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DOE OSTI2020

Electrodeposited Aluminum Oxide as Alternative to Conventional Pretreatments

Iron and zinc phosphate pretreatments are still heavily used in both the oil & gas and automotive industries as adhesion promoters for paints and E-coat systems. These solutions are known to generate hazardous sludges and rinse water which must be periodically disposed of, a problem made worse by the increasing desire for aluminum alloy incorporation in vehicles. This presentation will introduce novel electrodeposited aluminum oxide pretreatments as a sustainable alternative to phosphates. The aluminum oxide coatings improve corrosion resistance and paint adhesion, generate no hazardous waste streams, are cost-effective, and can be applied to any metal surface. This new type of surface pretreatment can conform to TT-C-490 Type IV and VI for Military applications on both ferrous and non-ferrous surfaces as well as automotive specifications for equivalent civilian markets. The thin aluminum oxide treatment also supports the development of lightweight coatings systems for automotive and aerospace applications without sacrificing performance and is a perfect complement to the E-coating process. Since aluminum oxide uses a chemical binding mechanism for paints, the surface can even be modified to offer excellent paint adhesion and corrosion resistance directly to top-coats without the need for primer. This opens a pathway to fewer coating steps for simplified paint application and lightweight, next-generation coatings systems.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Final Report on Aerosol Pretreatment Technology Performance and Benchmarking

Solvent-based post-combustion CO 2 capture (PCC) technology remains one of the leading methods to combat global CO 2 emissions produced from large-scale coal-fired power production. Advanced solventbased PCC technology has made significant improvements in design and performance that reduce capital and operating costs to enable its commercial use. Key to low cost, manageable logistics, and environmentally safe operation of solvent-based PCC technology are minimal solvent losses from the process through the treated gas stream exiting PCC plant absorbers. High flue gas aerosol particle concentrations (>10 5 particles/cm 3 ) for particles in the range of 70-200 nm have been shown to cause significant amine solvent losses for solvent-based PCC processes through several mechanisms including absorption of solvent and water into growing aerosol particles. Flue gas aerosol pretreatment technology is the only realistic and economically attractive method to reduce very high aerosol particle concentrations (>10 7 particles/cm 3 ) to enable solvent-based PCC for existing power plants lacking sufficient particle removal systems, such as baghouses. The overall goal of this project was to design, construct, independently test, and evaluate three flue gas aerosol pretreatment technologies identified to significantly reduce high aerosol particle concentrations (>10 7 particles/cm 3 ) in the 70-200 nm particle size range: (1) a novel, high-velocity water injection spray concept developed by RWE and tested by Linde, (2) an innovative electrostatic precipitator (ESP) device with optimized operating conditions developed by Washington University in St. Louis (WUSTL), and (3) a non-regenerative sorbent-based filter technology developed by InnoSepra for SO x and NO x removal from coal-fired power plant flue gas. Each technology has been validated with tests on 500-1000 scfm of actual coal-fired flue gas and evaluated in terms of particle removal efficiency (%), cost competitiveness, and environmental impact. Aerosol measurements were performed upstream and downstream of each aerosol reduction unit during independent testing of each technology using advanced instrumentation and analytical methods provided by WUSTL. To perform aerosol measurements, isokinetic probes were inserted into flanged pipes attached to the flue gas piping, and a small suction pump was used to sample gas containing aerosol particles. Aerosol particle number concentrations (# particles/cm 3 ) and size distributions were then measured using a scanning mobility particle sizer (SMPS, TSI Inc.) for very fine particles (<1,000 nm) and a particle counter manufactured by GRIMM for particles larger than 1,000 nm. This report summarizes the aerosol removal performance results from pilot scale testing of each technology. Performance results have been benchmarked against pre-defined targets and other flue gas aerosol pretreatment technologies with documented performance. Linde Gas North America LLC has been the prime contractor to DOE responsible for overall project management and provided the design for the high-velocity water spray-based aerosol removal technology based on a design concept developed by the German utility company RWE.

