Removal Of Urea Research Articles

Double-Layered Electrospun Nanofiber Filter for the Simultaneous Removal of Urea and Ammonium from Blood.

A major challenge in the development of wearable artificial kidneys (WAKs) lies in the efficient removal of urea, which is found at an extremely high concentration in the blood of patients with chronic kidney disease (CKD). Urease is an enzyme that hydrolyzes urea. While it can efficiently remove urea, toxic ammonium is produced as a byproduct. In this study, nanofibers capable of removing both urea and ammonium from the blood were fabricated. Specifically, urease was immobilized on electrospun poly(ethylene-co-vinyl alcohol) (EVOH)/chitosan nanofiber membranes via covalent cross-linking. Chitosan not only helped covalent immobilization via its free amino groups but also improved hemocompatibility by suppressing protein adhesion. The resulting urease-immobilized EVOH/chitosan nanofibers exhibited an outstanding urea removal performance of 690 mg/g per hour. For ammonium removal, EVOH nanofiber membranes containing sodium cobalt(II) hexacyanoferrate(II) (NaCoHCF), an ammonium adsorbent, were prepared. The fabricated EVOH/NaCoHCF membranes exhibited an ammonium adsorption capacity of 135.5 mg/g. The two types of nanofiber membranes were combined to form a double-layered nanofiber membrane that was placed in a filter holder for continuous-flow cycling experiments. Under such conditions, all urea at a concentration similar to that in the blood of CKD patients was degraded within 1 h, and ammonium production was reduced by approximately 90% of the normal level. This double-layered nanofiber membrane can achieve both urea degradation and ammonium adsorption and is expected to advance the development of WAKs, a game changer in the treatment of CKD.

Characterization of New Experimental Materials for Hemodialysis Membranes and Simulation of Urea Dialysis Process with Their Use

The acute shortage of hemodialysis cartridges in Russia, caused by restrictions imposed by the European Union on the supply of high-tech equipment, has led to the nessesity for the production of domestic inexpensive and effective membranes for hemodialysis. In this work, experimental membranes based on polysulfone were obtained and their characterization was carried out. The influence of the blowing agent (polyethylene glycol and polyvinylpyrrolidone) on the structure and transport properties of the obtained membranes was compared. A non-steady state one-dimensional mathematical model of urea dialysis is proposed. A special feature of the model is the accounting the membrane microheterogeneous structure. A comparison of the modeling results with experimental data on the urea concentration time dependences in the dialysate compartment of the dialysis system allows us to conclude that the model adequately describes the system under study. A theoretical assessment of the obtained membrane material efficiency under conditions corresponding to the hemodialysis process, as well as a comparison of urea removal performance with Nephral ST hemodialysis cartridges from Baxter (a company widely represented on the world market) was carried out. It was shown that a polysulfone-based membrane obtained using polyvinylpyrrolidone demonstrates results slightly inferior to those of commercially produced cartridges, which indicates its promise for the production of hollow fiber membranes for hemodialysis cartridges.

Enrichment of marine microbes to remove nitrogen of urea wastewater under salinity stress

Salinity (NaCl) and urea concentration significantly affect the diversity, structural and physiological function of microbial communities in the biological treatment of wastewater. However, the responses of microbial in high salt and urea wastewater remain elusive. Here, we investigated microbial community function and assembly of four regions using gradient domestication experiment combined with 16S rRNA gene sequencing and statistical methods. The results showed that with the increase of salinity and urea concentration, the consortium Xiamen could still remove most urea, while the other three consortia could not. The alpha diversity of microbial community initially decreased and then increased, showing a recovery trend. After domestication, the consortium Xiamen exhibited high physiological activity and complex network structure, and the community assembly process changed from stochastic to deterministic during the domestication. Furthermore, the keystones with low abundance were associated with urea removal and important for maintain the complexity of the networks, while Arenibacter and Oceanimonas were found to be keystones in maintaining efficient urea removal in harsh environments. To sum up, environmental effects dominated by salinity and urea concentration stress drove the community assembly and species coexistence that underpinned the microbial differentiation pattern at a geographic scale. These results provided new sights for elucidate how microbial response to salinity and urea during wastewater treatment.

