As the core driving force of green mine transformation, cemented paste backfill(CPB) has a wide range of application scenarios and development trends. The thickening of low-concentration tailings is a crucial process in CPB. The tailings particle settling velocity and underflow concentration are two important indicators. This study investigates tailings from four different mines, using Computational Fluid Dynamics (CFD) theory and the k-epsilon model to simulate the static (SS) and dynamic settling (DS) processes in a deep cone thickener(DCT). The mechanisms by which tailings density (TD), particle size distribution (PSD), and mud layer height (MLH) influence tailings settling velocity and underflow concentration are revealed. The study found that, when the settling time was 3 h, the underflow concentrations for the four tailings with densities K1 to K4 were 38.54%, 39.28%, 40.88%, and 42.01%, respectively. The times required for the underflow concentration of tailings with average particle sizes of 61 & micro;m, 46 & micro;m, 86 & micro;m, and 49 & micro;m to reach 35% were approximately 1086 s, 2745 s, 433 s, and 1876 s, respectively. When the initial MLH increased from 4.6 m to 10.6 m, the average underflow concentration increased by 3.33%. The study explains the different sedimentation behaviors of tailings using Stokes' law, the Terzaki's principle of effective stress, and size-dependent continuous separation mechanisms. It was found that high-density and coarse-particle tailings are more likely to overcome resistance in the structure, promoting tailings particle settling and thickening. Furthermore, the relationship between underflow concentration and settling velocity was fitted, revealing a power-law correlation between the two. This study provides theoretical support for the continuous and stable thickening of tailings in CPB systems, with significant practical implications for the safety and efficiency of mining operations.

Solid amine adsorbents are among the most promising materials for direct air capture (DAC) of CO2, yet their practical deployment is severely limited by rapid capacity decay arising from hydrothermal amine loss and oxidative degradation under realistic regeneration conditions. Herein, we propose an ethylene glycol diglycidyl ether (EGDE)-induced crosslinking strategy to simultaneously suppress these two dominant deactivation pathways. The EGDE-PEI@D500 adsorbents were synthesized via physically impregnating EGDE-modified polyethyleneimine (PEI) onto a porous resin (D500) support, and systematic characterization confirmed that EGDE crosslinking reduced the fraction of oxidation-prone primary amines and introduced hydroxyl functionalities without perturbing the pore structure. Accelerated hydrothermal leaching and oxidation exposure tests demonstrated that the 10%EGDE-PEI@D500 adsorbent retained over 80% of its original CO2 capacity, in sharp contrast to the severe capacity loss observed for the unmodified PEI@D500 adsorbent. Ex-situ and in-situ FT-IR spectroscopy revealed a pronounced delay in the formation of irreversible oxidation products, evidencing suppressed oxidative degradation in the EGDE-crosslinked amine network. Under DAC-relevant adsorption-regeneration conditions in a rapid-bed unit, the EGDE-PEI@D500 adsorbents exhibited significantly enhanced longterm cyclic stability compared with the unmodified counterpart. The combined suppression of hydrothermal amine loss and oxidative deactivation originates from the reduced primary-amine content, the restricted aminechain mobility, and the introduction of hydroxyl functionalities. This work demonstrates that EGDE-induced crosslinking provides a practical and scalable molecular engineering strategy to achieve durable solid amine adsorbents for continuous DAC operation.

