Alternative Gas Research Articles

Studies on RPC detectors operated with environmentally friendly gas mixtures in LHC-like conditions

Resistive Plate Chambers (RPC) are gasesous detectors employed at CERN LHC experiments thanks to their trigger performance, timing capabilities and contained production costs. High Pressure Laminate RPCs are operated with a three-component gas mixture, made of 90–95% of C_2H_2F_4, around 5% of i-C_4H_{10} and 0.3% of SF_6. Due to the presence of leaks at detector level and to the greenhouse characteristics of C_2H_2F_4 and SF_6, RPCs in ATLAS and CMS were accounting for about 87% of CO_2 equivalent emissions during LHC Run 2. To address this, several alternative gases were studied, including R-1234ze as a possible substitute for R-134a. Furthermore, the addition of some amount of CO_2 into the RPCs gas mixture was explored as a possible short-to-medium term solution to lower the total greenhouse gas emissions and reduce the usage of C_2H_2F_4. A dedicated data taking campaign was performed at the Gamma Irradiation Facility at CERN, where RPCs detectors performance were studied with muon beam and gamma background. The detectors were operated with the addition of 30% and 40% and 50% of CO_2 to the standard gas mixture, together with an increased fraction of SF_6. Two different amounts of i-C4H10 were also evaluated to assess compatibility with the CMS and ATLAS requirements. Results from these beam tests with the above-mentioned gas mixtures are reported in this work.

Theoretical Characterizations on the Eco-Friendly Gas Tetrafluoropropyne for Electrical Insulation to Replace Sulfur Hexafluoride.

Gases for electric insulation are essential for various types of high-voltage power equipment. Sulfur hexafluoride (SF6) has been a dielectric medium commonly used in electrical grids for decades but it is the most potent industrial greenhouse gas. The continuous increase of SF6 emissions in the atmosphere exerts a significant impact on global warming. The identification of suitable drop-in replacements for all SF6-filled apparatuses has been elusive experimentally and theoretically. We claim that tetrafluoropropyne, C3F4, is a breakthrough in chemical alternatives to SF6. The performance of C3F4 was assessed systematically in a 6-dimensional manner, including dielectric strength, liquefaction temperature, global warming potential, thermal stability, toxicity, and arc interruption. On the basis of the extensive ab initio calculations, it has been demonstrated rigorously that C3F4 is an environmentally sustainable solution that may fulfill the complex combination of performance, stability, safety, and environmental properties, namely, the dielectric strength is about 50% higher than that of SF6, the boiling point is -50 °C, the GWP for 100 year time horizons is only 3, the decomposition temperature is above 600 °C, the toxicity is as low as HFOs, and the interruption capability is two-thirds of SF6. Two protocols are suggested for the practical use of C3F4. First, equivalence to 0.5 MPa SF6 could be obtained by filling 0.33 MPa C3F4 pure gas and lead minimum operating temperature down to -21 °C. Second, by taking advantage of synergism effect, the 40% C3F4/60% CO2 mixture is a viable alternative to SF6 with the operating temperature -30 °C without causing any environmental and safety concerns. The present theoretical work sheds new light on the challenging topic of the development of alternative dielectric gases and may stimulate experimental tests on the electrical applications of C3F4 in the future.

Short-Term Reliability Assessment of Integrated Power-Gas Systems With Hydrogen Injections Using Universal Generating Function

Injecting alternative gas (e.g., green hydrogen from wind generation) into the gas system is a promising way to decarbonize the energy sector. However, the fluctuating renewable generation could lead to time-varying alternative gas injections. Then, the gas composition in the gas system may become uncertain, increasing the short-term risk of the integrated power-gas systems during the operation. This paper proposes a short-term reliability assessment approach for IPGS with alternative gas injections. First, the multi-performance and multi-state universal generating functions (UGF) are constructed to efficiently model the short-term reliability of the power-to-gas facility and the wind farm, respectively. Then, a reliability management UGF operator is proposed to minimize both load shedding and gas security violation. A set of novel reliability indices is proposed to comprehensively assess the gas security violations under uncertain gas compositions. Moreover, an analytical short-term reliability assessment approach is proposed, where the state-based sequential approximation and state-based McCormick envelope techniques are tailored and embedded. By optimizing the solution order by the system states, the nonconvexities in the reliability management optimization problem can be handled tractably without increasing the computation burden. Finally, the IEEE 24 bus Reliability Test System and the Belgium gas system are used to validate the proposed approach.

