Boundary Reaction Research Articles

Enhanced mechanical properties and mechanism of iron ore tailings-based geopolymers modified by municipal solid waste incineration fly ash

Iron ore tailings, coal fly ash and municipal solid waste incineration fly ash (MSWI FA), as solid waste, must be disposed of. Iron ore tailings, coal fly ash and MSWI FA were successfully prepared into high-performance geopolymer. The compressive strength of optimal geopolymer reached 57.89 MPa. Based on XRD, FTIR, SEM and chemical extraction analysis, C-(A)-S-H was the main gel product along with N-A-S-H. It was found that the dominant hydration process of geopolymer was changed from diffusion process (D) to phase boundary reaction process (I) after MSWI FA addition based on hydration reaction rate curves and dynamic simulation, releasing more hydration heat and generating more C(N)-A-S-H gels. Heavy metal content in the optimal geopolymer was below the limits of Class I screening value of development land (GB 36600-2018). Ef and Cf of the optimal geopolymer were 30.9 MJ/ton/MPa and 6.88 kg CO2/ton/MPa, affirming the viability of utilizing iron ore tailings, coal fly ash and MSWI FA as raw materials for geopolymer production, which provides a promising collaborative resource method of processing them.

Kinetic Analysis of Molten Oxide Reduction Using Bottom-Blown Hydrogen Injection

Hydrogen-based smelting reduction has received widespread attention as an important technology for realizing low-carbon development in hydrogen metallurgy. In this study, the thermodynamics of smelting reduction was firstly analyzed by using FactSage 8.1 thermodynamic software, on the basis of which smelting reduction experiments of iron oxides by using bottom-blown hydrogen were carried out. The experiments used oxidized pellets as experimental materials, and the effects of the reduction process were analyzed in terms of the reduction temperature, the reduction time, and the hydrogen flow rate. The experimental results show that under the experimental conditions of a temperature of 1550 °C and a hydrogen flow rate of 0.2 Nm3/h, the reduction rate of iron oxides in the process of reducing iron oxides by hydrogen is significantly faster in the first 10 min than after 10 min. The hydrogen utilization rate reached a maximum of 41.87%, then decreased continuously and finally maintained at about 20%. Using the method of model fitting, it was found that the hydrogen-based molten reduction conformed to the phase boundary reaction model (Gα=1−(1−α)1/2), the corresponding mechanism function is fα=2(1−α)1/2, where α stands for the reduction conversion, and the reaction rate constant k(T) is 2.37 × 10−4 s−1 under the experimental conditions.

Property Effect and Mechanism of Sodium Salicylate on Magnesium-based Curing Plugging Materials

Abstract Lost circulation is a common problem in drilling and completion. Magnesium-based curing material has the advantages of effective plugging and formation damage control, and controlling curing time can extend the use. In this paper, the main agent of magnesium-based curing materials is magnesium salt, the influence of sodium salicylate with different dosage on the curing time in different curing states was analyzed, the optimal addition was determined, and the curing product and hydration process were analyzed under the optimal addition to determine the retarding effect of sodium salicylate. In static curing, the optimal addition of AR grade sodium salicylate was 15-17%, and the curing time was 3-4 h. The dynamic curing time at atmospheric pressure was obviously less than the static curing time, but clear right-angle thickening could be seen. The optimal addition of industrial grade sodium salicylate was 18%, and the static curing time was about 3 h. At high temperature and high pressure, it’s proved that pressure had little effect on curing time, but the curing time decreased significantly under high temperature environment. Through SEM, XRD and TGA, it was found that sodium salicylate was more conducive to the growth of the cured product, and more 517 phases was generated, but it did not affect the acid dissolution, with the acid dissolution rate reached more than 95%, which could realize the reservoir protection. By studying the hydration process, it’s showed that sodium salicylate could delay the hydration and reduce the heat release by about 2/3, and the hydration process was controlled by the phase boundary reaction. The retarding effect of sodium salicylate for magnesium-based curing material can guide the efficient application in different environments.

