Adsorption Of Urea Research Articles

Adsorption of urea, creatinine, and uric acid from three solution types using spherical activated carbon and its recyclability

In this paper, we propose that the urinary toxins from the wastewater be adsorbed on an adsorbent such as spherical activated carbon and the latter be regenerated by subjecting it to high temperatures to recycle activated carbon and also to recycle the water used in dialysis. We studied the adsorption of artificial waste dialysate, which is a mixed solution of urea, creatinine, and uric acid, and the separate solutions for each of these and found that their extents of adsorption onto the spherical activated carbon material were nearly identical. The amount of adsorption was approximately 1.4 mg·g −1 for urea, 18 mg·g −1 for creatinine, and 20 mg·g −1 for uric acid. The urea, creatinine, and uric acid adsorbed onto the spherical activated carbon decomposed on heat treatment at 500 °C, and the adsorption capacity of the spherical activated carbon was regenerated. Our study successfully demonstrated that the spherical activated carbon can be recycled in the waste dialysate treatment process.

Adsorption of urea, creatinine, and uric acid onto spherical activated carbon

This study primarily aims to understand the adsorption mechanism of urea, creatinine, and uric acid on spherical activated carbon. The adsorption of urea, creatinine, and uric acid onto spherical activated carbon underwent with a pseudo-second-order rate and in accordance with the Halsey formula. The adsorption of urea may have occurred because of interaction between the urea dipole and the dipole induced in the porous surface by the urea as well as because of dipole–dipole interaction between surface oxygen groups on the spherical activated carbon surface and the urea. The interaction among urea molecules, such as hydrogen bonding, induced multilayer adsorption. The adsorption model of creatinine was similar to that of urea. Because uric acid molecules are very strongly hydrophobic, their adsorption onto spherical activated carbon is caused by attractive forces between the hydrophobic surface of activated carbon and the similarly hydrophobic uric acid molecules, in addition to van der Waals forces. Moreover, uric acid molecules adsorbed onto spherical activated carbon and uric acid molecules in water are considered to undergo additional multilayer adsorption because of hydrophobic interactions.

Catalyst-Electrolyte Interactions in Aqueous Reline Solutions for Highly Selective Electrochemical CO2 Reduction.

Achieving high product selectivities is one challenge that limits viability of electrochemical CO2 reduction (CO2 R) to chemical feedstocks. Here, it was demonstrated how interactions between Ag foil cathodes and reline (choline chloride + urea) led to highly selective CO2 R to CO with a faradaic efficiency of (96±8) % in 50 wt % aqueous reline at -0.884 V vs. the reversible hydrogen electrode (RHE), which is a 1.5-fold improvement over CO2 R in KHCO3 . In reline the Ag foil was roughened by (i) dissolution of oxide layers followed by (ii) electrodeposition of Ag nanoparticles back on cathode. This surface restructuring exposed low-coordinated Ag atoms, and subsequent adsorption of choline ions and urea at the catalyst surface limited proton availability in the double layer and stabilized key intermediates such as *COOH. These approaches could potentially be extended to other electrocatalytic metals and lower-viscosity deep eutectic solvents to achieve higher-current-density CO2 R in continuous-flow cell electrolyzers.

Polysulfone/amino-silanized poly(methyl methacrylate) dual layer hollow fiber membrane for uremic toxin separation

A new strategy to recycle dialysate within a system is needed to foster the progress of developing wearable artificial kidney as an alternative to conventional hemodialysis practices. This study presents an attractive approach to collectively remove uremic toxins by combining membrane filtration and adsorption process. In this work, dual layer hollow fiber (DLHF) membranes consisting of polysulfone (PSf) inner layer well attached to PSf/amino-silanized poly(methyl methacrylate (N-PMMA) outer layer were prepared via co-extrusion spinning process based on non-solvent induced phase separation. The PSf/N-PMMA DLHF membranes were characterized and evaluated in terms of urea adsorption capacity and filtration performance. It was revealed that the urea adsorption onto N-PMMA is a non-spontaneous physical process that follows Freundlich isotherm model and pseudo-second-order kinetic model. Results showed that the membrane exhibited urea adsorption capacity of up to 27.6 mg/g depending on N-PMMA content. Under dynamic filtration condition, the membranes demonstrated significant urea removal (39.2%) and showed desired sieving characteristics for other solutes. The design of DLHF membrane with adsorptive property is an exciting prospect that would become a key solution for dialysate regeneration.

