea hydrolysis. The optimum EC and pH values at 60 min were found to be 1·50–1·80 mS/cm and 8·82–9·02, respectively, to achieve consistent UCS performance of MICP-treated specimens with 0·25 M calcium (Ca) cementation medium.

Hollow-Structured Layered Double Hydroxide: Structure Evolution Induced by Gradient Composition.

The rational design of hollow-structured materials with high specific area, advanced mass transfer, and exposure of selected sites is of great significance in both fundamental scientific research and applicable industrialization fields. In this work, we report a CoAl layered double hydroxides (LDH) nanoring evolved from integrate nanosheet in a urea hydrolysis process, showing enhanced oxygen reduction reaction activity. Detailed investigations into the evolution nature suggest that a gradient-increased Al3+ composition exists in the core region of the nanosheet arised from distinctly lower solubility of Al3+ than Co2+ in the synthesis; therefore, the selective etching of Al3+ by OH- produced from urea hydrolysis leads to the formation of nanoring structure. Probed as an oxygen reduction reaction catalyst, the CoAl-LDH nanoring illustrates a half-wave potential lowered by around 110 mV compared to the integrate nanosheet counterpart, which might be due to the exposure of more edge sites with higher activity. This work paves a novel route for fabricating hollow-structured Al-contained metal hydroxides with defined outer edge and inner voids for multiple purposes.

Coal char affects soil pH to reduce ammonia volatilization from sandy loam soil

AbstractAmmonia (NH3) volatilization loss adversely affects N availability in soil‐plant systems, reduces crop yield, and negatively impacts environment. Char (coal combustion residue), which contains up to 293 g kg−1 total C by weight, has been shown to reduce NH3 volatilization due to its considerably high surface area and cation exchange capacity. The NH3 loss can be greatly affected by a shift in soil pH or urea hydrolysis. A 21‐d laboratory study was conducted to evaluate the effects of char on soil pH, N transformations, and subsequent NH3 volatilization in sandy loam soil. Two char rates (0 and 13.4 Mg C ha−1) and two urea rates (0 and 200 kg N ha−1) were mixed in soil in four 2‐way combinations with four replications of each. There were 11 sets of all treatment combinations and each set was analyzed for soil moisture, pH, NH3 volatilization, and residual N (urea, NH4, and NO3) every other day for 3 wk. Char application reduced cumulative NH3 loss in the fertilized treatment. Reduction in NH3 loss due to char addition was evidenced by greater residual NH4–N on certain days in treatments with char compared to treatments without char. Char did not affect urea hydrolysis process but it lowered soil pH in the fertilized treatments in the first week. This study supported our hypothesis that char altered soil pH and thereby reduced NH3 volatilization loss from the fertilized soil.

Media Optimization, Strain Compatibility, and Low-Shear Modeled Microgravity Exposure of Synthetic Microbial Communities for Urine Nitrification in Regenerative Life-Support Systems.

Urine is a major waste product of human metabolism and contains essential macro- and micronutrients to produce edible microorganisms and crops. Its biological conversion into a stable form can be obtained through urea hydrolysis, subsequent nitrification, and organics removal, to recover a nitrate-enriched stream, free of oxygen demand. In this study, the utilization of a microbial community for urine nitrification was optimized with the focus for space application. To assess the role of selected parameters that can impact ureolysis in urine, the activity of six ureolytic heterotrophs (Acidovorax delafieldii, Comamonas testosteroni, Cupriavidus necator, Delftia acidovorans, Pseudomonas fluorescens, and Vibrio campbellii) was tested at different salinities, urea, and amino acid concentrations. The interaction of the ureolytic heterotrophs with a nitrifying consortium (Nitrosomonas europaea ATCC 19718 and Nitrobacter winogradskyi ATCC 25931) was also tested. Lastly, microgravity was simulated in a clinostat utilizing hardware for in-flight experiments with active microbial cultures. The results indicate salt inhibition of the ureolysis at 30 mS cm-1, while amino acid nitrogen inhibits ureolysis in a strain-dependent manner. The combination of the nitrifiers with C. necator and V. campbellii resulted in a complete halt of the urea hydrolysis process, while in the case of A. delafieldii incomplete nitrification was observed, and nitrite was not oxidized further to nitrate. Nitrate production was confirmed in all the other communities; however, the other heterotrophic strains most likely induced oxygen competition in the test setup, and nitrite accumulation was observed. Samples exposed to low-shear modeled microgravity through clinorotation behaved similarly to the static controls. Overall, nitrate production from urea was successfully demonstrated with synthetic microbial communities under terrestrial and simulated space gravity conditions, corroborating the application of this process in space.

