Sludge gasification provides a promising route for waste-to-energy conversion, but the mechanisms governing hydrogen enrichment over oxygen carriers remain insufficiently understood. A Ca-modified steel slag-derived Fe/Ca oxygen carrier was developed, and the role of interfacial reaction regulation in hydrogen-enriched sludge gasification was systematically investigated. Compared with raw sludge and steel slag-sludge, the Fe/Ca oxygen carrier-sludge consistently exhibited higher syngas yield, and the syngas yield reached about 0.35 Nm3·kg−1 at 730 °C. Interfacial analyses further revealed that C and CO were strongly adsorbed and readily activated on Fe sites, while CH4 adsorption remained weak and its conversion was limited by difficult deep dehydrogenation. Meanwhile, oxidation of C and CO proceeded through facile lattice‑oxygen extraction, with energy barriers of about 0.85 and 0.20 eV, respectively. Whereas CH4 conversion required stepwise H abstraction with the highest barrier reaching 2.41 eV. Furthermore, continuous lattice oxygen extraction promoted carrier reduction, oxygen-vacancy generation, and subsequent CO2 capture, while steam reforming and water-gas shift reactions were simultaneously strengthened. Therefore, hydrogen enrichment was governed by a Fe-site-controlled interfacial reaction network rather than by oxygen transfer alone. This work provides an interfacial perspective for designing Fe-based oxygen carriers for hydrogen-oriented and low-carbon sludge gasification.

Mixed matrix membranes (MMMs) incorporating metal organic frameworks (MOFs) have emerged as promising candidates for CO2 separation by combining the processability of polymers with the superior adsorption and molecular-sieving properties of MOFs. Unlike previous reviews that primarily focus on performance enhancement at the laboratory scale, this review provides a systematic evaluation of MOFs MMMs for CO2 capture specifically from the perspective of industrial scalability. First, synthesis routes of MOFs are compared with respect to their environmental footprint, production cost, and scalability. Subsequently, key membrane fabrication approaches, including solution casting and in situ growth, are critically assessed in terms of process feasibility, interfacial control, and scale-up potential. Various performance optimization strategies, including MOFs functionalization, composite fillers, hybrid design, defect engineering, and morphological regulation, are analyzed not only from the standpoint of separation enhancement but also with regard to their manufacturability and industrial readiness. Furthermore, the separation mechanisms governing CO2/N2, CO2/CH4, and CO2/H2 systems are discussed. Unlike previous reviews, particular emphasis is placed on the key barriers to practical implementation, including long-term operational stability, economic viability, membrane module scale-up, and environmental sustainability. Finally, future research directions are proposed to bridge the gap between laboratory-scale advances and commercial deployment. By centering the discussion on industrial scalability, this review offers actionable insights for researchers and engineers working toward the development of industrially viable MOFs MMMs for CO2 separation.

Alkali-activated geopolymer technology has emerged as an effective strategy for promoting the high-value utilization and environmental risk mitigation of municipal solid waste incineration fly ash (MSW-IFA). However, the widespread application of conventional liquid alkali activators is constrained by their strong corrosiveness, operational hazards, and environmental concerns. To address these limitations while facilitating the synergistic utilization of high-calcium industrial solid wastes, this study developed a solid alkali activation system based on calcium carbide slag (CS) and yellow phosphorus slag (YPS) for the preparation of geopolymer-based functional cementitious materials (GFCM) incorporating MSW-IFA. The primary objective was to simultaneously enhance reaction activity, structural integrity, and heavy metal immobilization performance. Through a combination of macroscopic performance evaluation and multi-scale microstructural characterization, the effects of different solid alkali systems on elemental release behavior, gel evolution, pore structure development, and heavy metal stabilization mechanisms were systematically investigated. The results demonstrated that the composite activation system established a stable alkaline environment and continuously promoted the dissolution and release of reactive Ca, Si, and Al species, thereby accelerating geopolymerization and facilitating gel formation. Compared with single-alkali activation, the synergistic activation strategy was more favorable for the generation of densely interconnected C-(A)-S-H gels and amorphous aluminosilicate networks, resulting in enhanced matrix compactness and a more refined pore structure. Furthermore, the optimized gel framework and reduced pore connectivity effectively inhibited heavy metal migration and facilitated the transformation of heavy metals into more stable chemical fractions. Notably, despite the relatively high Pb content in MSW-IFA, its leaching concentration remained consistently below regulatory limits throughout the stabilization process, indicating the excellent and long-term immobilization capability of the developed system toward Pb. Based on these findings, a comprehensive mechanistic pathway involving “alkaline environment regulation–continuous elemental release–gel network evolution–pore structure refinement–heavy metal stabilization” was established. This study provides new insights into the co-utilization of MSW-IFA and multiple industrial solid wastes and offers a theoretical basis for the development of low-carbon, environmentally sustainable geopolymer cementitious materials.

