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Application of tetramethylammonium hydroxide for the treatment of samples prior to elemental analysis over the last five years is approached in this review article. Characteristics and properties of this reagent are described for a better understanding of the treatment process. Its effect on analyte measurements performed by atomic spectrometry techniques (flame and graphite furnace atomic absorption spectrometry, atomic fluorescence spectrometry, inductively coupled plasma optical emission spectrometry and, inductively coupled plasma mass spectrometry) is discussed, mainly the possibilities of physical interferences. Ways of using the reagent in sample preparation, such as incubation at room temperature, use of ultrasound energy, microwave energy, among others, will be discussed, in addition to the use of the reagent in speciation and nanoparticles analyses. Tetramethylammonium hydroxide has proven to be a viable alternative in the treatment of samples that can improve the performance of methods based on atomic spectrometry in the determination of elements of great interest to society.

The rapid urbanization and industrialization in China have led to an urgent dilemma for controlling urban air pollution, including the intensified emission of gasoline vapor into the atmosphere. Herein, we selected highland barley straw as a raw material and KOH and tetramethylammonium hydroxide (TMAOH) as activators to synthesize nitrogen-doped layered porous carbon (K-thAC) by a three-step activation method. The obtained K-thAC materials had a high specific surface area, reaching 3119 m2/g. Dynamic adsorption experiments demonstrated a superior adsorption capacity of up to 501 mg/g (K-thAC-25) for gasoline vapor compared with other documented carbon adsorbents. Moreover, adjusting the ratio of raw materials with a series of active ingredients could further improve the pore properties of the obtained K-thACs and their adsorption performance for gasoline vapor. Furthermore, the K-thAC materials were also characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), synchronous thermogravimetry (STA), X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption tests. This study synthesized a novel plant-based material to treat gasoline vapor pollution efficiently. [ABSTRACT FROM AUTHOR]

The process of crystallization of LTA type zeolite promising for practical use has been studied; the influence of various factors on the rate and selectivity of synthesis using natural minerals from Nakhchivan has been considered. The influence of temperature in the range of 80–150°C, the weight ratio of the initial components of halloysite (H) and obsidian (O) H : O equal to 1 : 1, 1 : 2, 1 : 3, 2 : 1, and 3 : 1, the concentration of the used thermal NaOH solution in the range of 5–30%, and the process duration in the range of 10–100 h for the crystallization of LTA were studied. It has been determined that the optimal conditions for the synthesis of a single-phase zeolite of the LTA type with 100% crystallinity are the temperature of 100 ± 10°C, the concentration of thermal NaOH solution of 10–15%, the ratio of the initial components of halloysite (H) and obsidian (O) H : O equal to 1 : 1, and the processing time of 20 h. Synthesis of zeolite LTA using natural minerals of Nakhchivan was carried out in the presence of tetramethylammonium hydroxide (TMAOH). The effect of temperature, concentration of thermal NaOH solution, ratio of initial components, and duration of aging on the process of LTA crystallization has been studied. It has been shown that violation of the optimal synthesis conditions leads to a decrease in the selectivity of the process and the formation of other zeolites (X), aluminosilicates (sodalite, anorthite, sanidine), or their associations, as well as quartz. The process of aging of zeolite was studied for 1 to 3 days. It has been determined that an increase in the aging duration leads to an increase in the linear rate of crystallization of the LTA zeolite. [ABSTRACT FROM AUTHOR]

The sidewall condition is a key factor determining the performance of micro‐light emitting diodes (µLEDs). In this study, equilateral triangular III‐nitride blue µLEDs are prepared with exclusively m‐plane sidewall surfaces to confirm the impact of sidewall conditions. It is found that inductively coupled plasma‐reactive ion etching (ICP‐RIE) causes surface damages to the sidewall and results in rough surface morphology. As confirmed by time‐resolved photoluminescence (TRPL) and X‐ray photoemission spectroscopy (XPS), tetramethylammonium hydroxide (TMAH) eliminates the etching damage and flattens the sidewall surface. After ICP‐RIE, 100 µm2‐µLEDs yield higher external quantum efficiency (EQE) than 400 µm2‐µLEDs. However, after TMAH treatment, the peak EQE of 400 µm2‐µLEDs increases by ≈10% in the low current regime, whereas that of 100 µm2‐µLEDs slightly decreases by ≈3%. The EQE of the 100 µm2‐µLEDs decreases after TMAH treatment although the internal quantum efficiency (IQE) increases. Further, the IQE of the 100 µm2‐µLEDs before and after TMAH treatment is insignificant at temperatures below 150 K, above which it becomes considerable. Based on PL, XPS, scanning transmission electron microscopy, and scanning electron microscopy results, mechanisms for the size dependence of the EQE of µLEDs are explained in terms of non‐radiative recombination rate and light extraction. [ABSTRACT FROM AUTHOR]

