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.
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•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.
Polycrystalline silicon on silicon oxide (poly-Si/SiOx) passivating contacts can be used for ultra-high-efficiency interdigitated back contact (IBC) monocrystalline silicon solar cells. We evaluate ...the use of intrinsic poly-Si for the region that isolates the p- and n-type fingers at the back side of IBC devices. To mitigate shunt across the isolation region between the doped p- and n-type fingers, we demonstrate self-aligned subtractive processing by etching the poly-Si in the isolation region using SF6 plasma followed by etching in a tetramethylammonium hydroxide (TMAH) solution. After removal of the poly-Si, the isolation region was passivated with SiNx and Al2O3, which resulted in an 11.7% increase in the fill factor in a 19.8% efficient device. Furthermore, we evaluate the limitations of this device through Suns-Voc analysis and simulations using SunSolve and Quokka3 solar cell simulation software. Through Quokka3, we show that the most significant efficiency losses come from junction recombination current (J02) in the isolation region between doped fingers. We predict that the cell efficiency can be most improved with reduced J02 through better isolation of heavily doped fingers by etching the isolation region deeper into the bulk or through enhanced surface chemical passivation in this region.
•A novel method for simulating chalking of silicone rubber is proposed.•The similarity between naturally and artificially chalked samples is confirmed.•Diethylamine helps tetramethylammonium ...hydroxide work selectively at the interface.•Filler-polymer interface increases the probability of chalking.
Chalking is a universal aging phenomenon for silicone rubber (SR) used in external insulation. Under laboratory aging conditions, chalking is difficult to simulate. In this study, a new method based on the combination of tetramethylammonium hydroxide (TMAH) catalyst and diethylamine (DEA) solvent was proposed for the efficient artificial reproduction of SR chalking. Comparative analysis of the naturally and artificially chalked layers was performed through scanning electron microscopy, energy dispersive X-Ray spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy, among others. The macroscopic observation and microstructure analysis confirmed the similarity between the two chalking layers. According to the results of pyrolysis-gas chromatography-mass spectrometry, a mechanical model was established, which explained the reaction selectivity of TMAH on the filler–polymer interface, thereby resulting in the separation of the fillers and matrix (chalking). Finally, the proposed method for simulating chalking was used to verify the aging resistance of SR with different filler contents. The higher filler content introduced more interfaces, which increased the probability of chalking.
Chalking of silicone rubber (SR) is a universal and important aging phenomenon. However, performing chalking simulation to study the aging performance of SR in the laboratory is difficult. In this ...study, a controllable artificial chalking method, which was based on selective scission reactions using methylcyclohexane (MCH) and diethylamine (DEA) as solvents, and tetramethylammonium hydroxide as the catalyst, was developed. Through controlling the ratio between DEA and MCH, different chalking degrees of SR could be realized artificially. The macroscopic observation, scanning electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy were conducted to compare the differences of samples with various chalking degrees. Furthermore, the control mechanism of the degree of chalking and the function of DEA during the artificial chalking process was elucidated. The results demonstrated that the artificial chalking method was feasible and could help identify the anti-aging ability of SR.
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.
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•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.
Contemporary graffiti and murals became an artistic expression worthy of attention worldwide as well as their conservation. The application of spray paints with increasing technical performance ...mirrors the variety of the chemical composition of these increasingly common painting materials. An insight into the formulation and the ageing process is extremely important to predict and prevent the possible decay phenomena observed on outdoor urban artworks. This paper aims to investigate the relationship between the macroscopic outcomes and the chemical changes occurring on spray paints after the ageing by a multi-analytical approach. A systematic artificial ageing procedure was performed on multiple sets of concrete mock-ups painted with three different alkyd-based spray paints and in three different light-sensitive colours. The colour variation was assessed by colorimetric measurements, the changes in the paint cross section were observed by scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR) was applied both to characterize the spray paints and to detect the chemical changes of the organic compounds during the ageing. A significant and innovative contribution to this research is the application of the evolved gas analysis-mass spectrometry (EGA-MS) and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) with tetramethylammonium hydroxide in double-shot mode. These two analytical methodologies allowed an accurate classification of the different alkyd-based binders, the identification of plasticizers, organic pigments and other components often hard to spot in complex formulations, and an analysis of their fate following ageing.
•Py-GC/MS analyses were carried out in the double shot mode with TMAH.•Photooxidative ageing causes thinning of the spray paint layers.•Colour change of spray paints depends on the stability of pigments rather than binders.•The loss of adhesion and cohesion of spray paints depends on the ageing of binders.
An organic alkali such as tetramethylammonium hydroxide provides a viable alternative to the inorganic alkalis (NaOH / Na2CO3) as a pH-adjustment agent also acting as template molecule for the ...synthesis of Mg/Al-hydrotalcites with controlled texture. Its utilization overcame the disadvantages presented by the traditionally inorganic alkalis in terms of the solid contamination with alkaline cations, the amount of generated wastewaters and the energy consumption, etc. Moreover, the addition of the organo-alkali as cetyltrimethylammonium bromide (CTAB) in the synthesis mixture increases the control of the textural properties of the resulting solids. Both the basicity and the catalytic activities in the Claisen-Schmidt condensation between benzaldehyde and cyclohexanone followed a linear variation trend, e.g. mixed oxides > reconstructed layered structure > parent dried hydrotalcites. The conversion in the presence of these hydrotalcites synthesized using inorganic alkalis and CTAB reached 77.2%, while in the presence of the ones synthesized in the presence of TMAH of 74.3%. Further, the extraction of CTAB by ethanol, at RT or reflux temperature, led to an increase of the catalytic activity, while the corresponding mixed oxides generated 85.7% conversion of cyclohexanone. Also important, the specific texture of these afforded a total selectivity to 2,6-dibenzylidene-cyclohexanone. The presence of CTAB in the synthesis step seems to enhance the basicity and implicitly the catalytic activity of the hydrotalcites obtained using inorganic alkalis. Also, the resulted pore size favored a selective formation of the di-condensed compound. The derived mixed oxides also showed a good recyclability, since after five successive reaction cycles their catalytic activity decreased by less than 7%.
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•CTAB acts a template molecule for tailoring pure Mg/Al-hydrotalcites.•The CTAB extraction temperature plays an important role for the surface area.•The template molecule affords a tight pore distribution around of 100–110 Å.•All samples presented the memory effect.•Catalytic activities: mixed oxides > reconstructed HT > parent HT.
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.
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•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.
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.
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•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.