Recovery Of Urea Research Articles

Nutrient recovery from urine: Urea adsorption onto biochar integrated with Na-chabazite as urease inhibitor

This study presents an innovative technical integration for concomitant nutrient recovery from source-separated urine. While cation exchange is known for efficient K+ recovery, it faces competition due to the high molarity of NH4+ in hydrolyzed urine. This study proposes inhibiting urease activity to facilitate the recovery of K⁺ and urea from fresh urine. Na-chabazite was first proposed as a urease inhibitor in this study, reducing urease activity by 50 %. Wood biochar, with its high porosity (308.0 m²/g) and polar functional groups, shows a urea adsorption capacity of 25.4 mg/g, which can be further improved by steam activation. The isotherm analysis suggests that urea adsorption onto biochar follows a multi-layer adsorption process. Finally, an integrated process is suggested: "Na-chabazite and Biochar adsorption → urea hydrolysis → struvite precipitation + ammonia stripping-acid scrubbing", ensuring efficient recovery of urea, NH4+, PO43-, and K+ from source-separated urine.

Development and Validation of New HPLC Method for the Determination of Imidazolidinyl Urea in Topical Formulation

Introduction: In this study, a new, simple, selective, and fast liquid chromatographic method has been developed and validated for the determination of imidazolidinyl urea used as an anti-microbial agent in topical formulation. Methods: The developed HPLC method using a diode array detector for the determination of imidazolidinyl urea was applied to the topical formulation. Imidazolidinyl urea in the sample was analyzed in the cyano column (250 x 4,6 mm, 5 μm i.d.) under chromatographic conditions, where the flow rate was determined as 1.0 mL/min. The column oven was 40.0°C, and imidazolidinyl urea was detected at 210 nm. Isocratic application of acetonitrile-water (25:75, v/v) was used as the mobile phase system. The validation of the developed method was performed according to the International Conference on Harmonisation guidelines Q2 (R1). Results: The linearity range of the imidazolidinyl urea was 0.050-0.150 mg/mL, and the limits of detection and quantification were calculated to be 62.5x10-6 mg/mL and 125x10-6 mg/mL, respectively. Assay recovery and precision of imidazolidinyl urea from topical formulation at 0.050, 0.100, and 0.125 mg/mL concentrations were evaluated. The mean recoveries for imidazolidinyl urea in the topical formulation were calculated as 98.857-104.560%. Conclusion: The validated method was successfully applied to the determination of imidazolidinyl urea in a topical formulation. The proposed method is reproducible and reliable and can be used safely for routine analysis.

Effect of functional groups on the adsorption of urea on activated carbon

The recovery of urea, present in the urine of mammals, has the potential of converting a current wastewater pollutant into an energy source due to its high hydrogen content, in alignment with the waste-to-energy principles. Carbon-based materials enable this approach due to their relatively high urea adsorption capacities. This work reveals that the adsorption of urea from aqueous solutions on activated carbon is a combination of weak van der Waals interactions such hydrogen bonds with the aromatic structure of the pristine carbon surface and also with carboxyl groups on the functionalised carbon, showing no appreciable interaction with hydroxyl or lactone groups. The selective introduction and quantification of different oxygen functional groups on activated carbon reveals their independent effect on the urea adsorption capacity, bringing an end to previous discrepancies in the literature. It also demonstrates that the optimisation of carbon materials must balance the increase of carboxyl groups and the decrease of the surface area associated to functionalisation treatments, providing guidance for future developments of carbon-based materials for circular economy applications.

