Search NASA⌕ Search

SEARCH · Search NASA

Results for “REMOVAL”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

NiAl–MoO 2 S 2 Nanoparticles: Structural Evolution and Mechanistic Insights into High-Performance Selenium Oxyanion Removal across Diverse pH Conditions

Advancing sorbent materials for the selective removal of toxic oxyanions from water requires synthetic control, tunable chemistry, and an atomic-level understanding of structure–function relationships. Here, we report the synthesis and detailed characterization of NiAl–MoO 2 S 2 , a novel layered double hydroxide (LDH) nanomaterial designed for the efficient sequestration of selenium oxoanions (SeO 3 2– and SeO 4 2– ) from complex aqueous environments. The material is synthesized through a room-temperature ion-exchange process, wherein interlayer NO 3 – anions in NiAl–LDH are replaced with MoO 2 S 2 2– clusters, forming high-surface-area, flower-like nanoparticles. Comprehensive structural analysis using the synchrotron X-ray pair distribution function, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy reveals a distinct chemical transformation of intercalated [MoO 2 S 2 ] 2– into [Mo 2 O 2 S 6 ] 2– -like clusters, generating redox-active interlayers that drive selenium capture. This tailored interfacial chemistry underpins the material’s exceptional sorption performance, achieving distribution coefficients (K d ) ≥ 10 6 mL/g and maximum capacities of 343 mg/g for SeO 4 2– and 514 mg/g for SeO 3 2– , outperforming state-of-the-art inorganic sorbents. Importantly, NiAl–MoO 2 S 2 maintains high selectivity and capacity across acidic, neutral, and alkaline pH, efficiently removing selenium from ppm to sub-10 ppb trace levels, even in the presence of competing ions typical of natural and industrial waters. The selenium uptake proceeds via reductive precipitation coupled with the oxidation of molybdenum and sulfide within the LDH framework. This study highlights the power of strategic synthetic modification and interlayer functionalization in LDHs to unlock new structural motifs and redox chemistries, offering a scalable route to advanced materials for environmental remediation.

Adsorption↗
DOE OSTI2022

Catalytic Removal of Oxygen Impurities from Pressurized Oxy-Combustion Flue Gas for the Production of High-Purity Carbon Dioxide

Flue gas purification is important for pressurized oxy-combustion systems to produce pure carbon dioxide (CO 2 ) streams ready for storage or utilization. A catalytic approach to removing oxygen (O 2 ) impurities from pressurized oxy-combustion flue gas via reduction with methane (CH 4 ) was investigated in this work. Two types of catalysts were studied: palladium (Pd)-based catalysts supported on titania (TiO 2 ) prepared by incipient wetness impregnation and cobalt–manganese (CoMn) composite catalysts prepared by coprecipitation. The performance of the catalysts was evaluated in a high-pressure–high-temperature, fixed-bed reactor at a pressure of 15 bar and a gas hourly space velocity of 30 000 h –1 (standard conditions), with a simulated feeding gas composed of 3 vol % O 2 , 1.5 vol % CH 4 , and CO 2 as the balance gas. Among the Pd catalysts, 5% Pd/TiO 2 achieved the maximum 86% O 2 removal at ≥350 °C. The CoMn oxide catalysts displayed comparable or better activities for O 2 reduction compared with the Pd catalysts. Among them, the Co 40 Mn 1 catalyst exhibited the best performance, able to reduce 99.9% of O 2 impurities at ~370 °C with negligible carbon monoxide (CO) formation (<10 ppmv). Both trivalent and divalent Co and Mn were detected on the catalyst surface, and the superior activity of Co 40 Mn 1 might be associated with the resultant disordered structure. Furthermore, the activity of the catalyst was not affected by the presence of a trace amount of nitric oxide (NO) gas contaminant. Results of this study provide the basis for scale-up studies in both the synthesis and performance of non-noble metal catalysts.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Selective and Chemical-Free Removal of Toxic Heavy Metal Cations from Water Using Shock Ion Extraction

Electrochemical methods are known to have attractive features and capabilities when used for ion separations and water purification. In this study, we developed a new process called shock ion extraction (shock IX) for selective and chemical-free removal of toxic heavy metals from water. Shock IX is a hybrid process that combines shock electrodialysis (shock ED) and ion exchange using an ion exchange resin wafer (IERW), and this method can be thought of functionally as an electrochemically assisted variation of traditional ion exchange. In particular, shock IX exhibits greater ion removal and selectivity for longer periods of time, compared to the use of ion exchange alone. Here, the use of an IERW in shock ED also increases multivalent ion selectivity, reduces energy consumption, and improves the hydrodynamics and scalability of the system.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

