Al-DTPA microfiber assisted formwork construction technology for high-performance SiC membrane preparation

Development of an asymmetric composite PPS-based bag-filter material through membrane laminating and superfine fiber blending: Lab test, field application and development of numerical models

Dedusting is crucial for air pollution control, and nonwoven needle felt (NWNF) bag-filters are widely applied for this purpose. Surface treatment of the filter materials can enhance NWNF's performance, but the large discrepancy in pore size between the surface and NWNF layers causes interface effects, impairing reverse cleaning and shortening service life. In this study, a novel PTFE membrane-laminated asymmetrical composite bag-filter was developed, by blending superfine polyphenylene sulfide fiber (PPS) in the original NWNF structure. Image analysis shows a gradual increase in pore size from the surface to the downstream layer. In standard lab-scale tests, the novel M-PPSF-S filter showed moderately higher resistance, significantly longer service life, higher dedusting efficiencies and better cleaning performance, compared to filters without surface laminating and/or superfine fiber blending. Numerical modelling was performed, and the flow fields and pressure distribution in these filter materials were visualized, confirming that M-PPSF-S' unique structure facilitated the alleviation of interface effect and non-steady flow. M-PPSF-S was further scaled up to treat real flue gas from a coal-fired power plant, where constant good performance was observed over 5 months. This study offers a novel and practical way to develop low-cost, high-performance filter materials for high temperature flue gas treatment.

3D spray-coated gradient profile ceramic membranes enables improved filtration performance in aerobic submerged membrane bioreactor

Rational design of cross-sectional microstructure in ceramic membranes has shown to improve membrane filtration efficacy without affecting rejection performance. In this work, we adopted 3D spray-coating technique to generate multi-layered membrane layers on macro-porous flat-sheet ceramic supports. The thickness of each layer was controlled by spray-coating cycles, and a gradient membrane layer was rationalized by successively coating three ceramic slurries containing alumina powders of gradually refined particle sizes, followed by co-sintering. Gradient membrane layers on both sides of the various sized flat-sheet ceramic supports were fabricated. Compared to the non-gradient counterpart, the gradient membranes showed both higher pure water flux (at the same TMP) and lower membrane resistance, which clearly evidenced the benefits of gradient profile in the membrane layer. Further, their performance in aerobic membrane bioreactors (AeMBR) was comparably studied for the first time. The treatment performance was not significantly affected by the types of membranes used, while the gradient membrane showed better filtration performance (i.e., a slower rise in TMP). Although the fouling mechanisms were revealed to be similar, the fouling layer in the gradient membrane was composed of a higher percentage of smaller foulants compared to that of the non-gradient counterpart. The observed differences were closely correlated to the larger internal pore structure in the gradient membrane. The present work provides a feasible 3D spray-coating technique for the fabrication of gradient flat-sheet ceramic membranes, and clarifies the benefits in AeMBR for domestic wastewater treatment.

Ceramic Processing of Silicon Carbide Membranes with the Aid of Aluminum Nitrate Nonahydrate: Preparation, Characterization, and Performance

The development of a low-cost and environmentally-friendly procedure for the fabrication of silicon carbide (SiC) membranes while achieving good membrane performance is an important goal, but still a big challenge. To address this challenge, herein, a colloidal coating suspension of sub-micron SiC powders was prepared in aqueous media by employing aluminum nitrate nonahydrate as a sintering additive and was used for the deposition of a novel SiC membrane layer onto a SiC tubular support by dip-coating. The sintering temperature influence on the structural morphology was studied. Adding aluminum nitrate nonahydrate reduced the sintering temperature of the as-prepared membrane compared to conventional SiC membrane synthesis. Surface morphology, pore size distribution, crystalline structure, and chemical and mechanical stability of the membrane were characterized. The membrane showed excellent corrosion resistance in acidic and basic medium for 30 days with no significant changes in membrane properties. The pure water permeance of the membrane was measured as 2252 L h-1 m-2 bar-1. Lastly, the final membrane with 0.35 µm mean pore size showed high removal of oil droplets (99.7%) in emulsified oil-in-water with outstanding permeability. Hence, the new SiC membrane is promising for several industrial applications in the field of wastewater treatment.

Global characteristics and trends of research on construction dust: based on bibliometric and visualized analysis

The booming construction industry has led to many environmental and occupational health and safety problems. Construction dust caused irreversible damage to the health of frontline workers and polluted the surrounding air environment, which has attracted the attention of researchers and practitioners. In this study, to systematically sort and analyze the distribution of construction dust (CD) research, its hot areas, and the evolution of its fronts, papers with "construction dust" as the subject term in the Web of Science Core Collection Database since 2010 are visually analyzed using CiteSpace. The characteristics of these papers, including the quantity trend, quality, author group, affiliated institution type, and journal type, are summarized, and keyword co-appearance and paper co-citation knowledge maps are produced. The results show that (1) China is the backbone of CD research, and the research results account for a considerable proportion of the total. (2) Respiratory dust and atmospheric aerosols, marble dust, PM_2.5, and other hot issues have always attracted international attention. And exposure assessment and spatial distribution were the main focuses in the study of CD. (3) The direction of CD research will explore in a more subtle and intelligent direction in the future, for example, monitoring and control equipment under the technical support of big data technology and machine learning and face recognition. By combining bibliometrics with a systematic review, we aim to analyze the research foci and future development direction deeply, providing scholars with a comprehensive view of the field.

Gas Permeation Property of Silicon Carbide Membranes Synthesized by Counter-Diffusion Chemical Vapor Deposition

An amorphous silicon carbide (SiC) membrane was synthesized by counter-diffusion chemical vapor deposition (CDCVD) using silacyclobutane (SCB) at 788 K. The SiC membrane on a Ni-γ-alumina (Al₂O₃) α-coated Al₂O₃ porous support possessed a H₂ permeance of 1.2 × 10⁻⁷ mol·m⁻²·s⁻¹·Pa⁻¹ and an excellent H₂/CO₂ selectivity of 2600 at 673 K. The intermittent action of H₂ reaction gas supply and vacuum inside porous support was very effective to supply source gas inside mesoporous intermediate layer. A SiC active layer was formed inside the Ni-γ-Al₂O₃ intermediate layer. The thermal expansion coefficient mismatch between the SiC active layer and Ni-γ-Al₂O₃-coated α-Al₂O₃ porous support was eased by the low decomposition temperature of the SiC source and the membrane structure.