20 FOSSIL-FUELED POWER PLANTS↗

DOE OSTI2026

Diol-enhanced natural deep eutectic solvents for efficient poplar pretreatment

Natural deep eutectic solvents (NDESs) are promising biomass pretreatment media, but their industrial application is often hindered by high viscosity. To address this limitation, diol-enhanced ternary DESs (TDESs) were prepared by incorporating 1,4-butanediol (1,4-BDO) or ethylene glycol (EG) into a choline chloride (ChCl) and 3,4-dihydroxybenzoic acid (DHBA) system. The applied TDESs maintained a liquid state at room temperature and had significantly reduced viscosity compared to the binary DES (BDES). In addition, the applied diols increased lignin solubility and suppressed lignin condensation by intercepting reactive carbocation intermediates. As a result, the recovered lignins from diol-induced TDES pretreatments showed better preservation of β-O-4 linkages and reduced condensation, improving their potential for downstream valorization. The diol-assisted DES systems showed a synergistic effect from the reduced viscosity, enhanced lignin solubility, and suppression of unwanted condensation, resulting in more effective biomass pretreatment performance, including the enhanced delignification and higher enzymatic digestibility compared to BDES. The 1,4-BDO-enhanced DES was also successfully applied to DHBA-enriched transgenic poplar, highlighting its potential for the processing of engineered biomass feedstocks.

3,4-dihydroxybenzoic acid↗

DOE OSTI2020

Effects of CELF Pretreatment Severity on Lignin Structure and the Lignin-Based Polyurethane Properties

Conversion of technical lignin into performance biopolymers such as polyurethane offers environmental and economic advantages when combined with production of biofuels from biomass sugars, presenting significant interest toward studying the role of pretreatment on lignin structure and functionality. Co-solvent enhanced lignocellulosic fractionation (CELF) pretreatment, employing acidic aqueous tetrahydrofuran (THF) mixtures, was developed to effectively break down the lignin-carbohydrate matrix and promote extraction of lignin from lignocellulosic biomass with desirable purity and yield. In this study, we report the effects of CELF pretreatment reaction severity on the molecular structure of CELF-extracted lignin and its impact toward the mechanical properties of the resulting lignin-based polyurethanes. Reaction temperature was found to play the most significant role, compared to reaction time and acidity, in manipulating structural features such as molecular weight, functionality and intra-polymer structure. At the severe reaction conditions at 180°C, the order of reactivity for primary lignin interlinkages characterized by semiquantitative HSQC NMR analysis were found to be β-ether > phenylcoumaran (β−5′) > resinol (β−β′) facilitating a high degree of depolymerization and yielding a high frequency of free phenolics and reduced aliphatic hydroxyl groups. All side-chain interlinkages were depleted converting guaiacyl subunits into condensed forms, while still retaining uncondensed syringyl subunits. Under the mild 150°C temperature reaction, CELF lignin had higher molecular weight and retained more β-ether interlinkages. The results from CELF lignin-based polyurethane synthesis indicated that the tensile properties depended on the miscibility of CELF lignin with other components and low molecular weight cuts improved the dispersion of lignin in the polyurethane network. Pre-mixing of CELF with poly(ethylene glycol) (PEG) reduced the brittleness and improved the ductility of the CELF lignin-PEG polyurethanes.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2025

Evaluating Pretreatment Strategies with Modeling for Reducing Scaling Potential of Reverse Osmosis Concentrate: Insights from Ion Exchange and Activated Alumina

Reverse osmosis concentrate (ROC) treatment is critical for enhancing water recovery and minimizing concentrate volume for disposal, especially in regions facing water scarcity. This study investigates the application of ion exchange (IX) resins and activated alumina (AA) as pretreatment strategies to mitigate scaling in ROC due to high concentrations of total dissolved solids, hardness (Ca 2+ and Mg 2+ ), and silica. Through a series of Langmuir isotherms, continuous column experiments, and model simulation, two types of strong acid cation IX resins and three types of strong base anion IX resins alongside three types of AA were evaluated. Results indicate that AA exhibits superior performance in silica removal, achieving up to a 65% reduction and maintaining performance for up to 800 bed volume without reaching saturation. Model simulation of a secondary reverse osmosis treating ROC after the IX and AA pretreatment indicated an additional water recovery of ~70% using antiscalants. This study demonstrates the potential for achieving higher water recovery while also identifying opportunities for pretreatment improvement. Challenges such as the limited IX capacity treating ROC, which requires frequent regeneration and increases operational costs, along with the restricted regeneration capacity of AA, underscore the importance of innovation. These findings emphasize the critical need for developing advanced materials and optimized strategies to further enhance the efficiency of ROC treatment processes.

