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Different formulations of foaming polyurethane grout offer controlled expansion rates. This is crucial for precision in filling voids without exerting excessive pressure on surrounding structures, which could potentially cause damage. This study focuses on the impact of composition on the expansion performance of tailor-made polyurethane grouting materials. Initially, multiple unknown chemical reaction kinetic parameters were identified by combining free expansion tests, which involved measuring density and temperature changes, with the particle swarm optimization algorithm. A numerical simulation, integrating chemical kinetic models and fluid flow equations, was established to replicate the free expansion process of polyurethane grout in a cup, aligning with our experimental results. Subsequently, we analyzed the polymerization process of polyurethane grout with varying compositions to determine the effect of composition ratios on grout expansion. Our findings reveal that the expansion ratio of foaming polyurethane is predominantly influenced by the concentrations of physical and chemical foaming agents, followed by isocyanate concentration. Polyol, in contrast, exerts a relatively minor influence. Furthermore, the solubility of the physical foaming agent in the grout determines both its maximum allowable concentration and its maximum contribution to volume increase. This study provides valuable insights for the design and selection of polyurethane grout components tailored to diverse applications.

IntroductionThe theory of planned behavior (TPB) has dominated the limited number of green hotel visitation studies; however, those studies’ findings are often inconclusive or even controversial. Thus, research needs to move beyond using the TPB to measure consumers’ intention and behavior, and to experiment with alternative theoretical frameworks to explain behavioral change. Value-belief-norm theory of environmentalism (VBN) proposed that various facets of values can influence individuals’ beliefs, subsequently effecting their moral obligations, ultimately, their pro-environmental behaviors. Hence, this study aims to examine the relationship between value components (i.e., biospheric, altruistic, collectivistic), beliefs (i.e., explicit and implicit attitude), norms (i.e., social and personal norm), and green purchase intention to visit green hotels.MethodsAn online survey of convenience sampling technique was adopted for data collection. A total of 373 valid questionnaires were subjected to descriptive analysis, and confirmatory factor analysis and structural equation modeling were performed for the testing of the hypotheses.ResultsThe results suggested that biospheric and collectivistic value positively influence explicit environmental attitude while altruistic value positively influences intrinsic environmental attitude, but negatively influences extrinsic environmental attitude. Social norm was shown to have a positive impact on personal norm and green purchase intention. Furthermore, implicit environmental attitude was shown to influence personal norm and intention, while personal norm positively influences green purchase intention to visit green hotels.DiscussionThis study provided an alternative perspective on the selection of green hotels among consumers based on value-belief-norm theory in the tourism literature. These empirical findings would greatly benefit green hotel managers and other key stakeholders in the hospitality industry.

Due to overexploitation and habitat loss, the Chinese pangolin (Manis pentadactyla) is in such extreme decline that it is so rare in the wild as to be considered functionally extinct, even in Guangdong, which was historically a major distribution area for the species. This study sought to verify whether functional extinction has occurred using observation records from field surveys, infrared wildlife cameras, rescue and enforcement cases and the published literature. The results indicated that suitable habitat occurred within 63.4% of the forested land in Guangdong, but only 17.6% of this area was deemed highly suitable, and 82.3% of all suitable habitat occurred outside of protected areas. Thus, the Chinese pangolin is not yet functionally extinct in Guangdong, but urgent conservation and restoration actions must be taken to ensure its persistence. Chinese pangolins in Guangdong Province are primarily distributed in the Lianhua Mountain and Nanling Mountains, with 91.6% belonging to a single population. From 1980 to 2020, the urban area increased by 776 km2, largely via conversion from agricultural land (48.6%). Suitable habitat for Chinese pangolins was reduced and became more fragmented over this time period, highlighting the urgent need for the establishment of protected areas, habitat restoration and cooperation with local residents. [ABSTRACT FROM AUTHOR]

Environmental pollution and valuable resource waste exist commonly in current metallurgical processes of bastnaesite concentrates. A novel associated process of calcification roasting, mineral beneficiation and acid leaching was proposed. This paper focused on the prior calcification roasting decomposition procedure. By studying the influence of roasting conditions on cerium oxidation, the optimum technology conditions were obtained: operated at 650°C for 60 min with 20% calcium hydroxide. After roasting, the leaching rate of rare earths can reach 98.84%. Bastnaesite can be sufficiently decomposed at lower temperature with calcium hydroxide added and the emission rate of fluorine decreased by over 98% compared with that during the roasting without additives. After the roasting, the main existence form of fluorine turned calcium fluoride, which made it possible for resource utilization and environmental protection. Particle sizes and scanning electron microscope and energy dispersive spectrometer analyses indicated that rare earth oxides gathered in particles of >48 μm, while generated calcium fluoride with fluffy cotton morphology distributed evenly.

