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To enhance the stability of biomass gel foam used for inhibiting coal spontaneous combustion (CSC), a novel highly stable biomass gel foam (SA-Ca2+@TA-GF) based on a double cross-linked structure was prepared by introducing tannic acid (TA) into a gel form (sodium alginate/calcium L-lactate/composite foaming agent). FT-IR confirmed the formation of the double cross-linked structure. The effects of TA concentration on the performance of SA-Ca2+@TA-GF were analyzed, considering gelation time, half-life, film microstructure, and strength. With the addition of 1.6 wt% TA, SA-Ca2+@TA-GF forms a dense foam structure with a gelation time of 10 min. The half-life of the gel foam improves from 0.4 to 30 days and the strength increases by 72.9% compared to that of foam without TA. The inhibition experiments show that SA-Ca2+@TA-GF can asphyxiate coal, thus effectively inhibiting coal oxidation. Additionally, it can increase the temperature of coal at the rapid oxidation stage by 60 °C, and the CO inhibition rate is up to 79.6% at 200 °C. The fire-fighting experiment shows that SA-Ca2+@TA-GF can effectively cool coal and quickly extinguish fires. This study provides a simple method to prepare highly stable biomass gel foams, which is useful for improving the efficiency of gel foams in inhibiting CSC.

Coal gangue, as an associated product of coal mining, can cause a large number of piles to undergo slow oxidation and spontaneous combustion, resulting in the production of toxic and harmful gases, leading to casualties, environmental damage, and economic losses. Gel foam has been extensively employed as a fire-retardant material in coal mine fire prevention. The thermal stability and rheological properties of the newly developed gel foam were investigated in this study, as well as its oxygen barrier properties and fire extinguishing effect which were evaluated through programmed temperature rise and field fire extinguishing experiments. The experiment indicated that the temperature endurance of the new gel foam was around twice that of the ordinary gel foam, and this resistance decreased with the increment of foaming times. Moreover, the temperature endurance of the new gel foam with a stabilizer concentration of 0.5% was superior to that of 0.7% and 0.3%. Temperature has a negative effect on the rheological properties of the new gel foam, while the foam stabilizer concentration has a positive effect. The oxygen barrier performance experiment results showed that the CO release rate of coal samples treated with the new gel foam rose relatively slowly with temperature, and the CO concentration of coal samples treated with the new gel foam was only 159 ppm at 100 °C, which was significantly lower than 361.1 ppm after two-phase foam treatment and 715 ppm after water treatment. Through simulating the spontaneous combustion experiment of coal gangue, it was demonstrated that the new gel foam has a much better extinguishing effect than water and traditional two-phase foam. The new gel foam cools gradually and does not re-ignite during the fire extinguishing process, while the other two materials re-ignite after being extinguished.

In order to solve the problem of the spontaneous combustion of coal gangue, a coal gangue fire-extinguishing material of gel–foam was developed. The foaming agent was screened by the Waring blender method with varying foam amounts, and the superabsorbent foam stabilizer was synthesized by free radical polymerization. Moreover, the gel–foam was used in a spontaneous combustion of coal gangue mountain field practice. The results showed that when the mass fraction of sodium dodecyl sulfonate and coconut oil amide propyl betaine was 0.6% and 4:6, the foaming amount was as high as 1500 mL. When the mass ratio of chitosan to acrylic acid was 1:6, the neutralization degree was 80%, the cross-linking agent was 0.8%, and the initiator was 0.01%, the water absorption of the synthesized superabsorbent foam stabilizer reached 476 mL/g. The synthesized gel–foam was tested in a spontaneous combustion coal gangue hill in a certain area, and no reburning sign was found within one month.