Influence of Oxygen-containing Filling Gas Mixtures on the Interruption Capability of MV Load Break Switches

Nowadays SF6 is commonly used as filling gas for medium voltage load break switches due to its outstanding insulating and arc-quenching properties. However, due to its high global warming potential the interrupting performance of alternative eco-friendly gases are investigated for such devices. This contribution investigates the thermal interruption capability of a medium voltage load break switch using two different oxygen-containing gas mixtures: dry air and a mixture of nitrogen, oxygen and carbon dioxide. The findings indicate an improved performance in comparison to pure nitrogen when considering an admixture of oxygen. In gas mixtures containing 80\% nitrogen, the addition of oxygen results in an enhanced thermal interruption capability compared to an equivalent proportion of carbon dioxide.

Is a Carbon-Neutral Pathway in Road Transport Possible? A Case Study from Slovakia

Transformation of European transport belongs among the key challenges to achieve a reduction of 55% by 2030 and climate neutrality by 2050. This study focuses on GHG emissions in road transport in Slovakia, as it currently accounts for 19% of total GHG emissions (road transport emissions account for 99% of transport emissions). The main driver for this study was the preparation of Slovakia’s Climate Act and investigation of where are the limits of greenhouse gas emission reduction by 2050. With the aim of achieving maximum reduction in emissions by 2050 compared to 2005 levels, various scenarios were developed using the COPERT model to explore emission reduction strategies. The scenarios considered different subsectors of road transport, including passenger cars, light-commercial vehicles, heavy-duty vehicles (buses and trucks), and L-category vehicles and examined encompassed reduction of transport demand, improving energy efficiency, and utilizing advanced technologies with alternative fuels (hybrids, PHEV, CNG, LNG or LPG). However, the economic aspects of specific mitigation options were not considered in this analysis. The results show that there is a possibility of 77% GHG emission reduction by 2050 in comparison with the 2005 level. This reduction is accompanied by a shift in vehicle technologies to alternative fuels like electricity, hydrogen, and to a smaller extent biofuels and biomethane. This study shows that it will be possible to achieve 86.7% zero-emission cars and an additional 12.9% low emission and alternative fueled cars by 2050. By identifying and assessing these scenarios, policymakers and stakeholders can gain insights into the possibilities, challenges, and potential solutions for meeting the climate targets set by the European Union’s Fit for 55 climate package.

Water alternative gas (WAG) optimization for a heterogeneous Brazilian pre-salt carbonate reservoir

Abstract Water alternating gas (WAG) is a cyclical process that involves alternating water and gas injections with the primary goal to improve sweep efficiency by maintaining initial high pressure, slowing water and gas breakthrough, and lowering oil viscosity. The objective of this work is to apply and optimize a WAG strategy on a carbonate field with light oil, compare it to the initially planned water-flooding strategy, and investigate the capability of WAG to improve field production. In this research, a compositional reservoir simulator was used to model a WAG process by injecting produced gas into the reservoir, using the same well structure as an optimized water-flooding strategy. Subsequently, a WAG strategy was created, optimizing the number and locations of wells, to facilitate a comparative analysis of the two recovery methods. The WAG optimization involved a detailed assessment of variables such as bottom hole pressure (BHP), WAG cycle duration, maximum gas oil ratio (GOR), and well positioning, to achieve a high net present value (NPV). The study focuses on the application of WAG optimization modeling in unconventional reservoirs, specifically pre-salt carbonate reservoirs, and investigates its implications on production strategy and forecast, emphasizing its potential for maximizing NPV and oil recovery in a recently producing field. The results showed that WAG improved reservoir performance when compared to water injection and produced a greater amount of oil. This solution showed potential to be tested under uncertainties (reservoir heterogeneity, faults, fractures, karsts, vugs, etc.) as future steps.