Electrically charged forward osmosis for enhancing urea recovery from synthetic urine

Human urine, known as liquid gold, provides 80 % of the nitrogen sources in wastewater treatment plants through urea, making urea recovery an effective method for recycling nitrogen resources. In this work, a novel urea electrically charged forward osmosis (UEFO) system was used to treat human urine to enhance the accumulation of water penetration and urea recovery by overcoming concentration polarization and reverse solute flux. The system contained four chambers with an effective volume of 28 mL and was equipped with external glass vials. The feed solution was 40 mL of urine and the draw solution was 50 mL of potassium chloride solution. With the addition of an electric field, Cl−, SO42− and PO43− were transported from the feed solution (FS) to the anode chamber through the AEM, while OH– and SO42− were transported from the cathode chamber to the draw solution (DS) through the AEM, resulting in high osmotic pressure difference between the DS and FS, which enhanced the urea recovery. With the enhancement of current intensity from 0 to 0.04 A, water flux and urea increased from 8.02 LMH and 39.78 mg to 12.74 LMH and 56.16 mg (accounting for 76.82 % of total urea), respectively. These results demonstrated that the UEFO system could overcome the limitations of traditional FO systems (50 % recovery barrier) and showcased a promising performance for urea recovery from human urine by integrating electrochemical and osmotic-driven processes.

Designing and prototyping a novel biosensor based on a volumetric bar-chart chip for urea detection.

A volumetric bar-chart chip (V-chip) is a microfluidic device based on distance-based quantitative measurement that visualizes analyte concentration without the need for apparatus or data processing. This typically utilizes special receptors and catalysis parts that generate oxygen, so ink can be moved inside the channels, and enables instant visual quantitation of the analyte. However, the low stability of some macromolecules, the use of expensive catalysts, and difficulty in controlling the process cause inaccurate readings, and therefore, limit further development and the use of these systems. In this article, we introduced a novel approach that eliminates the use of catalysts in V-chips and provides an efficient and simple path in the design of biosensors. The product of the enzymatic reaction of urease with urea is bicarbonate, which turns into CO2 gas in an acidic environment. Therefore, the amount of gas produced is proportional to the amount of urea in the sample, and it can be quantitatively measured by visual detection from the amount of ink movement caused by CO2 gas pressure. This biosensor has a linear response range of 0 to 1000 μg ml-1 and a detection limit of 3.6 μg ml-1 in raw milk. The recovery of urea in raw milk at 100 and 400 μg ml-1 concentrations was 96.5% and 98.9%, respectively. This volumetric chip shows potential for determining urea levels in real samples without requiring additional equipment. The combination of the sensitivity and specificity of enzymatic reactions, inherent gas-generating reactions, and the processability of microchips discussed in this paper can be the basis for the comprehensive development of volumetric chips, which can create a new path for the development of efficient and cheap biosensors.

Simultaneous Urea and Phosphate Recovery from Synthetic Urine by Electrochemical Stabilization.

Urine is a widely available renewable source of nitrogen and phosphorous. The nitrogen in urine is present in the form of urea, which is rapidly hydrolyzed to ammonia and carbonic acid by the urease enzymes occurring in nature. In order to efficiently recover urea, the inhibition of urease must be done, usually by increasing the pH value above 11. This method, however, usually is based on external chemical dosing, limiting the sustainability of the process. In this work, the simultaneous recovery of urea and phosphorous from synthetic urine was aimed at by means of electrochemical pH modulation. Electrochemical cells were constructed and used for urea stabilization from synthetic urine by the in situ formation of OH- ions at the cathode. In addition, phosphorous precipitation with divalent cations (Ca2+, Mg2+) in the course of pH elevation was studied. Electrochemical cells equipped with commercial (Fumasep FKE) and developmental (PSEBS SU) cation exchange membranes (CEM) were used in this study to carry out urea stabilization and simultaneous P-recovery at an applied current density of 60 A m-2. The urea was successfully stabilized for a long time (more than 1 month at room temperature and nearly two months at 4 °C) at a pH of 11.5. In addition, >82% P-recovery could be achieved in the form of precipitate, which was identified as amorphous calcium magnesium phosphate (CMP) by using transmission electron microscopy (TEM).