Treatment of Organic Pollutant by Advanced Oxidation Processes

The investigation involved the oxidation of urea (UR) in a batch reactor, employing Fenton's reagent. Various parameters, namely reaction time, pH level, ferrous ion dose, and hydrogen peroxide dose, were scrutinized. The reaction time spanned from 30 minutes to 3 hours, revealing a notably positive impact. An optimal pH of 3 was identified for the medium. The concentrations of ferrous ions ranged from 0.2 g/l to 0.53 g/l, with hydrogen peroxide levels ranging from 1 g/l to 2.65 g/l. The impact of hydrogen peroxide was notably significant at a ferrous ion concentration of 0.3 g/l and a pH of 3. Evaluating urea removal efficiency through chemical oxygen demand (COD) calculations showed a maximum efficiency of 86.8%, with a minimum ammonia yield of 6%. Overall, the outcomes underscored the efficacy of the Fenton process in urea treatment.

Testing of various membranes for removal of chemical oxygen demand in real fresh human urine using a cross-flow filtration system

ABSTRACT Urine is primarily composed of water (about 95%), with urea (around 2%), creatinine (approximately 0.1%), uric acid (about 0.03%), and various ions. Although human urine constitutes 1% of the volume of domestic wastewater, it contains significant amounts of chemical oxygen demand (COD) (∼10%). This study focused on the elimination of COD in urine using a cross-flow filtration system and testing the effectiveness of various membranes (microfiltration (MCE01), ultrafiltration (UP005 and UP010), and nanofiltration (NP010 and NF270)). The steady-state flux of the NF270 membrane increased from 10.8 to 23.9 L/m2/h as the pressure increased from 10 to 25 bar. A significant COD removal efficiency was obtained for the NF270 membrane at an operating pressure of 25 bar. COD concentration decreased from 7,392 to 1,270 mg/L with 82.8% rejection. In contrast, none of the membranes performed well in terms of urea removal efficiency. According to the findings, urea concentration decreased from 6,712 to 6,043 mg/L with 9.9% rejection. Moreover, ion contents (calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), ammonium (NH4+), phosphate (PO43−), sulfate (SO42−), and chloride (Cl−)) of the membrane permeates were also measured.

Insight into simultaneous urea hydrolysis and total nitrogen removal in textile printing wastewater: Focus on the impact of sodium sulfate salinity

The textile printing industry discharges large volumes of effluent containing high concentrations of urea and nitrogenous compounds. Anoxic-oxic (AO) treatment is a promising method for treating printing wastewater. However, the effect of sodium sulfate (Na2SO4) salinity on the urea hydrolysis and nitrogen removal simultaneously in the AO process has received little attention. In this study, five batch reactors were used to treat synthetic printing wastewater with high urea and nitrogen concentrations. A strategy was applied to increase the Na2SO4 concentration from 0 to 19 g/L in the anoxic stage of each reactor. The effect of Na2SO4 on urea hydrolysis, total nitrogen removal and COD removal, sludge characteristics, and bacterial community structure were investigated. The findings showed that urea hydrolysis increased with increasing Na2SO4 concentration. The main mechanism of urea removal was intracellular hydrolysis, with a urea removal efficiency (URE%) of approximately 98% in all batch reactors. In addition, under the stress of Na2SO4, the total nitrogen and COD removal performances were partially inhibited. The most significant removal performances after AO treatment were observed at 0 g/L Na2SO4, with nitrogen and COD removal efficiencies of 88% and 95%, respectively. When Na2SO4 concentration reached 19 g/L, the sludge settling performance and compactness were enhanced. The extracellular polymeric substance (EPS) components in the sludge were dependent on their ability of removing organics. Bacterial community diversity analysis revealed that the enrichment of the Proteobacteria, Firmicutes, and Gemmatimonadota phyla in the anoxic stages of batch reactors was related to intracellular urea hydrolysis. Bacteriodota and Chloroflexi were responsible for total nitrogen removal in all anoxic and oxic stages. This research will develop the understanding of Na2SO4 salinity impact on simultaneous urea hydrolysis and nitrogen removal during AO treatment process.