A rapid, cheap and feasible new approach was used to synthesize the Mg0.375Fe0.375Al0.25-LDH in the presence of tetramethylammonium hydroxide (TMAH), as a nontraditional hydrolysis agent, applying both mechano-chemical (MC) and co-precipitation methods (CP). For comparison, these catalysts were also synthesized using traditional inorganic alkalis. The mechano-chemical method brings several advantages since the number of steps and the energy involved are smaller than in the co-precipitation method, while the use of organic alkalis eliminates the possibility of contaminating the final solid with alkaline cations. The memory effect was also investigated. XRD studies showed Fe3O4 as stable phase in all solids. Regardless of the alkalis and synthesis methods used, the basicity of catalysts followed the trend: mixed oxides > parent LDH > hydrated LDH. The catalytic activity of the catalysts in the Claisen–Schmidt condensation between benzaldehyde and cyclohexanone showed a linear dependence to the basicity values. After 2 h, the calcined sample cLDH-CO32−/OH−-CP provided a conversion value of 93% with a total selectivity toward 2,6-dibenzylidenecyclohexanone. The presence of these catalysts in the reaction media inhibited the oxidation of benzaldehyde to benzoic acid. Meanwhile, for the self-condensation of cyclohexanone, the conversions to mono- and di-condensed compounds did not exceed 3.8%. [ABSTRACT FROM AUTHOR]

Nanofiltration (NF) is a promising technology in the treatment of microelectronic wastewater. However, the treatment of concentrate derived from NF system remains a substantial technical challenge, impeding the achievement of the zero liquid discharge (ZLD) goal in microelectronic wastewater industries. Herein, a ZLD system, coupling a two-stage NF technology with anaerobic biotechnology was proposed for the treatment of tetramethylammonium hydroxide (TMAH)-contained microelectronic wastewater. The two-stage NF system exhibited favorable efficacy in the removal of conductivity (96 %), total organic carbon (TOC, 90 %), and TMAH (96 %) from microelectronic wastewater. The membrane fouling of this system was dominated by organic fouling, with the second stage NF membrane experiencing a more serious fouling compared to the first stage membrane. The anaerobic biotechnology achieved a near-complete removal of TMAH and an 80 % reduction in TOC for the first stage NF concentrate. Methyloversatilis was the key genus involved in the anaerobic treatment of the microelectronic wastewater concentrate. Specific genes, including dmd-tmd , mtbA , mttB and mttC were identified as significant players in mediating the dehydrogenase and methyl transfer pathways during the process of TMAH biodegradation. This study highlights the potential of anaerobic biodegradation to achieve ZLD in the treatment of TMAH-contained microelectronic wastewater by NF system. [Display omitted] • The TMAH removal exceeded 96 % for microelectronic wastewater by the NF process. • Membrane fouling of NF system was dominated by organic fouling. • Anaerobic biotechnology achieved near-complete removal of TMAH from NF concentrate. • Methyloversatilis played a key role in biodegradation of TMAH from the NF concentrate. • Genes of dmd-tmd , mtbA , mttB and mttC were identified in the biodegradation of TMAH. [ABSTRACT FROM AUTHOR]

Tetramethylammonium hydroxide (TMAH), which is a chemical used in the electronic industry, is classified as a hazardous material (HAZMAT class 8) that threatens aquatic ecosystems and human health. Consequently, numerous studies have attempted to remove TMAH using various treatment methods, including advanced oxidation processes such as ozone, UV, or Fenton oxidation. However, prior research has indicated a low kinetic rate of TMAH removal. In this context, we proposed an alternative to TMAH degradation by combining a cold plasma (CP) process with periodate oxidation. As for the kinetics of TMAH removal, the kinetic constant was improved by 5 times (0.1661 and 0.0301 for 40.56 and 2.2 W, respectively) as the electric power of a CP system increased from 2.2 to 40.56 W. The kinetic constant of a 40.56 W CP system further increased by 54 times (1.6250) than a 2 W CP system when 4 mM periodate was used simultaneously. As a result, the integrated CP/periodate system represented 2 times higher TMAH removal efficiency (29.5%) than a 2 W CP system (14.4%). This excellent TMAH degradation capability of the integrated CP/periodate system became pronounced at pH 10 and 25 °C. Overall, the integrated CP/periodate system is expected to be a viable management option for effectively controlling hazardous TMAH chemicals. [Display omitted] • The integrated CP/periodate system successfully removed TMAH. • The CP/periodate process showed a higher kinetic constant than the other processes. • The optimal CP power and periodate concentration led to a 2 times higher removal rate. • The CP process reduced toxicity by over 50% in 1 h. • The integrated CP/periodate system performed best at pH 10 and 25 °C. [ABSTRACT FROM AUTHOR]

