A combined passivator of zeolite and calcium magnesium phosphate fertilizer: Passivation behavior and mechanism for Cd (II) in composting

• Published in: Environmental research 2023-08, Vol.231 (Pt 3), p.116306-116306, Article 116306
• Main Authors: Jiang, Wei, Li, Dian, Yang, Junlin, Ye, Yuanyao, Luo, Jiwu, Zhou, Xiaojuan, Yang, Lin, Liu, Zizheng
• Format: Article
• Language: English
• Subjects: Cd passivation; Combined passivator; Composting; Correlation analysis; Microbial community
• ISSN: 0013-9351; 1096-0953
• DOI: 10.1016/j.envres.2023.116306

Passivation of heavy metals is one of the most efficient techniques to improve the quality of compost. Many studies confirmed the passivation effect of passivators (e.g., zeolite and calcium magnesium phosphate fertilizer) on cadmium (Cd), but passivators with single component could not effectively passivate Cd in the long-term operation of composting. In the present study, a combined passivator of zeolite and calcium magnesium phosphate fertilizer (ZCP) was used to explore its impacts of adding at different composting periods (heating period, thermophilic period, cooling period) on the Cd control, compost quality (e.g., temperature, moisture content and humification), microbial community structure as well as the compost available forms of Cd and addition strategy of ZCP. Results showed that Cd passivation rate could be increased by 35.70–47.92% under all treatments in comparison to the control treatment. By altering bacterial community structure, reducing Cd bioavailability and improving the chemical properties of the compost, the combined inorganic passivator could achieve high efficiency for Cd passivation. To sum up, the addition of ZCP at different composting periods has effects on the process and quality of composting, which could provide ideas for the optimization of the passivators addition strategy. •A combined passivator positively contributes to the Cd control in compost.•Adding the passivator in the thermophilic period improved humification.•The passivation rate of Cd was positively correlated with GI and pH.•Actinobacteria showed a significant negative correlation with organic matter.•The pH value plays a key role during composting with ZCP passivation.