An experimental study of CO2 injection strategies for enhanced oil recovery and geological sequestration in a fractured tight sandstone reservoir

Carbon dioxide enhanced oil recovery has been considered and tested in unconventional oil reservoirs due to its additional environmental benefits from simultaneous CO2 geological sequestration. However, it will require a proper injection strategy to overcome unfavorable sweep efficiency in CO2 displacement, which is even magnified in unconventional oil reservoirs due to strong heterogeneity caused by natural and artificial fractures. In this study, we investigated three immiscible CO2 injection strategies at reservoir conditions using tight fractured sandstone cores from the Ordos Basin, China: water alternative gas injection, cyclic CO2 injection, and CO2 foam/surfactant alternative gas injection. A pressurization and miscible CO2 injection were then added after each injection strategy to examine the influence of residual liquid distributions on the miscible displacement efficiency after the tested injection schemes. The core plugs with comparable porosity and permeability were selected, and all cores reached a similar recovery factor (∼11%) after primary CO2 flooding. We found that the cyclic CO2 injection had best performance, with the highest incremental and accumulative oil recovery at 23.6% and 32.26%. Its relatively higher sweep efficiency indicated a uniform CO2 distribution at the end of the cyclic injection, which further led to the highest incremental recovery of 4.94% in the following miscible injection. Comparable CO2 storage capacities were observed in the three fractured core samples (12.21%, 12.98%, and 9.71%, respectively) after completing the miscible displacements. In general, cyclic CO2 injection is recommended as an effective CO2 EOR and geo-storage in tight fractured rocks.

Climate Change and the Geography of the U.S. Economy

This paper examines how the spatial distribution of people and jobs in the United States has been and will be impacted by climate change. Using novel county-level weather data from 1951 to 2020, we estimate the longer-run effects of weather on local population, employment, wages, and house prices using a panel distributed lag model. The historical results point to long-lasting negative effects of extreme temperatures on each of these outcomes. We highlight that a long lag structure is necessary to appropriately capture the longer-run effects of climate change, as short-run effects are often small and imprecisely estimated. Using county-level weather projections based on alternative greenhouse gas emissions scenarios, we use the estimated models to project the spatial distribution of these local economic outcomes out to 2050. The results point to substantial reallocations of people and jobs across the country over the next three decades, with mobility increasing by between 33 and 100 percent depending on the scenario. Population and employment are projected to shift away from the Sunbelt and toward the North and Mountain West. We document that this would, in fact, be a continuation of a historical pattern: Over the past four decades the relationship between population growth and hot climates across the United States has turned from strongly positive to slightly negative. We present a spatial equilibrium model to interpret the results, highlighting the impacts of climate change on amenities and productivity, and find significant roles for both channels in accounting for our empirical findings.

EU Climate and Energy Security after 24 February 2022

Before 2022, EU conceptions of climate and energy security had begun to converge in a ‘virtuous synergy’ that supported the Union’s continuing attempts at international climate policy leadership. This paper argues that the more orthodox military security problem posed by Russia’s invasion of Ukraine coupled with extreme weather events in the same period has profoundly altered both the immediacy and the location of the perceived threats. The Union’s responses have been dramatic in terms of a re-orientation of established energy and security policies. Ending the dependence upon Russian gas provides the chance to accelerate the achievement of the European Green Deal and ‘Fit for 55’ but also involves an immediate quest for alternative gas supplies. The unresolved question is whether the Union can use this opportunity to enhance rather than dissipate its climate security and policy leadership.