Unraveling the Role of Glycine in K 2 CO 3 Solvent for CO 2 Removal

Carbon dioxide (CO 2 ), a main composition of greenhouse gases, is believed to be responsible for global warming. Both potassium carbonate (K 2 CO 3 ) and amino acids have been studied for CO 2 removal. In this study, for the first time, carbamate formation in the absence of CO 2 was discovered in K 2 CO 3 solvents when small amounts of amino acids like glycine were added, and the mechanism of carbamate formation and CO 2 absorption in such solvents are detailed and supported the observed fast CO 2 absorption in the presence of amino acids. Here, in the mixed solvent of K 2 CO 3 and glycine, bicarbonate and hydroxide were formed from carbonate hydrolysis, and the deprotonated amino acid reacted with bicarbonate to form carbamate in the absence of CO 2 and, in the presence of CO 2 , reacted with CO 2 to form carbamate which could subsequently hydrolyze into bicarbonate. As a result, amino acid (even with a small amount) significantly enhanced the CO 2 absorption kinetics in the mixed solvents, and a high CO 2 loading (0.62 mol CO 2 /mol K 2 CO 3 ) was achieved in multiple (e.g., 10) cycles. Such mixed solvents of K 2 CO 3 and amino acid therefore may overcome the limitations of each individual component and may be ideal candidates for CO 2 removal.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Electrocoagulation in Water Treatment: Targeted Contaminant Removal and Laboratory Best Practices

Electrocoagulation for water treatment offers many advantages over traditional treatment technologies, including improved energy efficiency and modularity. One challenge with electrocoagulation is the lack of standardization in the methodology and reporting. This review provides a novel contribution by examining the past literature using a uniform metric (charge loading) as a basis for comparison, highlighting the importance of uniform reporting practices in this field. Furthermore, this review provides practical guidance for experimentalists in standardizing the electrocoagulation design and operating procedures. First, we present a comprehensive overview of contaminant-specific electrocoagulation as an electrochemical treatment technology for processing industrial, municipal, and agricultural water, with a focus on aluminum and iron electrocoagulation. We detail the fundamental mechanisms that allow for constituent removal during pretreatment. Specifically, we highlight electrocoagulation’s potential for organics, metalloids, microbes, and hardness remediation, examining the optimal removal conditions in terms of charge loading and current density. We conclude this work with some experimental best practices for lab-scale electrocoagulation experiments.

aluminum↗
DOE OSTI2020

Synthesis, Characterization, and Utilization of a Lignin-Based Adsorbent for Effective Removal of Azo Dye from Aqueous Solution

How to effectively remove toxic dyes from the industrial wastewater using a green low-cost lignocellulose-based adsorbent, such as lignin, has become a topic of great interest but remains quite challenging. In this study, cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment and Mannich reaction were combined to generate an aminated CELF lignin which is subsequently applied for removal of methylene blue and direct blue (DB) 1 dye from aqueous solution. 31P NMR was used to track the degree of amination, and an orthogonal design was applied to determine the relationship between the extent of amination and reaction parameters. The physicochemical, morphological, and thermal properties of the aminated CELF lignin were characterized to confirm the successful grafting of diethylenetriamine onto the lignin. The aminated CELF lignin proved to be an effective azo dye-adsorbent, demonstrating considerably enhanced dye decolorization, especially toward DB 1 dye (>90%). It had a maximum adsorption capacity of DB 1 dye of 502.7 mg/g, and the kinetic study suggested the adsorption process conformed to a pseudo-second-order kinetic model. The isotherm results also showed that the modified lignin-based adsorbent exhibited monolayer adsorption. The adsorbent properties were mainly attributed to the incorporated amine functionalities as well as the increased specific surface area of the aminated CELF lignin.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Improving Aerosol Radiative Forcing and Climate in E3SM: Impacts of New Cloud Microphysics and Improved Wet Removal Treatments

