Capacity For NH4 Research Articles

P8: A Coated ZrP Cation Exchanger with Excellent Ammonium Selectivity and Chemical Stability: An Oral Sorbent for End-Stage Kidney Disease (ESKD)

A sorbent with high enough capacity for NH4+ could serve as an oral binder to lower urea levels in end-stage kidney disease patients (Figure 1). A hydrogen-loaded cation exchanger such as zirconium phosphate (ZrP) is a promising candidate for this application. However, the NH4+ binding selectivity versus other ions must be improved. A gas-permeable and hydrophobic surface coating was first attached to an amorphous form of ZrP using tetraethyl orthosilicate and methoxy-terminated polydimethylsiloxane (PDMS). The coating prevents ions in solution from reaching the ion-exchanger but allows NH3 transfer to the ZrP. The selectivity of the coating was measured with NH4+ and Ca2+ solutions versus uncoated ZrP. X-ray photoelectron spectroscopy and scanning electron microscopy measurements showed the coating successfully modified the surface of ZrP. Water contact angle (WCA) studies indicated coated ZrP was hydrophobic (149.8° ± 2.5°). The in vitro studies showed coated ZrP removed 94% (± 11%) more NH4+ than uncoated ZrP in the presence of Ca2+. And Ca2+ binding decreased by 64% (± 6%). The increase in NH4+ selectivity was due to the applied coating. But the material’s selectivity decreased by 72% after exposure to stomach acid conditions. An alternative hydrophobic (WCA = 145.0° ± 3.2°) and gas permeable coating was investigated – perfluorooctyltriethoxysilane (FOTS). The coating was attached to a polysiloxane membrane on ZrP’s surface. In vitro studies in Figure 2b indicated the FOTS structure attached to ZrP offers complete selectivity for NH4+ over Ca2+ with similar NH4+ capacity as the PDMS coating. FOTS-coated ZrP maintained its selectivity and NH4+ removal capacity after stomach acid exposure. The results indicate FOTS-coated ZrP could work as an oral sorbent for ESKD patients.Figure 1. The recirculation of urea and oral sorbent’s methodology for NH4+ adsorption. Figure has been adapted from Barret’s original artwork.1Figure 2. (a): SEM images of uncoated, PDMS-coated and FOTS-coated ZrP at 10,000x magnification. (b): Binding study results of uncoated, PDMS-coated and FOTS-coated ZrP.

Developing a Selective Zirconium Phosphate Cation Exchanger to Adsorb Ammonium: Effect of a Gas-Permeable and Hydrophobic Coating.

A sorbent with a high enough capacity for NH4+ could serve as an oral binder to lower urea levels in end-stage kidney disease (ESKD) patients. A hydrogen-loaded cation exchanger such as zirconium phosphate Zr(HPO4)2·H2O (ZrP) is a promising candidate for this application. However, the NH4+ binding selectivity versus other ions must be improved. Here, we have developed a gas-permeable and hydrophobic surface coating on an amorphous form of ZrP using tetraethyl orthosilicate and methoxy-terminated polydimethylsiloxane. The hydrophobic coating serves as a barrier to ions in water solution from reaching the ion-exchanger's surface. Meanwhile, its gas-permeable nature allows for gaseous ammonia transfer to the cation exchanger. In vitro studies were designed to replicate the small intestine's expected ion concentrations and exposure time to the sorbent. The effectiveness of the coating was measured with NH4+ and Ca2+ solutions and uncoated ZrP as the negative control. X-ray photoelectron spectroscopy and scanning electron microscopy measurements show that the coating successfully modifies the surface of the cation exchanger─ZrP. Water contact angle studies indicate that coated ZrP is hydrophobic with an angle of (149.8 ± 2.5°). Simulated small intestine solution studies show that the coated ZrP will bind 94% (±11%) more NH4+ than uncoated ZrP in the presence of Ca2+. Meanwhile, Ca2+ binding decreases by 64% (±6%). The nearly fourfold increase in NH4+ selectivity can be attributed to the gas-permeable and hydrophobic coating applied on the ZrP surface. This work suggests a novel pathway to develop a selective cation exchanger for treating ESKD patients.

