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.
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.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.
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.
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.
•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.
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.
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.
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.
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.