Poultry litter increased irrigated cotton N uptake with limited improvement on 15N-labelled urea recovery over one season

Poultry litter increased irrigated cotton N uptake with limited improvement on 15N-labelled urea recovery over one season

Recovery of Urea from Human Urine Using Nanofiltration and Reverse Osmosis

Recovery of Urea from Human Urine Using Nanofiltration and Reverse Osmosis

A hybrid nanofiltration and reverse osmosis process for urine treatment: Effect on urea recovery and purity

Human urine can be treated and concentrated using reverse osmosis (RO), but this process also concentrates pharmaceuticals and undesirable salts along with valuable nutrients such as urea. The final fertilizer product, therefore, has limited use on salt-sensitive crops or edible crops as the effects of pharmaceuticals remain a concern.Tight and loose nanofiltration (NF) pre-treatment was investigated as a method to recover urea in the permeate (which could then be further concentrated using RO), whilst pharmaceuticals and undesirable salts would be removed in the brine. Both NF options removed pharmaceuticals (NF90 – 99%, NF270 – 70%). Using a loose NF membrane, 78% of the urea was recovered in the permeate (80% water removal), however, the salt removal was poor (44%), and the urea purity only increased from 37 to 56%. Tight NF membranes provided better rejection of salts and organics (96% and 90% removed respectively). The urea purity in the permeate (75% water removal) from the tight NF process was 89%, however, the urea recovered was lower (48%). The tight NF permeate was then further concentrated with RO. At an overall water removal of 80%, 32.7% of the urea could be recovered with a purity of 85%. A decision tree was also developed to determine the optimum treatment process based on the desired final product. This decision tree could be used to determine the economic feasibility of each treatment process based on the final product choice and product value.

Design and Analysis of Artificial Neural Network (ANN) Models for Achieving Self-Sustainability in Sanitation

The present study investigates the potential of using fecal ash as an adsorbent and demonstrates a self-sustaining, optimized approach for urea recovery from wastewater streams. Fecal ash was prepared by heating synthetic feces to 500 °C and then processing it as an adsorbent for urea adsorption from synthetic urine. Since this adsorption approach based on fecal ash is a promising alternative for wastewater treatment, it increases the process’ self- sustainability. Adsorption experiments with varying fecal ash loadings, initial urine concentrations, and adsorption temperatures were conducted, and the acquired data were applied to determine the adsorption kinetics. These three process parameters and their interactions served as the input vectors for the artificial neural network model, with the percentage urea adsorption onto fecal ash serving as the output. The Levenberg–Marquardt (TRAINLM) and Bayesian regularization (TRAINBR) techniques with mean square error (MSE) were trained and tested for predicting percentage adsorption. TRAINBR was demonstrated in our study to be an ideal match for improving urea adsorption, with an accuracy of R = 0.9982 and a convergence time of seven seconds. The ideal conditions for maximum urea adsorption were determined to be a high starting concentration of 13.5 g.L−1; a low temperature of 30 °C, and a loading of 1.0 g of adsorbent. For urea, the improved settings resulted in maximum adsorption of 92.8%.

Urea recovery from stabilized urine using a novel ethanol evaporation and recrystallization process

Urea is a raw material in the production of various chemicals and is a key nitrogen-based fertilizer. The conventional process to manufacture synthetic urea operates at high temperatures and pressures and is therefore energy intensive. The aim of this work was to investigate the feasibility of recovering and purifying urea crystals from human urine using a novel ethanol evaporation and recrystallization process that exploits the solubility differences of urea and impurities in water and ethanol. This approach could provide an alternative method to produce urea that operates at atmospheric pressure and low temperatures (< 30°C).Synthetic and real human urine was treated with Ca(OH)2 to prevent urea hydrolysis and then dried to recover the solids. These solids were dissolved in a predetermined amount of ethanol and the urea present was recrystallized. A complex synthetic urine solution (with various organics and inorganics) had a urea solubility of 56.7 g L−1 at 22°C. It was determined that the solubility of urea in ethanol increased when more organics were present in the solution. Urea was recovered from inorganic synthetic urine (SI), organic synthetic urine (SO) and real human urine (RU) with yields of 88%, 77% and 67%, respectively. The purity of urea increased from 41%, 41% and 43% to 91%, 76% and 76% for SI, SO and RU using the ethanol evaporation and recrystallization process.