Methane emissions from shale gas production sites in southern Sichuan, China: A field trial of methods

Shale gas is an important alternative natural gas source that can meet China's growing energy demand. However, methane emissions during shale gas production could largely determine whether it could be considered as a bridging clean energy source. In this study, we performed methane emission measurements using three methods (on-site optical gas imaging, on-site methane patrolling, and downwind measurement) at shale gas production sites in Sichuan province, China, covering 18 well sites with 81 wells. The results showed that flowback water tanks were the major methane sources, with valves, separators, chemical injection pumps, and pneumatic controllers as other sources. The methane concentrations inside the 18 sites ranged from 1.42 to 459 μmol mol−1, with over 59% of the sites having the highest concentration less than 50 μmol mol−1. The optical gas imaging method, with its low detection limit over 5000 μmol mol−1, could not capture the emission effectively. The three successful downwind measurements resulted in site level emission rates between 0.02 and 0.17 kg h−1. When divided by the number of wells at each site, the emission intensity was 4%–28% of the wellhead emission factor for natural gas production in China. More measurements are required to better quantify methane emissions from shale gas sites in China. For sites in mountainous regions or long-term low-wind regions, detection methods other than downwind measurements should be suitable for quantifying site-level emissions.

Cylindrical Acoustic Gas Thermometry

We review recent determinations of the Boltzmann constant kB and the differences T − T90 that used cylindrical acoustic gas thermometry (c-AGT). These determinations measured the acoustic resonance frequencies of argon gas enclosed by metal-walled, cylindrical cavities. (Here, T is the thermodynamic temperature and T90 is the temperature measured on the International Temperature Scale of 1990, ITS-90.) In the range 234–303 K, the standard uncertainty of c-AGT ranges from 1.9 × 10−6T to 2.6 × 10−6T. This uncertainty is much smaller than the errors in ITS-90; therefore, c-AGT can help improve ITS-90. Moreover, we are extending c-AGT up to 1358 K. With increasing temperatures, c-AGT becomes advantageous relative to AGT based on quasi-spherical cavities because long cylindrical cavities (1) naturally fit into cylindrical heat pipes or multi-shelled thermostats; (2) provide the immersion required by transfer temperature standards, such as long-stemmed platinum resistance thermometers; and (3) have more useful, low-frequency acoustic resonances. In preparation for high-temperature c-AGT, we identified suitable materials for fabricating cylindrical cavities and we developed techniques for measuring acoustic resonance frequencies using sources and detectors outside the high-temperature thermostat. We also considered alternative test gases and optimal dimensions of cavities.

Tracking and Reducing SF6 Usage in Radiation Oncology: A Step Toward Net-Zero Health Care Emissions

Sulfur hexafluoride (SF6) is a widely used insulating gas in medical linear accelerators (LINACs) due to its high dielectric strength, heat transfer capabilities, and chemical stability. However, its long lifespan and high Global Warming Potential (GWP) make it a significant contributor to the environmental impact of radiation oncology. SF6 has an atmospheric lifespan of 3200 years and a GWP 23,000 times that of carbon dioxide. The amount of SF6 that can be emitted through leakage from machines is also concerning. It is estimated that the approximate 15,042 LINACs globally may leak up to 64,884,185.9 carbon dioxide equivalent per year, which is the equivalent greenhouse gas emissions of 13,981 gasoline-powered passenger vehicles driven for 1 year. Despite being regulated as a greenhouse gas under the United Nations Framework Convention on Climate Change, SF6 use within health care is often exempt from regulation, and only a few states in the United States have specific SF6 management regulations.This article highlights the need for radiation oncology centers and LINAC manufacturers to take responsibility for minimizing SF6 emissions. Programs that track usage and disposal, conduct life-cycle assessments, and implement leakage detection can help identify SF6 sources and promote recovery and recycling. Manufacturers are investing in research and development to identify alternative gases, improve leak detection, and minimize SF6 gas leakage during operation and maintenance.Alternative gases with lower GWP, such as nitrogen, compressed air, and perfluoropropane, may be considered as replacements for SF6; however, more research is needed to evaluate their feasibility and performance in radiation oncology. The article emphasizes the need for all sectors, including health care, to reduce their emissions to meet the goals of the Paris Agreement and ensure the sustainability of health care and our patients.Although SF6 is practical in radiation oncology, its environmental impact and contribution to the climate crisis cannot be ignored. Radiation oncology centers and manufacturers must take responsibility for reducing SF6 emissions by implementing best practices and promoting research and development around alternatives. To meet global emissions reduction goals and protect both planetary and patient health, the reduction of SF6 emissions will be essential.