Sustainable urea treatment by environmental-friendly and highly hydrophilic vesicle-like iron phosphate-based carbon

Despite the versatile potential applications of urea, its unfavorable characteristics for conventional treatment methods hinder its utilization. Therefore, this study developed vesicle-like iron phosphate-based carbon (IP@C400) as a breakthrough urea removal and recovery material for a wide range of urea-containing sources. IP@C400 rapidly exhibited an exceptional capacity (2242 mg/g in 1 h) across a wide range of pH, even in synthetic hemodialysis wastewater with high urea concentrations and diverse co-existing components, compared with the 60 prominent adsorbents. The adsorption process followed dual Pseudo-kinetic, Langmuir-isotherm models with the involvement of primary robust physical (i.e., H-bonding and electrostatic interaction) and chemical mechanisms (i.e., hydrolysis). Remarkably, IP@C400 can maintain high urea removal (90 %) or recovery efficiency (95 %) even after 10 cycles with minimal leakages of Fe and P (far below WHO and EUWFD standards)—a significant improvement over disposable options. IP@C400 could also perform efficiently on batch and a new approach integrating with a naturally accessible material based on the fixed-bed column using low-range urea realistic samples, achieving 65.2 L water over 10 cycles with undetected urea, neutral pH, and well-aligned water safety standards with a minimal adsorbent dose (0.1 g.L−1) and economical cost ($0.05 L-1). Lastly, its environmentally friendly nature, which contains essential nutrients for plant growth, further enhances its recyclability after release. Thus, IP@C400 offers a solution to environmental sustainability and the urgent ultrapure water issue that industries are facing.

Catalytic urea electrooxidation on nickel‐metal hydroxide foams for use in a simplified dialysis device

AbstractElectrocatalytic urea removal is a promising technology for artificial kidney dialysis and wastewater treatment. Urea electrooxidation was studied on nickel electrocatalysts modified with Cr, Mo, Mn, and Fe. Mass transfer limits were observed for urea oxidation at physiological concentrations (10 mmol L). Urea oxidation kinetics were explored at higher concentrations (200 mmol L), showing improved performance, but with lower currents per active site. A simplified dialysis model was developed to examine the relationship of mass transfer coefficients and extent of reaction on flowrate, composition, and pH of the reacting stream. For a nickel hydroxide catalyst operating at 1.45 V, 37 , and pH 7.1, the model shows a minimum geometric electrode area of 1314 cm2 is needed to remove 3.75 g urea h with a flow rate of 200 mL min for continuous operation.

Effective Ethyl Carbamate Prevention in Red Wines by Treatment with Immobilized Acid Urease.

Climate change poses several challenges in the wine industry, including increasing risks related to chemical food contaminants such as biogenic amines and ethyl carbamate (EC). In this work, we focused on urea removal in red wines by immobilized acid urease aiming at limiting EC formation during wine storage. By considering separable kinetics of catalyst deactivation and urea hydrolysis, it was possible to model the time course of urea removal in repeated uses in stirred batch reactors. Treatments based on immobilized urease of red wine enriched with 30 mg/L of urea allowed the reduction in the contaminant concentration to <5 mg/L. After 28.5 h of treatment, the observed urea level was reduced to about 0.5 mg/L, corresponding to a decrease in the potential ethyl carbamate (PEC) from 1662 μg/L to 93 μg/L, below the level of the non-enriched wine (187 μg/L). As a comparison, when treating the same wine with the free enzyme at maximum doses allowed by the EU law, urea and PEC levels decreased to only 12 mg/L and 415 μg/L respectively, after 600 h of treatment. These results show that, for red wines, urease immobilization is an effective strategy for urea removal and, thus, effective reduction in ethyl carbamate as a process contaminant. This study provides the scientific background for the future scaling-up of the process at an industrial level.