Direct air capture (DAC) of CO2 represents a critical technology for achieving net-zero emissions, yet its implementation is challenged by adsorbents with high capacity and stability, mechanical robustness, and process compatibility under ultra-low CO2 concentrations. Shaping the powdery solid amine sorbents into mechanically robust and low-resistance structures is essential for their practical deployment in DAC systems. In this work, extrusion-shaped PEI@B/MC-M560 adsorbents were developed using a composite bentonite/methyl-cellulose binder system to enhance structural integrity while preserving CO2 adsorption performance. The optimized B/MC-M560 pellet retained over 90% of the mesoporosity of raw M560 powder, supported high PEI loadings (45-50 wt%), and exhibited uniform amine dispersion. Under pure CO2 testing conditions, the synthesized PEI@2.5%B/MC-M560 adsorbent achieved an intrinsic CO2 uptake of 138.8 mg/g and demonstrated excellent stability, maintaining >98% capacity after 50 cycles. For practical DAC-relevant performance (400 ppm CO2), the material reached an uptake of approximately 60 mg/g. Pelletization significantly reduced pressure drop by more than an order of magnitude, creating well-defined interparticle channels that improve hydrodynamic behavior and lower air-handling energy consumption in DAC operation. Breakthrough experiments further showed that the extrusion-shaped adsorbents maintained tunable yet stable performance under different pellet diameters, humidity levels, and temperatures, with moderate humidity enhancing CO2 uptake via PEI plasticization and bicarbonate formation. Overall, this study establishes a scalable extrusion-shaping strategy that simultaneously improves mechanical strength, CO2 capture efficiency, and flow-performance. The structure-performance insights obtained provide practical guidance for designing next-generation solid amine sorbents for industrial-scale DAC applications.

To effectively manage the extensive risk of manganese (Mn) contamination in soils, the Mn content must be monitored through low-cost and efficient methods. Visible and near-infrared reflectance spectroscopy presents a promising alternative to traditional soil assessment methods. In this study, we constructed and evaluated a deep convolutional neural network (CNN) model for precisely predicting soil Mn contents on a continental scale. The correlation between the actual soil Mn content and the spectral under different preprocessing methods was analyzed. The results indicate that combining Savitzky-Golay smoothing and the second derivative could effectively improve the CNN predictive performance. After hyperparameter tuning, the R2, root mean square error, mean absolute error, and ratio of performance to deviation were 0.66, 132.02 mg/kg, 89.24 mg/kg, and 1.71 for the optimal CNN model on the test set, respectively. The distribution of soil Mn content predicted by the model was highly similar to the actual distribution. The uncertainty analysis shows that the CNN prediction was stable and reliable. Our model has shown a practical and effective predictive capability for soil Mn content on a large scale, providing an important tool and reliable method for agricultural management and environmental monitoring.

ABSTRACT Recent decades have witnessed a significant surge in research interest toward aerogels, driven by their exceptional physicochemical properties, including ultralow density, high porosity, and large specific surface area. However, conventional aerogels suffer from inherent brittleness, particulate release, and restricted service temperatures, severely impeding applications in complex structures or extreme environments. To overcome these constraints, researchers have innovatively replaced gel particles with ceramic fibers as building blocks, integrating the advantages of ceramic materials with fibrous architectures. This paradigm shift has yielded ceramic fiber aerogels (CFAs) characterized by superior flexibility and stable performance across a wide range of temperatures, demonstrating significant potential for thermal management under extreme conditions. This review comprehensively examines recent progress, optimization strategies, and application prospects of CFA‐based thermal insulation materials. We begin by outlining the classification of CFAs along with their respective advantages and limitations. Subsequently, we detail the characteristic features and synthetic methodologies of current predominant CFA structures. Building upon two pivotal performance metrics for thermal protection materials, mechanical robustness and thermal insulation efficacy, we systematically analyze state‐of‐the‐art optimization strategies for enhancing CFA performance. Furthermore, we highlight emerging applications of CFA thermal insulators in critical domains, including: battery thermal management (with focus on thermal runaway mitigation), personal thermal management systems, energy‐efficient building insulation, and aerospace thermal protection systems. Finally, we conclude with perspectives on future research trajectories and potential breakthroughs in the CFA domain.