Three-dimensional phase field modeling, orientation prediction and stress field analyses of twin-twin, twin-grain boundary reactions mediated by disclinations in hexagonal close-packed metals

Crystalline defects, such as dislocations, disclinations, twins and grain boundaries, play critical roles in determining the mechanical properties of metals and alloys. In particular, with multiple competitive deformation modes activated, the mechanical behaviors of hexagonal close-packed metals are strongly influenced by the interactions and reactions of various types of defects. Despite extensive studies on the elastic interactions of defects, a theoretical framework capturing crystallographic reactions, especially reaction products and associated local stress concentration, is still unavailable. Here we suggest a disclination-based method to quantify defect reactions. By using a combination of crystallographic calculations and phase field modeling/simulations, twin-twin and twin-grain boundary reactions in hexagonal close-packed metals have been quantitatively analyzed. It has been found that partial disclinations, accompanied with other defects (e.g., {112¯6} and {112¯2} high-index twins), can be generated by defect reactions as typical byproducts. The orientation change and stress fields caused by disclination formation have been systematically calculated, which offers a rigorous mathematical foundation to explore twin-twin, twin-grain boundary reactions. By quantitatively determining defect reactions and local stress fields, our work provides new insights into the deformation mechanism and microstructure-property relationship in metallic materials.

Thermal evolution of mercury from waste rare earth phosphor: Effect of thermal treatment conditions and kinetic analysis

Waste phosphor (WP) from fluorescent lamp is a hazardous waste and an important secondary resource for recycling mercury and rare earths. To avoid mercury pollution during rare earth recovery, it is necessary to conduct deep mercury removal before rare earth recovery. However, the mechanism of mercury removal in WP is not clear, which restricts the progress of efficient mercury removal methods. Effects of treatment temperature and time on thermal evolution of WP were analyzed by different characterization methods. Model-free, model-fitting and z(α) master plots method are used in combination to explain the complex mechanism of mercury removal in WP. The mechanism of mercury removal will change gradually with the process of mercury removal. The average Eα for mercury removal is 100.76 kJ/mol and 190.36 kJ/mol at conversion α (i.e. mercury removal efficiency) of 0.1–0.3 and 0.3–0.9, respectively. Simple mercury compounds are decomposed at α less than 0.3 (∼600 °C), according with the model of random nucleation and subsequent growth. A large amount of tightly combined mercury is released rapidly at α of 0.3–0.75 (600–700 °C), ascribing to the decomposition of carbonate and the structure transformation of silicon oxide. The process mechanism gradually change from 1D/2D diffusion to 3D diffusion, increasing the mass transfer resistance of mercury diffusion. Thermal desorption of residual bound mercury at α larger than 0.75 (∼700 °C) is controlled by phase boundary reaction. More efficient mercury removal effects can be obtained by adding additives to roasting. The results are beneficial to the research of deep mercury removal methods of WP.

Hydration characteristics and kinetic analysis of polyacrylamide (PAM) anti-dispersion cement-based materials

Abstract Through phase analysis and quantitative calculations of the hydration process, the inclusion of polyacrylamide (PAM) in Anti-dispersion Water Paste affects its hydration characteristics is discovered. Specifically, the presence of PAM reduces early reactivity while accelerating progress in the middle to late stages of hydration. By employing K-D hydration kinetic analysis, it is confirmed that the use of PAM results in the formation of a multi-nucleation homogeneous point system within the cement slurry. This system prolongs the NG (nucleation and growth) process time, increases the hydration degree during the transition from NG to I (induction) process, and inhibits the heterogeneous precipitation of hydration products. Consequently, the early hydration of cement is hindered. As the hydration reaction advances, the microstructure of the product under multi-nucleation points increases the specific surface area. This gradual breakthrough of the hydration threshold barrier shortens the duration of the phase boundary reaction process and reduces the hydration degree during the I and D (diffusion) processes. Consequently, the late-stage hydration rate is accelerated.