Fleet Operator Perspectives on Heavy-duty Vehicle Alternative Fueling Infrastructure

Despite the aggressive policy goals aiming to transition heavy-duty vehicles (HDVs) toward zero-emission technologies, the penetration rates of zero-emission or even alternative fuel technologies (including zero-emission and other fuels cleaner than petroleum) are still very low. Given that the majority of HDVs are used as fleet vehicles, a better understanding of fleet operator behavior and perspectives on clean fuel technologies is crucial to develop effective demand-side strategies to achieve such policy goals. Of many adoption barriers, a well-known major obstacle is the lack of fueling/charging infrastructure. However, there is limited understanding on how HDV fleet operators have navigated the issues involving the insufficient infrastructure. This study explores how HDV fleets have used alternative fueling infrastructure, how dis/satisfied fleet operators are with the infrastructure, and for what reasons they have decided to construct their own on-site fueling facilities, or to use off-site stations. Based on a case study of compressed natural gas, the most prevalent alternative fuel option so far in the HDV sector, 17 in-depth qualitative interviews were conducted with HDV fleet operators in California. Content and thematic analyses of the data yielded detailed qualitative inferences on use behavior, satisfaction, and fleet decisions between on-site versus off-site fueling. The study findings are the first step toward enhancing our understanding of HDV fleet behavior regarding alternative fueling infrastructure, which can contribute to filling the knowledge gap in this field and to developing further research questions to elicit policy recommendations that can support the adoption of clean fuel technologies in HDV fleets.

Optimal Energy Flow in Integrated Electricity and Gas Systems With Injection of Alternative Gas

This paper proposes an optimal energy flow technique for the integrated electricity and gas systems (IEGS) with injections of alternative gases. Firstly, we develop a novel optimal energy flow model of IEGS with alternative gases, where the physical characteristics (e.g., specific gravity) of the gas mixtures are modeled as variables to reflect the impacts of alternative gas injections more accurately. Security indices are introduced to restrain the gas composition variation. Then, convex optimization techniques are tailored to transfer the original highly nonlinear and nonconvex optimization problem into a tractable form. An advanced sequential programming procedure is proposed with self-adaptive convergence criteria to better balance the feasibility and convergency. Finally, the IEEE 24-bus RTS and Belgium gas transmission system, and the practical 160-bus Britain gas system are used to validate the proposed techniques. It can be observed from numerical studies that the computation efficiency of the proposed solution methods is 96.44% faster than traditional mixed-integer nonlinear solvers. The injection of alternative gas can cause up to 4.32% variations in the nodal gas pressure. Nonetheless, under various uncertainties from renewable generation, load level, etc., the proposed optimal energy flow model can maintain the security of IEGS.

The estimation of the engine power to the type of fuel for example diesel YAMZ-238

The transfer of agricultural machinery to work on cheaper alternative fuels-natural gas, methane-will improve the efficiency of agricultural production. Moreover, Kazakhstan occupies a leading place in the world in terms of its reserves. The simplest and most acceptable way for agriculture to transfer diesel to work on gaseous fuel is the use of a gas-diesel cycle, since it does not require significant changes in the design of the engine, the serial fuel equipment is preserved and the ability to work on both diesel fuel and its mixture with compressed (CNG) or liquefied natural gas. As a result of mathematical modeling, the power indicators of the experimental YAMZ-238 engine when it is transferred from liquid (diesel) to gaseous fuel (natural gas) are reduced by 10%, which shows the analysis of the formula for calculating this power, this effect occurs under the influence of the density of the fuel-air mixture entering the cylinder.