With the depletion of shallow resources, the transition from open-pit to underground mining has become an inevitable trend in the mining industry. Although the vertical longhole stage fill mining method is efficient and safe, its second-step stoping blasting is prone to damaging the underlying strategic rare orebody. To quantify the protective effect of the protective layer, this study established a three-dimensional fluid–structure interaction (FSI) numerical model for explosives-rock-backfill interactions using the ANSYS/LS-DYNA platform, based on the case of a large polymetallic mine. Systematic simulations were performed for six protective layer thicknesses ranging from 0.5 to 3.0 m, analyzing the cross-media propagation and attenuation characteristics of blasting stress waves and their dynamic damage mechanism to the underlying orebody.The results indicate that the protective layer thickness is a core parameter controlling damage, showing a significant negative correlation with the peak stress and displacement of the orebody. When the thickness is less than 1.5 m, the orebody response exceeds its damage threshold, leading to irreversible failure. When the thickness is ≥ 1.5 m, the peak stress can be reduced below the orebody’s ultimate compressive strength (74.871 MPa), and the displacement response is confined within the slight influence range (0.1–0.3 mm), achieving effective protection. The study innovatively applied the "Post Line Contour Mode" post-processing technique in LS-PrePost to achieve precise quantification of stress gradients and accurate localization of damage boundaries, validating the critical protective thickness of 1.5 m. This research clarifies the buffering mechanism and protection standards of the protective layer, providing a theoretical basis and design reference for safe and efficient coordinated mining of mineral resources under similar conditions.

Reducing the high regeneration energy penalty remains the paramount challenge for amine-based CO2 capture. While molecular structure modification is a promising strategy to enhance absorption-desorption performance, the fundamental relationship between substitution position and chemical speciation remains elusive. Herein, piperazine (PZ) was employed as the parent molecule to systematically investigate three methyl-substituted derivatives-2-methylpiperazine (2MPZ), 2,5-dimethylpiperazine (25DMPZ), and 2,6-dimethylpiperazine (26DMPZ)-with the objective of elucidating the influence of methyl substitution positions on CO2 reaction mechanisms. Among the tested absorbents, 25DMPZ exhibits the best overall performance, achieving a CO2 loading of 0.90 mol/mol-amine and a superior desorption capacity of 0.82 mol/mol-amine (twice that of PZ), while reducing regeneration energy consumption to 60.0% of that of the benchmark monoethanolamine (MEA). Integrated spectroscopic analyses and density functional theory (DFT) calculations establish a structure-speciation-energy correlation. Specifically, an ortho-methyl environment introduced by the 2,5-dimethyl substitution in 25DMPZ significantly destabilizes the adjacent carbamate intermediate, rendering it more susceptible to hydrolysis and thus favoring the formation of thermodynamically stable bicarbonate. Conversely, symmetric methyl substitution in 26DMPZ stabilizes dicarbamate species through synergistic steric and electronic interactions, leading to a distinct regeneration pathway. These findings provide a speciation-guided molecular design principle for developing amine-based absorbents with low regeneration energy for CO2 capture.

Solid amine adsorbents are promising candidates for CO2 capture, but their practical application is severely limited by oxidative degradation under high-temperature and oxygen-containing conditions. Conventional strategies mainly rely on chemical modification of amine species, which often compromises CO2 adsorption capacity or introduces complex synthesis routes. Herein, we report a simple yet effective strategy using K2CO3 as an inorganic additive to enhance the oxidative stability of polyethyleneimine (PEI)-based adsorbents. The introduction of K2CO3 make total PEI content was comparable, but significantly improves CO2 uptake retention after accelerated oxidation compared with the pristine counterpart. Systematic characterizations reveal that K2CO3 regulates the local microenvironment by tuning pore confinement and surface acid-base properties of the silica support, while modifying the interfacial chemical environment of PEI. In situ DRIFTS and mass spectrometry analyses demonstrate that K2CO3 suppresses the formation of carbonyl/imine-containing intermediates and reduces the evolution of volatile degradation products. Electron paramagnetic resonance and 1H NMR relaxation results indicate that K2CO3 inhibits radical accumulation and restricts polymer chain mobility. Density functional theory calculations further reveal that K2CO3 reduced the thermodynamic driving force for hydrogen abstraction and modulates local charge distribution at reactive sites, suggesting suppressed radical initiation difficult. This work provides a simple inorganic additive strategy for constructing durable solid amine adsorbents, offering a general design principle for durable CO2 capture applications under harsh oxidative conditions.