Immobilized Urease Vector System Based on the Dynamic Defect Regeneration Strategy for Efficient Urea Removal.

The clearance of urea poses a formidable challenge, and its excessive accumulation can cause various renal diseases. Urease demonstrates remarkable efficacy in eliminating urea, but cannot be reused. This study aimed to develop a composite vector system comprising microcrystalline cellulose (MCC) immobilized with urease and metal-organic framework (MOF) UiO-66-NH2, denoted as MCC@UiO/U, through the dynamic defect generation strategy. By utilizing competitive coordination, effective immobilization of urease into MCC@UiO was achieved for efficient urea removal. Within 2 h, the urea removal efficiency could reach up to 1500 mg/g, surpassing an 80% clearance rate. Furthermore, an 80% clearance rate can also be attained in peritoneal dialyzate from patients. MCC@UiO/U also exhibits an exceptional bioactivity even after undergoing 5 cycles of perfusion, demonstrating remarkable stability and biocompatibility. This innovative approach and methodology provide a novel avenue and a wide range of immobilized enzyme vectors for clinical urea removal and treatment of kidney diseases, presenting immense potential for future clinical applications.

Thermal Vapor Deposition of a Hydrophobic and Gas-Permeable Membrane on Zirconium Phosphate Cation Exchanger: An Oral Sorbent for the Urea Removal of Kidney Failure.

An oral sorbent with high capacity for NH4+ is desirable in lowering the blood urea level and mitigating the dialysis burden for end-stage kidney disease (ESKD) patients. Zirconium phosphate (ZrP) is an amorphous cation ion exchanger with high NH4+ binding capacity as a sorbent material, but its selectivity to remove NH4+ is limited in the presence of other competing ions in water solution. We previously have developed a gas-permeable and hydrophobic perfluorocarbon coating on ZrP, which improves ZrP's NH4+ selectivity. However, the coating preparation procedure, a wet chemistry approach, is complicated and time-consuming, and more importantly, the large amount of usage of acetone poses a concern for the application of ZrP as an oral sorbent. In this study, we developed a solventless coating protocol that effectively coats ZrP with tetraethyl orthosilicate (TEOS) and 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FOTS) via thermal vapor deposition (TVD) in a simplified manner. X-ray photoelectron spectroscopy (XPS) and contact angle measurements verify the two coatings are successfully deposited on the ZrP surface, and the coating condition was optimized based on an in vitro static binding study. The dynamic binding study of competing ions on Na-loaded ZrP with TVD coatings yields a maximum NH4+ removal (∼3.2 mequiv/g), which can be improved to ∼4.7 mequiv/g if H-loaded ZrP under the same coating condition is used in basic stock solutions. More importantly, both materials barely remove Ca2+ and show excellent acid resistance. The significant improvement in the NH4+ binding capacity and selectivity reported here establishes a highly promising surface modification approach to optimize oral sorbents for ESKD patients.

Can one long peritoneal dwell with icodextrin replace two short dwells with glucose?

Due to the slower dissipation of the osmotic gradient, icodextrin-based solutions, compared to glucose-based solutions, can improve water removal. We investigated scenarios where one icodextrin-based long dwell (Extraneal) replaced two glucose-based exchanges. The three-pore model with icodextrin hydrolysis was used for numerical simulations of a single exchange to investigate the impact of different peritoneal dialysis schedules on fluid and solute removal in patients with different peritoneal solute transfer rates (PSTRs). We evaluated water removal (ultrafiltration, UF), absorbed mass of glucose (AbsGluc) and carbohydrates (AbsCHO, for glucose and glucose polymers), ultrafiltration efficiency (UFE = UF/AbsCHO) per exchange, and specified dwell time, and removed solute mass for sodium (ReNa), urea (ReU), and creatinine (ReCr) for a single peritoneal exchange with 7.5% icodextrin (Extraneal®) and glucose-based solutions (1.36% and 2.27%) and various dwell durations in patients with fast and average PSTRs. Introducing 7.5% icodextrin for the long dwell to replace one of three or four glucose-based exchanges per day leads to increased fluid and solute removal and higher UF efficiency for studied transport groups. Replacing two glucose-based exchanges with one icodextrin exchange provides higher or similar water removal and higher daily sodium removal but slightly lower daily removal of urea and creatinine, irrespective of the transport type present in the case of reference prescription with three and four daily exchanges. One 7.5% icodextrin can replace two glucose solutions. Unlike glucose-based solutions, it resulted only in minor differences between PSTR groups in terms of water and solute removal with UFE remaining stable up to 16h.