Reed straw is an abundant biomass resource throughout the world. Arabinoxylan is the main component of the hemicellulose in reed straw. A probe into the structure and rheological behavior of arabinoxylan from reed straw (AXRS) is valuable for its effective utilization. In this study, AXRS was extracted using 20% tetramethylammonium hydroxide (TMAH) aqueous solution as a solvent. AXRS consisted mainly of D-xylose and L-arabinose with a low molecular weight (104 kDa) according to HPLC and GPC analysis. FT-IR and NMR analyses showed AXRS had similar structure to arabinoxylans from other plants, which was further verified by XRD. TG analysis displayed that water loss from AXRS occurred in the temperature range of 30 °C to 240 °C, while degradation mostly took place between 240 °C and 350 °C under both air and nitrogen atmospheric conditions. The rheological measurements indicated that AXRS was completely dissolved in 20% TMAH aqueous solution and aggregated after reaching the critical concentration of around 0.062 g mL−1. With the enhancement of AXRS concentration, the storage modulus gradually increased, suggesting that AXRS aggregates may form in 20% TMAH aqueous solution. [Display omitted] • The characterization of arabinoxylan from reed straw (AXRS) shows that its main components are D-xylose and L-arabinose. • Rheological behavior of AXRS in 20% TMAH aqueous solution shows that its critical concentration is about 0.062 g mL−1. • This study is helpful to understand the properties of AXRS and boost its applications. [ABSTRACT FROM AUTHOR]

The rapid urbanization and industrialization in China have led to an urgent dilemma for controlling urban air pollution, including the intensified emission of gasoline vapor into the atmosphere. Herein, we selected highland barley straw as a raw material and KOH and tetramethylammonium hydroxide (TMAOH) as activators to synthesize nitrogen-doped layered porous carbon (K-thAC) by a three-step activation method. The obtained K-thAC materials had a high specific surface area, reaching 3119 m2/g. Dynamic adsorption experiments demonstrated a superior adsorption capacity of up to 501 mg/g (K-thAC-25) for gasoline vapor compared with other documented carbon adsorbents. Moreover, adjusting the ratio of raw materials with a series of active ingredients could further improve the pore properties of the obtained K-thACs and their adsorption performance for gasoline vapor. Furthermore, the K-thAC materials were also characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), synchronous thermogravimetry (STA), X-ray powder diffraction (XRD), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption tests. This study synthesized a novel plant-based material to treat gasoline vapor pollution efficiently.

Densities for various Tetramethylammonium hydroxide (TMAH) solutions at different temperatures have been determined based on Archimedes’ principle using a hydrostatic balance and a vitreous body with a defined volume. Due to the toxicity of the compound, these data are important especially in the field of wet processing techniques for the automated dosage of TMAH.

Square-wave adsorptive stripping voltammetry (SWAdSV) was used to determine iron in ethanol and biodiesel using a bismuth-film electrode (BiFE) prepared onto the surface of a glassy carbon electrode (GCE) by electrochemical deposition to promote the reduction of Fe (III) previously complexed with 1-(2-pyridylazo)-2-naphthol (PAN) directly in the electrochemical cell. The supporting electrolyte was composed by mixture of acetate buffer (0.1 mol L−1, pH 4.5) and ethanol (40/60% v/v) into which 500 µL of a 0.1 mmol L−1 stock solution of PAN was added as complexing agent. The Fe (III)-PAN complex presented a well-defined current peak at −0.7 V. For biodiesel, a treatment with tetramethylammonium hydroxide (TMAH) was proposed as an efficient mean to minimized matrix interferences. A limit of detection of 6.0 × 10−8 mol L−1 (0.06 µmol L−1) and limit of quantification of 2.0 × 10−7 mol L−1 (0.2 µmol L−1) were obtained for Fe(III). Under the optimized conditions, there were no significant interferences from Cu(II), Al(III), Mn(II), Cr(III), Cd(II), Zn(II) and Ni(II) and Pb(II) while Ni(II) interfered significantly. The analytical curves produced linear responses with equations I (µA) = (-1.315 × 10−7 ± 5.158 × 10−8) + (-0.238 ± 0.01) [Fe (III)] (µmol L−1), R2 = 0.992 and I (µA) = (-6.836 × 10−7 ± 1.124 × 10−8) + (-0.408 ± 0.013) [Fe (III)] (µmol L−1), R2=0.998 for pure ethanol and biodiesel, respectively. The method produced satisfactory results in quantifying original quantities of Fe(III) in fuel ethanol (5.65 ± 0.71 µmol L−1) and biodiesel (1.28 ± 0.25 µmol L−1) at a 95% confidence limit (n = 3). [ABSTRACT FROM AUTHOR]