Selective recovery of phosphorus and urea from fresh human urine using a liquid membrane chamber integrated flow-electrode electrochemical system

Phosphorus (P) extraction from human urine is a potential strategy to address global resource shortage, but few approaches are able to obtain high-quality liquid P products. In this study, we introduced an innovative flow-electrode capacitive deionization (FCDI) system, also called ion-capture electrochemical system (ICES), for selectively extracting P and N (i.e., urea) from fresh human urine simply by integrating a liquid membrane chamber (LMC) using a pair of anion exchange membrane (AEM). In the charging process, negatively charged P ions (i.e., HPO42– and H2PO4–) can be captured by acidic extraction solutions (e.g., solutions of HCl, HNO3 and H2SO4) on their way to the anode chamber, leading to the conversion of P ions to uncharged H3PO4, while other undesired ions such as Cl– and SO42– are expelled. Simultaneously, uncharged urea molecules remain in the urine effluent with the removal of salt. Thus, high-purity phosphoric acid and urea solutions can be obtained in the LMC and spacer chambers, respectively. The purification of P in an acidic environment is ascribed largely to the competitive migration and protonation of ions. The latter contributes ~27% for the selective capture of P. Under the optimal operating conditions (i.e., ratio of the urine volume to the HCl volume = 7:3, initial pH of the extraction solution = 1.43, current density = 20 A/m2 and threshold pH ~ 2.0), satisfactory recovery performance (811 mg/L P with 73.85% purity and 8.3 g/L urea-N with 81.4% extraction efficiency) and desalination efficiency (91.1%) were obtained after 37.5 h of continuous operation. Our results reveal a promising strategy for improving in selective separation and continuous operation via adjustments to the cell configuration, initiating a new research dimension toward selective ion separation and high-quality P recovery.

Changes in Nitrogen Pools in the Maize–Soil System after Urea or Straw Application to a Typical Intensive Agricultural Soil: A 15N Tracer Study

A maize pot experiment was conducted to compare the difference of N distribution between bulk and rhizospheric soil after chemical fertilizer with or without soil straw amendment at an equivalent N rate using a 15N cross-labeling technique. Soil N pools, maize N and their 15N abundances were determined during maize growth. The urea plus straw treatment significantly (p &lt; 0.05) increased the recovery of urea N in soil and 26.0% of straw N was assimilated by maize. Compared with urea treatment in bulk soil, urea plus straw treatment significantly (p &lt; 0.05) increased the concentration and percentage of applied N as dissolved organic N (DON) and microbial biomass N (MBN) from milk stage to maturity, increased those as particulate organic N (PON) and mineral associated total N (MTN) throughout maize growth and decreased those as inorganic N (Inorg-N) from the eighth leaf to the silking stage. Compared with bulk soil, rhizospheric soil significantly (p &lt; 0.05) decreased the concentration and percentage of applied N as PON and increased those as Inorg-N and MTN in both applied N treatments from the silking stage, and significantly (p &lt; 0.05) decreased the concentration and percentage of applied N as microbial biomass N (MBN) in the urea plus straw treatment. Overall, straw N was an important N source and combined application of chemical fertilizer with straw increased soil fertility, with the rhizosphere regulating the transformation and supply of different N sources in the soil–crop system.

Equipment-free quantitative determination of urea based on paper-based sensor via urease-mediated chitosan viscosity change

In this study, a paper-based sensor combined with visual distance-readout technique for point of-care testing (POCT) of urea was developed by urease-mediated chitosan viscosity change. A series of factors that affect the performance of the sensor were investigated, including the type of filter paper, chitosan concentration, acetic acid concentration and enzymatic reaction conditions. Under optimal conditions, the proposed method for urea determination has good linearity between 3.8–15.1 mM. The limit of quantitation is 3.8 mM. Finally, the paper-based sensor was successfully applied to the determination of urea in two diesel exhaust fluid (DEF) samples. The recoveries of urea were 91.4 % and 109.9 % in DEF-1 and DEF-2, respectively. The present study provides a novel approach, which integrates paper-based sensor and visual distance-readout technique, for monitoring urea in POCT application, especially in remote or resource-limited regions.

