Novel Averrhoa carambola extract stabilized magnetite nanoparticles: a green synthesis route for the removal of chlorazol black E from wastewater

Abstract

Herein, Averrhoa carambola extract (ACE) was exploited as a novel and green stabilizer in the synthesis of stabilized magnetite nanoparticles (SMNPs), which were used for the removal of chlorazol black E from wastewater. Bare magnetite nanoparticles (BMNPs) were synthesized as the reference material and the nanoparticles were characterized with FTIR, XRD, TEM, SAED, EDX and VSM techniques. The bands at 580–790 cm⁻¹ and 3367 cm⁻¹ correspond to Fe–O vibrations and H-bonded OH groups. The diffraction planes at (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1) and (4 4 0) correspond to face-cantered cubic Fe₃O₄. The average particle sizes of the BMNPs and ACE-SMNPs were 10.39 nm and 2.38 nm, respectively. The presence of Fe and O in the nanoparticles was also confirmed from EDX spectra. The nanoparticles demonstrated high saturation magnetization, low remanent magnetization and coercivity, which facilitated easy magnetic separation and reuse. The dye removal efficiency of the ACE-SMNPs was around 98.67% with a sequestration capacity of 38.64 mg g⁻¹. Pseudo-second-order kinetics and a Langmuir isotherm best represented the equilibrium data. The dye removal process was endothermic, spontaneous and governed by electrostatic and H-bonding interactions. The CBE-loaded nanoparticles were effectively regenerated and the renewed material showed a removal efficiency similar to the fresh nanoparticles.