Air filtration: All filters are not created equal

Ceramics play a vital role in environmental engineering due to their exceptional physical, mechanical, and chemical properties. This chapter explores the types, properties, and wide-ranging applications of ceramics in environmental contexts. Ceramics such as oxides, non-oxides, composites, and bioceramics offer high-temperature resistance, chemical inertness, mechanical strength, and thermal stability, which makes them an ideal material for use in water purification, air filtration, soil stabilization, and pollution control. Porous ceramics, in particular, exhibit properties like high permeability and chemical stability, enabling their use in filtration, catalysis, and medical applications. Advanced ceramics are employed in clean energy systems, structural components, and environmental sensors due to their ability to withstand extreme environments. Glass ceramics and white ware ceramics demonstrate versatility in both functional and aesthetic engineering contexts. The chapter highlights the challenges in ceramic processing, including brittleness, complex recycling, and environmental impact during manufacturing. Innovations in sustainable ceramic production and reuse strategies are essential for advancing their role in green technologies. Overall, this chapter explains the growing importance of ceramics in sustainable environmental solutions and technological innovation.

Developing recyclable, multifunctional air purification materials that minimize environmental impact represents a grand challenge in the pursuit of carbon neutrality. Herein, a multifunctional air filtration membrane is prepared through a thermally induced precursor crystallization (TIPC) process that drives the self-assembly of a supramolecular nanofibrous network from melamine (MA) and trimesic acid (TMA). Graphene oxide (GO) nanosheets, strategically incorporated as heterogeneous nucleation-templating agents, are critical for tailoring the hierarchical network morphology and endowing the membrane with multiple synergistic properties. The resulting membrane delivers exceptional particulate matter (PM) filtration efficiency (99.48% for PM1.0), potent antimicrobial activity against (Escherichia coli) E. coli (99.4%) and (Staphylococcus aureus) S. aureus (99.8%), and a high formaldehyde removal capacity (95%). Beyond purification, the membrane also demonstrates effective thermal management for wearer comfort and superior UV-blocking (< 0.4% transmittance). Crucially, the inherent thermoreversibility of the supramolecular network enables complete, closed-loop recycling of the membrane using only green solvents under mild conditions. This work presents a comprehensive and sustainable strategy for preparing advanced air filtration materials, demonstrating that high performance, integrated multifunctionality, and complete lifecycle circularity can be co-designed from the molecular level up.

Antimicrobial resistance (AMR) presents an ever increasing challenge to health globally. Until now, all conventional antibiotics and antivirals are struggling to keep up with minimum efficacy and eradication rate in both civilian and military contexts. The purpose of this review is to compile all current research on the use of functionalized biopolymer nanocomposites, highlighting them as the next-generation of antimicrobial platforms. The emphasis is placed on natural and synthetic biopolymers such as chitosan, alginate, cellulose, and polyvinyl alcohol, all of which are engineered with a range of nanofillers. The nanofillers themselves include silver, zinc oxide, copper oxide, titanium dioxide, graphene derivatives, and metal–organic frameworks. The synergy of these materials not only enhances but broadens antimicrobial activity. Key mechanisms underlying AMR have been elucidated. These include but are not limited to genetic mutation, efflux pump activation, enzymatic inactivation, and viral adaptation. Besides this the multifaceted antimicrobial actions imparted by biopolymer–nanofiller composites have also been thoroughly described. Additionally, chemical modifications such as sulfation, carboxymethylation, and amination are discussed as critical strategies to further improve antimicrobial efficacy. Regarding practicality, real-world applications including wound care, medical device coatings, air filtration, packaging, biosensors, and military-grade protective equipment have been presented along with all pros and cons as well as limitations and challenges. As for drawbacks, such as toxicity, scalability, regulatory considerations, and the potential for environmental impact, this paper has attempted to critically evaluate these and provide directions for future research.