Potential of carbide slag-lignite's chemical looping gasification to generate hydrogen-rich syngas containing 80 % hydrogen has been established. However, the impact of trace constituents in carbide slag has not been investigated. This study aims to elucidate the enhancement mechanism of trace constituents in carbide slag to the production of hydrogen-rich syngas during lignite's CLG process. The investigation utilized the actual composition of carbide slag as a benchmark. Specific trace constituents were individually incorporated after using main constituent (Ca(OH)2) of carbide slag as a control. A comprehensive approach combining theoretical analysis with experimental characterization was employed for cross-validation. The results indicate that SiO2, Al2O3, Fe2O3, and Na2O play significant roles in boosting hydrogen generation, leading to a 7.18 % increase in yield from 1376.74 to 1475.53 mL. Different oxide components contribute to this process through distinct reaction pathways: SiO2 primarily reacted via the R1 pathway, Al2O3 through the R9 route, Fe2O3 participated in CH4 conversion (R12), and Na2O facilitated H2S capture. These results elucidate the distinct roles and transformation mechanisms of individual oxides in the reaction system. It unveiled the reaction mechanisms of trace constituents in carbide slag during lignite's CLG, offering essential insights for the development of hydrogen-rich syngas.

ABSTRACT Titanium gypsum (TG) is an abundant sulfate waste, yet its strong oxidizing nature and unclear oxygen chemistry hinder its use as an oxygen carrier for hydrogen‐oriented lignite gasification. Here, TG was introduced into steam‐assisted lignite gasification, and the operating window and vacancy‐associated radical oxygen activation mechanism were investigated. Thermodynamic calculations predict a CO 2 ‐dominated equilibrium endpoint, whereas the experimentally observed H 2 ‐rich syngas arises from a non‐equilibrium regime governed by interface‐controlled oxygen release. Under optimal conditions including 0.5 of TG/lignite mass ratio, 35 g·min −1 of steam flow and 850°C–950°C of temperature, the syngas yield reaches 0.95 Nm 3 ·kg −1 , with H 2 yield higher than 0.75 m 3 ·kg −1 and 53% carbon conversion. During gasification, TG undergoes dehydration, reduction, and reconstruction, generating a Ca─Ti─O framework that stabilizes oxygen transport. Oxygen is decoupled from sulfate‐bound species into mobile lattice oxygen (O latt ) and defect oxygen associated with surface‐enriched oxygen vacancies (V O ). These vacancies activate O 2 /H 2 O to form reactive oxygen intermediates (O 2 · − /O 2 2 /·OH), which participate in C─O bond formation and interfacial carbon conversion. Radical consumption may couple with vacancy regeneration, enabling repeated oxygen transfer at the gas‐solid interface under non‐equilibrium gasification conditions. These insights provide a design rule for converting sulfate wastes into recyclable oxygen carriers for efficient lignite‐to‐hydrogen conversion.

Substantial amounts of agricultural and forestry waste remain underutilized, leading to disposal issues and missed opportunities for resource recovery. In light of the concerns above, MnO2-modified biochar (MnO2-BC) was synthesized from Hypericum rhizome residues, and its efficacy for metal-ion adsorption was assessed using Ni(II). The investigation batch and packed-bed column adsorption kinetics studies, coupled with accurate computational fluid dynamics (CFD) simulations, were employed comprehensively to validate the efficiency of the modified biochar materials, from fundamental mechanisms to practical applications. Batch experiments demonstrated that adsorption had a significant dependence on pH, with increased absorption seen under neutral to acidic settings. The behavior of fixed-bed column breakthrough is closely related to influent concentration, bed height, and flow rate. Experimental breakthrough curves were described well by the Thomas and Bohart-Adams models. Furthermore, CFD results corroborated the measured breakthrough trends, and the Freundlich isotherm provided the best overall agreement when coupled into the simulation framework, consistent with batch adsorption analysis. This study illustrates a biomass-residue valorization pathway and an integrated process for batch, packed-bed, and CFD-based analysis, offering a viable foundation for the design of biochar-based adsorption systems.