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.

Comparative study on the urea removal by different nanoporous materials

The current hemodialysis system is not efficient in removing uremic toxins, especially urea. Huge amount of fresh dialysate is required for a dialysis treatment. Poor uremic toxins removal result in toxic waste accumulation in the patients’ bodies, which would lead to cardiovascular diseases and death. Nanoporous materials with excellent pore characteristics and adsorption capacity could be introduced to the hemodialysis system to enhance the urea removal efficiency and regenerate the dialysate. In this study, the viability of using nanoporous materials i.e., oil palm biomass-based activated carbon and mesoporous silica for urea removal was explored. Results indicate that the sulfuric acid-treated activated carbon fiber, palm kernel shell-based activated carbon and amine functionalized silica yielded high urea adsorption capacity. The presence of surface functional groups and excess surface area facilitated the urea adsorption by the synthesized nanoporous materials.

Enhanced adsorption and removal of urea from aqueous solutions using eco-friendly iron phosphate nanoparticles

This work reports of using iron phosphate nanoparticles (nano-FePh) as adsorbent for removing urea. Hence, the adsorption of urea on nano-FePh was investigated as a function of reaction time, temperature, catalyst weight, shaking speed and solution pH. Amorphous iron phosphate is synthesized by a cost-effective method reflux. The nano-FePh is characterized by different techniques including; X-ray diffraction (XRD), transmission electron micrograph (TEM), field-emission scanning electron microscopy (FE-SEM), energy dispersive X-Ray Spectroscopy (EDX), FT-IR and BET surface area determination. Highest adsorption extent obtained at pH range of 7–9 with uptake of urea equals to 1.2 × 102 mg/g (gram of nano-FePh). The reaction kinetics of the adsorption of urea follows a pseudo-first-order model. Application of homogenous film diffusion model and matrix diffusion model is carried out and analyzed. The model of the diffusion liquid film controls the process at the first adsorption step and then at the final stage is under control by matrix diffusion model. Frumkin adsorption isotherm is found to fit with the experimental data. The kinetics and thermodynamic parameters have been determined and analyzed. The nano-FePh adsorbent was stable and the adsorption capacity was remaining excellent after 10 cycles.

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.

Highly adsorptive oxidized starch nanoparticles for efficient urea removal

Portable dialysis is a need to implement daily and nocturnal hemodialysis. To realize portable dialysis, a dialysate regeneration system comprising superior adsorbents is required to regenerate the used dialysate. This study aims to develop a nano-adsorbent, derived from corn starch for urea removal. Oxidized starch nanoparticles (oxy-SNPs) were prepared via liquid phase oxidation, followed by chemical dissolution and non-solvent precipitation. The oxy-SNPs possessed Z-average size of 177.7 nm with carbonyl and carboxyl contents of 0.068 and 0.048 per 100 glucose units, respectively. The urea adsorption achieved the equilibrium after 4 h with 95% removal. The adsorption mechanism fitted Langmuir isotherm while the adsorption kinetics obeyed pseudo-second-order model. This new material has a maximum adsorption capacity of 185.2 mg/g with a rate constant of 0.04 g/mg.h. Moreover, the oxy-SNPs exhibited the urea uptake recovery of 91.6%. Oxy-SNPs can become a promising adsorbent for dialysate regeneration system to remove urea.