Tetramethylammonium hydroxide (TMAH) is widely used as a developer and etchant in the thin-film transistor liquid crystal display industry, which is the main component of developer wastewater with low C/N ratio. This study investigated TMAH degradation by combined anaerobic/integrated fixed film activated sludge (A/IFAS) process, especially for nitrogen removal. Effects of process condition on the TMAH degradation were studied, including dissolved oxygen concentration in IFAS reactor and the temperature of anaerobic reactor. Especially, the nitrogen removal was studied through the monitoring of intermediate products during TMAH biodegradation. The results indicated that lower the anaerobic treatment temperature can provide more available organic matters to enhance the denitrification in the subsequent IFAS reactor. Less oxygen supply in the IFAS reactor contributed to simultaneous nitrification and denitrification. Removal efficiency of total organic carbon and total nitrogen was up to 95.8% and 80.7%, when the temperature of anaerobic treatment was controlled at 30 °C with the DO kept at 0.7 mg/L. It indicated that A/IFAS process was efficient in carbon and nitrogen removal for TMAH degradation. The results also confirmed intermediate products of TMAH biodegradation can be used as the electron donor during denitrification, including trimethylamine, dimethylamine and methylamine. Illumina MiSeq sequencing showed that Proteobacteria was the dominant phylum contribute to nitrogen removal. Compared to sludge flocs in IFAS reactor, richer community and higher microbial diversity were observed in the biofilm. [Display omitted] • Anaerobic/IFAS process was established for TMAH degradation. • Low anaerobic temperature and DO enhanced nitrogen removal. • TMAH degradation intermediates were more accessible for denitrification. • Biofilm had richer community and higher microbial diversity than sludge floc in IFAS. [ABSTRACT FROM AUTHOR]

Abstract Background Tetramethylammonium hydroxide (TMAH) is a quaternary ammonium compound that is both a base corrosive and a cholinergic agonist, and it is widely used in the photoelectric and semiconductor industries. It causes corrosive skin injuries and systemic cholinergic toxicity with death primarily resulting from respiratory failure without efficacious early decontamination. Methods A retrospective observational study was performed of all cases of TMAH exposure reported to the Taiwan Poison Control Center between July 2010 and October 2017. Retrieved medical records were independently reviewed by two trained clinical toxicologists. Results Despite immediate (

A rapid, cheap and feasible new approach was used to synthesize the Mg0.375Fe0.375Al0.25-LDH in the presence of tetramethylammonium hydroxide (TMAH), as a nontraditional hydrolysis agent, applying both mechano-chemical (MC) and co-precipitation methods (CP). For comparison, these catalysts were also synthesized using traditional inorganic alkalis. The mechano-chemical method brings several advantages since the number of steps and the energy involved are smaller than in the co-precipitation method, while the use of organic alkalis eliminates the possibility of contaminating the final solid with alkaline cations. The memory effect was also investigated. XRD studies showed Fe3O4 as stable phase in all solids. Regardless of the alkalis and synthesis methods used, the basicity of catalysts followed the trend: mixed oxides > parent LDH > hydrated LDH. The catalytic activity of the catalysts in the Claisen–Schmidt condensation between benzaldehyde and cyclohexanone showed a linear dependence to the basicity values. After 2 h, the calcined sample cLDH-CO32−/OH−-CP provided a conversion value of 93% with a total selectivity toward 2,6-dibenzylidenecyclohexanone. The presence of these catalysts in the reaction media inhibited the oxidation of benzaldehyde to benzoic acid. Meanwhile, for the self-condensation of cyclohexanone, the conversions to mono- and di-condensed compounds did not exceed 3.8%.

Quorum quenching (QQ) has been extensively studied in sewage treatment membrane bioreactors (MBRs) to alleviate biofouling, but its application in industrial-wastewater MBRs remains limited. This study confirmed the applicability of QQ in MBRs treating wastewater from the display manufacturing process. QQ alginate and QQ polyvinyl alcohol (PVA)/alginate beads, which entrapped Bacillus sp. SDC-U1, a QQ isolate from tetramethylammonium hydroxide (TMAH)-wastewater treatment sludge, were applied to a lab-scale MBR treating real wastewater containing TMAH, a developer used in the display manufacturing process. To immobilize pH-sensitive SDC-U1 on PVA/alginate beads, the first cross-linking solution's pH was adjusted to 5, followed by a 4 h incubation in Luria-Bertani broth to enhance the activity of SDC-U1. MBRs with QQ alginate and QQ PVA/alginate beads showed a 40 % and 365 % longer time to reach 30 kPa TMP, respectively, compared to MBRs without beads. QQ beads significantly reduced the concentration of various N -acyl homoserine lactones, which are signaling molecules involved in quorum sensing, in the MBR. The observation of biofilm on the membrane surface confirmed the biofouling mitigation by QQ application. This study demonstrates that biofouling can be effectively mitigated using appropriate QQ bacteria and their immobilization methods in industrial wastewater MBRs containing toxic substances like TMAH. [Display omitted] • Quorum quenching (QQ) could mitigate biofouling in display wastewater treatment MBR. • Bacillus sp. SDC-U1 was immobilized on polyvinyl alcohol(PVA)/alginate bead. • A method for immobilizing pH-sensitive bacteria on PVA/alginate beads was developed. • QQ PVA/alginate beads lengthened the recovery cleaning cycle by 4.8 times. • The activity of QQ PVA/alginate bead was maintained in the MBR for over 50 d. [ABSTRACT FROM AUTHOR]