Arsenic-containing desulfurization gypsum (ADG) is a typical solid waste in the metallurgical industry, and its resource utilization is restricted by the high toxicity and difficulty in removal of arsenic. In this work, using ADG as the raw material, the effects of pressurized hydrothermal conditions on the conversion of alpha-hemihydrate gypsum (alpha-HH) and simultaneous arsenic removal were systematically investigated. The results showed that hydrothermal temperature, reaction time, sulfuric acid concentration, and liquid-solid ratio (L/S) all had significant impacts on the crystal form of the product and arsenic removal efficiency. Under the conditions of 140 degrees C, 5 % H2SO4, reaction duration of 120 min, and L/S of 7:1, gypsum could be completely converted into dense columnar alpha-HH, and the arsenic removal rate reached 95.7 %. H+ could directionally destroy the lattice of Ca-As compounds, enabling arsenic to migrate to the liquid phase in a dissolved state; meanwhile, the phase transformation from calcium sulfate dihydrate (DH) to alpha-HH was completed simultaneously during the dissolutionrecrystallization process. The arsenic removal process was controlled by chemical reaction in the initial stage and then turned into diffusion control. The arsenic removal process conformed to the Avrami model ( - ln(1 c) = 8.47exp( - 21080/RT)t0.47), with an activation energy of 21.1 kJ/mol. Aluminum sulfate crystal modifier could effectively regulate the crystal form of alpha-HH and improve arsenic removal efficiency. This study reveals the action law of pressurized hydrothermal conditions on alpha-HH conversion and simultaneous arsenic removal as well as the characteristics of mass transfer control, providing a theoretical basis for the synergistic high-value and harmless utilization of ADG.

Although carbide slag enhances hydrogen production during the chemical looping gasification (CLG) of lignite, the intrinsic relationship among hydrogen evolution, interfacial adsorption, electron transfer, and reaction pathways remains unclear. This study systematically investigates the hydrogen production mechanism using an integrated macro-micro approach. In situ gas detection and hydrogen equilibrium analysis were employed to reveal gaseous product evolution, and kinetic modeling was used to describe hydrogen formation quantitatively. H2, CH4, and H2O accounted for more than 99.9% of the gaseous products. Two key stages were identified: low-temperature lignite devolatilization and carbide-slag-enhanced gasification, which were described by the Parabola law function model and the Valensi equation model, respectively. DFT calculations and in situ XRD further elucidated the interfacial reaction mechanisms. Ca(OH)2 exhibited a synergistic electronic response, and Ca, O, and H atoms played distinct roles in carbon capture, oxidation, and hydrogen supply. Only C, CO2, and H2S underwent chemisorption. C preferentially adsorbed on H/O sites, whereas CO2 selectively bound to Ca sites. The dominant CLG-driven hydrogen production pathway (Path I) was identified, establishing a multi-scale correlation between hydrogen evolution and interfacial reaction behavior.

Tar formation during sewage sludge gasification severely reduces process efficiency and causes operational and environmental problems. In this work, FeO-rich steel slag was employed as a low-cost oxygen carrier to assist sludge gasification, and the transformation behaviour of major tar compounds was systematically investigated. Under optimal conditions, the total tar yield decreased by over 70 %, and syngas production reached about 3.5 m3/kg with an H2/CO ratio close to 1:1. Besides, sludge-derived aliphatics and oxygenated organics preferentially evolved into phenolic and N-containing tars, whose polar functional groups and conjugated structures were removed by >80 %, accompanied by fluorescence quenching and blue-shift. Theoretical calculation revealed that FeO promotes adsorption (-1.2 to- 2.4 eV) and CC/CH/CN bond cleavage via lattice-oxygen migration and redox pathways, thereby suppressing heavy tar formation and enhancing gas yield. These findings provide molecular-level guidance for in-situ tar control and syngas upgrading in sludge gasification.

