The growing demand for rare earth elements (REEs) creates the need to search for new sources of their extraction. This experimental study aimed to investigate behavior of selected REEs during a hydrothermal liquefaction (HTL) of sewage sludge (SS) focused on their partitioning in the HTL products. The HTL experiments were carried out at 350 degrees C and for 30 min. residence time in a batch reactor, without and with addition of different catalysts. Among the tested REEs, Dy, Er, Eu, Gd, Ho, La, Lu, Nd, Pr, Sm, Tb, Tm, Y and Yb showed high affinity for the HTL biochar (above 99 %). Sc and Ce migrated into the aqueous phase (AP), but only at the level from thousandths to tenths of mg/dm3. The highest Ce content (53.2---874 mg/kg) was found in HTL biochar, but it should also be emphasized that the Y content (11.0---19.8 mg/kg) and La content (5.6---43.2 mg/kg) were relatively high. The presence of CeO2 as a catalyst resulted in significant increase in the contents of Gd, Ce, Nd and Sm in biochar. The trend towards binding to the post-process biochar is promising in terms of recovering critical raw materials from sewage sludge.
Soil-rock mixture (SRM) slopes are widely distributed in nature, and their failure analysis is of great importance for engineering safety as well as disaster prevention and mitigation. Two sequential tasks are involved in slope failure analysis: stability assessment and the post-failure run-out prediction. Existing studies typically address these tasks using separate numerical approaches. In this study, a unified nodal-integration based finite element method (UNI-FEM) is proposed, enabling both tasks to be performed within a single computational framework. The proposed approach integrates nodal integration, mathematical programming, and particle finite element concepts within a unified framework, thereby enhancing numerical stability and robustness. Slope stability is first assessed through nodal-integration based elastoplastic analysis. Once failure is detected, particle-based remeshing is activated within the same framework for post-failure large-deformation analysis. Therefore, model transformation between the stability assessment and post-failure stages, including the transfer of state variables and model parameters, is not required. Furthermore, when conducting post-failure slope analysis involving remeshing for large-deformation evolution, nodal-based integration eliminates the need for variable transfer between meshes. In addition, an efficient SRM slope generation procedure is developed by combining random irregular rock block generation with developed contact detection algorithms for overlap checking. Several numerical examples are conducted to validate the unified approach for SRM slope failure analysis, and parametric studies further examine the effects of mesh size ratio, rock block content, and rock block size. Results demonstrate that the proposed unified approach provides a reliable and efficient tool for comprehensive SRM slope failure analysis.
Background Active site leaching of CaO-based catalysts severely limits their durability and reusability in biodiesel production. To address this issue, this study aims to enhance the stability of CaO catalysts through cerium (Ce) modification and rational design of Ce/Ca bimetallic metal-organic frameworks (MOFs). Methods A series of Ce/Ca MOF-derived catalysts were synthesized by varying the Ce/Ca molar ratio and calcination temperature. The effects of composition and structural evolution on catalytic performance were systematically investigated using TG, XRD, BET, FTIR, SEM, and XPS techniques. Significant Findings Results indicate that the incorporation of Ce would induce lattice distortions of Ca, thus increasing the oxygen vacancies. To maintain electrical neutrality, electrons tend to cluster around Ca; as a result, the electron density around Ca increased. This confirms the strong electronic interaction between Ca and Ce, which is the reason for the enhanced stability of CaO. The optimized catalyst, C3-800N (Ce:Ca = 3:10, calcined at 800 °C under N2) exhibited remarkable reusability and strong tolerance to water and free fatty acids, with only a 2.17% decline in activity after eight cycles under mild conditions (65 °C, 8 wt.% catalyst, methanol-to-oil molar ratio = 9:1, 1 h). This work demonstrates a feasible strategy for developing durable and efficient MOF-derived Ca-based solid base catalysts for sustainable biodiesel production.
Heritage sites are designed to foster in-depth cultural experiences for tourists at destinations and are well suited for promoting slow travel. However, cultural differences and tourist’ limited awareness often hinder its practice. While augmented reality (AR) is typically used to provide immediate destination information, its potential to build cultural competence and influence slow travel intentions has not been examined. Grounded in zone of proximal development theory, this study reveals that the perceived enjoyment of AR is positively associated with cultural competence, but only for highly engaged users. For less engaged users, personal innovativeness moderates the relationship between perceived advantage and cultural competence. Across both groups, cultural competence strengthens both empathy and slow travel intentions. These findings offer guidance for implementing slow travel initiatives at cultural heritage sites.
Developing high-performance reactant-adaptive electrocatalysts for oxygen evolution reaction (OER) and urea oxidation reaction (UOR) is of great importance for sustained green hydrogen generation and simultaneously water remediation. Enabling the efficient and reversible interconversion of active sites can intrinsically address the sluggish reaction kinetics. Herein, we fabricated a heterostructure (Ni(OH)2/Co MOF/NF) featuring nickel (Ni) sites with efficient and reversible interconversion between Ni3+ and Ni2+. These sites exhibit exceptional reactant-adaptive catalytic performance: the current density of 100 mA cm- 2 is achieved in the OER process at an overpotential of only 290 mV, and current densities of 10 and 100 mA cm- 2 are attained in the UOR process at potentials of merely 1.25 and 1.33 V versus reversible hydrogen electrode, respectively. The Ni(OH)2/Co MOF/ NF catalyst maintains stability for more than 110 h at 10 mA cm- 2 for both OER and UOR. In situ spectroscopy measurements and density functional theory calculations reveal that the heterostructure regulates the electronic structure of nickel sites, modulates the interaction between key intermediates and nickel sites, and lowers the reaction energy barrier, thereby accelerating reaction kinetics and enhancing UOR and OER performance. This work provides new insights for developing highly efficient electrocatalysts in the clean energy and wastewater treatment fields.
