Synthesis and characterisation of stable and efficient nano zero valent iron

Abstract

Nano zero valent iron (nZVI) is an excellent adsorbent/reductant with wide applicability in remediation of persistent contaminants in soil, water and groundwater aquifers. There are concerns about its environmental fate, agglomeration, toxicity and stability in the air. Several modification methods have applied chistosan, green tea, carboxyl methyl cellulose and other coating substances to ensure production of nZVI with excellent air stability and effectiveness. The synthesis of a novel green nZVI (gNZVI) with Harpephyllum caffrum leaf extracts was successfully executed in the current study. Production of gNZVI involved the simultaneous addition of an optimum amount of the NaBH₄ and H. caffrum extract to FeCl₃ in an inert environment (Nitrogen). The solution was stirred for 30 min, washed with dilute ethanol (50%) and freeze dried. This procedure offered the best option for the synthesis of gNZVI in terms of nontoxic and inexpensive choice of stabiliser/reductant. Systematic characterisations using TGA, TEM, SEM, XRD, FT-IR and XPS confirmed the synthesis of crystalline, stable, reactive, well-dispersed and predominantly 50 nm diameter sized gNZVI compared to the conventionally synthesised nZVI which is 65 nm. The activity testing using Orange II sodium salt (OR2) confirmed the effectiveness of the synthesised gNZVI as an excellent Fenton catalyst with 65% degradation of 20 ppm OR2 dye in 1 h reaction time.