Nitric oxide (NO) is a common acidic air pollutant, primarily emanating from coal-fired power plants and motor vehicle exhaust. Investigating the oxidation of NO is instrumental for improving the removal efficiency of nitrogen oxides in various mainstream emission control technologies. In this study, a series of perovskite catalysts, La1-xCexCoO3 (x = 0-0.3), were prepared by replacing La in the A-site of LaCoO3 perovskite with Ce to enhance the NO oxidation activity. The results indicated that Ce-doping effectively enhanced the NO oxidation activity, among which La0.9Ce0.1CoO3 exhibited the highest oxidative activity and the lowest activation energy over La1-xCexCoO3 (x = 0-0.3) perovskites (85.1 % at 300 degrees C, 54.9 +/- 3.4 kJ/mol). Through characterizations and DFT analysis, the Ce-doping technology enhanced the NO adsorption capacity and weakened the Co-O bond, which was conducive to the formation of oxygen vacancies and the improvement of surface reactive oxygen species. Furthermore, the charge transfer ability was also strengthened, so that the reaction energy requirement of the La0.9Ce0.1CoO3 was reduced, and finally it developed in the direction of NO oxidation. This study elucidated the mechanisms by which Ce-doping influenced the catalytic properties of LaCoO3 catalysts, providing valuable insights for the future development of advanced perovskite catalysts.

To overcome insufficient H2 production, CO2 build-up, and the narrow H2-rich window in lignite gasification, titanium gypsum (TG) was introduced as a sulfate solid-waste oxygen carrier into a lignite gasification system, and its effects on hydrogen-oriented gas formation, CO/CO2 partitioning, and kinetic behavior were investigated. The results show that TG markedly enhanced steam gasification at medium-high temperatures. The syngas yield increases from about 0.18 to 0.70 Nm3 center dot kg-1, carbon conversion reaches about 52%, and H2 yield rises from 0.122 at 600 degrees C to 0.532 Nm3 center dot kg-1 at 950 degrees C, an approximately 5-fold increase. Although equilibrium calculations predict a CO2-rich oxidized endpoint for sulfates, the experimental process exhibits distinct temperature-zoned CO/CO2 evolution. CO2 is continuously buffered rather than accumulating, whereas a certain degree of CO2 re-release occurs at higher temperatures. This arises from concurrent sulfate-to-sulfide conversion and Ca-Ti-S scaffold reconstruction, which creates coupled oxygen donation, sulfur immobilization, and transient CO2 buffering that sustains a low-CO2 microenvironment favorable for H2 formation. Furthermore, kinetic analyses indicate that the apparent activation barrier increases with conversion in the main stage with diffusion-influenced characteristics, while the tail stage transitions to an apparent first-order regime, which reflects a stage-wise shift from reaction intensification to ash-layer densification and transport limitation. This work establishes a mechanistic chain linking phase reconstruction, gas partitioning, and rate-controlling steps for TG-assisted hydrogen-oriented lignite gasification, providing mechanistic support for co-gasification of lignite with active-oxygen solid wastes toward H2-rich syngas production.

Ammonium sulfate wastewater is a common type of industrial wastewater. Its sources are extensive and its composition is complex. Traditional treatment methods have problems such as low treatment efficiency and secondary pollution. Compared with these methods, electrodialysis (ED) technology has advantages such as high separation efficiency, no phase change and good stability. Therefore, ED technology shows a promising application prospect in the treatment of ammonium sulfate wastewater. However, ion-exchange membranes (IEM) have problems such as low selectivity, easy contamination and poor stability. These are the difficulties in its industrial promotion. For this reason, this paper focuses on the ammonium sulfate wastewater treatment system and delves deeply into the performance bottlenecks of IEM. This paper also systematically reviews the research progress of three mainstream modification strategies: surface coatings, interfacial polymerization (IP), and organic/inorganic composites. At the same time, this paper also analyzes its potential in enhancing membrane selectivity, anti-pollution performance and operational stability. This paper provides a theoretical basis and modification path for constructing high-performance IEM suitable for ammonium sulfate wastewater systems, thereby promoting the large-scale application of ED technology in this field.

