Initial Urea Concentration Research Articles

Acclimatization of a sequencing batch vertical oxidation pond with simulated agricultural wastewater using duckweed as vegetation: analysis of efficiency, Biomass, and Soil properties.

Vertical oxidation pond operated in sequencing batch mode (HRT: 1.25day) with duckweed as the vegetation was used to acclimatize with simulated agricultural wastewater. The maximum removal rate of urea [371g/(m3.d)] and COD [222.4g/(m3.d)] were observed at moderate concentrations of urea (500mg/L), N-P-K (60mg/L), and pesticide (20mg/L). Inhibition and toxicity posed by higher concentrations, decreased the removals of urea (83% to 61%), COD (81% to 51%), and TDS (76% to 50%) at the end of the acclimatization. Steady removal (> 99%) of PO43--P was observed during acclimatization. Effluent pH increased due to the generation of NH4+-N (maximum 370 ± 5mg/L) from the assimilation of urea. Oxidation of ammonia led to the maximum generation of NO2--N and NO3--N of 10mg/L and 9mg/L, respectively. Particles less than 300μm increased, and both specific gravity (from 2.62 to 2.42) and maximum dry density (from 1.73 to 1.30g/cm3) of the base soil decreased with an increase in urea, N-P-K, and pesticide. Reactor biomass increased (1.42 to 1.90g/L) up to initial concentrations of urea (500mg/L), N-P-K (60mg/L), and pesticide (20mg/L), then decreased (1.68g/L) with an increase in concentration.

How mass and heat transfers could affect chitosan membrane formation via an enzymatic gelation

Herein, a 1D numerical model was developed to simulate the enzymatic gelation of chitosan in thin film geometry, corresponding to a thin polymer solution cast onto a support. Mass and heat transfer phenomena were taken into account in the mathematical model and coupled to the chemical reactions involved during the chitosan gelation process (urea hydrolysis, equilibrium reactions, deprotonation of chitosan). External mass transfers involving water and ammonia evaporation as well as carbon dioxide intake and evaporation (depending on the gelation process stage) were integrated in the model. A comparison was done in deep cell geometry between the numerical results obtained with the 1D and a 0D model developed and validated in a previous work. The 1D model was then able to predict the influence of the external transfers on the chitosan gelation kinetics. More precisely the model developed herein exhibited that minimum initial concentrations of urease and urea are necessary to reach the advanced gelation pH during the process, which is a prerequisite for preparing thin chitosan membrane.

Will the photocatalytic ceramic membrane be the solution for the next generation of photocatalysis? - A comprehensive comparison between g-C3N4 powder and g-C3N4 modified ceramic membrane

To address the catalyst recovery issue in traditional photocatalysis processes, photocatalytic membrane reactors have emerged as a novel technology in recent years. However, the understanding of the differences in photocatalytic performance and mechanism between the membrane and slurry systems is missing. The current study provided a comprehensive comparison between the photocatalytic slurry system (CN-P) and membrane system (CN-M) in terms of bisphenol A (BPA) degradation and mineralization, in which the well-developed g-C3N4 was chosen as the catalyst. The fabrication of CN-M was optimized via tuning initial urea concentration, and a series of characterization technologies confirmed the successful incorporation of g-C3N4 onto the membrane. Different reaction mechanisms were proposed in two systems via the identification of contributed reactive species and the degradation products. The “sea anemone effect” in the membrane system enhanced the mass transfer between the reactive species and the BPA molecules and promoted the BPA mineralization with less toxic intermediates. Furthermore, the CN-M exhibited excellent anti-fouling and self-cleaning properties with a much lower irreversible fouling resistance than the original membrane and could be regenerated rapidly after visible light irradiation. These findings provided new insights for the CN-M system as a promising and reliable alternative to the traditional photocatalytic process, which is of great significance and importance in promoting the practical application of photocatalytic membranes in water treatment.