Selective fractionation of hemicelluloses is of great significance for realizing high-value application of hemicelluloses and comprehensive utilization of lignocellulosic biomass. Tetramethylammonium hydroxide (TMAH) solvent has been confirmed as a promising solvent to selectively fractionate hemicelluloses from holocellulose. Herein, TMAH solvent was adopted to pretreat poplar thermomechanical pulp (PTMP) for the selective fractionation of hemicelluloses and enhancement of enzymatic hydrolysis performance of residues. The maximal hemicelluloses yield (65.0 %) and excellent cellulose retention rate (93.3 %) were achieved after pretreatment by the 25 wt% TMAH solvent, while the delignification was only 33.9 %. The hemicelluloses fractions could be selectively fractionated with high molecular weights (109,800–118,500 g/mol), the contents of Klason lignin in them were low (3.2–5.9 %), and the dominating structure of them was 4- O -methylglucurono- β -D-xylan. Compared to the H 2 SO 4 and NaOH methods, the hemicelluloses fractionated by TMAH method exhibited higher yields, more complete structures and higher molecular weights. Furthermore, the crystalline structure of cellulose practically remained stable, and the highest yield of enzymatic hydrolysis glucose was 57.5 %, which was 3.3 times of that of PTMP. The fractionation effectiveness of TMAH solvent was not significantly reduced after repeatedly recycling. This work demonstrated TMAH solvent could selectively fractionate hemicelluloses from PTMP and efficiently promote sustainable poplar-based biorefinery. • TMAH could selectively fractionate hemicelluloses from PTMP at room temperature. • Hemicelluloses showed a relatively good homogeneity in the form of macromolecules. • The contents of Klason lignin in hemicelluloses fractions were low (3.2–5.9 %). • The residues represented excellent cellulose retention rates (>93.3 %). • TMAH solvent exhibited recyclability for hemicelluloses fractionation. [ABSTRACT FROM AUTHOR]

In this study, an efficient method for O-methylation of phenolic compound using tetramethylammonium hydroxide (TMAOH) as a new alkylating agent under microwave irradiation was developed. Ethanol was selected as a green reaction media to accomplish this protocol under environmentallybenign conditions. Less than half hour time is needed to obtain good to excellent yields of products at temperature of about 120°C. Using this procedure, phenolic compounds could be converted to the corresponding aryl methyl derivatives quickly. The results indicated that different phenolic compounds bearing both electron-withdrawing and electron-donating groups are O-methylated effectively using TMAOH under microwave irradiation. This novel protocol has many improvements in view point of reaction yields, selectivity and conditions compared to previous studies. Trimethylamine and water were the side products of O-methylation reaction which can be recovered easily from the product mixture. This methodology showed high selectivity for O-methylation and no C-methylated products were observed.

Novel magnetic CoFe2O4-embedded MIL-101(Cr) with tetramethylammonium hydroxide (CoFe2O4/MIL-101T) was prepared through the facile hydrothermal method. Tetramethylammonium hydroxide acts as a template molecule and avoids the recrystallisation of terephthalic acid. The material was applied as the adsorbent in the magnetic solid-phase extraction (MSPE) process coupled with high-performance liquid chromatography to detect the five flame retardants in environmental water samples. Several parameters affecting MSPE efficiency were systematically investigated, such as MIL-101T content, material amount, desorption solvents, adsorption time, solution pH, theoretical maximum enrichment factor (EFmax) and the reusability. Under optimised conditions, good linearities were achieved for five flame retardants with correlation coefficients R2 > 0.9961. The limits of detections for analytes at the signal-to-noise ratio of three were 0.013–0.071 μg·L−1. This method was applied to the analysis of tap, pond, lake and river waters. The recoveries were in the range of 81.5 ± 3.2–107.0 ± 2.3% with the relative standard deviations ranging from 0.11% to 8.66% in four real water samples. The adsorption mechanism was the hydrophobic interaction between the material and the analytes besides pore adsorption action of the material. [ABSTRACT FROM AUTHOR]

This study investigated the feasibility of the methanogenic treatment of electronic industry wastewater containing tetramethylammonium hydroxide (TMAH), monoethanolamine (MEA) and sulfate in a lab-scale mesophilic up-flow anaerobic sludge blanket reactor. Feeding a mixture of electronic industry wastewater and co-substrate organics to the reactor for smooth acclimatization of sludge gave complete degradation of each organics within five days. When the reactor was fed only electronic industry wastewater, total COD removal, TMAH removal and MEA removal were achieved over 80, 99 and 99%, respectively, at an organic loading rate of 11.5 kg-COD m−3 day−1. 173 mg-S L−1 of influent sulfate was almost reduced simultaneously with the COD removal. In order to evaluate performance stability, the TMAH shock load event was performed under the conditions of 11,000 mg-COD L−1 for 24 h. Inflow of high TMAH concentration inhibited TMAH degradation and sulfate reduction for more than one month, however, not MEA. The batch feeding experiment and specific activity measurement revealed degradation pathways of each organics. TMAH was degraded via methanogenic pathway without sulfate reduction, MEA was degraded via methanogenic pathway with sulfate reduction. The results indicated that methanogenic treatment was applicable to electronic industry wastewater by appropriate reactor handling. [ABSTRACT FROM AUTHOR]

