Synergetic interactions between zero-valent iron and schwertmannite for enhanced arsenic (III) removal: Role of morphological variations

Although the enhanced removal of heavy metals using zero valent iron (ZVI) assisted by schwertmannite (Sch) was achieved in previous studies, their interactions between Sch and ZVI seems to be bidirectional and impact on the As(III) removal by ZVI/Sch mixture remains elusive. This study investigated As(III) removal in the mixed suspensions of ZVI and Sch with various premixing times and mass ratios. Batch experiments demonstrated that ZVI/Sch mixture with the premixing time of 3 h and mass ratio of 2:1 exhibited excellent performance in As(III) removal. The results indicated that synergetic interactions between ZVI and Sch during premixing process played crucial roles, particularly in terms of morphological variations. Results of FTIR and XPS revealed the mass and electron transfer occurred between Sch and ZVI during the premixing process, resulting in the accelerated recrystallization of Sch and the corrosion process of ZVI. Furthermore, the premixing process was found to significantly improve the As(III) removal capacity of ZVI/Sch mixture without altering the As(III) removal pathway, including the adsorption/precipitation/oxidation processes of ZVI and surface complexation/ion exchange/channels inlay of Sch. These findings shed light on the complex interactions between ZVI and Sch in As(III) removal and offer promising opportunities for the development of efficient treatment strategies in As(III)-contaminated environments.