Importance of carbon to nitrogen ratio in microbial cement production: Insights through experiments and genome-scale metabolic modelling

Microbial cement production based on microbially induced calcium carbonate precipitation (MICP) is a technology with high potential but is economically limited. Lower medium costs are expected to improve the economic attractiveness of microbial cement production. We report the effect of an important medium parameter, the carbon-to-nitrogen (C/N) ratio (2, 5, 10, 15, and 20) on the intracellular urease activity (IUA) of ureolytic bacteria, Sporosarcina pasteurii (ATCC 11859) through experiments and analysis of a relevant genome-scale metabolic model (GSMM). A positive correlation was observed between IUA and C/N ratio until an optimal C/N ratio of 15. At a C/N ratio of 15, the IUA was 29.5 U/(g dry-cell-weight). Further, the ammonium (nitrogen waste) generation decreased by 7.7-fold at the optimal C/N ratio of 15 compared to that at 2, which is environmentally significant. Despite the decrease in initial urea concentration with an increasing C/N ratio, no decline in the biomass was observed, which is advantageous. Analysis of the GSMM provided the insights that the optimal C/N ratio of 15 also ensures an efficient bio-mineralization process and that increasing the ratio beyond 15 may negatively impact bio-mineralization. The results will be of significance while selecting a low-cost medium for field-scale MICP applications.

Enzyme-induced carbonate precipitation utilizing fresh urine and calcium-rich zeolites

Enzyme-induced carbonate precipitation (EICP) is a biocementation technique that produces comparatively fewer carbon dioxide emissions than traditional cementation. However, the use of synthetic reagents for EICP is costly, and the process produces an ammonium byproduct that is a water pollutant. This study utilized fresh human urine as a source of urea and calcium-rich zeolites as an ammonium adsorbent and a source of calcium ions for the EICP cementation technique. Batch hydrolysis, adsorption, and biocementation experiments were conducted to determine the effects of zeolite type, zeolite form (i.e., exchangeable ion), ammonium adsorption, and calcium release. The results showed that calcium-rich chabazite adsorbed comparable ammonium ions and released 2.7-times more calcium ions on average than calcium-rich clinoptilolite; calcium-rich chabazite also released calcium ions in excess without the addition of calcium chloride in solution. Additionally, synthetic-fresh urine and real-fresh urine had comparable ammonium adsorption and calcium release trends. Finally, inclusion of a pre-hydrolysis step reduced the ammonium adsorption by 3.9-times; additionally, longer adsorption times led to CaCO3 precipitation outside of the sand column, which is an undesirable outcome for soil biocementation. Even with this limitation, the CaCO3 content of sand columns ranged from 0.48% to 0.92%, which signifies the potential of the proposed process for cementation, given a higher initial concentration of urea. The results from this work show the ability to use both a waste stream, human urine, and a naturally occurring material, zeolites, to greatly reduce the economic and environmental stressors of conventional soil binders for applications such as liquefaction mitigation (e.g., Portland cement) and dust suppression (e.g., synthetic polymers).

Electrochemical removal of urea from wastewater by anodic oxidation using a new cell design: An experimental and modeling study

Chlorine-mediated electrochemical urea oxidation was investigated using a new electrochemical cell design with horizontally oriented electrodes. By virtue of the novel electrode configuration, the new electrochemical cell is self-stirred by the H2 bubbles evolving at the cathode surface and contains a built-in cooler to remove excess heat generated during electrolysis. The effect of current density, pH, NaCl concentration and initial urea concentration on the urea removal and specific electrical energy consumption were investigated. The % urea removal ranged from 55% to 90% depending on the operating conditions. The rate of urea removal increased with increasing current density and NaCl concentration, while increasing the solution pH and initial urea concentration were found to decrease the rate of removal. Energy consumption decreased with increasing NaCl concentration and increasing initial urea concentration. A kinetic approach and response surface methodology were used to model the temporal profile of urea oxidation and to optimize the process variables. After 33.4 min of electrolysis of a solution containing 348.6 ppm urea, 3% NaCl concentration and an initial pH of 5.6 using an applied current density of 4.6 mA/cm2 (2.6 A), 73.8% urea removal could be achieved with an extremely low energy consumption of 9.58 kW hkg urea. The influential priorities of the five operating parameters on % urea removal and specific energy consumption were different. The obtained results revealed that the use of kinetic and statistical modeling is an adequate approach to optimize the process variables of electrochemical urea degradation.