A novel route for urea abatement in UPW production: Pre-chlorination/VUV/UV under acidic circumstances and its enhancement mechanisms

Urea abatement has been a prominent challenge for UPW production. This research proposed a productive strategy combining pre-chlorination and VUV/UV processes under acidic conditions to settle this problem. This study first revealed the reaction kinetics between urea and free chlorine in a large pH range from 2.5 to 9.6, where the reaction constant rate varied from 0.06 to 0.46 M−1·s−1. Substitution reaction mediated by Cl2 was the dominant process at low pH (pH<3). The differences of dominant pathways resulted in the differences in reaction products: The detected concentration of dichloramine at pH 2.5 was twice that at pH 4.5 and 6.5. Further, this study found that pre-chlorination/VUV/UV process could achieve the thorough removal of 2-mg/L urea with chlorination of less than 5 min and VUV/UV irradiation of less than 200 mJ/cm2. Chloride ions, low pH, and higher chlorine dosage were found to be the positive factors to improve urea removal efficiency in pre-chlorination/VUV/UV process. The reaction rate constants between chlorourea with·OH and·Cl were calculated to be 3.62 × 107 and 2.26 × 109 L·mol−1·s−1, respectively.·Cl,·OH and photolysis contributed 60.5 %, 22.9 % and 16.6 % in chlorourea degradation, respectively. Pre-chlorination/VUV/UV achieved a DOC removal efficiency of 78.5 %. And nitrogen in urea was converted into inorganic nitrogenous compounds. Finally, compared with direct VUV/UV/chlorine and VUV/UV/persulfate processes, this process saved more than 70 % of energy in VUV/UV unit.

Linker-induced hollow MOF embedded into arginine-modified montmorillonite for efficient urea removal: Adsorption behavior and mechanism analysis

The precise regulation of hollow metal–organic framework (HMOF) and the effective assembly with excellent guest materials present limitless potential for pollutant removal. In this work, the arginine-modified montmorillonite (AMMT) was preferentially prepared via room temperature impregnation approach, and then the AMMT-HMOF composite was effectively constructed through a one-pot method. During this process, linker-induced MOF to MOF route was proposed, i.e., solid ZIF-67 transformed into hollow MOF-74 (thicknesses: ∼25 nm). Of note, this route involves the transition from solid to hollow structures, as well as the change between different topologies. Next, the AMMT-HMOF composite was evaluated for adsorption experiments with urea in aqueous solution as the target molecule. Further speaking, the optimization experiments were conducted to analyze the impact of pH, contact time, adsorbent mass and original urea concentration towards the adsorption process. The as-fabricated absorbent presented a maximum adsorption capacity of 298.5 mg/g within 1 h, demonstrating adherence to pseudo-second-order kinetics and the Langmuir model. The excellent adsorption performance can be ascribed to the enlarged layer spacing of AMMT, as well as the fast mass transport and abundant diffusion channels in HMOF. Additionally, the mechanistic analyses revealed the existence of hydrogen bonding interactions between the adsorbent and urea. Meanwhile, the adsorbent displayed the outstanding morphological and structural stability after usage. According to our survey, this is the first time to use this linker-induced MOF-to-MOF strategy and predictably assemble with functionalized montmorillonite to construct the hollow MOF composite for urea adsorption.