activated alumina↗

NASA NTRS1973

Combination of an electrolytic pretreatment unit with secondary water reclamation processes

The design and fabrication of a flight concept prototype electrolytic pretreatment unit (EPU) and of a contractor-furnished air evaporation unit (AEU) are described. The integrated EPU and AEU potable water recovery system is referred to as the Electrovap and is capable of processing the urine and flush water of a six-man crew. Results of a five-day performance verification test of the Electrovap system are presented and plans are included for the extended testing of the Electrovap to produce data applicable to the combination of electrolytic pretreatment with most final potable water recovery systems. Plans are also presented for a program to define the design requirements for combining the electrolytic pretreatment unit with a reverse osmosis final processing unit.

Wells, G. W.↗

NASA NTRS1983

Urine pretreatment for waste water processing systems

Recovery of high quality water from urine is an essential part of life support on a Space Station to avoid costly launch and resupply penalties. Water can be effectively recovered from urine by distillation following pretreatment by a chemical agent to inhibit microorganism contamination and fix volatile ammonia constituents. This paper presents the results of laboratory investigations of several pretreatment chemicals which were tested at several concentration levels in combination with sulfuric acid in urine. The optimum pretreatment formulation was then evaluated with urine in the Hamilton Standard Thermoelectric Integrated Membrane Evaporation Subsystem (TIMES). Over 2600 hours of test time was accumulated. Results of these laboratory and system tests are presented in this paper.

Winkler, H. E.↗

NASA NTRS1993

Microbiological test results of the environmental control and life support systems vapors compression distillation subsystem recycle tank components following various pretreatment protocols

Microbiological samples were collected from the recycle tank of the vapor compression distillation (VCD) subsystem of the water recovery test at NASA MSFC following a 68-day run. The recycle tank collects rejected urine brine that was pretreated with a commercially available oxidant (Oxone) and sulfuric acid and pumps it back to the processing component of the VCD. Samples collected included a water sample and two swab samples, one from the particulate filter surface and a second from material floating on the surface of the water. No bacteria were recovered from the water sample. Both swab samples contained a spore-forming bacterium, Bacillus insolitus. A filamentous fungus was isolated from the floating material. Approximately 1 month after the pretreatment chemicals were changed to sodium hypochlorite and sulfuric acid, a swab of the particulate filter was again analyzed for microbial content. One fungus was isolated, and spore-forming bacteria were observed. These results indicate the inability of these pretreatments to inhibit surface attachment. The implications of the presence of these organisms are discussed.

Huff, Tim↗

NASA NTRS1994

Thermal-oxidative Pretreatment and Evaluation of Poly (hexafluoropropene Oxide) Fluids

Two commercial poly(hexafluoropropene oxide) fluids were thermally pretreated at 343 C in pure oxygen. IR and NMR spectra indicate that this pretreatment was effective in removing hydrogen end-capped impurities. Decrease in the quantity of volatile material produced during thermal oxidative decomposition and increase in the thermal decomposition temperature indicated improvement in the stability of the fluids. However, this pretreatment failed to render the fluids completely stable in oxidizing atmospheres at 316 C in the presence of metal alloys.

Paciorek, K. J. L.↗

NASA NTRS1995

Thermal-oxidative pretreatment and evaluation of poly(hexafluoropropene oxide) fluids

Two commercial poly(hexafluoropropene oxide) fluids were thermally pretreated at 343 C in pure oxygen. IR and nuclear magnetic resonance(NMR) spectra indicate that this pretreatment was effective in removing hydrogen end-capped impurities. A decrease in the quantity of volatile material produced during thermal oxidative decomposition and increase in the thermal decomposition temperature indicated improvement in the stability of the fluids. However, this pretreatment failed to render the fluids completely stable in oxidizing atmospheres at 316 C in the presence of metal alloys.