Transport of reactive contaminant in a wetland flow with the effects of reversible and irreversible reactions on the bed surface

Wetlands are crucial for maintaining biodiversity in ecosystems. The reversible chemical reactions can significantly affect the pollutant reduction capacity in wetland flow. The spatial transport of contaminants in wetlands is further complicated by phase exchange kinetics due to reversible reactions in the wetland bed. This paper provides an analytical solution for studying the multi-dimensional concentration distribution of solutes in wetland flow, considering both reversible and irreversible boundary reactions. Unlike previous one-dimensional studies (Jiang et al. (2022), Zhan et al. (2024)), our approach offers a comprehensive view of wetland contaminant transport, accounting for complex interactions between different phases and environmental factors. The solute may undergo reversible sorptive phase exchange between the immobile (wetland bed phase) and the mobile phase (fluid phase). Multi-scale homogenization methods are used to determine the dispersion coefficient, mean concentration, longitudinal and vertical real concentration distributions, rate of variation of vertical concentration distribution under the influence of vegetation force, and reversible and irreversible reactions at a stationary wetland bed. The effects of retention parameter (θ), Damkohler number (Da), vegetation effect (α), dispersion time (τ), and first-order irreversible boundary reaction (β′) on solute mixing are thoroughly analyzed. The study's analytical results are validated by numerical results obtained using the finite difference method with a Shishkin mesh, and other comparisons are made with the limiting case of Taylor dispersivity. Results show that an increase in Damkohler number and vegetation force weakens contaminant transport in wetland flow, but an increase in Da enhances contaminant concentration in the mobile phase. The presence of reversible phase exchange kinetics causes non-uniform vertical concentration variation across the wetland cross-section. Critical values where the multi-scale homogenization technique may fail are suggested as θ≤0.5 and Da≥1. The study's findings have potential applications to pollution control in wetlands.

Interplay between dislocation type and local structure in dislocation-twin boundary reactions in Cu

Interplay between dislocation type and local structure in dislocation-twin boundary reactions in Cu

Hydration mechanism and kinetic response of a C4A3$-C2S binary system

The physical properties of C4A3$-C2S (ye´elimite-belite) clinker system will change with the proportion of C4A3$ or C2S, but the effect of mineral proportion change on hydration mechanism is not systematic and unclear. The C4A3$-C2S binary system was established by experiments, and its hydration process was characterized. The kinetic response of C4A3$-C2S binary hydration system was studied by Kondo model. The results showed that the change of design mineral ratio directly affects the hydration process and the hydration mechanism. The experiment and analysis show that when the design mineral ratio of C2S was lower than 65 wt%, the dominant factor of hydration was mainly controlled by nucleation mechanism (The hydration acceleration period is particularly significant), and when the ratio of C2S was higher, it would be controlled by diffusion mechanism. The precise value of the boundary reaction control is between 65 wt% (design mineral ratio of C2S) to 75 wt%. Only when the hydration kinetics of the binary system is controlled by the diffusion mechanism, the CH product can be stably crystallized. The classical Kondo model is suitable for the C4A3$-C2S hydration system.

Effect of side chain ionizability of polycarboxylate superplasticizer on cement hydration

Although the side chain ionizability (the adsorption group density and adsorption space are changed) of polycarboxylate superplasticizer (PCE) serve as the key structural parameter in affecting the cement hydration, its effect on cement hydration is unclear. Based on PCE with nonionizable side chain (NSC-PCE) and the PCE with ionizable side chain (ISC-PCE), the influence of the side chain ionizability of PCE on the hydration behavior of cement was studied. Compared with NSC-PCE, ISC-PCE has a stronger ability to change the migration of water and ions, thus delaying the crystal nucleation and growth of cement hydration (better morphology and distribution, the crystal size was reduced by more than 20 %), increasing the crystal growth index (tendency toward spherical growth), prolonging the phase boundary reaction (reduce micro-cracks), which was conducive to the formation of more uniform and dense crystals (good strength, ISC-PCE: 50.0 MPa > NSC-PCE: 49.2 MPa > Blank: 48.7 MPa). These findings provide the design basis and theoretical guidance for the innovative development of PCE.