Sustainable recovery of plant essential Nitrogen and Phosphorus from human urine using industrial coal fly ash

Coal-based thermal power plants play a pivotal role in meeting global energy demand. The amount of fly ash generated from these plants increases every year, and its successful use has posed a significant environmental risk in the last decade. In this study, coal fly ash was packed in a fixed-bed adsorption column to remove Urea–N from synthetic human urine. To assess the efficacy of fly ash in the removal of Nitrogen, various process parameters were tested, including initial urea concentration in urine (20, 40, 60%), fly ash loading in column (100, 150, 200 g), and urine flow rate through the column (2, 4, 6 L h−1). The initial urea concentration and bed height were found to have a major impact on nutrient recovery. Following nitrogen removal, the effluent urine was de-phosphatized using struvite precipitation and approximately 83% of phosphorus was recovered. High inlet urine concentration (60%), high flow rate (6 L h−1) and minimal adsorbent loading (100 g) resulted in maximum struvite precipitation. The column breakthrough and characteristic parameters of four different models were predicted using kinetic modelling of the adsorption data, in which Yoon–Nelson and Thomas’ models suggested efficient removal and recovery of plant essential nutrients. Findings in this study suggests that the coal fly ash appears to be a promising adsorbent for extracting these important plant nutrients. The effect of initial urine concentration, fly ash loading in the column, and urine flow rate on dephospatisation was calculated. The findings of this study will shed light on the process of nutrient adsorption process selection and detail the comparative differences between continuous and batch nutrient recovery of human urine.

Preparation of microbial dust suppressant and its application in coal dust suppression

To promote the application of microbially induced carbonate precipitation (MICP) technology for coal dust suppression, two urease-producing bacteria (SZS1-3 and SZS1-5) in a coal mine soil were screened. 16 s rDNA sequencing of these bacteria indicated sequences similar to those of Acinetobacter guillouiae CIP 63.46 and Staphylococcus caprae ATCC 35538, respectively. Strains SZS1-3 and SZS1-5 had their largest urease activity at the initial urea concentration of 0.5 mol/L, under slightly alkaline (pH = 9) and neutral (pH = 7) initial pH levels, respectively. Their final mineralized products were vaterite-type and calcite-type calcium carbonate. Although dust suppression results indicated that both bacteria can effectively bind coal dust particles, consolidated coal dust treated with SZS1-5 had a stronger resistance to wind and rain. The screening, mineralization and dust suppression potential analysis of these two urease-producing bacteria can provide reference for the application of MICP technology in coal dust suppression.

Preparation protocol of urea cross-linked chitosan aerogels with improved mechanical properties using aqueous aluminum ion medium

Chitosan has drawn tremendous interest in both academic and industrial fields due to its non-toxicity, antibacterial activity, biodegradability and high biocompatibility. This work presents a method to synthesize a class of chitosan aerogels with improved mechanical properties, deriving from chitosan sols in an aqueous aluminum ion medium. The initial urea concentration had a significant effect on the microstructure of chitosan aerogels. The pores in chitosan aerogels with low concentrations were primary mesoporous, for high urea concentrations the pores were dominated by macropores. Besides, the obtained chitosan aerogels can sustain a compressive strain of 80% without fracture or cracks and recover 5–15%. Thus, this work can provide a reference for preparation of chitosan aerogels with improved mechanical properties in the future.

Assessment of a Novel Oleaginous Filamentous Microalga Klebsormidium sp. Lgx80 (Streptophyta, Klebsormidiales) for Biomass and Lipid Production1.

Commercial cultivation of eukaryotic microalgae has so far employed a unicellular form of species only (e.g., Chlorella pyrenoidosa, Dunaliella salina, and Haematococcus pluvialis). In this study, we assessed the feasibility of using the filamentous eukaryotic microalga Klebsormidium sp. LGX80 as a new cultivar for biomass and lipid production. The effects of different forms and concentrations of nitrogen on growth and lipid production of Klebsormidium sp. LGX80 were studied by using a glass column (ø4.5×60cm) photobioreactor under laboratory conditions. Growth and lipid production of the new strain were further evaluated in an outdoor pilot-scale tubular photobioreactor. The results showed that when supplied with urea as a source of nitrogen Klebsormidium sp. LGX80 yielded a final biomass concentration of 8.49±0.10g·L-1 in which a cellular lipid content was 59.2±0.4% DW. Under such conditions, the biomass and lipid productivities were 471.7±5.9 and 248.1±0.0mg·L-1 ·d-1 , respectively. Fatty acid analysis revealed that the main fatty acids of Klebsormidium sp. LGX80 were palmitic acid (C16:0), linoleic acid (C18:2ω6), and linolenic acid (C18:3ω3), of which linoleic acid (C18:2ω6) accounted for up to 67.5±0.1% of total fatty acids. When grown outdoors in a 13,000-L tubular photobioreactor with an initial nitrogen concentration of 3mM urea, Klebsormidium sp. LGX80 reached the highest biomass concentration of 2.63±0.09g·L-1 with the cells containing 38.0±0.5% lipids (% DW), resulting in the volumetric biomass and lipid productivities of 147.2±3.6 and 37.9±0.9mg·L-1 d-1 , respectively. The results of light:dark cycle experiment showed that a durative and prolonged light irradiation hindered the biosynthesis of chlorophyll a and chlorophyll b in the cells, but promoted the carotenoid accumulation. These results suggested that Klebsormidium sp. LGX80 can be a potential oleaginous filamentous microalga for commercial production of microalgal oils.

