Objective In pursuit of carbon neutrality， China is actively advancing the development of a comprehensive carbon capture industry cluster. There exists a pressing demand for economically viable and low-cost technologies for the capture， sequestration， and utilization of CO₂ gas. Zeolite molecular sieves have garnered significant attention due to their tunable pore structure and selective adsorption properties. However， challenges arise in their widespread adoption and mass production due to issues with selectivity， thermal stability during CO₂ capture， and the high production costs involved. China possesses vast and diverse quantities of rare earth tailings， yet secondary recovery costs are prohibitive due to immature technology. Mineralogical analysis of these tailings reveals significant concentrations of Si and Al elements， both crucial constituents of synthetic molecular sieves. Moreover， active metal elements such as Fe， Ca， and Ce are present in the tailings， which can enhance CO₂ gas adsorption. To develop low-cost and highly efficient CO₂ adsorbents， we target rare earth tailings， which pose challenges due to their large accumulation and difficult management. We analyze the physical and chemical properties of rare earth tailings， synthesize molecular sieves， and determine optimal synthesis ratios and temperatures conducive to CO₂ adsorption. The aim is to produce molecular sieves with morphological structures， specific surface areas， and pore structures optimized for CO₂ adsorption efficiency. Additionally， we investigate the kinetic equation governing the synthesis of rare earth tailings for CO₂ adsorption， aligning with the kinetic equations applicable to molecular sieves synthesized from rare earth tailings. This research contributes to exploring the high-value utilization of rare earth tailings within the context of carbon capture， emphasizing stability， high efficiency， and low cost in CO₂ adsorbent development.

Methods Thermogravimetric mass spectrometry （TGMS） and thermoanalytical kinetics （TAK） were employed to investigate the mass ratios of silicon and aluminium under optimal synthesis conditions for molecular sieves derived from rare earth tailings. Surface micromorphology， specific surface area， and pore structure characterization of these molecular sieves were conducted using scanning electron microscopy （SEM）， energy-dispersive X-ray spectroscopy （EDS）， and Brunauer-Emmett-Teller （BET） analysis， respectively. Furthermore， the cyclic stability of green synthetic molecular sieves derived from activated rare earth tailings solids was assessed through multiple thermal stability experiments conducted under identical operating conditions. Additionally， four kinetic models， including the quasi-primary adsorption model， quasi-secondary adsorption model， fractional kinetic model， and Elovich kinetic model， were employed to fit adsorption curves at temperatures of 30℃，50℃， and 70℃. This analysis aimed to identify the most effective curve representing the adsorption behavior of rare earth tailings synthetic molecular sieves for CO₂ capture.

Results and Discussion The findings indicate that the molecular sieve synthesized from rare earth tailings exhibits its highest CO₂ adsorption capacity when the silicon-to-aluminium mass ratio is 1：1. 5. Specifically， the adsorption efficiency for CO₂ peaked at 0. 15 mmol/g when tested at 50 ℃ and with a 1% CO₂ volume fraction. Moreover， the thermal stability of the molecular sieves derived from rare earth tailings was evaluated， revealing consistent and stable adsorption performance over four cycles. To elucidate the CO₂ gas adsorption mechanism at various temperatures， quasi-primary kinetics， quasi-secondary kinetics， Fractional， and Elovich models were employed to fit the experimental data. Among these models， the Fractional model demonstrated the highest degree of fitting， suggesting its suitability for describing CO₂ gas adsorption on the molecular sieve surface.

Furthermore， the optimal adsorption performance observed at 50 ℃ was attributed to the significant driving force generated by the appropriate operating temperature， facilitating CO₂ gas diffusion into the adsorbent with minimal resistance.

Conclusion The green synthetic molecular sieve derived from activated rare earth tailings solids exhibits a notable adsorption capacity for CO₂ gas. Specifically， under a 1% concentration environment at 50℃，the maximum adsorption capacity of the molecular sieve for CO₂ gas reached 1. 5×10^-4 mol/g.This adsorption process demonstrates strong selectivity， attributed to the larger molecular polarity of CO₂ gas compared to N₂. Moreover， the adsorption process of CO₂ gas by the concatenated molecular sieves is reversible and exhibits excellent thermal cycle stability. Furthermore， through a kinetic study of adsorption at various temperatures， it was observed that the Fractional equation， with a fit superiority index R² higher than 0. 983 32 across different temperatures， provides a more accurate reflection of the adsorption process of molecular sieves on CO₂ gas. This finding offers a

valuable kinetic model for the utilization of rare earth tailings in the field of CO₂ gas adsorption， paving the way for future research and applications in this area.