Exploring microfine magnesite based on thermal decomposition and sintering kinetics: A new direction in the one-step preparation of high-density sintered magnesia

The thermal decomposition and sintering kinetics of microfine magnesite were investigated to inaugurate a new One-step process for preparing high-density sintered magnesia. The optimal parameters for the discharging particle size of magnesite through ball milling were determined using an orthogonal experiment and Three-Way Measures ANOVA. The model for the thermal decomposition process of microfine magnesite was established through TGA-DSC and nonlinear regression analysis. Meanwhile, by describing the sintering process of microfine magnesite in detail through microstructure and CTE, the kinetic mechanisms of grain growth at different sintering stages were obtained. The results revealed that increasing the ratio of ball to powder can quickly obtain microfine magnesite which the bulk density reaches 3.45 g·cm−3 after One-step sintering. The thermal decomposition process required an activation energy of only 124.98 kJ·mol−1, which is much lower than existing technology and followed the Two-dimensional phase boundary reaction mechanism R2. Additionally, the densification process was dominated alternatively by grain boundary diffusion and volume diffusion. This paper provided a detailed theoretical basis and leads a new direction in the One-step preparation of high-density sintered magnesia.

Effect of an inclined magnetic field on dispersion of solute in a pulsatile flow through a channel of absorptive porous walls

The present investigation gives an insight to comprehend the complex mechanism of species transport through porous walls, which has applications for crude oil refining, oil reservoir engineering, and separation of metal from fluids. The paper analyzes the impact of an inclined magnetic field on mass transport phenomena of solute through an unsteady, viscous, incompressible, and electrically conducting fluid flowing between two parallel plates. Both plates are permeable, and the flow is driven by a periodic pressure gradient. At both channel walls, the first order boundary reaction is applied. The governing time depending advection and diffusion equation is solved numerically based on Aris's method of moments. To determine the axial mean concentration distribution of solute, the first four central moments are used in a Hermite polynomial representation. It is significant to note that the dispersion of tracer is more significant for the low frequencies rather than the high frequencies. The behavior of the dispersion process of the tracer is studied for various flow parameters such as the angle of inclination of the magnetic field (α), Hartmann number (M), absorption parameter (β), suction Reynolds number (R), injection Reynolds number (R′), Womersley number (ω), and dispersion time (t) for both purely oscillatory and combined flows. It is significant to note that with the increment of R, α, and M, the amplitude of the dispersion coefficient of the solute reduces. On the other hand, an opposite phenomenon is observed for R′. It is seen that the transport coefficient moves cyclically with a double frequency period for all values of R and R′. Also, it is found that the peak of the mean concentration distribution enhances with the increment of α and M because the flow velocity decreases.

Mechanism underlying effects of CaO-MgO combined expansive agent on hydration kinetics of cement-based systems

With the order of better understanding the early hydration process and reaction mechanism of CaO-MgO combined expansion agent-involved cement-based systems (CMEA-CBS), CMEA dosage, CaO to MgO ratio (Ca/Mg), MgO activity, hydration temperature, and water-binder ratios (w/b) were chosen as the influencing factor. Accordingly, isothermal calorimetry was implemented to analyze the hydration heat release law, and the Krstulovic–Dabic model was applied to investigate the hydration kinetic. Moreover, the activation energy of CMEA-CBS was calculated. The findings of this study are as follows. The incorporation of CMEA can accelerate the hydration of cementitious systems. Hydration temperature increase markedly promote the hydration reaction of CMEA-CBS. The hydration reaction of CMEA-CBS is a complex associated reaction process dominated by multiple reaction mechanisms in sequence. At both 20 °C and 45 °C, the hydration process of CMEA-involved cement-based systems experienced three stages of crystallization nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D), and the hydration mechanism was NG → I → D. However, the hydration of CMEA-CBS at 65 °C switched from the NG stage to the D stage directly. The hydration promotion effect of increasing temperature on I and D process of CMEA-CBS is less than I and D process of pure cement. Compared to the other groups, the temperature increase had the least effect on the early hydration process of 10%-C1M1-M-0.4 with the lowest apparent activation energy.