KINETIKA DESORPSI UREA DARI KARBON BERPORI TEROKSIDASI ASAM SULFAT SEBAGAI SLOW RELEASE FERTILIZER

Urea is an important nitrogen source for plant but the price of urea fertilizer is relatively high. Urea uptake from urea manufacture waste water and its application as fertilizer is of high interest. The purpose of this study is to find out desorption ability of urea adsorbed porous carbon to be applied as fertilizer. Theoritically, urea released from porous carbon to environment has slower rate of mass transfer compare to conventional urea fertilizer because urea molecules in porous carbon has to pass through pores of carbon during its movement out of carbon. The porous carbon as adsorbent was made from coconut shell by pyrolysis, followed by sulfuric acid oxidation treatment Oxidation treatment carried out to extent adsorption capacity as well as to give additional sulfur nutrient when applied as fertilizer. Oxidation of carbon surface was performed using sulfuric acid (50%w) to soak porous carbon followed by heating at 90oC temperature for 2 hours. Desorption was conducted by placing porous carbon into beaker contain water and the raising of urea concentration in water recorded after 3,5,10, 30, and 60 minutes. Results reveal that the value of mass transfer coefficient (kc) and effective diffusivity (De) of urea desorption from porous carbon are 0,0293 – 0,0743 cm/s and 8 x 10-10 – 5 x 10-9 cm2/s with initial concentration of urea 1000, 2000, and 4000 mg/L. Release rate of urea from porous carbon and urea prill are 0,07 ppm/s and 1,23 ppm/s. Slower release rate of urea off porous carbon than urea prill shows the promising of urea recovery using porous carbon as slow release fertilizer.

Pilot-Scale Assessment of Urea as a Chemical Cleaning Agent for Biofouling Control in Spiral-Wound Reverse Osmosis Membrane Elements.

Routine chemical cleaning with the combined use of sodium hydroxide (NaOH) and hydrochloric acid (HCl) is carried out as a means of biofouling control in reverse osmosis (RO) membranes. The novelty of the research presented herein is in the application of urea, instead of NaOH, as a chemical cleaning agent to full-scale spiral-wound RO membrane elements. A comparative study was carried out at a pilot-scale facility at the Evides Industriewater DECO water treatment plant in the Netherlands. Three fouled 8-inch diameter membrane modules were harvested from the lead position of one of the full-scale RO units treating membrane bioreactor (MBR) permeate. One membrane module was not cleaned and was assessed as the control. The second membrane module was cleaned by the standard alkali/acid cleaning protocol. The third membrane module was cleaned with concentrated urea solution followed by acid rinse. The results showed that urea cleaning is as effective as the conventional chemical cleaning with regards to restoring the normalized feed channel pressure drop, and more effective in terms of (i) improving membrane permeability, and (ii) solubilizing organic foulants and the subsequent removal of the surface fouling layer. Higher biomass removal by urea cleaning was also indicated by the fact that the total organic carbon (TOC) content in the HCl rinse solution post-urea-cleaning was an order of magnitude greater than in the HCl rinse after standard cleaning. Further optimization of urea-based membrane cleaning protocols and urea recovery and/or waste treatment methods is proposed for full-scale applications.

Urea recovery from fresh human urine by forward osmosis and membrane distillation (FO–MD)

This proof-of-concept study illustrated that FO–MD provides a technology platform for urea recovery from fresh human urine, which currently does not have an established method for recovery.