Biomass gasification is a viable pathway for low-carbon energy recovery, but its deployment is often limited by high heat demand and kinetic barriers during char conversion. Phosphogypsum (PG) is a large industrial solid waste that can pose environmental and land-use issues if stored long-term. In light of the challenges above, this study presents a novel strategy that utilizes PG to prepare composite gasification agents (M-PG) to enhance biomass gasification performance, with a particular focus on low-temperature initiation. Three isoconversional methods were applied to estimate key kinetic parameters, including the apparent activation energy. Insights into the reaction mechanism were gained through thermodynamic analysis, in situ characterization, and density functional theory (DFT) calculations. With FeNi-PG, the initial temperature of the gasification section decreased from above 800 degrees C to 600 degrees C, and the reaction activation energy was reduced by approximately one-third (from 301.84 kJ & sdot;mol- 1 to 206.51 kJ & sdot;mol- 1). FeNi-PG was therefore identified as the most effective gasification agent among the tested agents. Overall, an energy-efficient route to low-temperature syngas production was demonstrated by coupling PG utilization with the valorization of agricultural and forestry residues, thereby mitigating the environmental burdens associated with PG stockpiling and the disposal of biomass waste.

Lanthanum cobalt oxide (LaCoO3) perovskite has attracted significant attention for its excellent and stable catalytic performance in nitric oxide (NO) oxidation. In this study, a series of La1-xKxCoO3 (x = 0-0.6) perovskite catalysts was synthesized via potassium (K) doping at the A-sites of LaCoO3 perovskite. The results demonstrate that K doping significantly enhances NO oxidation activity. Structural characterization reveals that increasing K doping content leads to the formation of a Co3O4 phase, resulting in a composite material comprising La1-xKxCoO3 perovskite and Co3O4. Furthermore, K doping facilitates the conversion of Co2+ to Co3+, which exhibits stronger electronegativity and increase the generation of more surface-adsorbed oxygen, providing a structural basis for NO oxidation. Magnetic analysis demonstrate that K doping alters the magnetism of La1-xKxCoO3 (x = 0-0.6) and modifies the Co ionic magnetic moment. Notably, a positive correlation is observed between the Co ionic magnetic moment and NO oxidation activity, with La0.6K0.4CoO3 exhibiting the highest magnetic moment and achieving an NO oxidation efficiency of 88%. In addition, K doping enhances oxygen vacancies, redox properties, and active oxygen species in La0.6K0.4CoO3, further improving its catalytic performance and exhibits a positive correlation. These structural modifications contribute to a greater availability of active sites for NO oxidation. This study provides insights into enhancing perovskite catalytic performance through structural modulation. (c) 2025 Chinese Society of Rare Earths. Published by Elsevier B.V.

To overcome the low-H2/high-CO2 challenge in converting municipal sludge to clean syngas, a novel Fe/Ca-based oxygen carrier (FCOC) was produced using waste steel slag by Ca modification. At 730 °C, FCOC-assisted sludge gasification increased H2 yield by 54.16 % and limited CO2 to below 20 vol%, as in situ carbonation created a low-CO2 atmosphere that thermodynamically favoured H2 formation. Multi-level oxygen species were established, where adsorbed oxygen (Oads) and bridge oxygen (Obridge) accelerated initial conversion and lattice oxygen (Olattice) maintained structural stability, while abundant •O2-/•O- radicals opened low-barrier pathways for organics conversion. These features defined a critical "temperature switch" at 730 °C. In the synergistic zone (≤ 730 °C), CO2 mineralization continuously drives hydrogen-forming reactions, whereas in the decoupling zone (> 730 °C), CaCO3 decomposition triggers H2-consuming reverse reactions. This work proposes a waste-derived oxygen-carrier strategy for hydrogen-rich syngas production and low-carbon valorization of municipal sludge and steel slag.

Solid waste-derived membranes (SWDMs) represent an emerging class of sustainable materials that integrate carbon capture functionality with circular utilization of industrial and agricultural residues. This review systematically summarizes the transformation of solid wastes including fly ash, steel slag, plastics, and biomass into functional membranes for CO2 separation, and highlights their potential in reducing landfill burden and offsetting carbon-intensive materials. Various fabrication strategies such as dip-coating, phase inversion, and electrospinning are discussed, along with structure-function mechanisms that govern gas separation performance. Special attention is paid to interface engineering, porosity control, and chemical compatibility, which underpin selective CO2 transport. Furthermore, those reported techno-economic and life-cycle data were analyzed and indicated that under favorable, proxy-based assumptions SWDM-based systems could in principle approach capture costs below 30 US$ per ton CO2 and offer reduced embodied emissions and material consumption relative to conventional membranes. Next, the current limitations, data gaps, especially regarding long-term stability under industrial conditions, and research bottlenecks of SWDMs were critically analyzed. Finally, a development roadmap is proposed to align membrane innovation with net-zero goals, offering a prospective pathway toward low-carbon manufacturing and sustainable industrial decarbonization.