Abstract Numerous Earth system models exhibit excessive aerosol effective forcing at the top of the atmosphere (TOA), including the Department of Energy's Energy Exascale Earth System Model (E3SM). Here, in the context of the E3SM version 3 effort, the predicted particle property (P3) stratiform cloud microphysics scheme and an enhanced deep convection parameterization suite (ZM_plus) are implemented into E3SM. The ZM_plus includes a convective cloud microphysics scheme, a multi‐scale coherent structure parameterization for mesoscale convective systems, and a revised cloud base mass flux formulation considering impacts of the large‐scale environment. The P3 scheme improved cloud and radiation particularly over the Northern Hemisphere and the frequency of heavy precipitation over the tropics, and the ZM_plus improved clouds in the tropics. P3 decreases aerosol effective forcing by 0.15 W m −2 , while the ZM_plus increases it by 0.27 W m −2 , resulting from excessive direct (0.31 W m −2 ) and indirect forcing (−1.79 W m −2 ). The excessive aerosol forcings are due to aerosol overestimation associated with insufficient aerosol wet removal. By improving the physical treatments in the aerosol wet removal, we effectively mitigate anthropogenic aerosol overestimation and thus attenuate direct (0.09 W m −2 ) and indirect aerosol forcing (−1.52 W m −2 ). Adjustment to primary organic matter hygroscopicity reduces direct and indirect forcing to more reasonable values: −0.13 W m −2 and −1.31 W m −2 , respectively. On climatology, improved aerosol treatments mitigate overestimation of aerosol optical depth.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2020

99 TcO 4 - removal from legacy defense nuclear waste by an alkaline-stable 2D cationic metal organic framework

Removal of 99 TcO 4 - from legacy defense nuclear tank waste at Savannah River Site is highly desirable for the purpose of nuclear safety and environmental protection, but currently not achievable given the extreme conditions including high alkalinity, high ionic strength, and strong radiation field. Herein, we present a potential solution to this long-term issue by developing a two-dimensional cationic metal organic framework SCU-103, showing ultrahigh stability in alkaline aqueous media and great resistance to both β and γ radiation. More importantly, it is very effective for 99 TcO 4 - separation from aqueous media as demonstrated by fast exchange kinetics, high sorption capacity, and superior selectivity, leading to the successful removal of 99 TcO 4 - from actual Savannah River Site high level tank waste for the first time, to the best of our knowledge. In addition, the uptake mechanism is comprehensively elucidated by molecular dynamics simulation and density functional theory calculation, showing a unique chemical recognition of anions with low charge density.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2024

ContScout: sensitive detection and removal of contamination from annotated genomes

Contamination of genomes is an increasingly recognized problem affecting several downstream applications, from comparative evolutionary genomics to metagenomics. Here we introduce ContScout, a precise tool for eliminating foreign sequences from annotated genomes. It achieves high specificity and sensitivity on synthetic benchmark data even when the contaminant is a closely related species, outperforms competing tools, and can distinguish horizontal gene transfer from contamination. A screen of 844 eukaryotic genomes for contamination identified bacteria as the most common source, followed by fungi and plants. Furthermore, we show that contaminants in ancestral genome reconstructions lead to erroneous early origins of genes and inflate gene loss rates, leading to a false notion of complex ancestral genomes. Taken together, we offer here a tool for sensitive removal of foreign proteins, identify and remove contaminants from diverse eukaryotic genomes and evaluate their impact on phylogenomic analyses.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Deployment expectations of multi-gigatonne scale carbon removal could have adverse impacts on Asia’s energy-water-land nexus

Abstract Existing studies indicate that future global carbon dioxide (CO 2 ) removal (CDR) efforts could largely be concentrated in Asia. However, there is limited understanding of how individual Asian countries and regions will respond to varying and uncertain scales of future CDR concerning their energy-land-water system. We address this gap by modeling various levels of CDR-reliant pathways under climate change ambitions in Asia. We find that high CDR reliance leads to residual fossil fuel and industry emissions of about 8 Gigatonnes CO 2 yr −1 (GtCO 2 yr −1 ) by 2050, compared to less than 1 GtCO 2 yr −1 under moderate-to-low CDR reliance. Moreover, expectations of multi-gigatonne CDR could delay the achievement of domestic net zero CO 2 emissions for several Asian countries and regions, and lead to higher land allocation and fertilizer demand for bioenergy crop cultivation. Here, we show that Asian countries and regions should prioritize emission reduction strategies while capitalizing on the advantages of carbon removal when it is most viable.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗
DOE OSTI2024