Paciorek, K. J. L.↗

NASA NTRS2012

Nonhazardous Urine Pretreatment Method

A method combines solid phase acidification with two non-toxic biocides to prevent ammonia volatilization and microbial proliferation. The safe, non-oxidizing biocide combination consists of a quaternary amine and a food preservative. This combination has exhibited excellent stabilization of both acidified and unacidified urine. During pretreatment tests, composite urine collected from donors was challenged with a microorganism known to proliferate in urine, and then was processed using the nonhazardous urine pre-treatment method. The challenge microorganisms included Escherichia coli, a common gram-negative bacteria; Enterococcus faecalis, a ureolytic gram-positive bacteria; Candida albicans, a yeast commonly found in urine; and Aspergillus niger, a problematic mold that resists urine pre-treatment. Urine processed in this manner remained microbially stable for over 57 days. Such effective urine stabilization was achieved using non-toxic, non-oxidizing biocides at higher pH (3.6 to 5.8) than previous methods in use or projected for use aboard the International Space Station (ISS). ISS urine pretreatment methods employ strong oxidants including ozone and hexavalent chromium (Cr(VI)), a carcinogenic material, under very acidic conditions (pH = 1.8 to 2.4). The method described here offers a much more benign chemical environment than previous pretreatment methods, and will lower equivalent system mass (ESM) by reducing containment volume and mass, system complexity, and crew time needed to handle pre-treatment chemicals. The biocides, being non-oxidizing, minimize the potential for chemical reactions with urine constituents to produce volatile, airborne contaminants such as cyanogen chloride. Additionally, the biocides are active under significantly less acidic conditions than those used in the current system, thereby reducing the degree of required acidification. A simple flow-through solid phase acidification (SPA) bed is employed to overcome the natural buffering capacity of urine, and to lower the pH to levels that fix ammoniacal nitrogen in the non-volatile and highly water soluble NH4 + form. Citric acid, a highly soluble, solid tricarboxylic acid essential to cellular metabolism, and typically used as a food preservative, has also been shown to efficiently acidify urine in conjunction with non-oxidizing biocides to provide effective stabilization with respect to both microbial growth and ammonia volatilization.

Akse, James R.↗

NASA NTRS2015

Development of a Low Toxicity Urine Pretreatment for Water Recovery in Space

Wastewater stabilization was an essential component of the spacecraft water cycle. The purpose of stabilizing wastewater was two-fold. First, stabilization prevents the breakdown of urea into ammonia, a toxic gas at high concentrations. Second, it prevents the growth of microorganisms, thereby mitigating hardware and water quality issues due to due biofilm and planktonic growth. Current stabilization techniques involve oxidizers and strong acids (pH=2) such as chromic and sulfuric acid, which are highly toxic and pose a risk to crew health. The purpose of this effort was to explore less toxic stabilization techniques, such as food-grade and commercial care preservatives. Additionally, certain preservatives were tested in the presence of a low-toxicity organic acid. Triplicate 300-mL volumes of urine were dosed with a predetermined quantity of stabilizer and stored for two weeks. During that time, pH, total organic carbon (TOC), ammonia, and turbidity were monitored. Those preservatives that showed the lowest visible microbial growth and stable pH were further tested in a six-month stability study. The results of the six-month study are also included in this paper. Additionally, the pretreatment formulations were tested to determine if the pretreated urine could be distilled to remove 85% of the water, as would occur on the ISS. The goal of the pretreatment was to produce no solids in the resulting brine at 85% water recovery.

Adam, Niklas↗

NASA NTRS2015

NASA and ESA Collaboration on Hexavalent Chrome Alternatives - Pretreatments with Primers Screening Final Test Report