Chemical looping gasification (CLG) is an eco-friendly energy conversion technology widely used in the production of hydrogen-rich syngas. Due to the high Ca(OH)2 content in industrial solid waste carbide slag, many studies have explored its use as an oxygen carrier (OC) in CLG. However, SiO2 is the second most abundant component in carbide slag after Ca(OH)2, and the effect of SiO2 on the CLG of lignite, along with its migration and transformation pathways, remains insufficiently studied. Therefore, this study analyzed the effect of SiO2 and its migration and transformation pathways during the carbide slag and lignite CLG process. To achieve this, FactSage™ simulation calculations were employed, and tube furnace experiments were conducted. Additionally, characterization experiments involving combined lignite, Ca(OH)2, and SiO2 were carried out. The results indicated that at 650 °C, the simultaneous presence of Ca(OH)2 and SiO2 promoted the generation of H2, CO, and CH4, facilitated lignite decomposition, and enhanced the hydrogen enrichment effect of the syngas to some extent. SiO2 reacted with CaO to form Ca2SiO4 during the CLG of lignite and could be converted back to SiO2 through CO2 adsorption. Overall, this study provides novel insights into enhancing the efficiency and yield of hydrogen-rich syngas production in lignite CLG processes.

The synergistic mechanism between oxygen carriers and catalysts is crucial for optimizing the chemical looping gasification (CLG) process. In carbide slag, both Fe2O3 and the main component Ca(OH)2 have been identified as key active species in lignite CLG. This study systematically investigated the synergistic interactions between Fe2O3 and Ca(OH)2 in carbide slag, with a focus on their combined effects on enhancing hydrogen-rich syngas production and the underlying reaction kinetics of the CLG process. Phase transformations and equilibrium conditions were analyzed using FactSage 7.1, while the migration behavior of solid-phase products and kinetic characteristics were elucidated. Syngas composition was monitored by gas chromatography. After analyses, the results show that increasing the Fe2O3 content significantly elevated the H2 concentration, thereby promoting the conversion of CH4 and CO into H2 and CO2 in the gas phase. The kinetic functions for lignite CLG with the Ca (OH)2-Fe2O3 system can be expressed as d alpha dt = 8.18 x 1022 exp -284.914x103 x (1-alpha) (400-500 degrees C) and d alpha 2.66 x 1014 exp -195.63x103 2(1 + a)2/3[ ]-1 x 3 (1 + a)1/3-1 (500-650 degrees C). The evolution pathways of Fe2O3 during CLG were determined to be Fe2O3 -> Fe3O4 -> FeO -> Ca2Fe2O5 and Fe2O3 -> Ca2Fe2O5. This work elucidated the intrinsic synergistic mechanism between Fe2O3 and Ca(OH)2, provided a scientific basis for controlling hydrogen production quality, and demonstrated the feasibility of utilizing carbide slag in CLG processes.

To resolve the pollution caused by massive stockpiled phosphogypsum (PG) and high-carbon footprint challenges in its decomposition, this study employs a low-carbon approach for PG resource utilization. H2S was used as a reductant to efficiently convert PG into CaS in a fluidized bed. Through the thermogravimetric-differential thermal analysis (TG-DTA), computational particle fluid dynamics (CPFD) simulations, and density functional theory (DFT) calculations, the thermal decomposition behavior and reaction mechanism of PG under an H2S were systematically investigated. The results of TG-DTA indicated that PG could be reduced by H2S to form CaS within the temperature range of 670-870 degrees C. The activation energies obtained from non-isothermal kinetics was 260.91 kJ/mol. The CPFD simulation successfully reproduced the complex gas-solid flow and reaction behavior inside the fluidized bed. The temperature distribution and yield were significantly influenced by factors such as bed height, particle size, and H2S concentration. The optimal reaction conditions were identified as an initial bed height of 0.2 m, particle sizes ranging from 150 to 250 mu m, and an H2S content of 10%. DFT calculations revealed multiple intermediates and four transition states in the reduction pathway of PG to CaS, with OH* and HS* intermediates facilitating the breakdown of CaSO4 by lowering its decomposition energy barrier. The desorption of the first O atom from CaSO4 was identified as the rate-controlling step, with an energy barrier of 3.63 eV. The multi-scale coupled analysis method constructed in this study provides a mechanism basis for optimizing the conversion process of PG to CaS.