The treatment of tetramethylammonium hydroxide (TMAH)-bearing wastewater, generated in the electronic and semiconductor industries, raises significant concerns due to the neurotoxic, recalcitrant, and bio-inhibiting effects of TMAH. In this study, we proposed the use of an anaerobic hydrolysis bioreactor (AHBR) for TMAH removal, achieving a high removal efficiency of approximately 85%, which greatly surpassed the performance of widely-used advanced oxidation processes (AOPs). Density functional theory calculations indicated that the unexpectedly poor efficiency (5.8–8.0%) of selected AOPs can be attributed to the electrostatic repulsion between oxidants and the tightly bound electrons of TMAH. Metagenomic analyses of the AHBR revealed that Proteobacteria and Euryarchaeota played a dominant role in the transformation of TMAH through processes such as methyl transfer, methanogenesis, and acetyl-coenzyme A synthesis, utilizing methyl-tetrahydromethanopterin as a substrate. Moreover, several potential functional genes (e.g., mprF , basS , bcrB , sugE) related to TMAH resistance have been identified. Molecular docking studies between five selected proteins and tetramethylammonium further provided evidence supporting the roles of these potential functional genes. This study demonstrates the superiority of AHBR as a pretreatment technology compared to several widely-researched AOPs, paving the way for the proper design of treatment processes to abate TMAH in semiconductor wastewater. [Display omitted] • AOP was limited for TMAH removal due to electrostatic repulsion and tightly-held electrons. • Anaerobic hydrolysis bioreactor (AHBR) achieved TMAH removal efficiency of 85%. • Proteobacteria and Euryarchaeota were dominant microorganisms in AHBR. • Methyl transfer, methanogenesis and acetyl-CoA synthesis were pivotal in TMAH metabolism. • Molecular docking revealed the role of choline lyase and trimethylamine methyltransferase. [ABSTRACT FROM AUTHOR]

TMAH is quaternary ammonium salt, consists of a methylated nitrogen molecule, and is widely used in the electronics industry as a developer and silicon etching agent. This substance is toxic and fatal if ingested. It can also cause skin burns, eye damage, and organ damage. Moreover, TMAH exhibits long-lasting toxicity to aquatic systems. Despite this known toxicity, the authorities currently do not provide emission limits (i.e., discharge concentrations) for wastewater by EU regulation. The current scenario necessitates the study of the processes for industrial wastewater containing TMAH. This work aims to present a successful example of the treatment process for the degradation of TMAH waste solutions of the E&S industry. Research was conducted at the pilot scale, and the process feasibility (both technical and economic) and its environmental sustainability are demonstrated. This process, which treats three exhausted solutions with a high concentration of toxic substances, is considered to be innovative.

The optimization of etchant parameters in wet etching plays an important role in the fabrication of semiconductor devices. Wet etching of tetramethylammonium hydroxide (TMAH)/isopropyl alcohol (IPA) on silicon nanowires fabricated by AFM lithography is studied herein. TMAH (25 wt %) with different IPA concentrations (0, 10, 20, and 30 vol %) and etching time durations (30, 40, and 50 s) were investigated. The relationships between etching depth and width, and etching rate and surface roughness of silicon nanowires were characterized in detail using atomic force microscopy (AFM). The obtained results indicate that increased IPA concentration in TMAH produced greater width of the silicon nanowires with a smooth surface. It was also observed that the use of a longer etching time causes more unmasked silicon layers to be removed. Importantly, throughout this study, wet etching with optimized parameters can be applied in the design of the devices with excellent performance for many applications.

Abstract In nano-electronics manufacturing, tetramethylammonium hydroxide (TMAH) is extensively used in the photo-lithography and etching processes, leading to a waste disposal issue. The present study focuses on TMAH wastewater treatment in nano-electronics industries by using membrane distillation technology. Actual TMAH wastewater samples were collected at imec, Belgium. An air gap membrane distillation bench unit was employed to perform the experiments for different operating conditions i.e., feed temperatures and flow rates. High quality water is recovered after reducing the TMAH concentration to 1 ppm and lowering the TOC to 0.8 ppm from 8 ppm. For the industrial scale TMAH wastewater treatment, industrial waste heat driven and district heating driven membrane distillation systems are designed and analyzed. It is determined that 14 GWh thermal energy is required annually to treat 20,000 m3 of TMAH wastewater/year while considering 65 °C as the membrane distillation feed temperature. Expected unit water treatment cost is found as low as 16 $/m3 of TMAH wastewater, roughly 80% lower than current disposal costs. Highlights • TMAH wastewater treatment in nano-electronics facility via membrane distillation. • TMAH concentration reduced up to 99% in permeate. • Designed waste heat driven and district heating driven membrane distillation systems. • Annual thermal energy demand: 14 GWh to treat 20,000 m3 of TMAH wastewater/year. • Expected unit water treatment cost: 16 $/m3, 80% less than current disposal cost. [ABSTRACT FROM AUTHOR]