Foam stabilized by nanoparticles and surfactants demonstrates potential in developing environmentally friendly foam extinguishing agent for liquid fuel fire. However, many properties on foams must be investigated first before application. The present study focuses on thermal stability of gel foams co-stabilized by nanoparticles and surfactants. Nano-aluminum hydroxide (nano-ATH), short-chain fluorocarbon surfactant (FS-50), and hydrocarbon surfactant (APG-0810) were selected to prepare foam dispersions. Surface activity, viscosity, conductivity, and foamability were characterized. Foam coarsening, drainage, and decay process under high temperature were systematically analyzed. Results indicate that the surface activity and conductivity of nano-ATH/FS-50/APG-0810 dispersions decrease gradually, but the viscosity increases with increasing nano-ATH concentration. The foamability of the dispersions decreases with addition of nano-ATHs and slightly increases with increasing nano-ATH concentration. The viscosity of foam dispersions increases sharply, foamability shows an apparently increase, and foam flowability decreases upon nano-ATH concentration is above 5%. Foam coarsening, drainage, and height decay decrease with increasing nano-ATH concentration. Foam thermal stability under 200°C is enhanced with increasing nano-ATH concentration. These findings can provide a reliable theoretical basis for the application of nano-ATH in developing fire extinguishing agents for liquid fuel fires. Graphical abstract Highlights Foamability of FS-50/APG-0810 solution was enhanced by nano-ATH with a high content. Foam drainage and coarsening under heat was decelerated by addition of nano-ATH. Foam thermal stability of FS-50/APG-0810 was enhanced as nano-ATH content increases.

The combination of nanoparticles (NP) and surfactant has been intensively studied to improve the thermal stability and optimize the performance of foams. This study focuses on the influence of silica NPs with different concentration on the thermal stability of gel foams based on a mixture of fluorocarbon (FS-50) and hydrocarbon (APG0810) surfactants. The surface activity, conductivity, viscosity, and foaming ability of the APG0810/FS-50/NPs dispersions are characterized. The effects of NP concentration on coarsening, drainage, and decay, as well as of the gel foams under thermal action, are systematically studied. Results show that NP concentration has a significant effect on the molecular interactions of the APG0810/FS-50/NP dispersions. The surface tension and conductivity of the dispersions decrease but the viscosity increases with the increase in NP concentration. The foaming ability of APG0810/FS-50 solution is reduced by the addition of NPs and decreases with the increase in NP concentration. The coarsening, drainage, and decay of the gel foams under thermal action slow down significantly with increasing NP concentration. The thermal stability of the gel foams increases with the addition of NPs and further increases with the increase in NP concentration. This study provides a theoretical guidance for the application for gel foams containing NPs and surfactants in fire-extinguishing agents.

Coal spontaneous combustion causes both human casualties and environmental pollution. Owing to special flow behaviors, foam materials used in fire-fighting technology can effectively bring water and solid non-combustible substances into the fire-fighting area, greatly preventing spontaneous combustion. This paper systematically elucidates three foam materials, three-phase foam, gel foam and curing foam, and analyzes their physical and chemical inhibition mechanisms on coal spontaneous combustion. In particular, the preparation, performance and latest chemical modification methods of the foam materials are summarized in detail. It is found that foam materials with environmental friendliness, economy and excellent anti-fire performance need to be consistently explored. The primary application areas for cement-based foamed materials remain the building materials and civil engineering industries, and their modification should be studied accordingly based on the specific application context. Furthermore, a new component of foam materials, coal gasification slag (a solid waste), is proposed. In addition, the seepage properties of fire-fighting foam in porous media should be fully studied to accurately grasp the dispersion of foam materials in mine goafs. This review provides new insights and guidance for the development of fire-fighting foam materials.

Gel foam extinguishing agent (gel foam) has promising applications in the prevention and management of mine coal spontaneous combustion. Based on the research on coal spontaneous combustion and prevention technology, this article discusses recent studies on using gel foam to extinguish coal mines. The structural properties and principles of gel foam are described briefly. The research developments of three significant varieties of gel foam are then presented in detail, including silicate gel foam, acrylamide copolymer gel foam, and natural polymer gel foam. Meanwhile, the research status of gel foam anti-fire technology’s rheological properties, stability property, plugging property, and inhibitory properties are introduced. Furthermore, in conjunction with the research state, the prospects of the research direction of gel foam are proposed, which serve as a reference for future research on gel foam.