Background Food waste (FW) management can contribute to emission reduction when low-carbon pathways such as anaerobic digestion or composting are adopted instead of landfilling.Methods This study quantified emissions across four treatment modules for five household (HHFW), one kitchen (KW), and two fruit and vegetable (FVW) waste sites.Results Baseline operations emitted 66,086.2 t CO2, with HHFW and KW contributing 69.9% and 22.9%, respectively. Pollutant treatment dominated (93.4%), mainly from residue and sewage management. FW intensities ranged from 54.34-162.13 kg CO2/t-HHFW, 122.1 kg CO2/t-KW, and 59.2-84.3 kg CO2/t-FVW. Resource recovery presented both offsets and burdens: grease recycling avoided up to -10.87 kg CO2/t-KW, while composting added 74.7 kg CO2/t-FVW. Compared to landfill disposal, the project reduced carbon intensity 7-16 fold, exceeding 800 kg CO2/t at top-performing sites (V1 and H4). Relative to incineration, reductions were smaller and site-dependent, though most treatment streams still achieved net savings. Scenario optimization highlighted the transformative potential of advanced interventions: a Moderate pathway integrating anaerobic acid production (AOP) cut emissions 1.6-1.7 fold, while optimistic pathways, anaerobic digestion (AD) and insect bioconversion (BSFL), achieved net-negative emissions of -308.4 kg CO2/t for HHFW and -117.41 kg CO2/t for FVW, respectively.Conclusion These findings demonstrate that source separation, targeted resource recovery, and coupling bioenergy with value-added products can convert FW management from a carbon source to a net sink, supporting deep decarbonization strategies.

Calcium aluminate cement (CAC), characterized by superior properties and low-carbon emission, shows strong potential to replace traditional ordinary Portland cement (OPC) in in-situ phosphogypsum (PG) backfill. Although the microstructural characteristics and pollutant immobilization have been investigated, its hydration kinetics, microstructural evolution, and carbon reduction behavior remain insufficiently explored. This study aims to investigate the intrinsic links between hydration mechanisms and macroscopic properties. The flowability, setting behavior, strength development, hydration characteristics and carbon footprints of CAC-based and OPC-based backfill systems were systematically evaluated through experiments and thermodynamic simulations. The results show that PG alters the hydration of CAC, exerting a dual effect on its macroscopic properties. Thermodynamic simulations indicate sequential formation of amorphous Al (OH)3, ettringite and OH-hydrotalcite, with synergistic interactions enhance strength development. The comparison of both systems shows that differences in product types, formation conditions and interactions fundamentally govern their macroscopic variations.

Abstract Converting lignocellulosic biomass to syngas represents a promising way to integrate renewable hydrogen and carbon resources into sustainable carbon-neutral energy systems. However, the conventional biomass gasification process typically relies on excessive steam input, resulting in significant energy penalties and CO2 emissions. This study proposed a novel integrated gasification process for syngas production from straw, featuring the self-reforming of straw volatiles and utilization of process CO2, enabled by the cooperation of Ca(OH)2 and Fe2O3. The contents of Ca(OH)2 and Fe2O3 were optimized to direct straw hydrogen into the volatiles and straw carbon into the solid phase during pyrolysis, thereby facilitating subsequent H2 and CO production. The cooperation of Ca(OH)2 and Fe2O3 was manifested in two aspects: generating in situ steam for the self-reforming of volatiles into H2 and promoting the secondary conversion of biochar and process CO2 into CO. The optimized C0.3F0.2 reached a syngas yield of 19.3 mmol/gstraw with a H2 selectivity of 35.8% and a CO selectivity of 28.0%. 34.8% of process CO2 was captured and utilized as CO rather than emitted. This work provides a sustainable and eco-friendly way for converting the hydrogen and carbon resources into efficient syngas production and falls in the domain of carbon-neutral energy system development.