#1744 Characteristics of patients on long-term dialysis for more than 30 years in our hospital

Abstract Background and Aims In Japan, the prognosis of dialysis patients has improved over the years. The number of patients on dialysis for more than 20 years dramatically increased from less than 1% in 1992 to 8.6% in 2021. We analyzed the factors that contribute to the prolonged prognosis of dialysis patients. Method Of our 117 maintenance dialysis patients, we examine the dialysis profile of 26 (22.2%) long-term dialysis patients who have been on dialysis for more than 30 years. Results The mean age of dialysis induction is 32 years (13-55, ±10), the mean age is 71 years (46-87, ±9), and the longest duration of dialysis is 42 years. 12 patients are male. The majority cause of hemodialysis in them is chronic glomerulonephritis (22 patients). In addition, there are no patients with diabetes complications, 4 patients with hypertension, and 2 patients with coronary artery disease. 12 patients have carpal tunnel syndrome or destructive spondyloarthropathy. On-line HDF is generally used in 19 patients, mean blood flow is 215 ml/min (180-260, ±24), and mean dialysis time is 4.2 hours (3.5-5.0, ±0.4). Mean Kt/V is 1.76 (0.97-2.23, ±0.30), urea removal rate is 75.1% (57.8-84.2, ±6.6), β2-microglobulin is 23.8 μg/L (12.9-31.0, ±5.0). Mean DW is 51.0 kg (36.8-67.0, ±9.2), body mass index is 20.3 kg/m2 (16.1-24.4, ±2.5). Mean inter-dialysis weight gain is DW × 3.5% (2.9-4.9, ±0.9), nPCR is 0.9 g/kg/day (0.6-1.3, ±0.2), mean Albumin is 3.7 g/dl (3.2-4.4, ±0.3), whole-PTH is 160.4 pg/mL (0.0-902.7, ±178.8), Hemoglobin is 10.2 g/dL (7.8-13.9, ±1.4), 4 patients don't use ESA products. Conclusion According to the Japanese statistical survey of dialysis patients in 2020, 2.3% of the patients have been on dialysis for more than 30 years, which means that our hospital has a larger rate of long-term dialysis patients. These patients exceed the Japanese average in terms of both nutritional status and dialysis efficiency. The reasons for this may include the fact that our patients were on dialysis for at least 4 hours, and we intended to adhere to very mild dietary restrictions, specifically, the same diet as the family and that we did not recommend a low-protein diet.

Thin-Film Nanocomposite Membranes Functionalized with Fe-Based Metal–Organic Frameworks for Enhanced Removal of Urea from Water

Thin-Film Nanocomposite Membranes Functionalized with Fe-Based Metal–Organic Frameworks for Enhanced Removal of Urea from Water

Powdered activated carbon (PAC)-assisted peroxymonosulfate activation for efficient urea elimination in ultrapure water production from reclaimed water

Urea is a problematic pollutant in reclaimed water for ultrapure water (UPW) production. The sulfate radical-based advanced oxidation process (SR-AOP) has been recognized as an effective method for urea degradation. However, conventional metal-based catalysts for peroxymonosulfate (PMS) activation are unsuitable for UPW production due to issues related to metal ion leaching. In this study, the use of powdered activated carbon (PAC) was investigated for the removal of urea from reclaimed water. The PAC exhibited a high degree of defects (ID/IG = 1.709) and various surface oxygen functional groups (C–OH, C=O, and C–O), which greatly enhanced its catalytic capability. The PAC significantly facilitated PMS activation in the PMS + PAC system, leading to the complete urea decomposition. The PMS + PAC system demonstrated excellent urea removal efficiency within a wide pH range, except for pH < 3. Among the various anions present, the CO32− and PO43− inhibited urea degradation, while the coexistence of Cl− promoted urea removal. Furthermore, the feasibility test was evaluated using actual reclaimed water. The quenching test revealed that SO4−·, ·OH, and O2−· played crucial roles in the degradation of urea in the PAC-assisted SR-AOP. The oxygen functional groups (C–OH and O–C=O) and defect sites of PAC clearly contributed to PMS activation.