Gel foam has the advantages of gel and foam and shows good prospects for applications in the fields of fire prevention and extinguishing. Rheology has a significant impact on the application of gel foam, but there is little related research. In the present study, hydrophilic silica nanoparticles (NPs) and water-soluble polymer xanthan gum (XG) were combined with fluorocarbon surfactant (FS-50) and hydrocarbon surfactant (APG0810) to create gel foam. The foaming ability and foam drainage were evaluated. The gel foam’s rheology, including its flow behavior and viscoelasticity, was systematically investigated. The results show that the foaming of the FS-50/APG0810 mixture decreases but the foam drainage increases in the presence of NPs and/or XG. All of the foams belong to the category of non-Newtonian fluids with shear thinning behavior. The flow curves of the foams are consistent with the Cross model. The presence of XG/NPs enhanced the foam viscoelasticity of the FS-50/APG0810 mixture. The silica NPs showed a better ability to enhance foam viscoelasticity but a worse ability to stabilize the foam compared to XG. This research can offer theoretical support for the industrial usage of gel foam.

Otitis externa (OE), or swimmer's ear, is a common inflammatory condition affecting the external auditory canal, leading to symptoms such as ear pain, itching, and hearing impairment. It is caused by various pathogens, including Pseudomonas aeruginosa and Staphylococcus aureus. Treatment typically involves antibiotics, analgesics, and aural packing. To compare the clinical effectiveness of antibiotic-steroid ointment wicks versus antibiotic-steroid drops-soaked gel foam in pain management for patients with otitis externa. A prospective study was conducted at Aarupadai Veedu Medical College and Hospital from September 2022 to September 2023. One hundred patients, aged 18–60 years, with acute otitis externa, were randomly assigned to two groups: Group A received antibiotic-steroid ointment wicks, and Group B received antibiotic-steroid drops-soaked gel foam. Pain levels were assessed using the Wong-Baker Pain Assessment Scale, Visual Analog Scale, and Numerical Rating Scale on Days 1, 3, and 5. Statistical analysis was performed using SPSS software, with significance set at p < 0.05. Group A experienced a significant reduction in pain compared to Group B. On Day 1, there was no significant difference in pain scores between the groups (p = 0.728). However, on Day 3 and Day 5, Group A reported significantly lower pain levels than Group B (Day 3: p = 0.001*, Day 5: p = 0.001*). Within-group analysis revealed substantial pain reduction over time in both groups, with the most pronounced decrease observed in Group A. Group A's pain scores decreased from 6.36 on Day 1 to 0.08 on Day 5, while Group B's scores decreased from 5.70 on Day 1 to 2.84 on Day 5. The study demonstrates that antibiotic-steroid ointment wicks are more effective than antibiotic-steroid drops-soaked gel foam in reducing pain associated with acute otitis externa. While both treatments significantly alleviated pain over time, the ointment wick showed superior efficacy, making it a preferred option for managing this condition.

Background and Aims To evaluate outcomes and adverse events of uterine artery embolization (UAE) using the GELFOAM technique for cervical and cesarean scar ectopic pregnancies at a single tertiary center. Methods We conducted a descriptive cross‐sectional case series over 1 year. Maternal age, β‐hCG levels, mass size, obstetric history, complications, and treatment success were ed from records. Descriptive statistics are presented as mean ± SD for approximately normally distributed variables and median (IQR) for skewed variables. Results Among 41 patients, uterine preservation was achieved in 40 (97.6%), with no procedure‐specific complications and one non‐specific postoperative hematoma (2.4%). The single failure occurred in a delayed presentation and required further surgical intervention. For uterine preservation (40/41), the 95% confidence interval for the success proportion is 87.4%–99.6% (Wilson). Conclusion UAE with GELFOAM appears to be an effective, fertility‐preserving option for cervical and cesarean‐scar ectopic pregnancy in selected patients. Larger studies with longer follow‐up are warranted.