Fault stability is critical to the safety of underground mining under complex in-situ stress and excavation disturbances. This study evaluates the F001 fault in a Chinese iron ore mine by combining the Mohr–Coulomb failure criterion, Shapley-effect analysis, borehole exploration, and numerical simulation. Seven factors were considered: the three principal stresses (σv, σH, σh), fault dip angle (θ), angle between the principal stress and fault plane (β), cohesion (c), and internal friction angle (φf). The calculated stability criterion g ranges from − 11.7 to − 4.0, indicating that the F001 fault remains stable under undisturbed conditions. The importance of the factors is ranked as φf > σv > σH > σh > c > θ > β. The internal friction angle is the dominant factor, with a Shapley value of 95.8 and an importance index of 73.9%. Numerical simulations for fault-to-stope distances of 0, 10, and 20 m show that increasing the distance enhances the isolation and buffering effect of the intervening rock mass, thereby reducing mining-induced stress and displacement disturbances. This study provides a quantitative basis for identifying key factors controlling fault stability and optimizing mining layout near faults.

Supplementary cementing materials (SCM) have gained significant attention as a substitute for ordinary Portland cement in cementitious paste backfill (CPB). Fly ash (FA) has been proven to be an economic and efficient SCM, however, the high cost of commercial activators needs to be well controlled. In this study, the alkaline solid waste, red mud (RM), was utilized as an activator couple with FA to prepare CPB. The results show that mechanical properties of CPB with 1.5-4.5 wt% RM after 28 d decreased by 7.0-34.5 % compared to the control group (0 wt% of RM). The hydration products analysis revealed that the aluminum (from RM and FA) substitute silicon within CPB system, leading to the formation of more poorly compacted C(Na)-A-S-H gels. However, the enhancement of the microstructure of CPB specimens with RM could partially mitigate the negative effects of reduced hydration products within CPB specimens containing RM. Finally, the preparation cost of CPB specimens with 1.5 wt% RM is 20 % lower than that of specimens activated solely with NaOH. These results demonstrate potential of RM in alkaliactivating FA, which advances its application in CPB fields.

Expansive cemented paste backfill involves in-situ volume expansion of the filling material through the foaming of an expansion agent, which theoretically mitigates the non-roof-contact effect caused by the self-shrinkage of the slurry. However, conventional expansion agents exhibit rapid foaming rates, causing bubbles to escape during pipeline transportation and filling in the mining area, resulting in suboptimal expansion effects. This study, therefore, the azodicarbonamide-based materials with a low foaming rate was selected as the chemical foaming agent (CFA) and the correlation between the expansion and mechanical properties of expansive cemented paste backfill (ECPB) was investigated using both macro- and micro-scale tests. The findings indicate that the bubbles generated by the CFA lead to an increased expansion ratio, decreased unconfined compression strength (UCS), and enhanced ductility. Increases in the cement-to-sand ratio (CSR) and mass concentration (MC) improve both the expansion ratio and UCS. The expansion process induced by CFA is completed within 6 h, during which hydration products (AFt and CH) accumulate at the upper section of ECPB. When the CFA content is below 0.6 wt%, the expansion process can be effectively modeled using a first-order kinetic equation. After curing, the pore diameters in the ECPB samples range from 200 mu m to 500 mu m, with larger pores generally concentrated at the upper section. This phenomenon promotes the " pore wall failure-pore compression and collapse " failure mode in the upper portion of the ECPB. Finally, this study suggests that regulating the foaming rate, incorporating additives to improve interface properties, and adjusting the particle size distribution are promising strategies to enhance strength while maintaining expansion.