Assessing carrying capacity of receiving water bodies – A case study in Southern waterways of Binh Duong province

The carrying capacity of receiving water bodies is one of the important data for water quality management, pollution source control towards harmonizing with the economic development and environment protection. Therefore, this research aimed atevaluating the carrying capacity of receiving water bodies in the south of Binh Duong province up to 2030. 06 key water quality indicators (COD, BOD, TSS, PO43--P, NO3--N, NH4+-N) were exmained with 02 wastewater treatment scenarios. Results showed the investigated area hardly had carrying capacity for NH4+-N and PO43--P, followed by TSS, BOD, and COD. In case of improving wastewater treatment status till 2030, the carrying capacity of receiving water bodies would be increased, but not significant. The carrying capacity of several basins needs to be paid special attention are: Suoi Con 1 basin (BOD, COD, NH4+-N), Suoi Cai basin (BOD, TSS and NH4+-N), the upstream of Cay Bang – Cau Dinh basin (BOD, COD, TSS, NH4+-N), the upstream of Chom Sao – Rach Bung basin (05 parameters, excepting NO3--N), the upstream of Binh Hoa – Vinh Binh basin (BOD, COD, PO43--P, NH4+-N). These findings are an important basis for formulating strategies and proposing measures for local pollution source control and surface water management.

Nitrogen Removal from Anaerobically Digested Swine Waste Centrate Using a Laboratory-Scale Chabazite-Sequencing Batch Reactor

Abstract Anaerobic digestion (AD) is widely used for the treatment of livestock waste because the biogas produced can be utilized as energy source. Further treatment of AD effluents is often required for total nitrogen (TN) removal, which is typically carried out using biological nitrogen removal processes. However, the high free ammonia (FA) concentrations present in AD effluents can inhibit nitrification processes. This research tested a sequencing batch reactor (SBR) amended with particulate chabazite (chabazite-SBR) for removal of TN from anaerobically digested swine waste centrate. In the chabazite-SBR, zeolitic material with a high ion exchange (IX) capacity for NH4+ is used to ease nitrification inhibition. Once nitrification is complete, an external organic electron donor is supplied during an anoxic stage to promote denitrification. An overall TN removal efficiency of 84% was achieved in a laboratory-scale chabazite-SBR, with specific nitrification and denitrification rates of 0.43 and 1.49 mg-N/...

Zeolite synthesis from paper sludge ash with addition of diatomite

AbstractBACKGROUND: This study aimed to investigate the synthesis of zeolites from paper sludge ash (PSA) with added diatomite to remove both NH4+ and PO43− for water purification. The PSA had low Si and significant Ca contents. Four types of diatomite: white (T‐W) and brown (T‐B) from deposits of marine origin in Takanosu, and white (S‐W) and gray (S‐G) from lacustrine deposits in Shonai, were added to NaOH solution to increase the Si content and thereby synthesize zeolites with high cation exchange capacity (CEC).RESULTS: The order of the amounts of Si extracted from the diatomite to the alkali solution was S‐W > T‐W = T‐B > S‐G, which correlates with the amorphous SiO2 content of diatomite. The original ash without addition of diatomite yielded hydroxysodalite with CEC of about 1.0 mmol g−1. For all samples, the addition of diatomite to the solution yielded zeolite‐P with a higher CEC, but the addition of excess Si inhibited the synthesis of zeolite‐P, and the CEC of the product was low. A product with high CEC including zeolite‐P was obtained in a solution with around 500 mmol L−1 of Si concentration, and had the ability to remove both NH4+ and PO43−.CONCLUSION: Diatomite has the potential for used as an additive for the synthesis of high CEC zeolite from PSA. The product with zeolite‐P exhibited relatively high CEC, capacity for NH4+ uptake, and the ability to remove PO43− by precipitation, which is preferable for water purification applications. Copyright © 2008 Society of Chemical Industry

Chronic Atmospheric NO 3 − Deposition Does Not Induce NO 3 − Use by Acer saccharum Marsh.

