Urea hydrolysis and recovery of nitrogen and phosphorous as MAP from stale human urine

Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volumetric ratios of stale urine to fresh urine,on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP.With a volumetric ratio of stale to fresh urine>10% and at temperature≥20℃,urea hydrolysis could be completed in two days.Alkaline pH inhibited urea hydrolysis progress.The final pH values were all around 9.0 following urine hydrolysis,while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis.Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl;·6H;O and Na;HPO;·12H;O as precipitation agents at pH 8.5,molar ratio of Mg;:NH;-N:PO;-P at（1.2-1.3）:1:1,mixing speed of 120 r/min,and precipitation time and reaction time of 3 h and 15 min,respectively.The precipitate has a structure resembling pure MAP crystal.

Catalytic urea hydrolysis by composite metal oxide catalyst towards efficient urea-based SCR process:performance evaluation and mechanism investigation

As a promising option to provide gaseous NH_(3) for SCR system,catalytic urea hydrolysis has aroused great attention,and improving surface area and activity of catalysis are the crucial issues to be solved for efficient urea hydrolysis.Therefore,a composite metal oxide(TiO_(2)@Al_(2)O_(3))catalyst was prepared by a simple hydrothermal method,with mesoporous alumina(γ-Al_(2)O_(3))as substrate.The results verify the mesoporous structure and submicron cluster of TiO_(2)@Al_(2)O_(3),with exposed crystal faces of(101)and(400)for TiO_(2)andγ-Al_(2)O_(3),respectively.The electronegativity difference of Ti4+and Al3+changes the charge distribution scheme around the interface,which provides abundant acid/base sites to boost the urea hydrolysis.Consequently,for an optimal proportioning with nano TiO_(2)content at 10 wt.%,the hydrolysis efficiency can reach up to 35.2%at 100℃ in 2 h,increasing by~7.1%than that of the blank experiment.^(13)C NMR spectrum measurements provide the impossible intermediate species during urea hydrolysis.Theoretical calculations are performed to clarify the efficient H_(2)O decomposition at the interface of TiO_(2)@Al_(2)O_(3).The result offers a favorable technology for energy-efficiency urea hydrolysis.

Urea transport and hydrolysis in the rumen: A review

Inefficient dietary nitrogen(N)conversion to microbial proteins,and the subsequent use by ruminants,is a major research focus across different fields.Excess bacterial ammonia(NH3)produced due to degradation or hydrolyses of N containing compounds,such as urea,leads to an inefficiency in a host’s ability to utilize nitrogen.Urea is a non-protein N containing compound used by ruminants as an ammonia source,obtained from feed and endogenous sources.It is hydrolyzed by ureases from rumen bacteria to produce NH_(3) which is used for microbial protein synthesis.However,lack of information exists regarding urea hydrolysis in ruminal bacteria,and how urea gets to hydrolysis sites.Therefore,this review describes research on sites of urea hydrolysis,urea transport routes towards these sites,the role and structure of urea transporters in rumen epithelium and bacteria,the composition of ruminal ureolytic bacteria,mechanisms behind urea hydrolysis by bacterial ureases,and factors influencing urea hydrolysis.This review explores the current knowledge on the structure and physiological role of urea transport and ureolytic bacteria,for the regulation of urea hydrolysis and recycling in ruminants.Lastly,underlying mechanisms of urea transportation in rumen bacteria and their physiological importance are currently unknown,and therefore future research should be directed to this subject.

