Transferring waste red mud into ferric oxide decorated ANA-type zeolite for multiple heavy metals polluted soil...

Herein, a novel "waste reclamation for soil remediation" strategy has been developed for both alkaline waste red mud (RM) recycling and heavy metal (HM) polluted soil remediation. Through a direct one-pot hydrothermal reaction process, the Al, Si, alkali, and Fe₂O₃ components in waste RM have been transferred into ferric oxide decorated ANA-type zeolite (Fe₂O₃-ANA). As tested by the HMs polluted soil remediation and oilseed rape planting experiment, when 25 g/kg Fe₂O₃-ANA is added into the Pb²⁺, Cu²⁺, Cr³⁺ and anionic AsO₂^- polluted soil (HM concentration: 100-200 mg/kg), it can effectively suppress the HMs mobility in soil and reduce the bio-accumulation concentrations of HMs in the harvested oilseed rape (reduce ratio: 37.9-69.5%). The detailed mechanism study using energy dispersive X-ray energy spectroscopy, in-depth X-ray photoelectron spectroscopy and density function theory calculation concludes that the Cu²⁺, Pb²⁺ and Cr³⁺ in soil have been adsorbed and trapped in the framework structure of ANA in Fe₂O₃-ANA mainly via the cation exchange process. While the anionic AsO₂^- species are mainly caught by the Fe₂O₃ component in Fe₂O₃-ANA via surface adsorption. Overall, this work firstly transforms waste RM into Fe₂O₃-ANA for soil remediation, which is valuable to waste resource recycling and environmental conservation.