Preparation of magnetically recoverable mesoporous silica nanocomposites for effective adsorption of urea in simulated serum

Abstract In this study, SBA-15/Fe3O4 nanocomposites were prepared by conjugating Fe3O4 nanoparticles to mesoporous silica SBA-15 particles as magnetically recoverable adsorbents. The physicochemical and magnetic properties of bare and as-prepared samples were characterized using the X-ray diffractometer, transmission electron microscope, Fourier transform infrared spectroscope, porosimeter, and vibrating sample magnetometer. The performance of SBA-15, Fe3O4, and SBA-15/Fe3O4 nanocomposites for adsorption removal of uremic toxin urea in simulated serum was compared at 25 and 37 °C. Except for Fe3O4, both SBA-15 and SBA-15/Fe3O4 showed a high and equivalent adsorption ability for urea. Although the surface area of SBA-15/Fe3O4 nanocomposites decreased from 1167 m2/g (bare SBA-15) to 311 m2/g, the pore volume of SBA-15/Fe3O4 was not greatly decreased because most of Fe3O4 nanoparticles were coated onto the surface of SBA-15 particles. The adsorption mechanism of urea on SBA-15/Fe3O4 was proposed. Finally, the cytotoxicity of SBA-15/Fe3O4 nanocomposites before and after urea adsorption for fibroblast L929 cells was studied.

Evaluation of Urea Adsorption by Various Nanoporous Biomaterials

Evaluation of Urea Adsorption by Various Nanoporous Biomaterials

Adsorption of urea onto granular activated alumina: A comparative study with granular activated carbon

ABSTRACTThis study investigated the ability of granular activated alumina to remove urea from wastewater through adsorption, and compared its performance with granular activated carbon. XRF, EDX, XRD, and TGA were used to investigate the adsorbents. The removal of urea as a function of pH value was studied. The point of zero charge for activated alumina was found to be 8.8, while that for activated carbon was found to be 7.1. The experimental data of the adsorption process were explored by fitting to different kinetic models to determine the adsorption kinetics and mechanisms. Then, the equilibrium data were examined by fitting to various two-parameter and three-parameter isotherm models. Results showed that the removal efficiency increased with the increasing pH value. The maximum removal efficiencies were 24% and 31% for granular activated alumina and granular activated carbon, respectively, at pH = 9.0. Kinetic studies showed that adsorption of urea onto both activated alumina and activated carbon can be expressed by pseudo second order kinetics. Equilibrium studies showed that the adsorption isotherms could be expressed by the Redlich-Peterson isotherm and Temkin isotherm for activated alumina and activated carbon, respectively. Adsorbents were investigated using FTIR and SEM, and results showed the occurrence of adsorption.

Chitosan-smectite composite on the urea adsorption–desorption study for slow-release fertilizer application

PurposeThe purpose of this study is to prepare composite of chitosan-modified smectite clays consisting of montmorillonite and saponite clay minerals and their urea adsorption–desorption study. Prepared materials were designed for slow-release fertilizer application.Design/methodology/approachPreparation of the composites was conducted by a simple intercalation of chitosan solution and clay suspension followed by hydrogel beads formation. Physicochemical characterization of materials was performed by X-ray diffraction, gas sorption analysis by using Brunauer–Emmett–Teller surface areas and pore volume, water absorbency and Fourier transform-infrared. Urea adsorption and desorption studies of prepared materials were conducted by using batch method, and the adsorbed and desorbed urea content was analyzed by using high-performance liquid chromatography method.FindingsThe results revealed that the composites have higher absorptivity and lower absorptivity toward urea from and into water solution compared to raw clay minerals. Adsorption capacity and slow desorption rate of urea from the composites suggested the potential application of the composites as slow urea-releasing agent.Originality/valueThere are many papers that study the formation of chitosan-clay composites, but the study on the urea adsorption–desorption properties based on chitosan-smectite minerals have not been reported. Intensive study related to physicochemical properties and its related kinetics study is an important basic finding for further applications.