Hexavalent chromium (hex chrome or Cr(VI)) is a widely used element within applied coating systems because of its self-healing and corrosion-resistant properties. The replacement of hex chrome in the processing of aluminum for aviation and aerospace applications remains a goal of great significance. Aluminum is the major manufacturing material of structures and components in the space flight arena. The National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA) are engaged in a collaborative effort to test and evaluate alternatives to hexavalent chromium containing corrosion coating systems. NASA and ESA share common risks related to material obsolescence associated with hexavalent chromium used in corrosion-resistant coatings. In the United States, Occupational Safety and Health Administration (OSHA) studies have concluded that hexavalent chromium is carcinogenic and poses significant risk to human health. On May 5, 2011, amendments to the Defense Federal Acquisition Regulation Supplement (DFARS) were issued in the Federal Register. Subpart 223.73 prohibits contracts from requiring hexavalent chromium in deliverables unless certain exceptions apply. Subpart 252.223-7008 provides the contract clause prohibiting contractors and subcontractors from using or delivering hexavalent chromium in a concentration greater than 0.1 percent by weight for all new contracts associated with supplies, maintenance and repair services, and construction materials. ESA faces its own increasingly stringent regulations within European directives such as Registration, Evaluation, Authorization and Restriction of Chemical (REACH) substances and the Restriction of Hazardous Substances Directive (RoHS) which have set a mid-2017 sunset date for hexavalent chromium. NASA and ESA continue to search for an alternative to hexavalent chromium in coatings applications that meet their performance requirements in corrosion protection, cost, operability, and health and safety, while typically specifying that performance must be equal to or greater than existing systems. The overall objective of the collaborative effort between NASA TEERM and ESA is to test and evaluate coating systems (pretreatments, pretreatments with primer, and pretreatments with primer and topcoat) as replacements for hexavalent chrome coatings in aerospace applications. This objective will be accomplished by testing promising coatings identified from previous NASA, ESA, Department of Defense (DOD), and other project experience. Additionally, several new materials will be analyzed according to ESA-identified specifications.

coating↗

DOE OSTI2025

Impact of low-chemical storage pretreatment of loblolly pine bark on biochar from microwave pyrolysis

Forest product residues such as bark represent a low-cost, abundant feedstock for bioenergy, but their high ash and alkali and alkaline earth metal (AAEM) content limit thermochemical conversion efficiency. This study evaluates the use of low-severity chemical pretreatments during anaerobic storage to improve the performance of microwave pyrolysis for loblolly pine bark. Bark was treated with dilute sulfuric acid (0.1% and 1%, w/w) or sodium hydroxide (4%, w/w) and incubated anaerobically for one or two weeks to simulate in-pile biorefinery storage. The most effective treatment—1% H2SO4 for two weeks—reduced AAEM content by 35.7% and increased bio-oil yield by 11% compared to untreated controls, while also reducing pyrolysis gas production. In contrast, alkali treatment did not reduce AAEM levels and led to decreased bio-oil yields with increased gas formation. Although biochar yields were relatively stable across treatments, their physicochemical characteristics varied significantly. Acid-treated bark yielded biochars with higher carbon content, lower O/C and H/C ratios, greater surface area, and enhanced heating values. These improvements suggest that chemical pretreatment during storage can tailor biochar quality for specific end uses. Biochars produced under optimized conditions exhibited properties suitable for soil amendment, carbon sequestration, and solid fuel applications. This integrated approach—combining storage, mild chemical conditioning, and microwave pyrolysis—provides a viable pathway to enhance the value and sustainability of bark-derived bioenergy products.

09 - BIOMASS FUELS↗

DOE OSTI2022

Improved valorization of sewage sludge in the circular economy by anaerobic digestion: Impact of an innovative pretreatment technology

Anaerobic digestion (AD) of sewage sludge shows low carbon conversion efficiency (CCE) due to the poor biodegradability of sewage sludge. Here, the lack of digestibility is specifically linked to the waste-activated sludge (WAS) making up the majority of sewage sludge along with a smaller portion of primary sludge, depending on the wastewater treatment plant configuration. In this study, we examine the Advanced Wet Oxidation & Steam Explosion process (AWOEx) for improving the CCE of digested sewage sludge (DSS) by thermophilic AD. The effect of the pretreatment temperature in the range between 160 and 185 °C at a fixed residence time of 20 min with and without oxygen added at a dosage of 5 % of the organics present was tested. Methane yield improved by 97.92 % to 183.91 ± 4.93 mL/g vS over the untreated DSS (control), whose methane yield was 92.92 ± 9.07 mL/g vS We have demonstrated for the first time that 84 % of the organics in sewage sludge can successfully be transformed into biogas following AWOEx pretreatment, which can contribute significantly to the circular economy instead of greenhouse gas emissions from landfilling.