The ability of an ecosystem to retain anthropogenic nitrogen (N) deposition is dependent upon plant and soil sinks for N, the strengths of which may be altered by chronic atmospheric N deposition. Sugar maple (Acer saccharum Marsh.), the dominant overstory tree in northern hardwood forests of the Lake States region, has a limited capacity to take up and assimilate NO 3 − . However, it is uncertain whether long-term exposure to NO 3 − deposition might induce NO 3 − uptake by this ecologically important overstory tree. Here, we investigate whether 10 years of experimental NO 3 − deposition (30 kg N ha−1 y−1) could induce NO 3 − uptake and assimilation in overstory sugar maple (approximately 90 years old), which would enable this species to function as a direct sink for atmospheric NO 3 − deposition. Kinetic parameters for NH 4 + and NO 3 − uptake in fine roots, as well as leaf and root NO 3 − reductase activity, were measured under conditions of ambient and experimental NO 3 − deposition in four sugar maple-dominated stands spanning the geographic distribution of northern hardwood forests in the Upper Lake States. Chronic NO 3 − deposition did not alter the V max or K m for NO 3 − and NH 4 + uptake nor did it influence NO 3 − reductase activity in leaves and fine roots. Moreover, the mean V max for NH 4 + uptake (5.15 μmol 15N g−1 h−1) was eight times greater than the V max for NO 3 − uptake (0.63 μmol 15N g−1 h−1), indicating a much greater physiological capacity for NH 4 + uptake in this species. Additionally, NO 3 − reductase activity was lower than most values for woody plants previously reported in the literature, further indicating a low physiological potential for NO 3 − assimilation in sugar maple. Our results demonstrate that chronic NO 3 − deposition has not induced the physiological capacity for NO 3 − uptake and assimilation by sugar maple, making this dominant species an unlikely direct sink for anthropogenic NO 3 − deposition.

Osmosensitivity associated with insertions in argP (iciA) or glnE in glutamate synthase-deficient mutants of Escherichia coli.

An ampicillin enrichment strategy following transposon insertion mutagenesis was employed to obtain NaCl-sensitive mutants of a gltBD (glutamate synthase [GOGAT]-deficient) strain of Escherichia coli. It was reasoned that the gltBD mutation would sensitize the parental strain even to small perturbations affecting osmotolerance. Insertions conferring an osmosensitive phenotype were identified in the proU, argP (formerly iciA), and glnE genes encoding a glycine betaine/proline transporter, a LysR-type transcriptional regulator, and the adenylyltransferase for glutamine synthetase, respectively. The gltBD+ derivatives of the strains were not osmosensitive. The argP mutation, but not the glnE mutation, was associated with reduced glutamate dehydrogenase activity and a concomitant NH4+ assimilation defect in the gltBD strain. Supplementation of the medium with lysine or a lysine-containing dipeptide phenocopied the argP null mutation for both osmosensitivity and NH4+ assimilation deficiency in a gltBD background, and a dominant gain-of-function mutation in argP was associated with suppression of these lysine inhibitory effects. Osmosensitivity in the gltBD strains, elicited either by lysine supplementation or by introduction of the argP or glnE mutations (but not proU mutations), was also correlated with a reduction in cytoplasmic glutamate pools in cultures grown at elevated osmolarity. We propose that an inability to accumulate intracellular glutamate at high osmolarity underlies the osmosensitive phenotype of both the argP gltBD and glnE gltBD mutants, the former because of a reduction in the capacity for NH4+ assimilation into glutamate and the latter because of increased channeling of glutamate into glutamine.