Influence of Zr on the performance of Mg-Al catalysts via hydrotalcite-like precursors for the synthesis of glycerol carbonate from urea and glycerol

A series of Zr-containing Mg-Al hydrotalcite-like (HTl) precursors were prepared using co-precipitation method with Zr4+: (Al3+ + Zr4+) from 0 to 0.7. It was demonstrated by X-ray diffraction that the yield of the HTl phase declined on increasing of Zr content. Then, Mg-Al-Zr mixed oxide (CHT-Zr) catalysts were obtained by calcining of the corresponding HTl precursors and they all exhibited mesoporous structure after heat treatment. Based on systemic characterization, it was observed that the amount of Zr additive showed a great effect on the structure and acidic-basic property of CHT-Zr samples. Meanwhile, such CHT-Zr catalysts were effective catalysts for the glycerol carbonate (GLC) synthesis from glycerol and urea. Afterwards, the function of acidic and basic sites in each reaction path identified in this research was elucidated based on the reactant conversion and product selectivity. It proved that the acidic sites were inclined to promote the reaction towards GLC synthesis, while all the paths towards the by-products were significantly catalyzed by the basic sites. However, the catalysts with extra strong acidity did not facilitate the GLC production due to poisoning of surface active sites by urea adsorption. So, a well-balanced acidic-basic property was important to obtain high GLC yield with good selectivity. Among all the catalytic samples, the catalysts with Zr4+: (Al3+ + Zr4+) = 0.3 showed the best catalytic performance with 87.8% yield of GLC. Moreover, different reaction parameters such as reaction temperature, reaction time, catalyst amount and vacuum degree were investigated and optimum conditions were established. Additionally, this catalyst could be readily recycled and reused for at least four times without any activation treatment, while still possessing high activity.

Acid-base sites synergistic catalysis over Mg-Zr-Al mixed metal oxide toward synthesis of diethyl carbonate.

In heterogeneous catalysis processes, development of high-performance acid–base sites synergistic catalysis has drawn increasing attention. In this work, we prepared Mg/Zr/Al mixed metal oxides (denoted as Mg2ZrxAl1−x–MMO) derived from Mg–Zr–Al layered double hydroxides (LDHs) precursors. Their catalytic performance toward the synthesis of diethyl carbonate (DEC) from urea and ethanol was studied in detail, and the highest catalytic activity was obtained over the Mg2Zr0.53Al0.47MMO catalyst (DEC yield: 37.6%). By establishing correlation between the catalytic performance and Lewis acid–base sites measured by NH3-TPD and CO2-TPD, it is found that both weak acid site and medium strength base site contribute to the overall yield of DEC, which demonstrates an acid–base synergistic catalysis in this reaction. In addition, in situ Fourier transform infrared spectroscopy (in situ FTIR) measurements reveal that the Lewis base site activates ethanol to give ethoxide species; while Lewis acid site facilitates the activated adsorption of urea and the intermediate ethyl carbamate (EC). Therefore, this work provides an effective method for the preparation of tunable acid–base catalysts based on LDHs precursor approach, which can be potentially used in cooperative acid–base catalysis reaction.

Electrochemical and SEIRAS studies of urea and biuret adsorption on polycrystalline gold

The potential dependent adsorption of urea and its self-condensation product, biuret, have been studied on polycrystalline gold electrodes using electrochemical and in situ infrared spectroscopy. Voltammetry reveals that biuret displays a wider double-layer region compared to its parent compound and can only be oxidized at potentials that overlap with Au oxidation. Chronocoulometric measurements indicate that the adsorption of biuret is stronger than that of urea and the surface coverage is potential dependent. Surface enhanced infrared absorption spectroscopy (SEIRAS) experiments have been performed on both urea and biuret adsorption from neutral solutions made from heavy water. Urea provides low intensity IR signals consistent with relatively weak adsorption over a very restricted potential domain whereas biuret is spectroscopically much more pronounced. Analysis of the SEIRAS results support at least two distinct configurations of adsorbed biuret involving oxygen coordination to the metal surface. At the limit of the positive potentials studied spectroscopic evidence of the adsorption of partially oxidized biuret (ureayl-type species) is provided.