Hydrogen or Helium Conservation in Gas Chromatography Mass Spectrometry: How We Chose What Was Right for Our Laboratory

Helium is getting more and more difficult to obtain, and it does not look like that will change anytime soon. The only alternative carrier gas to helium that Agilent recommends for gas chromatography mass spectrometry is hydrogen. Converting a gas chromatograph mass spectrometer (GCMS) to use hydrogen presents additional safety concerns and may not be possible for some systems. Helium conservation, having the GCMS system use nitrogen as a carrier gas when idle, may be a viable alternative when conversion to hydrogen is not possible.

Adsorption of a MoSe2-Based Sensor for Fluorocarbon Gas Decomposition Products in Gas-Insulated Switchgear: A First Principles Analysis

Gas-insulated switch cabinets play a significant role in the power industry, and eco-friendly switch cabinets are the hotspot of current development. With the research of alternative gases for SF6, fluorocarbon insulating gases possessing stable physicochemical properties provide a new insight for scientists. This work studies the sensing and adsorption properties of the Pt–MoSe2 monolayer for fluorocarbon gas characteristic decomposition products of COF2, CF4, and C2F6 in terms of stability, adsorption energy (Ead), charge transfer (QT), band structure (BS), and density of states (DOS) as well as electronic structure based on first principles. The simulation results described Pt as an electron donor in the doping process on the MoSe2 monolayer with a binding force (Eb) of −3.739 eV. The Ead values of the COF2, CF4, and C2F6 gas systems are −0.689, −0.176, and −0.266 eV, respectively. By comparing the BS and DOS of the adsorption system before and after, gas systems become more active, especially the COF2 system. Besides, gas molecules all play the role of an electron acceptor in the adsorption process and the QT of the COF2 system is up to −0.259e. According to the analysis of this paper, Pt-doping can improve the sensing and adsorption properties of the MoSe2 monolayer and the monolayer shows different adsorption phenomena for three gases. The monolayer has a better adsorption effect on COF2, which provides a strong basis for the selective detection of gas sensors.

Investigation of the discharge coefficient in the laminar boundary layer regime of critical flow Venturi nozzles calibrated with different gases including hydrogen

This study represents the first step towards the introduction of critical flow Venturi nozzles into the traceability scheme for gaseous hydrogen and addresses the characterisation of the hydrogen discharge coefficient in the laminar boundary layer regime and the identification of a potential alternative gas for nozzle calibration. The experimental study presented was performed for two nozzles with a throat diameter of 0.175 mm and 0.436 mm. The tests were performed with six different gases, including hydrogen, covering a Reynolds number range from 1.5·103 to 6·104. The experimental results show that the discharge coefficient depends not only on the Reynolds number but also on the isentropic exponent of the gas. Based on the experimental data, theoretical models taking into account the isentropic exponent and the Prandtl number of the gas were evaluated. The study indicates possibilities to use inert gases instead of hydrogen in calibration processes.

Theoretical process for the investigation of dielectric characteristics of F3NO as an alternative gas for SF6

To examine the possibility of using a gas molecule as an SF6 alternative gas, the insulation properties of the molecule must be estimated. In this work, we present a theoretical approach to calculate geometry parameters, electron scattering cross sections, and transport properties of nitrogen fluoride oxide (F3NO), which we have selected as an alternative to SF6. The molecular minimum structure of F3NO was optimized using the ɷB97X-D functional combined with the aug-cc-pVTZ basis set. Using this initial geometry obtained by the molecular structure calculation, the R-matrix calculation was done to obtain the elastic and momentum transfer cross section. The BE-f method was used for electronic excitation cross section. For the ionization cross section, the binary encounter Bethe method was used. From the calculated cross section data, the electron transport coefficients and reaction coefficients were calculated by solving the two-term approximated Boltzmann equation to investigate the discharge and insulation characteristics.

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.