CaO-based adsorbents have emerged as highly promising solid materials for CO2 capture due to their abundant availability and high reactivity. However, sintering-induced deactivation under realistic industrial flue gas conditions remains a critical bottleneck restricting their large-scale application. This study examines the synergistic mechanical mixing-thermal activation effects on CaO performance and stability using coal fly ash (CFA) as a stabilizer. The impact of typical flue gas impurities (water vapor, NOx, and SO2) on adsorbent performance are also comprehensively evaluated. Experimental results demonstrated that the incorporating 10 wt% CFA as an inert support effectively mitigates framework collapse during cyclic operations. An optimal balance between crystalline phase and pore structure is achieved through thermal activation at 900 degrees C combined with high-speed ball milling at 400 rpm. Under the optimized synthesis conditions (90 wt%-900 degrees C-400 rpm), the prepared adsorbents exhibit a significantly enhanced CO2 uptake capacity of 397 mg/g within 60 min, along with remarkable cyclic stability, with only 33 % capacity decay after 20 carbonation-calcination cycles. The introduction of 10 vol% water vapor further improves both adsorption capacity (539 mg/g) and cyclic durability (29 % capacity loss after 20 cycles), primarily attributed to the synergistic effects of hydroxylation and carbonation mechanisms. Conversely, excessive water vapor (>15 vol%) promotes surface passivation and pore structural degradation, deteriorating adsorption performance. To maintain operational reliability, the acidic impurity concentrations in flue gas should be controlled below 100 ppm NO, 50 ppm NO2, and 10 ppm SO2. Overall, this approach provides an effective strategy to enhance both CO2 uptake and cyclic stability of CaO-based adsorbents, offering a viable solution for CO2 capture from high-emission sources such as coal-fired power plants and cement kilns.

Confined spaces such as mines, submarines, and space stations often suffer from poor ventilation, leading to the CO2 accumulation to hazardous levels and endangering human health. Therefore, efficient CO2 removal (CDR) is crucial, which prioritizes the solid amine adsorption technology. A key challenge remains in developing superior porous support to reduce diffusion resistance and enhance adsorption capacity. In this study, mesoporous silica foam (MSF) with a large pore volume of 2.87 cm3/g was synthesized, into which 55 %-75 % polyethyleneimine (PEI) was evenly impregnated. The synthesized 55 %PEI@MSF adsorbent possessed the highest CO2 adsorption capacity of 126 mg/g under 2.5 vol% CO2 atmosphere, and exhibited the outstanding cyclic stability with minimal capacity loss of 2.7 % after 15 cycles under realistic confined spaces conditions. Furthermore, the PEI@MSF adsorbents demonstrated the strong adaptability across a wide range of operational conditions, including temperatures of 25-65 degrees C, humidity levels of 0 %-100 % RH, and CO2 concentrations of 0.5-2.5 vol%. Serial characterization techniques confirmed that the PEI@MSF adsorbents had strong resistance to water vapor interference, amine leakage deactivation and urea formation deactivation over cycles. The successful development of this material paves the way for the large-scale implementation of CDR systems in confined spaces and future carbon-neutral buildings, offering an efficient solution that outperforms traditional methods by preventing energy losses associated with heat exchange.

The reverse water-gas shift (RWGS) reaction plays an important role for converting the greenhouse gas CO2 and renewable H2 into liquid hydrocarbons under moderate conditions. Yet, the development of low-temperature RWGS catalysts remains a significant challenge, considering the CO2 conversion, CO selectivity, long-term stability. This study presents a novel strategy to encapsulate the Cu-Fe nanoclusters within a hollow silica shell, addressing the key challenges of low-temperature activity and sintering resistance. The synthesized SiO2@CuFe@H-SiO2 catalyst achieved superior RWGS performance, with CO2 conversion reaching 50.7 % at 500 degrees C (30,000 mL center dot gcat-1 center dot h-1, H2/CO2 = 4:1) and nearly 100 % CO selectivity maintained over a wide temperature range (300 degrees C-750 degrees C). Stability tests under stringent conditions confirmed the remarkable durability of the catalyst during a continuous 100-h run. Based on the serials of characterization, the innovative sandwich-like SiO2@CuFe@H-SiO2 nanostructure significantly enhanced the metal dispersion and prevented agglomeration under the demanding reaction conditions; meanwhile, the introduction of Fe improved the Cu-Fe interfacial interactions and enhanced the surface basicity, which was critical for activating CO2 molecule and improving catalytic efficiency. Comparative analysis reveals that this system outperformed many state-of-the-art RWGS catalysts, offering competitive activity and selectivity while being economically viable due to its noble-metal-free composition. This work underscores the potential of encapsulation strategy in designing high-performance, sintering-resistant catalysts for CO2 utilization, paving the way for scalable and sustainable CO production from CO2 and renewable hydrogen under mild conditions.