Nowadays, environmental concern and the search for environmentally friendly techniques have contributed to industrial development towards sustainability. Production without social and environmental impact is one of the main goals of engineering research. Although analysis is carried out, some manufacturing processes still require studies, such as grinding, for example. In this process, the interaction between the grinding wheel and workpiece generates a significant amount of heat, due to shearing, friction, and scratching caused by the contact of the numerous abrasive grains with the workpiece surface. The heat generated at the interface has a more intense flow to the workpiece, which can cause several microstructural damages, as well as providing shape errors and increased grinding wheel wear. Thus, the application of cutting fluid is indispensable to minimize the harmful effects caused by heat to the grinding wheel and the workpiece during the process. However, the industry commonly uses soluble cutting fluid, having oil in its composition, in addition to chemical components that prevent its degradation, due to recirculation in the system and the need to avoid the accumulation of bacteria, whereas its application has a flow rate of tens of liters per minute. These cutting fluids will be discarded at some point, which will require complex waste treatment processes for proper disposal. An alternative to this type of application is the minimum quantity lubrication (MQL), which consists of a few milliliters per hour, but which has low refrigerant power. Some techniques have been developed to enhance its application and make it more refrigerant, such as the application of a jet of compressed air directed to the grinding wheel cutting surface to perform the cleaning, minimizing the heat generation by the reduced agglomeration of chips in the grinding wheel pores. Therefore, this work analyzed the cylindrical plunge grinding of hardened steel workpiece with cubic boron nitride grinding wheel on different cooling conditions, comparing the conventional cutting fluid application method (flood) with the MQL technique, MQL simultaneously with the wheel cleaning jet (MQL + WCJ) and MQL with cutting fluid applied at 0 °C (MQL + CA). The performance of each method was analyzed by using the measurements of surface roughness (Ra), roundness error, diametral wheel wear, power consumed during the process, specific energy grinding, microhardness, and microstructural analysis to investigate possible modifications of the microstructure of the workpiece. It was found that in none of the cases, there were microstructural alterations, but the MQL application method presented the worst values of the variables among the techniques studied, whereas the application on low temperature showed potential to be used in a large scale. Nevertheless, the MQL application method applied simultaneously with the wheel cleaning jet (WCJ) has presented the closest values of the conventional method; it becomes the most feasible method for application in the industry towards the protection of the environment and health of the workers.

Eco-design of a low-cost adsorbent produced from waste cherry kernels

Quarantine policies during the coronavirus disease 2019 (COVID-19) pandemic prolonged time spent at home, leading to an unintended occurrence of sick building syndrome (SBS) symptoms. The aim of this study was to investigate the prevalence of SBS symptoms among residents in Suzhou, China, during the COVID-19 pandemic. A questionnaire survey was conducted online from February to May 2022. A total of 442 adults were included in this study. The prevalence of SBS symptoms was much higher during the COVID-19 pandemic, and the proportions of general, mucosal, and skin symptoms were 59.3%, 45.5% and 49.1%, respectively. The influences of building characteristics, occupant lifestyle, indoor environment and perception of indoor environment were analysed using a multivariate logistic regression model. Neighbourhood pollutant sources, older residences, non-ownership and humidity indicators were significant risk factors for SBS symptoms. Frequent use of air fresheners was significantly associated with general (adjusted odds ratio (AOR): 4.9, 95% confidence interval (CI: 2.4–10.0), mucosal (AOR: 5.3, 95% CI: 2.4–11.5), and skin symptoms (AOR: 4.6, 95% CI: 1.6–13.1), while the use of disinfectants was significantly correlated with skin symptoms (AOR: 4.0, 95% CI: 1.5–10.7). Residents’ perception of an uncomfortable indoor environment was a significant predictor of general (AOR: 2.2, 95% CI: 1.2–4.0) and mucosal symptoms (AOR: 3.1, 95% CI: 1.6–6.0). The use of air cleaners can reduce the prevalence of general symptoms. An important finding of this study is that the psychological impact of staying at home for a long time was associated with general symptoms (AOR: 1.3, 95% CI: 1.1–1.7), which means that attention should also be paid to the mental health of residents during the COVID-19 pandemic. Although the quarantine period has now ended, our results can still serve as a reference for the impact of the indoor environment on the health of people with SBS, especially for those who stay at home for a long time, such as the elderly.

The aluminum recycling industry produces aluminum filter dust (AFD), a waste byproduct of the aluminum recycling process composed mainly of aluminum oxide in a percentage between 60–70%, 8% calcium oxide, almost 15% sodium chloride, and between 5–10% potassium chloride. Due to its aluminum content, this waste can be used as a raw material in the manufacture of ceramic bricks, at the same time reducing the environmental impact produced in landfill. In this work, the partial substitution of a clay mixture (40% black, 30% red, and 30% yellow clay) by different proportions of AFD in the range 0–25 wt % for the production of fired clay brick was studied. The raw materials, clays, and waste were characterized by XRF and XRD. The brick specimens were fired at 950 °C and their physical and mechanical properties, such as water absorption, water suction, loss of ignition, linear shrinkage, bulk density, and compressive strength, were analyzed. The more relevant results were obtained with the addition of up to 20 wt % AFD, obtaining bricks with physical properties comparable to pure clay-based bricks used as a reference and better compressive strength and thermal conductivity due to the balance between the melting and pore-forming effects of the waste. These sustainable bricks also comply with the regulations of heavy metals leached to the environment, as indicated by the leaching test.