Highlights • THM-GC was applied to monitor the change in copolymer composition of film samples during soil burial test. • 3 HHx moieties in the polymer chains were preferentially biodegraded owing to their low crystallinity. • Local variation in the degree of biodegradation using only 30 μg of P(3HB-co-3HHx) film sample. Abstract Soil burial biodegradation behavior of poly(3-hydroxybutyrate- co -3-hydroxyhexanoate) [P(3HB- co -3HHx)] was studied based on its copolymer composition determined by thermally assisted hydrolysis and methylation-gas chromatography (THM-GC). The change in copolymer composition of P(3HB- co -3HHx) film samples during soil burial degradation test was monitored in detail by THM-GC. As a result, the copolymer compositions of 3HB units gradually increased, while those of 3HHx units decreased with soil burial time, almost correlating with recovery weight. Based on these results, the biodegradation mechanism of P(3HB- co -3HHx) was elucidated with considering the influence of the crystallinity on the biodegradability. Furthermore, local differences in biodegradability of a given P(3HB- co -3HHx) film after soil burial test were also successfully evaluated from the copolymer compositions obtained by THM-GC. [ABSTRACT FROM AUTHOR]

In this study, a continuous flow experiment was conducted in which a lab-scale upflow anaerobic sludge blanket (UASB) reactor at psychrophilic conditions (18-19°C) was fed with artificial wastewater, containing tetramethylammonium hydroxide (TMAH) and isoplophyl alcohol (IPA), from the electronics industry. This was done to evaluate process performance and microbial properties of the granular sludge that was retained in the reactor. The inoculated granular sludge was precultured with IPA containing wastewater but not TMAH; as a result, no degradation was observed in 30 days of operation. To enhance degradation, the reactor was seeded with 2% weight of the TMAH-enriched sludge, after which TMAH was enhanced. Consequently, the total COD removal efficiency reached 90% at an organic loading rate of 7.5 kg COD/m3/day. The TMAH inflow decreased the diameter of the retained granular sludge, but the sludge retained its settleability. The proliferation of the Methanometylovorans microorganisms present in the enrichment culture was confirmed by analysis of the 16 S rRNA gene in the retained sludge. In addition, TMAH degradation was inhibited by addition chloroform, a methanogen inhibitor. These results suggested species in the genus Methanometylovorans in the granular sludge contributed significantly to methanogenic TMAH degradation. [ABSTRACT FROM AUTHOR]

Determination of microplastics and nanoplastics (MNPs), especially small MPs and NPs (<150 μm), in solid environmental matrices is a challenging task due to the formation of stable aggregates between MNPs and natural colloids. Herein, a novel method for extracting small MPs and NPs embedded in soils/sediments/sludges has been developed by combining tetramethylammonium hydroxide (TMAH) digestion with dichloromethane (DCM) dissolution. The solid samples were digested with TMAH, and the collected precipitate was washed with anhydrous ethanol to eliminate the natural organic matter. Then, the MNPs in precipitate were extracted by dissolving in DCM under ultrasonic conditions. Under the optimized digestion and extraction conditions, the factors including sizes and concentrations of MNPs showed insignificant effects on the extraction process. The feasibility of this sample preparation method was verified by the satisfactory spiked recoveries (79.6-91.4%) of polystyrene, polyethylene, polypropylene, poly(methyl methacrylate), polyvinyl chloride, and polyethylene terephthalate MNPs in soil/sediment/sludge samples. The proposed sample preparation method was coupled with pyrolysis gas chromatography-mass spectrometry to determine trace small MPs and NPs with a relatively low detection limit of 2.3-29.2 μg/g. Notably, commonly used MNPs were successfully detected at levels of 4.6-51.4 μg/g in 6 soil/sediment/sludge samples. This proposed method is promising for evaluating small solid-embedded MNP pollution.

We have developed a method of food sample preparation for gamma spectrometry involving the use of tetramethylammonium hydroxide (TMAH) and/or enzymes such as α-amylase or cellulase for sample homogenization. We demonstrated the effectiveness of this method using food matrices spiked with Co, I, Cs, and Am radionuclides, homogenized with TMAH (mixed salad, parmesan cheese, and ground beef); enzymes (α-amylase for bread, and cellulase for baked beans); or α-amylase followed by TMAH (cheeseburgers). Procedures were developed which are best compromises between the degree of homogenization, accuracy, speed, and minimizing laboratory equipment contamination. Based on calculated sample biases and z-scores, our results suggest that homogenization using TMAH and enzymes would be a useful method of sample preparation for gamma spectrometry samples during radiological emergencies. [ABSTRACT FROM AUTHOR]