Comparison of the effects of carbon-based and inorganic nanomaterials on early cement hydration

This study delves into the impact of nanomaterials on early cement hydration, aiming to elucidate their mechanism of action. Four nanomaterials were selected, including carbon-based nanomaterials (multi-walled carbon nanotubes (CNT) and graphene oxide (GO)) and inorganic nanomaterials (nano-SiO2 and nano-CaCO3). Initially, the zeta potential was employed to examine nanomaterial adsorption on relevant ions in simulated solutions. Subsequently, SEM NMR, XRD, and TGA were utilized to assess the influence of different nanomaterials on hydration product morphology, content, and structure. Utilizing the Krstulovic-Dabic model, the hydration kinetics based on the heat of hydration in cement paste containing nanomaterials was simulated. Results revealed nanomaterials exhibited stronger Ca2+ ion adsorption than cement particles, with CNT and GO particles displaying weaker adsorption relative to SO42- ions. Conversely, nano-SiO2 and nano-CaCO3 particles exhibited a stronger adsorption capacity for Ca2+ ions than SO42- ions. This robust adsorption facilitated hydration product generation, yielding fine and regular C-S-H particles in carbon-based nanomaterial-containing cement pastes, contrasting with coarse and irregular particles in inorganic nanomaterial-containing pastes. Nanomaterial introduction increased polymerization and the average chain length of hydration products. Furthermore, it heightened exothermic peak intensity and total exothermic amount, while reducing the induction period and exothermic peak length. Hydration kinetics, simulated through the Krstulovic-Dabic model, aligned with the nucleation and growth (NG)-phase boundary reaction (I)-diffusion (D) process. In the NG stage, nanomaterials accelerated hydration by reducing reaction stages (n) and increasing the rate constant (K1'). In the I stage, hindered Ca2+ ion migration led to decreased K2', slowing hydration. Stage D witnessed a rapid decline in K3'.

Hydration mechanism and photocatalytic antibacterial performance of cement-based composites modified by hydrophilic nano-TiO2 particles

In this paper, the hydration process of cement paste with hydrophilic nano-TiO2 particles was studied by microcalorimeter and electrochemical impedance spectroscopy, and the hydration mechanism was explored based on Krstulovic-Dabic kinetic model. Meanwhile, the photocatalytic activity and antibacterial properties of TiO2-modified cement pastes were investigated by ultraviolet spectrophotometer and enzyme activity analyzer respectively. The results show that TiO2 nanoparticles can promote the hydration rate of cement in the acceleration stage, increase the cumulative heat release of early hydration, but delay the hydration process in the later stage. The Krstulovic-Dabic model can effectively simulate the hydration process of cement pastes with TiO2. Nano-TiO2 helps to increase the hydration rate of the crystal nucleation and growth process (NG) and shorten the duration of phase boundary reaction process (I), but has a negative impact on ion diffusion process (D). The functional relationship between the resistivity ρ of TiO2 cement-based composites and the hydration kinetic parameters was established: ρ(t)=−1k1ln[β1+t50t−t0].The degree of hydration of cement can be assessed by electrochemical in-situ non-destructive monitoring of the sample. In addition, the photocatalytic oxidation rate of TiO2-modified cement-based composites was up to 69.4%. Compared with the control sample without nano TiO2, the antibacterial ability was increased by 72.35%. In this paper, nano-TiO2 was applied to cement system, which provided a new idea for the preparation and application of photocatalytic antibacterial cement-based composites.