A series of the CeO2–WO3/TiO2 catalysts doping polyethylene oxide (PEO) were synthesized by coprecipitation method and applied to selective catalytic reduction of NOx with NH3. The PEO doping catalysts showed better low-temperature activity, which demonstrated a prominent wide operation window ranging from 220 to 526 °C. A series of characterization methods were performed to demonstrate the influence of PEO addition on the internal structure, physical and chemical properties and catalytic reaction mechanism for the CeO2–WO3/TiO2 catalysts. More importantly, the addition of PEO could significantly modify and optimize the pore structure of catalysts, meanwhile, it was verified that the addition of PEO can enhance the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]

Since ultraviolet (UV) light, as well as blue light, which is part of visible light, is harmful to skin, samarium—cerium compounds containing Sm2O2S were synthesized by co-precipitation method. This kind of compounds blocks not only UV light, but also blue light. The minimum values of average transmittance (360–450 nm) and band gap of samarium—cerium compounds were 8.90% and 2.76 eV, respectively, which were less than 13.96% and 3.01 eV of CeO2. Elemental analysis (EA), X-ray diffraction (XRD), Fourier transformation infrared (FTIR), and Raman spectra determined that the samples contained Ce4O7, Sm2O2S, Sm2O3, and Sm2O2SO4. The microstructure of samples was analyzed by scanning and transmission electron microscopies (SEM and TEM). X-ray photoelectron spectrum (XPS) showed that cerium had Ce3+ and Ce4+ valence states, and oxygen was divided into lattice oxygen and oxygen vacancy, which was the direct cause of the decrease of average transmittance and band gap. [ABSTRACT FROM AUTHOR]

A series of glass fibre doped Ce–W/TiO2 catalysts were investigated for the selective catalytic reduction of NOx by NH3. The adhesion and mechanical strength of the CeO2–WO3/TiO2 catalyst was greatly enhanced by the addition of 6% glass fibre. However, the glass fiber contains a small amount of alkali metals, which occupied the active site on the surface of the CeO2–WO3/TiO2 catalysts, thus the catalytic performance of catalyst was inhibited by the addition of glass fibre. Furthermore, BET, XRD, XPS, TPR and TPD methods revealed that the addition of glass fiber can inhibit the formation of catalyst pore structure and reduce the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]

In this paper, a Ce-W/TiO2-mSiO2 catalyst was prepared by a co-precipitation method with the addition of silicon acid to enhance and broaden the denitrification (deNOx) efficiency and temperature range of the Ce-W/TiO2 catalyst. The test results of deNOx performance showed that temperature ranges of the 80% and 90% deNOx efficiencies of the Ce-W/TiO2 catalyst with 30% silicic acid were increased by 35 °C and 30 °C, respectively, and the highest deNOx efficiency was increased to 99.53% compared with that without silicic acid. Moreover, the XRD, BET, SEM, XPS, NH3-TPD and H2-TPR analysis revealed that strong water absorption of silicic acid provided more SiO2 for the catalyst to increase its specific surface area. Meanwhile, the volume of a TiO2 cell increased and the crystallinity of CeO2 decreased, which enhanced the number of Lewis and Brønsted acid sites on the catalyst surface and promoted the deNOx reaction. Besides, the ratios of Ce3+ and Oα on the catalyst surface were about doubled with the addition of 30% silicic acid, thus improving the deNOx performance of the catalyst. [ABSTRACT FROM AUTHOR]

The catalytic performance of CeO2–Fe2O3 catalysts for the selective catalytic reduction of NO by CO was studied. The results showed that the addition of CeO2 can reduce the catalytic reaction temperature. The NO conversion of CeO2–Fe2O3 catalyst (Ce/Fe = 0.1) was more than 90% in the reaction temperature range of 250–650 °C. XRD, BET, XPS, TPR, TPD and in situ DRIFTS showed that with increasing Ce/Fe, the main phase of the catalyst was gradually transformed from iron oxide (Fe2O3) to ceria (CeO2), and the specific surface area gradually increased, which can facilitate the enrichment of Ce on the catalyst surface and improve the redox capacity and adsorption properties. The lattice oxygen released by CeO2 was converted into adsorbed oxygen, and the redox reaction of Ce4+/Ce3+ and Fe3+/Fe2+ on the catalyst surface was beneficial to the storage and release of oxygen, CO and NO on the surface, thus improving the denitration performance. Moreover, the reaction of in situ infrared surface catalysts was a combination of the Langmuir–Hinshelwood mechanism and the Eley–Rideal mechanism. [ABSTRACT FROM AUTHOR]

A series of the CeO2–WO3/TiO2 catalysts doping polyethylene oxide (PEO) were synthesized by coprecipitation method and applied to selective catalytic reduction of NOx with NH3. The PEO doping catalysts showed better low-temperature activity, which demonstrated a prominent wide operation window ranging from 220 to 526 °C. A series of characterization methods were performed to demonstrate the influence of PEO addition on the internal structure, physical and chemical properties and catalytic reaction mechanism for the CeO2–WO3/TiO2 catalysts. More importantly, the addition of PEO could significantly modify and optimize the pore structure of catalysts, meanwhile, it was verified that the addition of PEO can enhance the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]

A series of glass fibre doped Ce–W/TiO2 catalysts were investigated for the selective catalytic reduction of NOx by NH3. The adhesion and mechanical strength of the CeO2–WO3/TiO2 catalyst was greatly enhanced by the addition of 6% glass fibre. However, the glass fiber contains a small amount of alkali metals, which occupied the active site on the surface of the CeO2–WO3/TiO2 catalysts, thus the catalytic performance of catalyst was inhibited by the addition of glass fibre. Furthermore, BET, XRD, XPS, TPR and TPD methods revealed that the addition of glass fiber can inhibit the formation of catalyst pore structure and reduce the content of Ce3+, adsorbed oxygen and the Brönsted and Lewis acid sites on the catalyst surface, thereby affecting the redox abilities, nitrogen oxides and ammonia adsorption capacity of catalysts. [ABSTRACT FROM AUTHOR]