Performance and mechanisms of enhanced retention of aged microplastics by magnetite-loaded biochar

ANG Yu-chen; XIONG Cun; LUO Chang-jian; QIU Yu-ping

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China Environmental Science ›› 2026, Vol. 46 ›› Issue (1) : 429-439.

Emerging Contaminants

Performance and mechanisms of enhanced retention of aged microplastics by magnetite-loaded biochar

ANG Yu-chen, XIONG Cun, LUO Chang-jian, QIU Yu-ping

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Abstract

To compare their capture efficiency, four types of iron (hydro)oxide-loaded biochar functionalized with ferrihydrite, goethite, hematite, or magnetite were synthesized via co-precipitation method at a consistent iron-to-biochar mass ratio. The modification significantly improved electrostatic attraction between the biochar and aged microplastics, thereby increasing retention capacity. Among these materials, magnetite-loaded biochar demonstrated the highest removal efficiency exceeding 90% and maximum adsorption capacity of 25.02mg/g, representing a 5.53-fold improvement over unmodified biochar. This superior performance is likely attributed to its highest iron oxide loading (4.15wt%). Adsorption data followed both the Langmuir monolayer model and pseudo-first order kinetics. Notably, magnetite-loaded biochar maintained over 95% retention under varying ionic strengths, cation valences, and pH conditions. It also preserved greater than 90% of microplastics in multi-bed volume tests and real-water samples. Moreover, after multiple alkaline washing regeneration cycles, the material remained stable adsorption performance, demonstrating its excellent reusability potential.

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aged microplastics / magnetite-loaded biochar / physical retention

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ANG Yu-chen, XIONG Cun, LUO Chang-jian, QIU Yu-ping. Performance and mechanisms of enhanced retention of aged microplastics by magnetite-loaded biochar[J]. China Environmental Science. 2026, 46(1): 429-439

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