Synthesizing hydrotalcite-like (HT) CO2 adsorbents from blast furnace slag (BFS) is regarded as a promising strategy for industrial waste valorization while mitigating steel industry emissions. Conventional methods acid extraction face challenges due to their high reagent consumption and energy-intensive processes. This proposes an economical alkaline hydrothermal synthesis method for conversion of wet-milled BFS slurry into like adsorbents. Synthesized BFS-HT achieves a CO2 adsorption capacity of 0.27 mmol CO2/g after 400 calcination and subsequent CO2 capture at 200 degrees C, representing 68.8% increase over unmilled samples. minerals synthesized in Si-rich solutions exhibit a consistent crystalline structure with chemical-sourced layered double hydroxides. Hydrothermal post-treatment in deionized water partially removes interlayer further increasing CO2 uptake to 0.30 mmol CO2/g but requiring additional energy input. 27Al nuclear magnetic resonance (NMR) analysis identifies Al coordination changes in HT during calcination, showing Al-O-Si formation with interlayer Si. Density functional theory (DFT) modeling reveals strong interfacial interactions between defective CaO surfaces and silica nanoparticles, which may inhibit carbonation/rehydration. reducing production costs to 21.3% of those of conventional acid methods per gram of sequestered CO2, optimized alkaline method shows promising potential as a scalable solution for reducing overall carbon sions in the steel industry.

Geopolymers are increasingly used to immobilize heavy metals in solid wastes, yet the molecular-level mechanisms for different metals remain unclear. This study synthesized pure geopolymer precursors with Si/Al ratios of 1:1 and 3:1, incorporating cationic (Pb2+ and Zn2+) and oxyanionic (Cr2O72- and AsO2-) heavy metals, followed by alkali activation reactions to elucidate the immobilization mechanisms. The higher Si/Al ratio of 3:1 was found to enhance the polymerization degree of aluminosilicate, thereby improving the immobilization efficiency (IE). Leaching experiments (HJ/T 299-2007) demonstrated the following IE of: Pb2+ (99.93 %) > Zn2+ (99.30 %) > AsO2- (81.62 %) > Cr2O72- (20.70 %). The incorporation of Pb2+, Zn2+, and AsO2- led to significant changes in the chemical environment of Si, with a noticeable reduction in the proportions of the Q(4)(2Al) unit. Furthermore, AsO2- significantly increased the Si-IV-O-Al-IV bond angle from 145.60 degrees to 151.17 degrees and reduced the electric field gradient (EFG) around the Al nuclei. Characterization results demonstrated that Pb2+ and AsO2- are integrated into the geopolymer structure primarily through forming Si-O-Pb/Al-O-Pb and Si-O-As covalent bonds. Zn2+ is primarily immobilized through ion-exchange, where it replaces Na+ and functions as a charge-balancing ion within the [AlO4](-) tetrahedra. Conversely, Cr2O72- is not incorporated into the geopolymer network and is predominantly immobilized through physical encapsulation. Density functional theory (DFT) calculations further substantiated these immobilization mechanisms, with adsorption energies (Delta E) of -14.43 eV for Si-O-Pb/Al-O-Pb bonds, -1.63 eV for Si-O-As bonds, and -6.45 eV for Zn ionic bonds. This study advances understanding of geopolymer-based heavy metal immobilization, aiding safe solid waste disposal.