Removal of urea in ultrapure water system by urease-coated reverse osmosis membrane

Among the various substances found in the feed source for the production of ultrapure water (UPW), urea is challenging to remove because it is a small molecular weight molecule that is not easily oxidized and does not carry a charge under neutral pH conditions. Urease enzyme, found in various organisms such as plants and bacteria, catalyze the hydrolysis of urea into carbon dioxide and ammonia. In this study, urease was immobilized on the polyamide layer of a reverse osmosis (RO) membrane to remove urea in UPW systems. The removal efficiency of urea by urease-coated RO membrane showed up to 27.9 % higher urea removal efficiency compared to the pristine membrane. This increase in urea removal can be attributed to both physical and biological effects from the urease coating on the membrane. Firstly, urease on the membrane surface can act as an additional physical barrier for urea to pass through. Secondly, urea can be hydrolyzed by the enzyme when it passes through the urease-coated RO membrane. In a two-pass RO system typical for UPW production, the removal of urea by a urease-coated membrane would be enhanced by twofold. This overall method can significantly increase the removal efficiency of urea in UPW systems, especially when considering the compounded removal by the urease coating, rejection by RO, and additional reactions by other treatment processes. Moreover, urea in UPW systems can be removed without the installment of additional processes by simply coating urease on the existing RO membranes.

Synergistic Adsorptive Removal of Urea from Agricultural Effluents Using Ball Clay and Sepiolite Composite

Agriculture effluents have become a big problem since water is the basic component of all operation in agriculture practice. These effluents composed of agrochemicals such as fertilizer, pesticides, herbicides, crop residues are the pollutants of agricultural effluents. Lakes, rivers and streams often receives water run-off from farmlands. Nitrates and urea in the water bodies are toxic to aquatic lives by causing depletion of oxygen in water making it unfit for human and aquatic life. This research assessed the adsorptive removal of urea from agricultural effluent by means of thermally activated ball clay and sepiolite composite (TABCSC) and non-activated ball clay and sepiolite composite (NABCSC) as absorbent. The adsorption process was done at Varying amounts TABCSC (0.6g - 4.5g), pH range of 3 - 11, time (30 - 90 minutes) and temperature (25 – 45°C) as recommended by design expert version 13. TABCSC and NABCSC characterized by means of Fourier transformed infrared spectroscopy (FTIR) and scanning electron microscope (SEM) reveals the presence of large surface area, porosity as well as the functional groups: hydroxyl, carboxylic, hydrogen bonding and aldehyde group that aids adsorptive removal of urea. The highest adsorptive removal efficiency by TABCSC was found to be 99.23% (at pH = 7, temperature = 25°C, dosage = 0.6 g and time = 60 minutes) while that of NABCSC was at 93.23% (at pH = 11, temperature = 35°C, dosage = 0.6 g and time = 60 minutes). The adsorptive removal of urea was found to increase with increase in pH value and contact time. The adsorptive removal mechanism of Urea by TABCSC was more fitting to the second order kinetics (R2 = 0.9770) while removal by NABCSC aligns with the pseudo first order kinetics (R2 = 0.9770). The isotherm of the removal process conforms more to the Freundlich isotherm of TABCSC (R2 = 0.9995) and NABCSC (R2 = 0.9671) respectively.

Urease immobilized poly(AAm-AGE) cryogel for depletion of urea from human serum

Polyacrylamide-allyl glycidyl ether [poly(AAm-AGE)] cryogel monolith was prepared for covalent immobilization of urease enzyme and aimed for usage of urea depletion from human serum by immobilized urease. Immobilization was succeeded via epoxy groups of allyl glycidyl ether with an immobilization yield of 71.9 ± 2.65%. Characterization was performed by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray (EDX) analysis and swelling analysis to reveal functionalities and morphological, elemental and macroporous structure of the cryogel. Effects of pH, temperature and urea concentration on catalytic activity profiles of free and immobilized urease were investigated. Thermal and storage stabilities of free urease were enhanced upon immobilization. Additionally, urea removal from artificial human serum was achieved by 92% and immobilized urease was reusable up to ten reuses.