Turning plastics/microplastics into valuable resources? Current and potential research for future applications.

Plastics are a wide range of synthetic or semi-synthetic materials, mainly consisting of polymers. The use of plastics has increased to over 300 million metric tonnes in recent years, and by 2050, it is expected to grow to 800 million. Presently, a mere 10% of plastic waste is recycled, with approximately 75% ended up in landfills. Inappropriate disposal of plastic waste into the environment poses a threat to human lives and marine species. Therefore, this review article highlights potential routes for converting plastic/microplastic waste into valuable resources to promote a greener and more sustainable environment. The literature review revealed that plastics/microplastics (P/MP) could be recycled or upcycled into various products or materials via several innovative processes. For example, P/MP are recycled and utilized as anodes in lithium-ion (Li-ion) and sodium-ion (Na-ion) batteries. The anode in Na-ion batteries comprising PP carbon powder exhibits a high reversible capacity of ∼340 mAh/g at 0.01 A/g current state. In contrast, integrating Fe3O4 and PE into a Li-ion battery yielded an excellent capacity of 1123 mAh/g at 0.5 A/g current state. Additionally, recycled Nylon displayed high physical and mechanical properties necessary for excellent application as 3D printing material. Induction heating is considered a revolutionary pyrolysis technique with improved yield, efficiency, and lower energy utilization. Overall, P/MPs are highlighted as abundant resources for the sustainable production of valuable products and materials such as batteries, nanomaterials, graphene, and membranes for future applications.

Current and potential approaches on assessing airflow and particle dispersion in healthcare facilities: a systematic review.

An indoor environment in a hospital building requires a high indoor air quality (IAQ) to overcome patients' risks of getting wound infections without interrupting the recovery process. However, several problems arose in obtaining a satisfactory IAQ, such as poor ventilation design strategies, insufficient air exchange, improper medical equipment placement and high door opening frequency. This paper presents an overview of various methods used for assessing the IAQ in hospital facilities, especially in an operating room, isolation room, anteroom, postoperative room, inpatient room and dentistry room. This review shows that both experimental and numerical methods demonstrated their advantages in the IAQ assessment. It was revealed that both airflow and particle tracking models could result in different particle dispersion predictions. The model selection should depend on the compatibility of the simulated result with the experimental measurement data. The primary and secondary forces affecting the characteristics of particle dispersion were also discussed in detail. The main contributing forces to the trajectory characteristics of a particle could be attributed to the gravitational force and drag force regardless of particle size. Meanwhile, the additional forces could be considered when there involves temperature gradient, intense light source, submicron particle, etc. The particle size concerned in a healthcare facility should be less than 20 µm as this particle size range showed a closer relationship with the virus load and a higher tendency to remain airborne. Also, further research opportunities that reflect a more realistic approach and improvement in the current assessment approach were proposed.

Systematic study on the relationship between particulate matter and microbial counts in hospital operating rooms.

In this study, a systematic procedure for establishing the relationship between particulate matter (PM) and microbial counts in four operating rooms (ORs) was developed. The ORs are located in a private hospital on the western coast of Peninsular Malaysia. The objective of developing the systematic procedure is to ensure that the correlation between the PMs and microbial counts are valid. Each of the procedures is conducted based on the ISO, IEST, and NEBB standards. The procedures involved verifying the operating parameters are air change rate, room differential pressure, relative humidity, and air temperature. Upon verifying that the OR parameters are in the recommended operating range, the measurements of the PMs and sampling of the microbes were conducted. The TSI 9510-02 particle counter was used to measure three different sizes of PMs: PM 0.5, PM 5, and PM 10. The MAS-100ECO air sampler was used to quantify the microbial counts. The present study confirms that PM 0.5 does not have an apparent positive correlation with the microbial count. However, the evident correlation of 7% and 15% were identified for both PM 5 and PM 10, respectively. Therefore, it is suggested that frequent monitoring of both PM 5 and PM 10 should be practised in an OR before each surgical procedure. This correlation approach could provide an instantaneous estimation of the microbial counts present in the OR.

Recent progress in research on PM2.5 in subways.

