Recovery of NiFe2O4 from wastewater containing nickel citrate complexes and its application to activate peroxymonosulfate

treatment method for wastewater containing nickel citrate complexes was first proposed, which conformed to strategy of treating waste with waste. Nickel was recovered from wastewater containing nickel citrate complexes using ferrate (VI) and the recovered product was converted to the magnetic nanocatalyst iron-nickel spinel NiFe2O4 (NFO) via calcination. Subsequently, NFO was used to activate peroxymonosulfate (PMS) to degrade the nickel citrate complexes in wastewater. The morphology and crystallinity of NFO are controlled by changing the calcination temperature of the precursor, which in turn affects the catalytic properties and mag-netic properties of NFO. The characterization results show that the increase of the calcination temperature can positively affect the crystallization and magnetic properties of NFO. The morphology of NFO-900 after calci-nation at 900 degrees C was octahedral nanoparticles with a maximum saturation magnetization intensity of 47.43 emu center dot g-1. This implies that it can be easily magnetically recovered from the wastewater. Experiments on the degradation of nickel citrate complexes by the NFO/PMS system showed that NFO-900 had the best potential to activate PMS. Electron spin resonance and quenching experiments confirmed that the main reactive oxygen species of the system were SO4 center dot-, 1O2, center dot O2- , and center dot OH. NFO-900 also exhibited good reusability and catalytic performance after five consecutive cycles. This study provides a green and promising technology for the treat-ment of wastewater containing nickel citrate complexes.

Automated summary

A treatment method for wastewater containing nickel citrate complexes was proposed, utilizing ferrate (VI) to recover nickel and converting it into magnetic nanocatalyst NiFe2O4 (NFO). The morphology, crystallinity, and magnetic properties of NFO were controlled by changing the calcination temperature. NFO-900 showed the best potential to activate PMS and degrade the nickel citrate complexes in wastewater.