尿素の土壌吸着(第2報) : 赤外線吸収スペクトルによる尿素の土壌吸着機構解析

尿素の土壌吸着(第2報) : 赤外線吸収スペクトルによる尿素の土壌吸着機構解析

Effects of Preparation Conditions and Environmental Conditions on Rice-straw-biochar Adsorption of Urea

To investigate the feasibility of using biochars to adsorb urea in aqueous solution, we extracted biochar which was generated at pyrolysis temperature of 400℃, 600℃ and 800℃ respectively from rice-straw combustion residues. In this study we evaluated the effect of adsorption time, the pH of environment, the contents of urea and biochar yield on the ability of adsorption for urea using a solution adsorption method. The results showed that all biochars could sorb the higher amounts of urea at pyrolysis temperature of 800℃, which was larger than 600℃ and 400℃ successively with prolonging adsorption time, increasing environmental pH, larger amounts of urea and greater the addition of biochars. However, biochars particle size of 1.91mm and 0.38mm had no significant effect. We conclude that rice-straw derived biochars can be used for adsorbing urea under the conditions where the pyrolysis temperature of 800℃, adsorption time of 3 hours, environmental pH of 7, biochar particle size of 2.0mm, initial urea concentration of 3mol/L and lesser usage of biochars.

Conversion and characterization of activated carbon fiber derived from palm empty fruit bunch waste and its kinetic study on urea adsorption

Urea removal is an important process in household wastewater purification and hemodialysis treatment. The efficiency of the urea removal can be improved by utilizing activated carbon fiber (ACF) for effective urea adsorption. In this study, ACF was prepared from oil palm empty fruit bunch (EFB) fiber via physicochemical activation using sulfuric acid as an activating reagent. Based on the FESEM result, ACF obtained after the carbonization and activation processes demonstrated uniform macropores with thick channel wall. ACF was found better prepared in 1.5:1 acid-to-EFB fiber ratio; where the pore size of ACF was analyzed as 1.2 nm in diameter with a predominant micropore volume of 0.39 cm3 g−1 and a BET surface area of 869 m2 g−1. The reaction kinetics of urea adsorption by the ACF was found to follow a pseudo-second order kinetic model. The equilibrium amount of urea adsorbed on ACF decreased from 877.907 to 134.098 mg g−1 as the acid-to-fiber ratio increased from 0.75 to 4. During the adsorption process, the hydroxyl (OH) groups on ACF surface were ionized and became electronegatively charged due to the weak alkalinity of urea solution, causing ionic repulsion towards partially anionic urea. The ionic repulsion force between the electronegatively charged ACF surface and urea molecules became stronger when more OH functional groups appeared on ACF prepared at higher acid impregnation ratio. The results implied that EFB fiber based ACF can be used as an efficient adsorbent for the urea removal process.

Translational Entropy and Dispersion Energy Jointly Drive the Adsorption of Urea to Cellulose.

The adsorption of urea on cellulose at room temperature has been studied using adsorption isotherm experiments and molecular dynamics (MD) simulations. The immersion of cotton cellulose into bulk urea solutions with concentrations between 0.01 and 0.30 g/mL led to a decrease in urea concentration in all solutions, allowing the adsorption of urea on the cellulose surface to be measured quantitatively. MD simulations suggest that urea molecules form sorption layers on both hydrophobic and hydrophilic surfaces. Although electrostatic interactions accounted for the majority of the calculated interaction energy between urea and cellulose, dispersion interactions were revealed to be the key driving force for the accumulation of urea around cellulose. The preferred orientation of urea and water molecules in the first solvation shell varied depending on the nature of the cellulose surface, but urea molecules were systematically oriented parallel to the hydrophobic plane of cellulose. The translational entropies of urea and water molecules, calculated from the velocity spectrum of the trajectory, are lower near the cellulose surface than in bulk. As urea molecules adsorb on cellulose and expel surface water into the bulk, the increase in the translational entropy of the water compensated for the decrease in the entropy of urea, resulting in a total entropy gain of the solvent system. Therefore, the cellulose-urea dispersion energy and the translational entropy gain of water are the main factors that drive the adsorption of urea on cellulose.