Transient dispersion of a reactive solute in an oscillatory Couette flow through an anisotropic porous medium

This research discusses the significance of reactive solute dispersion relevant to ecological, biological, and geological contexts. It examines solute movement under oscillatory Couette flow through anisotropic porous media between parallel plates under the effect of heterogeneous boundary reactions. The flow is driven by the combined effect of upper plate oscillation in its plane and time-dependent pressure gradient. The lower plate is assumed rough, which introduces slip velocity. A semi-analytical approach, with the method of moments and finite difference scheme, is utilized to explore the transient dispersion in steady and oscillatory flows with or without a non-zero mean. Using the Hermite polynomial, the mean concentration for purely oscillatory and combined flow is obtained, highlighting notable variations based on flow factors. The results suggest that increment in anisotropic angle ϕ reduces dispersion and enhances mean concentration for permeability ratio K < 1, but this reverses for K > 1. Three dispersion phases emerge: diffusive, anomalous, and Taylor's regimes. Gaussian cloud distribution occurs at small and large times, with intermediate stages displaying anomalous dispersion and asymmetric longitudinal distribution. Effects of boundary absorption stabilize over time. The research focuses on the practical significance of different permeabilities of porous media, emphasizing applications of anisotropic porous media in fields such as chemical engineering and industrial processes.

Insight into the high-temperature reaction characteristics of CaS with CO2: Experimental study and theoretical calculation

To address the challenge of optimizing the utilization of industrial by-product gypsum, this study proposes a two-step reductive decomposition process for the production of quicklime from industrial by-product gypsum. In the initial step, a blend of CaS and CaO is generated through the low-temperature reductive decomposition of gypsum. Subsequently, the decomposition products undergo oxidation in a carbon dioxide environment, yielding activated quicklime. While the reductive decomposition of gypsum has been extensively documented, there exists a significant research gap concerning the reaction between CaS and CO2 at elevated temperatures. This study investigates the high-temperature reaction characteristics and reaction mechanism of the CaS and CO2 system through a combination of experiments, isothermal kinetic analysis, and density functional theory (DFT) calculations. Furthermore, it offers a comparative analysis of the physicochemical properties of quicklime produced via three different methods, using desulfurization gypsum as an illustrative example. It was observed that the reaction rate of CaS with CO2 markedly increased with rising temperature and CO2 concentration. The reaction of CaS in a CO2 atmosphere adhered to the phase boundary reaction model. DFT calculations were employed to determine the reaction pathway for the interaction between CaS and CO2, which can be summarized as follows: CaS + CO2 → CaSO + CO, CaSO + CO2 → CaSO2 + CO, CaSO2 + CO2 → CaSO3 + CO, CaSO3 → CaO + CO2. The lime generated through the two-step process of desulfurization gypsum (FGD) exhibited a superior pore structure and reactivity when compared to lime produced via the one-step process of FGD gypsum and that obtained through limestone calcination.

Phase decomposition behavior and its impact on mechanical properties in bulk nanostructured Cu-20 at.%Fe supersaturated solid solution

Extended solid solution of immiscible systems, achieved by extreme processing approaches, can be transformed into nanostructured composites via phase decomposition, which are drawing great research attention for their excellent thermal stability and high strength. Here we fabricated the supersaturated solid solution of Cu-20 at.%Fe, a typical immiscible alloy, in bulk state by high pressure torsion, which provides a great freedom over powders for studying the microstructure evolution and mechanical properties in the process of the phase decomposition in immiscible alloys. We found that in the Cu-Fe solid solution, spinodal decomposition of the Fe phases took place at the initial stage of annealing through volume diffusion. This process gives rise to: (1) metastable γ-Fe particles in the Cu grains with coherent Fe/Cu interface, and (2) the more stable α-Fe phase at the grain boundaries. This process was accompanied by moving boundary reaction which first proceeded in the pattern of spinodal decomposition and then changed into classical nucleation-growth mode with the depletion of Fe atoms in Cu. The resultant Cu-Fe nanocomposites were jointly strengthened by the ultrafine Cu and α-Fe grains according to the rule of mixture, including grain boundary strengthening and the hardening of nanoscale γ-Fe precipitates in the Cu grains. The effects of different strengthening mechanisms were scrutinized and their contributions to mechanical properties were quantitatively evaluated. This work sheds light onto the opportunity of designing and fabricating nanostructured composites via phase decomposition in immiscible systems.