Entropy removal of medical diagnostics

Shannon entropy is a core concept in machine learning and information theory, particularly in decision tree modeling. To date, no studies have extensively and quantitatively applied Shannon entropy in a systematic way to quantify the entropy of clinical situations using diagnostic variables (true and false positives and negatives, respectively). Decision tree representations of medical decision-making tools can be generated using diagnostic variables found in literature and entropy removal can be calculated for these tools. This concept of clinical entropy removal has significant potential for further use to bring forth healthcare innovation, such as quantifying the impact of clinical guidelines and value of care and applications to Emergency Medicine scenarios where diagnostic accuracy in a limited time window is paramount. This analysis was done for 623 diagnostic tools and provided unique insights into their utility. For studies that provided detailed data on medical decision-making algorithms, bootstrapped datasets were generated from source data to perform comprehensive machine learning analysis on these algorithms and their constituent steps, which revealed a novel and thorough evaluation of medical diagnostic algorithms.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2023

Large global variations in the carbon dioxide removal potential of seaweed farming due to biophysical constraints

Abstract Estimates suggest that over 4 gigatons per year of carbon dioxide (Gt-CO 2 year −1 ) be removed from the atmosphere by 2050 to meet international climate goals. One strategy for carbon dioxide removal is seaweed farming; however its global potential remains highly uncertain. Here, we apply a dynamic seaweed growth model that includes growth-limiting mechanisms, such as nitrate supply, to estimate the global potential yield of four types of seaweed. We estimate that harvesting 1 Gt year −1 of seaweed carbon would require farming over 1 million km 2 of the most productive exclusive economic zones, located in the equatorial Pacific; the cultivation area would need to be tripled to attain an additional 1 Gt year −1 of harvested carbon, indicating dramatic reductions in carbon harvest efficiency beyond the most productive waters. Improving the accuracy of annual harvest yield estimates requires better understanding of biophysical constraints such as seaweed loss rates (e.g., infestation, disease, grazing, wave erosion).

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2025

Applying equity principles leads to higher carbon removal obligations in Canada

Despite net-zero pledges, consensus on national responsibilities for carbon dioxide removal (CDR) strategies is lacking. Here, we use integrated assessment modeling to examine equity-informed estimates of Canada’s remaining carbon budgets, exploring CDR’s role at net-zero and beyond. Gigaton-scale CDR efforts post-2050 are needed to address Canada’s carbon debt under various burden-sharing principles. Cumulative negative emissions (2050-2100) could increase from 7.5 GtCO 2 in the Net-Zero scenario to 20.3 GtCO 2 in equity-informed scenarios. By 2100, a CDR portfolio, including bioenergy with carbon capture and storage, direct air capture, and enhanced weathering could contribute up to ~500 MtCO 2 /year of removals. The projected average CDR growth rates, 2.8%-16%/year, align with the historical adoption rates of ammonia synthesis and biomass consumption in Canada, underscoring the importance of drawing lessons from past successes. Socio-economic and technological sensitivity analysis highlights that, despite variations in the role of individual CDR technologies, CDR remains essential for Canada’s post-net-zero commitments.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2023

CO 2 coverage on Pd catalysts accelerates oxygen removal in oxy-combustion systems

Oxy-combustion systems result in enriched CO 2 in exhaust gases; however, the utilization of the concentrated CO 2 stream from oxy-combustion is limited by remnant O 2 . CH 4 oxidation using Pd catalysts has been found to have high O 2 -removal efficiency. Here, in this study, the effect of excess CO 2 in the feed stream on O 2 removal with CH 4 oxidation is investigated by combining experimental and theoretical approaches. Experimental results reveal complete CH 4 oxidation without any side-products, and a monotonic increase in the rate of CO 2 generation with an increase in CO 2 concentration in the feed stream. Density-functional theory calculations show that high surface coverage of CO 2 on Pd leads to a reduction in the activation energy for the initial dissociation of CH 4 into CH 3 and H, and also the subsequent oxidation reactions. A CO 2 -rich environment in oxy-combustion systems is therefore beneficial for the reduction of oxygen in exhaust gases.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Aliovalent gallium dopants remove Ti 3+ defects and improve photocatalytic and photoelectrochemical water oxidation properties of LaTiO 2 N