Transformation and fate of urea in pit-toilet blackwater after discharge to environment.

Studies on urea transformation reactions in blackwater are limited as urea rapidly hydrolyses under anaerobic condition. Since ammonium content of blackwater mainly originates from urine-urea, studying urea hydrolysis reactions is important to predict potential nitrate loads in aquifers from on-site sanitation facilities. In this study, urea spiked blackwater samples from pour flush pit toilet are used to examine the urea-ammonium pathways at varying initial urea concentrations and temperature. Based on laboratory results, the annual nitrate load imposed by the urea constituent of blackwater in a hard rock aquifer is predicted. Laboratory results illustrated that experimental temperature of 37 °C and pH range of 6.7 to 8.1 facilitated optimum urease enzyme activity at the initial substrate concentration of 500 mg/L. The Q10 value for urea transformation reactions indicated that increase in temperature has positive influence on enzyme activity. The reduction in urea concentration with time followed first-order kinetics. Part of ammonium ions in blackwater oxidises as nitrate ions that travel to the aquifer. Upon mixing and dilution, the nitrate concentration in 1 km2 of hard rock aquifer would annually increase by 0.004 mg/L due to blackwater infiltration from single household pour flush toilet.

Robust charge carrier by Fe3O4 in Fe3O4/WO3 core-shell photocatalyst loaded on UiO-66(Ti) for urea photo-oxidation

In this study, a facile four-step hydrothermal method was utilized to deposit a core-shell structure on UiO-66(Zr/Ti) nanoflake (NFs) as a visible-light-driven photocatalyst. The core was magnetic Fe3O4 which served as a charge carrier coated with WO3 shell. The as-prepared photocatalyst was characterized by XRD, VSM, BET, FTIR, FE-SEM, UV–Vis-DRS, and PL techniques which proved successful deposition of Fe3O4@WO3 core/shell particle on UiO-66(Zr/Ti)-NFs. The obtained photocatalyst was subsequently applied for urea photo-oxidation. This magnetically recoverable photocatalyst exhibited superior activity due to its desirable band alignment, high stability, and generation of the photo-induced charge carriers, as well as providing a high surface area with low mass transfer resistance. Fe3O4 core acted as charge-carrier to transport the photogenerated charges of UiO-66(Zr/Ti)-NFs (electron-donor) to WO3 charge-collectors for effective photoconversion. The central composite design was applied to design the experiments matrix in which flow rate, pH, irradiation time, catalyst mass, and initial urea concentration were considered as operational factors. The optimized condition was found by defining the desirability function. 90% degradation percentage was achieved at 550 mL/min solution flowrate, pH = 7, 120 min irradiation time, 0.22 g UiO-66(Zr)-NFs-Fe3O4@WO3, and 40 mg/L of the initial concentration of urea with the desirability value of 0.89. Such a superior photocatalytic activity of UiO-66-Fe3O4@WO3 can be ascribed to the reclamation of Fe3O4 as a low bandgap carrier, which accelerated the conveyance of electrons and followed surpassing charge separation. Our present findings open a new strategy to produce a wide range of core-shell heterogeneous catalysts to be applied in photoreactors scale-up.

