Effect of magnetic stirring and different additives on the synthesis of zeolites from MSWI fly ash

As a kind of hazardous solid wastes, municipal solid waste incineration (MSWI) fly ash leads to serious environmental pollution. Converting MSWI fly ash into zeolites is an economically beneficial and environmentally sound way of disposal. In this paper, the effect of different additives (kaolin, milled glass powder, Na₂SiO₃) on the synthesis of zeolites by microwave-assisted hydrothermal process using MSWI fly ash was investigated through a series of single-factor experiments. The cation exchange capacity (CEC) was used to evaluate the synthesis effect and the adsorption property of zeolites. Na₂SiO₃ was found to be an ideal additive with the optimal dosage of 30 wt%, and the optimal time of magnetic stirring process was about 8 h. Na-P1 zeolite with high absorbability was synthesized in this condition, whose CEC was about 1.70 meq/g. In addition, the effect of Na₂SiO₃ dosage and various hydrothermal conditions on the CEC of zeolites were investigated through the orthogonal experiment and analysis of variance. It was found that the Na₂SiO₃ dosage had the strongest impact on the CEC of zeolites, followed by hydrothermal temperature, concentration of NaOH and hydrothermal time. The work of this paper provides a reference basis for synthesizing high-performance zeolites by MSWI fly ash.