Reaction of Ferralsol to Acidifying Effect of Nitrogen Fertilisation

Background: The objective of this study was to determine the short-term effect of urea fertiliser application on soil reactions in a Ferralsol, with particular thrust on P sorption. Methods: Two experiments were conducted for this purpose: 1) a screenhouse pot experiment; and 2) a laboratory P sorption component. The pot (10 litre capacity plastic pots) experiment was conducted at the Makerere University Agricultural Research, Kabanyolo in Uganda, using a Ferralsol. The study comprised of four urea N (46% N) fertiliser treatments, namely, 0, 40, 80 and 120 kg N·ha-1, equivalent to 0, 200, 400 and 600 mg N per pot. A completely randomised design was adopted with three replicates. Urea rates were applied in 50% split doses, one at planting and the other at 19 days after seedling emergence (to simulate farmer practice). This was followed by watering to field capacity using distilled water. Soil samples were taken at three daily intervals until day fourteen;thereafter, soil sampling was at an interval of seven days. The second urea split dose was applied at 21 days followed by soil sampling at an interval of three days till day fourteen. Thereafter, soil was sampled at seven day intervals until the end of experiment. Soil samples were analysed for exchangeable H+, Al3+, NH4+and NO3- ions. The reaction trends of the concentrations of these ions and Bray 1 P were used to structure different response curves representing the instantaneous reactions. As for the laboratory P-sorption study, treatments included the four rates of urea used in the pot experiment (0, 40, 80 and 120 kg N·ha-1) and seven levels of P (2.5, 5, 10, 20, 30, 40 and 50 ppm) as KH2PO4. The setup was incubated under laboratory conditions and soil samples were repeatedly taken at 10 days (after 4 days of urea incubation plus 6 days of P application). The P sorption data were fitted to Langmuir model. Results: The pot experiment revealed an abrupt drop in the concentrations of exchangeable Al3+ and H+ ions (p < 0.05) within the first 6 days after urea application, accompanied by a positive surge in the concentration of NH4+ ions. This phase (6 days) was followed by a rise in the levels of exchangeable Al3+, H+ and NO3- ion concentration, which was inversely mirrored by a drop in the concentration of NH4+ ions. Consequently, the patterns displayed by the soil reactions were delineated into four phases, with Phase 1 (6 days) being characterised by urea hydrolysis reactions of deamination and ammonification, Phase 2 (10 days) being dominated by nitrification and its acidifying properties, Phase 3 being a repeat of Phase 1, both occurring immediately after urea application (within 6 days);and Phase 4 being a repeat of Phase 2. As for the P-sorption study, the effects of urea hydrolysis in a Ferralsol markedly increased soil pH and surprisingly P sorption. The contradictory P sorption behavior, despite the drop in exchange acidity was attributed to presence of divalent calcium in the extraction reagent used. Conclusion: The short term insights obtained in response to urea N application in the Ferralsol, are eye openers to future use of N fertilisers as well as strategic management of the associated acidification process which is often more costly and complicated to manage.

β-Cyclodextrin-modified AuBi metallic aerogels enable efficient peroxidase mimicking for colorimetric sensing of urease-positive pathogenic bacteria

The detection of pathogenic bacteria with improved accessibility,reduced analysis time,and increased sensitivity is of great importance for diagnosing the infected disease.Nanozymes have attracted rising attention in the bioassay field.Designing a model nanozyme needs the combined merit of sensible nanostructures and a large specific surface area to guarantee exceptional enzyme-mimic activity.Herein,aβ-cyclodextrin modified AuBi aerogel is prepared by a one-pot reduction strategy.The introduction ofβ-cyclodextrin(featured with a hydrophobic cavity and hydrophilic surface)enhances the catalytic activity of AuBi aerogels by engendering host-guest complex and improving dispersity/stability.Based on the specific urea hydrolysis,which could produce NH_(3)to raise pH by urease,the pH up-regulation would inhibit the peroxidase-mimicking performances ofβ-cyclodextrin/AuBi aerogels.Therefore,the sensitive colorimetric detection platform for urease activity could be constructed.Moreover,the sensing platform can detect straightforwardly urease-positive Proteus mirabilis in urine circumstances with a wide detection range and a low limit of detection(LOD)of 4 colony-forming unit(CFU)·mL^(-1).The reproducibility,stability,and specificity of this approach are verified to be satisfactory.Also,as an inhibitor of urease activity,the fluoride ion could be detected by the constructed sensing platform sensitively and specifically.Overall,this work provides a blueprint for designing an ideal nanozyme and paves a new roadway for detecting pathogenic bacteria.