Sequestration of free and chelated Ni(II) by structural Fe(II): Performance and mechanisms

Ni(II) and chelated Ni(II) in wastewater are of environmental concern. This study explores the sequestration potential of structural Fe(II) in solid phase (equivalent to Fe(II)) on Ni(II) and EDTA-Ni(II) using freshly prepared ferrous hydroxyl complex (FHC) as the Fe(II)-bearing mineral. The 1 mM Ni(II) could be completely sequestrated in 20 min by 3 mM FHC, although the sequestrated Ni(II) was partially released after 20 min. It is calculated that up to 156 mg Ni(II)/g Fe(II) can be sequestrated by equivalent to Fe(II) under neutral pH and anaerobic condition. According to the characterizations of the solid products, the large surface area for Ni(II) adsorption and the high equivalent to Fe(II) reduction capacity for Ni(II) reduction are the main contributors to the Ni(II) sequestration. After the reaction, the FHC is transformed to stable Fe-Ni layered double hydroxides. The concomitant ions can be either promotional or inhibitory to the sequestration performance depending on the ion type. The combination of FHC and Fe (III) can effectively sequestrate EDTA-Ni(II), whereas FHC alone has a low efficiency. Fe(III) substitutes Ni(II) from the EDTA-Ni(II), benefiting the subsequent Ni(II) sequestration by equivalent to Fe(II). This study demonstrates that equivalent to Fe(II) suspension is an cost-effective option for remediating Ni(II)-containing wastewater.

Automated summary

This study investigates the sequestration potential of structural Fe(II) in solid phase on Ni(II) and EDTA-Ni(II) using ferrous hydroxyl complex, demonstrating that equivalent to Fe(II) suspension is a cost-effective option for remediating Ni(II)-containing wastewater.