Mimicking and Inhibiting Urea Hydrolysis in Nonwater Urinals.

Nonwater urinals are critical in the implementation of building-scale water conservation and urine diversion systems. However, because of the composition of urine and the prevalence of the urease enzyme that hydrolyzes urea, minerals readily precipitate in nonwater urinals and pipes. This leads to clogging, malodor, and possible replacement of nonwater urinals with flush urinals. Accordingly, the goal of this research was to provide an improved understanding of the urea hydrolysis process in nonwater urinals to benefit water conservation and phosphate recovery efforts. Acetic acid addition was used in nonwater urinals to inhibit the urea hydrolysis reaction by lowering the pH, thereby making the precipitation of calcium- and magnesium-containing minerals less favorable. Of the acids tested, 2.5 mL of 2500 mequiv/L acetic acid added after every urination event was able to inhibit urea hydrolysis in synthetic urine and real urine as indicated by the pH and conductivity of the effluent urine. Acid addition also allowed for 43% more phosphate recovery via struvite precipitation in the acetic acid addition synthetic urine than the synthetic urine with no acid addition.

Scanning Electrochemical Microscopy: A Tool to Study the Biomediated Calcification Process By Sporosarcina Pasteurii Biofilm

Sporosarcina pasteurii, are known to perform CaCO3 precipitation by hydrolyzing urea and increasing the local pH, in presence of the Ca2+ rich brine solution. We have developed a new electrochemical probes for scanning electrochemical microscopy (SECM) to study this calcification process in real time. We have used the newly developed ultramicrosensors, such as pH, Ca2+, and redox sensors, to monitor a real-time, bacteria-mediated urea hydrolysis process and subsequent changes in morphology due to CaCO3 precipitation. We observed a rapid local (500 μm above the biofilm) pH change from 7.4 to 9.2 within 2 min of addition of urea, whereas the bulk pH remains constant at 7.5. Similar Ca2+ profile was also recorded locally where the Ca2+ concentration above the biofilm depleted from 170 mM to 1 mM. Recent developments regarding the real-time live biofilm morphological change correlated with the chemical (Ca2+ and pH) information will be presented in the meeting.

Complete genome sequence of the Sporosarcina psychrophila DSM 6497, a psychrophilic Bacillus strain that mediates the calcium carbonate precipitation

Sporosarcina psychrophila DSM 6497 is a gram positive, spore-formation psychrophilic bacterial strain, widely distributed in terrestrial and aquatic environments. Here we report its complete sequence including one circular chromosome of 4674191bp with a GC content of 40.3%. Genes encoding urease are predicted in the genome, which provide insight information on the microbiologically mediated urea hydrolysis process. This urea hydrolysis can further lead to an increase of carbonate anion and alkalinity in the environment, which promotes the microbiologically induced carbonate precipitation with various applications, such as the bioremediation of calcium rich wastewater and bio-reservation of architectural patrimony.