09 BIOMASS FUELS↗

DOE OSTI2022

The bamboo delignification saturation point in alkaline hydrogen peroxide pretreatment and its association with enzymatic hydrolysis

A delignification saturation point (DSP) was observed for bamboo alkaline hydrogen peroxide pretreatment (AHP). Lignin removal was increased from 52.23% to ~70% when increasing H 2 O 2 dosage from 0% to 2% at the optimum pH, but it cannot be further reinforced as increasing the H 2 O 2 . With partial lignin preserved, the glucan hydrolysis yield was found to have a ceiling of ~80%. This work indicated a strong association between enzymatic digestibility and lignin removal. Anatomical analysis by fluorescence microscope and confocal Raman microscope revealed that the undegradable lignin was mainly existing in the cell corner of sclerenchyma fibers, causing the DSP in the bamboo AHP. Finally, the residual lignin in pretreated bamboo was characterized with GPC, HSQC NMR, and 31 P NMR, which revealed the nature of DSP. This study could help to understand the lignin modification during the AHP and further contribute to the establishment of a chemical-saving biorefinery.

09 BIOMASS FUELS↗

DOE OSTI2023

Atomistic origins of biomass recalcitrance in organosolv pretreatment

Separation of lignocellulosic biomass components for use in sustainable energy and biomaterials applications remains challenging, since biopolymers such as cellulose and hemicellulose carbohydrates and polyaromatic lignin are found in close proximity within the plant secondary cell wall. Organic solvents have been used to pretreat recalcitrant biomass and separate the interacting polymers, solubilizing the lignin fraction for lignin-first valorization approaches. However, no single organosolv pretreatment approach has proven superior for heterogeneous biomass samples. Here we present a complementary atomic view of interactions between biomass components using molecular simulations, specific to lignin and cellulose, resolving mechanistic hypotheses for how lignin-cellulose composition influences separation processes. Further, using lignin-cellulose binding free energy calculated using molecular simulations, we find polar protic solvents such as methanol and ethanol separate lignin from cellulose, irrespective of the charge on the lignin monomer. Aprotic organic solvents (DMSO, THF, 1,4-dioxane) separate uncharged lignin (phenols and monolignols) from cellulose, while charged lignin (cinnamates) prefer binding to cellulose.

09 BIOMASS FUELS↗

DOE OSTI2020

The effect of lignin degradation products on the generation of pseudo-lignin during dilute acid pretreatment

Pseudo-lignin is an insoluble material that tends to deposit on acidic pretreated fiber surface and negatively impacts the biological conversion of biomass to valued added products. Employing a laboratory generated acidic hydrolysate solution from dilute acid pretreatment of bamboo residues, we sought to seek an improved understanding of pseudo-lignin formation from fragmented carbohydrates. In addition, we also performed experiments to investigate how lignin model compounds interact with carbohydrates en route to pseudo-lignin’s formation. The yields of pseudo-lignin generated from xylose (CXPL) were higher than those generated from glucose (CGPL). Gas chromatography-Mass spectrometry and Foloin-Ciocalteau analysis suggested that there were more aromatic compounds in hydrolyzate during CGPL’s formation. The presence of lignin phenolic model compounds had both a positive and negative effect upon quantitative yields of pseudo-lignin. Gel permeation chromatography and NMR analysis ( 31 P and 2D-HSQC NMR) of the pseudo-lignin samples generated in the presence and absence of 4-hydroxybenzoic acid (4-HA), employed as a lignin model compound, revealed drastic differences in molecular weight, changes in hydroxyl group content, and hydrocarbon bonds, suggesting significant differences in the pseudo-lignin reaction pathways when certain lignin model compounds are present. Finally, our findings demonstrate the effects of both hemicellulose carbohydrate makeup and lignin model compound impact on the formation of pseudo-lignin and its chemical properties, suggesting a potential way to minimize pseudo-lignin formation.

59 BASIC BIOLOGICAL SCIENCES↗