Insight into waste polyurethane pyrolysis pathways: Mechanism functions analysis and in-situ coupling online monitoring

Pyrolysis is one of the promising techniques to recycle organic resources and remove hazardous substances during the treatment of waste polyurethane (WPU) in refrigerator. However, knowledges on pyrolysis mechanism and pathways from WPU to complex products are insufficient, limiting its application for producing high-valued oil and gas. Here, this study applied the mechanism functions analysis and in-situ coupling online monitoring for the insightful illustration of WPU pyrolysis process. The results suggested that the pyrolysis mechanism function calculated by Šesták-Berggren method was expressed as: , indicating that the WPU pyrolysis was controlled by the combined processes of diffusion, nucleation and phase boundary reactions. Moreover, the online TG-FTIR-MS and in-situ FTIR analysis for pyrolysis intermediates detection demonstrated that WPU pyrolysis began with the rupture of urethane bonds in WPU to produce isocyanates and polyols. Then, the polyols decomposed into the small molecular polyols, ethers, alkanes and alkenes, where the further decomposition of isocyanates led to the formation of aniline and its derivatives. The results offered the theoretical basis for converting waste to fuels and high-valued products through pyrolysis techniques.

Optimal metal immobilization of oxygen-enriched co-combustion of Zn/Cd hyperaccumulator and textile dyeing sludge with natural or modified kaolin

Eco-friendly disposal of post-harvest and metal-enriched hyperaccumulator biomass is critical for the industrialization of phytoremediation. The addition of Al/Si-based materials, such as sludge and natural mineral additives, is intended to solve the issue of HM metal stabilization in the oxygen-enriched combustion of hyperaccumulator and slow down ash sintering. This study aimed to quantify and reveal the effects of 10% kaolin or modified kaolin on the oxygen-enriched (co-)combustions of Sedum alfredii Hance (SAH) and textile dyeing sludge (TDS) and their combustion kinetics, metal enrichment rates, and immobilization/stabilization mechanisms. The activation energies for the (co-)combustions of SAH and SAH mixed with 10% additives (ST31) were estimated at 75.84–260.97 kJ/mol and 65.58–327.59 kJ/mol, respectively. The (co-)combustion mechanism model was complex, including phase boundary, diffusion, and chemical reaction order. The co-combustion of SAH with 10% modified kaolin increased Cd and Zn immobilization by approximately 66.6% and 3.2%, respectively, compared with the theoretical data at 550 °C. The co-combustion of ST31 with 10% modified kaolin increased Cd immobilization by approximately 160.9% compared with the theoretical data at 750 °C. Obtained via thermal-acid modified treatment, modified kaolin increased the immobilization efficiencies of Zn and Cd through aluminosilicate reactions to form the stable structures (Ca–Zn–Si, Ca–Zn–Al, K–Zn–Si, Zn–Al, Zn–Si, Cd–Al, and Cd–Si) as well as physical absorption. According to the combination of the experimental, multi-objective optimization, and simulation results, SAH mixed 10% modified kaolin at 550 °C and ST31 mixed with 10% modified kaolin at 750 °C were the ideal co-combustion environment. This study can provide new insights into how to best reduce the environmental risks of the hyperaccumulator disposals through the oxygen-enriched combustion technology.