Real-time monitoring of calcification process by Sporosarcina pasteurii biofilm

Sporosarcina pasteurii is known to produce calcite or biocement in the presence of urea and Ca(2+). Herein, we report the use of novel ultramicrosensors such as pH, Ca(2+), and redox sensors, along with a scanning electrochemical microscope (SECM), to monitor a real-time, bacteria-mediated urea hydrolysis process and subsequent changes in morphology due to CaCO3 precipitation. We report that the surface pH of a live biofilm changed rapidly from 7.4 to 9.2 within 2 min, whereas similar fast depletion (10 min) of Ca(2+) was observed from 85 mM to 10 mM in the presence of a high urea (10 g L(-1)) brine solution at 23 °C. Both the pH and the Ca(2+) concentration profiles were extended up to 600 μm from the biofilm surface, whereas the bulk chemical composition of the brine solution remained constant over the entire 4 h of SECM experiments. In addition, we observed a change in biofilm surface morphology and an increase in overall biofilm height of 50 μm after 4 h of precipitation. Electron microscopy confirmed the changes in surface morphology and formation of CaCO3 crystals. Development of the Ca(2+) profile took 10 min, whereas that of the pH profile took 2 min. This finding indicates that the initial urea hydrolysis process is fast and limited by urease or number of bacteria, whereas later CaCO3 formation and growth of crystals is a slow chemical process. The ultramicrosensors and approaches employed here are capable of accurately characterizing bioremediation on temporal and spatial scales pertinent to the microbial communities and the processes they mediate.

Study of the urea hydrolysis kinetics in the precipitation conditions of hydroxides and metal salts

The results of studies of the urea hydrolysis kinetics in the temperature conditions corresponding to the precipitation conditions of hydroxides and metal salts were presented. The research was carried out at temperatures of 80-100 °C. The process mechanism was determined - the first-order reaction takes place, the kinetic equation of the urea hydrolysis process was obtained, the dependence of the reaction rate on temperature was defined. The activation energy - 88 kJ, indicating the process flow in the kinetic region was calculated. The rates of accumulation of the hydrolysis products - ammonia and carbon dioxide, which are precipitators of hydroxides and metal salts, in the solution were experimentally studied. It was found that in the hydrolysis process, the amount of ammonia and carbon dioxide in the solution decreases. The temperature at which the there is the highest amount of hydrolysis products in the solution is 90 °C.

Biogenic concrete protection driven by the formate oxidation by Methylocystis parvus OBBP.

The effectiveness of Microbiologically Induced Carbonate Precipitation (MICP) from the formate oxidation by Methylocystis parvus OBBP as an alternative process for concrete protection was investigated. MICP was induced on Autoclaved Aerated Concrete (AAC), the model material, by immersing the material in 109 M. parvus cells mL−1 containing 5 g L−1 of calcium formate. A 2 days immersion of the material gave the maximum weight increase of the specimens (38 ± 19 mg) and this was likely due to the deposition of calcium carbonate, biomass, and unconverted calcium formate. The solid deposition mainly occurred in the micropores of the specimen, close to the outer surface. A significantly lower water absorption was observed in the bacterially treated specimens compared to the non-treated ones (up to 2.92 ± 0.91 kg m−2) and this could be attributed to the solid deposition. However, the sonication test demonstrated that the bacterial treatment did not give a consolidating effect to the material. Overall, compared to the currently employed urea hydrolysis process, the formate-based MICP by M. parvus offers a more environmentally friendly approach for the biotechnological application to protect concrete.

Statistical Modeling of Environmental Factors on Microbial Urea Hydrolysis Process for Biocement Production

Calcium carbonate is a widely used raw material by many industries. It can be precipitated through microbial process within soil pores as cementitious bonding agent between grains for geotechnical applications. It is called microbially induced calcium carbonate precipitation (MICP). Designing an appropriate biogrout material for injection into soil is essential for controlling the amount, type, time, and place of the biocement production within pores. For this purpose, understanding the active reactions and the kinetics of bacterial growth and urea hydrolysis is necessary. A conductometric method and spectrophotometry were used in this study to, respectively, monitor the urea hydrolysis reaction progress and bacterial growth inS. pasteurii-inoculated urea-NB-NH4Cl solution at different level of the environmental factors that are initial cell concentration, urea concentration, and temperature. Variation in conductivity of the solution versus logarithmic scale of time was depicted as microbial ureolysis characteristic curve (MUCC) through which lag duration, specific rate, and potential of urea hydrolysis at each condition were obtained. Central composite face-centered (CCF) design, which is one of the response surface methodologies, was employed to statistically fit polynomial models explaining the bacterial growth and the characteristics obtained from MUCCs in terms of the environmental factors and their interactions. An optimization analysis based on the urea-normalized responses was also carried out.