Thermally-assisted hydrolysis and methylation-gas chromatography-mass spectrometry (THM-GC-MS) using tetramethylammonium hydroxide (TMAH) is an effective approach for the characterization of condensation polymers with ester linkages such as ultraviolet (UV)-cured acrylate resins. However, for intractably cured acrylic resins, reliable structural characterization is often difficult by conventional THM-GC-MS owing to insufficient THM reactions. In this study, a pretreatment to effectively improve THM efficiency was proposed, in which the resin sample was preliminarily soaked and dissolved in a TMAH-methanol solution in a microtube. An aliquot of the TMAH solution was then introduced into the pyrolyzer at 400 °C to produce THM-GC-MS. The effectiveness of the proposed pretreatment was demonstrated using a UV-cured acrylate copolymer consisting of bulky and high-molecular weight bifunctional acrylate (9,9-Bis[4-(2-acryloyloxy ethoxy) phenyl]fluorene) and monofunctional acylate (2-(9 H-Carbazol-9-yl)ethyl acrylate) monomers, for which THM reactions did not proceed efficiently in conventional THM-GC-MS. Conversely, by the modified THM-GC-MS process with a pretreatment involving immersion at room temperature for 24 h or at 60 °C for 30 min, the characteristic decomposition products for each monomer unit were clearly observed in the chromatograms, and the copolymer composition could be precisely estimated from the relative yields of the observed decomposition products. In addition, a methyl acrylate peak, formed from unreacted acrylate moieties in the photocured copolymer, appeared in the chromatogram. Its relative yields were correlated to the double bond conversion in the cured sample. The observed results were successfully interpreted to clarify the curing process of the photocured acrylate copolymer samples. [Display omitted] • A THM-GC-MS method applicable to intractable UV-cured acrylate was developed. • The cured resin sample was preliminarily immersed and dissolved into a TMAH solution. • The copolymer composition of the intractable acrylate resin was precisely determined. • The double bond conversion was estimated by the modified THM-GC-MS method. • The observed results were interpreted in terms of the photocuring reactions. [ABSTRACT FROM AUTHOR]

Tetramethylammonium hydroxide (TMAH) is a corrosive alkaline and neuronal toxic compound, which is widely used in the thin-film transistor liquid crystal display industry. In this study the performance of the anaerobic sequencing batch reactors (SBR) for treating synthetic TMAH wastewater under different organic influent loads was evaluated thoroughly over a 208 day period. The results indicated that when the influent organic load was below 376.4 mg TOC/(L·day), total organic carbon (TOC) removal was enhanced with influent organic load increasing. And the maximum TOC removal efficiency and CH 4 production reached 92.5% and 589 mL/L reactor of one cycle, respectively. Further raising the load suppressed the TMAH degradation and microbiological activity. Only 6.0% organic nitrogen converted to ammonium and TOC removal efficiency declined to 13.5% at the influent organic load of 1130.5 mg TOC/ (L·day), with anaerobic sludge settling performance decline. And the biogas production of one cycle dropped to 60 mL/L reactor. It was also found that reducing influent organic load could not restore the system. Microbial diversity and richness also varied in response to the influent organic load. Illumina MiSeq sequencing analysis indicated Caldisericum , norank_f_KD1–131 , norank_f_Bacteroidetes_vadinHA17 , and Treponema were enriched at the influent load of 376.4 mg TOC/(L·day). RT-qPCR results confirmed that high influent organic load suppressed the expression of the ureC gene and mcrA gene , and then inhibited ammonification and methanogenesis. [Display omitted] • Performance of anaerobic SBR on TMAH removal was studied at different organic load. • The reactor started to deteriorate when organic load above 376.4 mg TOC/(L·day). • Reducing the organic load could not restore the reactor to its previous level. • High organic load caused a reduction in sludge settling performance. • Organic load could have an impact on the structure of the microorganisms community. [ABSTRACT FROM AUTHOR]

Lead titanate nanostructures with different phases and morphologies, layered hexagonal PbTiO2(CO3)0.3- (NO3)0.35(OH) nanosheets, pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates, have been synthesized via a conventional hydrothermal route assisted with different concentrations of tetramethylammonium hydroxide (TMAH). X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution TEM (HRTEM) were employed to characterize the phase, morphology and growth behavior of the synthesized samples. The results reveal that at low TMAH concentration the obtained samples are mainly of PbTiO2(CO3)0.3(NO3)0.35(OH) nanosheets. With the TMAH concentration increasing, the obtained samples change to pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates in turn. With the basis of the experimental results, the phase- and morphology-evolution mechanism of the lead titanate nanostructures is discussed by combining the analysis of the lattice structure feature and the properties of TMAH. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high electron mobility transistors (HEMTs) are fabricated using a gate recess process and a surface treatment with tetramethylammonium hydroxide (TMAH) prior to gate metal deposition. Electrical characterizations show improved extrinsic transconductance and saturation current, as well as more uniform off-state behavior with reduced off-current by a factor of 3.5 and gate leakage current by a factor of 4.2 in the devices with TMAH treatment. The analyses based on atomic force microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy show that the TMAH treatment effectively reduces the roughness of the recess-etched AlGaN surface and removes the native oxide layer on the AlGaN surface, suggesting a simple and viable route towards the fabrication of gate-recessed HEMTs based on AlGaN/GaN heterostructure with improved controllability and uniformity. [ABSTRACT FROM AUTHOR]