BiFeO3–BiOI impregnation to UiO-66(Zr/Ti) as a promising candidate visible-light-driven photocatalyst for boosting urea photodecomposition in a continuous flow-loop thin-film slurry flat-plate photoreactor

The BiOI/BiFeO3/UiO-66(Zr/Ti)-MOF composite as a new ternary separable visible light photocatalyst was synthesized and well-characterized through the XRD, FE-SEM, FTIR, PL, VSM and DRS analyses. The BiOI/BiFeO3/UiO-66 photocatalytic performance for urea photo-oxidation to N2, H2O and CO2 were evaluated in a continuous flow-loop thin-film slurry flat-plate photoreactor (TFSR) equipped to blue light-emitting diodes (LEDs) illumination. Results show that the introduction of BiFeO3 perovskite and BiOI on the UiO-66(Zr/Ti) surface improves the separation and migration rate of photo-induced charges and thereby boosting the photocatalytic efficiency. Additionally, the appropriate band alignment, photo-stability and electron-hole pairs separation improvement of BiOI/BiFeO3/UiO-66(Zr/Ti)-MOF cause to enhance the urea decomposition. Moreover, five operational parameters including solution flow rate, pH, initial urea concentration, photocatalyst mass and light irradiation time were analyzed and optimized using the central composite design (CCD) and desirability function (DF), respectively. The maximum urea photocatalytic oxidation and elimination efficiency (88.53%) with the desirability value of 0.84 was achieved at the optimum conditions: 603 ​ml/min, 0.12 ​g/L, 7, 136 ​min and 60 ​ppm for flow rate, photocatalyst mass, pH, irradiation time and initial urea concentration, respectively.

Pseudo-zwitterionic microvesicles for sustained urea release

Zwitterionic microvesicles formed by catanionic system, based on sodium dodecyl sulfate and hexadecyltrimethyl ammonium bromide, have been investigated for sustained urea release using UV?visible absorption spectroscopy. The change in variables such as temperature, sonication time and initial urea concentration was related to urea entrapment efficiency and release from microvesicles. Korsmeyer?Peppas model was applied to highlight release mechanism and kinetics. Both diffusion and erosion were responsible for urea release and rate constant varied with change in conditions. The quantification of association between urea and catanionic vesicles in terms of binding constant (Kbin) and binding free energy showed that urea binding was thermodynamically favored. Our results indicate that biocompatible pseudo-zwitterionic vesicles have enormous potential to act as sustained release system for nitrogenous fertilizers such as urea.

Application of microbe-induced carbonate precipitation for copper removal from copper-enriched waters: Challenges to future industrial application

Copper contamination in watercourses is a recent issue in countries where mining operations are prevalent. In this study, the application of copper precipitation through microbe-induced carbonate precipitation (MICP) was analyzed using urea hydrolysis by bacteria to evaluate precipitated copper carbonates. This article demonstrates the application of a copper precipitation assay involving Sporosarcina pasteurii (in 0.5 mM Cu2+ and 333 mM urea) and analyzes the resultant low removal (10%). The analysis indicates that the low removal was a consequence of Cu2+ complexation with the ammonia resulting from the hydrolysis of urea. However, the results indicate that there should be a positive correlation between the initial urea concentration and the bacterial tolerance to copper. This identifies a challenge in the industrial application of the process, wherein a minimum consumption of urea represents an economic advantage. Therefore, it is necessary to design a sequential process that decouples bacterial growth and copper precipitation, thereby decreasing the urea requirement.

PENGARUH AMONIA DALAM LARUTAN TERHADAP KAPASITAS ADSORPSI UREA DENGAN KARBON BERPORI

Urea is a primary nitrogen source for plant. Conventional urea fertilizer is made from reaction between ammonia and carbon dioxide. Wastewater of urea manufacture usually contains urea ammonia in a high concentration. They can be as high as 650-4000 ppm urea and 100 – 1300 ppm ammonia/m3 wastewater. High concentrated urea and ammonia disposal to environment may lead to eutrophication in aquatic ecosystem which cause adverse impact to aquatic organism. Therefore, treatment to take urea up from urea manufacture wastewater is of interest that give double benefits : reduce urea from wastewater to meet an environmentally safe condition and obtain a low cost urea fertilizer for plant. The purpose of this study is to determine urea adsorption capacity of porous carbon in aqueous solution contains ammonia. The porous carbon as adsorbent was made from coconut shell by pyrolisis. Oxidation treatment of carbon surface was performed using sulfuric acid (50%w) at 90oC temperature for 2 hours. The adsorption was conducted at room temperature with initial urea concentration in the range of 500-8000 ppm using urea-ammonia solution as simulation liquid. Results reveal that urea adsorption capacity increase significantly 41%.in urea-ammonia solution compare to urea solution, that is in the range of 27-444 mg/g carbon.