A High-Pressure Gas–Solid Carbonation Route to Produce Vaterite

A novel synthetic strategy based on a high pressure gas–solid reaction using urea as an additive to produce value-added CaCO3 material is reported. Results showed that at about 150 °C and 12 MPa the reaction attained complete carbonation with predominant spherical vaterite crystals via a self-sustained reaction. The influences of working conditions including pressure, temperature, Ca(OH)2/urea mass ratio, and reaction time on the mineralization process were studied. The as-prepared CaCO3 powder exhibited vaterite content as high as 94.2% and a surface area up to 32.9 m2/g. The mechanism study showed that the high-pressure CO2 acted as an inhibitor for urea decomposition at high temperature besides as a reactant; the urea entrapped Ca(OH)2 via its melt to stabilize vaterite formation by an amine functional group and initiated the carbonation process via tiny water triggered by its slight decomposition. The separation to obtain the fine product was simple and allowed high urea recovery (for example, 93.6%)....

Quantifying Foliar and Soil Uptake of Granular 15N‐Labeled Urea by Corn

Core Ideas Foliar uptake of nitrogen from granular urea placed in the corn whorl can be significant over short time periods. Foliar nitrogen applications cannot provide season total corn nitrogen requirements. Nitrogen recovery efficiency of whorl‐applied urea can be as high as 16.6% in the 11 d following application. Corn (Zea mays L.) “green‐up” in the absence of rainfall or irrigation following broadcast applications of urea led to the initiation of this experiment. The objective was to compare corn aboveground‐N (TN) content, fertilizer‐N recovery efficiency (FNRE), and mass of fertilizer‐N recovery (MFNR) of granular urea applied directly into the corn whorl and directly to the soil for 11 d after the V6 stage under greenhouse and field conditions. Nitrogen rates of 0, 56, 112, and 168 kg N ha−1 using 2.5 atom% 15N labeled‐urea were applied to compare N assimilation via foliar or soil pathways. In the greenhouse, FNRE (16.6%) and MFNR (27.8 kg N ha−1) were influenced by the two‐way interaction of N rate and N placement (p &lt; 0.0001) with values being maximized with 168 kg N ha−1 applied directly into the corn whorl at the V6 growth stage. The FNRE and MFNR of soil‐applied N were significantly lower than the whorl applications for all N rates (FNRE) and the two highest N rates (MFNR). Although not statistically compared, the FNRE and MFNR of the field trial were numerically lower than the values observed in the greenhouse. The FNRE of whorl‐applied N in the field trial was not influenced by N rate and averaged 7.1%, whereas the soil‐applied N varied across N rates, but was maximized at 1.9%. Results indicate that foliar uptake of granular urea applied directly into the corn whorl can be substantial over short time periods (&lt;11 d) but not sufficient for season‐total N uptake.

Simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC using a highly hydrophilic monolith

Urea and allantoin are two important additives in cosmetic products for the treatment of dry skin as well as for skin protection and regeneration. In this research, a highly hydrophilic monolith prepared by co-polymerization of N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and N,N’-methylenebisacrylamide (MBA) was first exploited for the simultaneous quantification of urea and allantoin in cosmetic products by nano-HPLC in the HILIC mode. The whole separation process could be completed within six minutes using isocratic elution. Due to the extremely high hydrophilicity of this monolithic column, a relatively low content (80%) of ACN in the mobile phase was required to achieve satisfactory separation, and therefore the solubility problems for polar compounds was also avoided in comparison with previously reported results on the commercial columns. Method validation was also accomplished with respect to linearity, reproducibility, selectivity, recovery, stability, LOD and LOQ. The recoveries of urea and allantoin from spiked cosmetic samples were 95.6%-100% and 94.1%-99.9%, respectively. Validation results indicate that this HILIC method based on the miniaturized poly(SPDA-co-MBA) monolith can be applied successfully to the fast and efficient determination of urea and allantoin in cosmetic samples. The miniaturized column format, the low sample consumption (20 nL), and excellent separation efficiency could make this highly hydrophilic monolith an attractive choice for the detection of trace polar analytes from complex samples in future.