LaTiO 2 N is a promising semiconductor for the water splitting reaction due to its 2.1 eV band gap and stability against corrosion. However, its solar energy conversion is limited by Ti 3+ recombination defects introduced during ammonolysis. Here we show for the first time that Ti 3+ defects in LaTiO 2 N can be suppressed with incorporation of 2, 5, and 10% aliovalent gallium (Ga 3+ ) dopants during synthesis via the layered La 2 Ti 2 O 7 intermediate. Electron paramagnetic resonance (EPR) spectroscopy on the solid powders confirms a reduction in the Ti 3+ donor density from 2.97 × 10 17 cm −3 for the non-doped material to ∼6.24 × 10 16 cm −3 for 5% Ga-doped LaTiO 2 N. The remaining Ti 3+ defects are concentrated near the LaTiO 2 N surface, according to X-ray photoelectron spectroscopy. The defect reduction shifts the optical absorption edge from 2.02 to 2.09 eV and eliminates a broad absorption band at 1050 nm from the optical absorption spectra. It also removes a 1.0–1.7 eV sub-band gap photovoltage signal from surface photovoltage spectra. This suggests that empty Ti 3+ d-orbitals are located 1.0–1.7 eV above the LaTiO 2 N valence band edge. Removing these recombination states with increasing Ga 3+ content enhances the photoconversion efficiency of LaTiO 2 N during water oxidation. The optimized 2 wt% CoO x -loaded 5% Ga-doped LaTi O2 N material has a 16% AQE (400 nm) for O 2 production from aqueous silver nitrate solution and a ∼2.1 mA cm −2 water oxidation photocurrent at 1.23 V under 100 mW cm −2 Xe arc lamp illumination. The water oxidation photocurrent is stable during a 50 min test, and the Faraday efficiency for O 2 generation is 97%, confirming short-term corrosion stability of LaTiO 2 N. Altogether, these results provide a better understanding of the distribution, concentration, and impact of Ti 3+ defects on the optical, photovoltage, and photoelectrochemical properties of LaTiO 2 N. In combination with other defect control strategies, aliovalent Ga 3+ doping can help bring the solar energy conversion efficiency of LaTiO 2 N closer to the theoretical limit.

Wang, Li [University of California, Davis, CA (Uni↗
DOE OSTI2020

Benchmark Simulation of the Natural Convection Shutdown Heat Removal Test Facility Using SAM

Natural convection systems are a promising method to passively remove heat from reactor cavities during loss of forced flow accident scenarios. In this work at Argonne National Laboratory (ANL), a highly instrumented Natural Convection Shutdown Heat Removal Test Facility (NSTF) was used to demonstrate the effectiveness of air-cooled natural convection systems. In previous work, RELAP5-3D simulations were performed on this facility with favorable comparisons to experiment for mass flow rate, pressure drop, air temperature increase, and air velocity. Both experimental and simulation efforts with this facility present a useful opportunity to perform a benchmark study with the System Analysis Module (SAM). SAM is an advanced thermal-hydraulic system code currently in development at ANL for advanced non-light water reactor safety analysis.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2020

Review of Ion Exchange Technologies for Cesium Removal from Caustic Tank Waste

This article reviews the historical uses of and current research into ion exchange for the removal of cesium (Cs) from defense-related nuclear waste streams. Emphasis is placed on key attributes of the two current leading ion exchangers for Cs removal: spherical resorcinol-formaldehyde, an elutable organic resin, and crystalline silicotitanate, a non-elutable crystalline solid. An understanding of the successes, issues, and limitations of past ion exchange experience may be helpful in better understanding current ion exchanger use. Emphasis is placed on Cs capacity, exchange kinetics, stability, and column hydrodynamics for processing alkaline wastes as well as the final waste forms of the ion exchangers.

Fiskum, Sandra K.↗
DOE OSTI2021

Removing Atmospheric Fringes from Zwicky Transient Facility i-band Images using Principal Component Analysis

The Zwicky Transient Facility is a time-domain optical survey that has substantially increased our ability to observe and construct massive catalogs of astronomical objects by use of its 47 square degree camera that can observe in multiple filters. However the telescope’s i-band filter suffers from significant atmospheric fringes that reduce photometric precision, especially for faint sources and in multi-epoch co-additions. Here we present a method for constructing models of these atmospheric fringes using Principal Component Analysis that can be used to identify and remove these artifacts from contaminated images. In addition, we present the Uniform Background Indicator as a quantitative measurement of the reduced correlated background noise and photometric error present after removing fringes. We conclude by evaluating the effect of our method on measuring faint sources through the injection and recovery of artificial stars in both single-image epochs and co-additions. Our method for constructing atmospheric fringe models and applying those models to produce cleaned images is available for public download in the open source Python package fringez.

79 ASTRONOMY AND ASTROPHYSICS↗