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.

Effects of ultraviolet-enhanced ozonation on the degradation of ammonia and urea in fertilizer plant wastewater

Ammonia and urea contained in fertilizer plant wastewater are pollutants to the environment. High concentration of ammonium and urea in wastewater can affects algae blooms in the ecosystem which will generate various diseases in aquatic biota. It is known that there are many methods for degradation of ammonium and urea contained in fertilizer plant wastewater. One of the potential method is ultraviolet-enhanced ozonation. Ozonation is oxidation with O3 that generates hydroxyl radicals which subsequently react with organic contaminants, while UV irradiation can break down O3 molecules and produce radical ions OH∗. The objectives of this study were to examine the effects of the utilization of the ultraviolet-enhanced ozonation method in degradation of various initial ammonium (100-300 ppm) and urea concentration (100-300 ppm) in inlet feed of ozonation-UV irradiation combination system. Some important variables such as contact time (0-120 minutes) and ozone feed rate of 0.2, 0.6, and 1.21 g/h were evaluated. Degradation process was carried out in two steps; ozonation and UV irradiation. Ozonation process was carried out in a contacting tank at a constant feed flow rate of 1.5 l/min and at room temperature, while UV irradiation process was conducted in pipeline equipped with a UV lamp at various contact time. The ultraviolet-enhanced ozonation could degrade ammonium and urea nitrogen up to 83.6% and 63.8%, respectively, at ozone feed rate 1,21 g/h, contacting time 60 and 120 min, initial feed concentration of ammonia (100 ppm) and urea (40 ppm).

Effects of Ultraviolet-Enhanced Ozonation on Degradation of Ammonia and Urea in Fertilizer Plant Wastewater

Ammonia and urea contained in fertilizer plant wastewater are pollutants to the environment. High concentration of ammonium and urea in wastewater can affects algae blooms in ecosystem which will generate various diseases in aquatic biota. It is known that there are many methods for degradation of ammonium and urea contained in fertilizer plant wastewater. One of potential method is ultraviolet-enhanced ozonation. Ozonation is oxidation with O3 that generates hydroxyl radicals which subsequently react with organic contaminants, while UV irradiation can break down O3 molecules and produce radical ions OH∗. The objectives of this study were to examine the effects of the utilization of the ultraviolet-enhanced ozonation method in degradation of various initial ammonium (100-300 ppm) and urea concentration (100-300 ppm) in inlet feed of ozonation-UV irradiation combination system. Some important variables such as contact time (0-120 minutes) and ozone feed rate of 0.2, 0.6, and 1.21 g/h were evaluated. Degradation process was carried out in two steps; ozonation and UV irradiation. Ozonation process was carried out in a contacting tank at constant feed flow rate of 1.5 l/min and at room temperature, while UV irradiation process was conducted in pipeline equipped with UV lamp at various contact time. The ultraviolet-enhanced ozonation could degraded ammonium and urea nitrogen up to 83.6% and 63.8%, respectively, at ozone feed rate 1,21 g/h, contacting time 60 and 120 min, initial feed concentration of ammonia (100 ppm) and urea (40 ppm).

MXene Sorbents for Removal of Urea from Dialysate: A Step toward the Wearable Artificial Kidney.

The wearable artificial kidney can deliver continuous ambulatory dialysis for more than 3 million patients with end-stage renal disease. However, the efficient removal of urea is a key challenge in miniaturizing the device and making it light and small enough for practical use. Here, we show that two-dimensional titanium carbide (MXene) with the composition of Ti3C2T x, where T x represents surface termination groups such as -OH, -O-, and -F, can adsorb urea, reaching 99% removal efficiency from aqueous solution and 94% from dialysate at the initial urea concentration of 30 mg/dL, with the maximum urea adsorption capacity of 10.4 mg/g at room temperature. When tested at 37 °C, we achieved a 2-fold increase in urea removal efficiency from dialysate, with the maximum urea adsorption capacity of 21.7 mg/g. Ti3C2T x showed good hemocompatibility; it did not induce cell apoptosis or reduce the metabolizing cell fraction, indicating no impact on cell viability at concentrations of up to 200 μg/mL. The biocompatibility of Ti3C2T x and its selectivity for urea adsorption from dialysate open a new opportunity in designing a miniaturized dialysate regeneration system for a wearable artificial kidney.