Nowadays, PM2.5 concentrations greatly influence indoor air quality in subways and threaten passenger and staff health because PM2.5 not only contains heavy metal elements, but can also carry toxic and harmful substances due to its small size and large specific surface area. Exploring the physicochemical and distribution characteristics of PM2.5 in subways is necessary to limit its concentration and remove it. At present, there are numerous studies on PM2.5 in subways around the world, yet, there is no comprehensive and well-organized review available on this topic. This paper reviews the nearly twenty years of research and over 130 published studies on PM2.5 in subway stations, including aspects such as concentration levels and their influencing factors, physicochemical properties, sources, impacts on health, and mitigation measures. Although many determinants of station PM2.5 concentration have been reported in current studies, e.g., the season, outdoor environment, and station depth, their relative influence is uncertain. The sources of subway PM2.5 include those from the exterior (e.g., road traffic and fuel oil) and the interior (e.g., steel wheels and rails and metallic brake pads), but the proportion of these sources is also unknown. Control strategies of PM mainly include adequate ventilation and filtration, but these measures are often inefficient in removing PM2.5. The impacts of PM2.5 from subways on human health are still poorly understood. Further research should focus on long-term data collection, influencing factors, the mechanism of health impacts, and PM2.5 standards or regulations.

Application of interface material and effects of oxygen gradient on the performance of single-chamber sediment microbial fuel cells (SSMFCs).

Single-chamber sediment microbial fuel cells (SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study. Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032mW/m2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28µm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants.

Novel bufferless photosynthetic microbial fuel cell (PMFCs) for enhanced electrochemical performance.

Photosynthetic microbial fuel cells (PMFCs) are novel bioelectrochemical transducers that employ microalgae to generate oxygen, organic metabolites and electrons. Conventional PMFCs employ non-eco-friendly membranes, catalysts and phosphate buffer solution. Eliminating the membrane, buffer and catalyst can make the MFC a practical possibility. Therefore, single chambered (SPMFC) were constructed and operated at different recirculation flow rates (0, 40 and 240 ml/min) under bufferless conditions. Furthermore, maximum power density of 4.06 mW/m2, current density of 46.34 mA/m2 and open circuit potential of 0.43 V and low internal resistance of 611.8â€¯Ω were obtained at 40 ml/min. Based on the results it was decided that SPMFC was better for operation at 40 ml/min. Therefore, these findings provided progressive insights for future pilot and industrial scale studies of PMFCs.

Synthesis, characteristics and sonocatalytic activities of calcined γ-Fe2O3 and TiO2 nanotubes/γ-Fe2O3 magnetic catalysts in the degradation of Orange G.

In this work, γ-Fe2O3 and TiO2 NTs/γ-Fe2O3 composites with good magnetism and sonocatalytic activity were prepared by a facile polyol method and utilize the principle of isoelectric point method, respectively. The structural and magnetic features of the prepared calcined γ-Fe2O3 and composite catalysts were investigated by transmission electron microscopy (TEM), powder X-ray diffraction (XRD), surface analysis, UV-Vis diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometry (VSM) and zeta potential analysis. The effects of calcination temperature on γ-Fe2O3 phase variation, physical properties and sonocatalytic properties were investigated. The porosity, specific surface area, band gap energy and sonocatalytic activity of γ-Fe2O3 were gradually decreased with calcination temperature increased. TiO2 NTs/γ-Fe2O3 with appropriate composition and specific structural features possess synergetic effects such as efficient separation of charge carriers and hydroxyl radicals produced by heterogeneous fenton and fenton-like reactions. This enhanced the sonocatalytic activity for the degradation of Orange G under ultrasonic irradiation. The sonocatalytic reactions obeyed pseudo first-order kinetics. All these information provide insight into the design and development of high-efficiency catalyst for wastewater treatment.

Transport and retention of engineered Al2O3, TiO2, and SiO2 nanoparticles through various sedimentary rocks.

Engineered aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanoparticles (NPs) are utilized in a broad range of applications; causing noticeable quantities of these materials to be released into the environment. Issues of how and where these particles are distributed into the subsurface aquatic environment remain as major challenges for those in environmental engineering. In this study, transport and retention of Al2O3, TiO2, and SiO2 NPs through various saturated porous media were investigated. Vertical columns were packed with quartz-sand, limestone, and dolomite grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolet-visible spectrophotometer. It was found that Al2O3 and TiO2 NPs are easily transported through limestone and dolomite porous media whereas NPs recoveries were achieved two times higher than those found in the quartz-sand. The highest and lowest SiO2-NPs recoveries were also achieved from the quartz-sand and limestone columns, respectively. The experimental results closely replicated the general trends predicted by the filtration and DLVO calculations. Overall, NPs mobility through a porous medium was found to be strongly dependent on NP surface charge, NP suspension stability against deposition, and porous medium surface charge and roughness.