Synthesis of zeolite molecular sieve from coal gangue and its performance on CO₂ capture

Coal gangue, a by-product of coal mining, is accumulating rapidly and As a by-product of coal mining, the amount of coal gangue is increasing in stock, which poses a serious threat to the environment. Due to the high content of SiO₂ and Al₂O₃ mass fraction, the use of gangue to prepare molecular sieves to capture CO₂ in order to realize the efficient resource utilization of coal gangue is a promising technology. In this paper, zeolite molecular sieves are prepared by hydrothermal crystallization method with coal gangue as raw material, and the effects of KOH addition and coal semi-coke doping on the structure and properties of molecular sieves are investigated; static adsorption test of CO₂ is carried out to study the CO₂ capture characteristics of coal gangue-based zeolite molecular sieves and amine-modified molecular sieves. The results show that when the mass ratio of KOH to coal gangue is 2∶1, the specific surface area of the molecular sieve is 100.17 m²/g. When the doping amount of coal semi-coke is 40%, the molecular sieve has a specific surface area of 249.86 m²/g, and the total pore volume is 0.249 cm³/g. Under the optimal preparation conditions, the CO₂ adsorption capacity of the molecular sieve is 1.16 mmol/g. Amine loading modification could effectively enhance the CO₂ capture capacity of the molecular sieves, but excessive polyethyleneimine will accumulate in the molecular sieve pores and block the pore channels, resulting in the weakening of the physical adsorption capacity of the molecular sieves.