Facile green synthesis of nickel-ferrite-rGO (NiFe2O4/rGO) nanocomposites for efficient water purification under direct sunlight

Abstract

• Green synthesis of NiFe 2 O 4 /rGO nanocomposites using peppermint leaf extract ( Mentha piperita ). • Efficient photocatalytic degradation of cationic and anionic dyes. • Detailed kinetic study of the photocatalytic reactions. • High magnetic separation and recyclability of the synthesized nanocomposites. Facile green synthesis of magnetically separable nickel-ferrite nanocomposites supported over reduced graphene oxide (NiFe 2 O 4 /rGO) using peppermint leaf extract as reducing agent is reported herein. The as-synthesized nanocomposites are magnetic in nature and can be used as fine photocatalysts. It is fascinating that the mixing of inert NiFe 2 O 4 with GO nanosheet produces highly active photocatalyst after the reduction of GO to reduced graphene oxide (rGO). The nanocomposites have been well characterized using different analytical techniques. Morphological and structural studies have shown the formation of spherical NiFe 2 O 4 nanocomposites with particle size 3-5 nm, regularly supported over the layers of rGO. The nanocomposites have actively participated in the photocatalytic degradation of different dyes under direct sunlight within a very limited time. Congo red and Malachite green are completely degraded in 18 mins, while Methylene blue and Methyl orange are completely degraded in 30 and 12 mins respectively. Moreover, study showed that 30 mgL -1 nanocomposite was sufficient to degrade all the dyes completely. However, depending on the Ni/Fe ratio, the photocatalytic activity has been varied. Recovery and reusability of the nanocomposites have been done very smoothly because of the magnetically separable behavior of the nanocomposites, which shows the efficiency of the catalysts up-to 4 th cycle with very minimal loss in activity. This green strategy of the synthesis and utilization of magnetically separable NiFe 2 O 4 /rGO nanocomposites for the waste water purification is remarkable.