Synergistic approach towards the sustainable management of heavy metals in wastewater using mycosynthesized iron oxide nanoparticles: Biofabrication, adsorptive dynamics and chemometric modeling study

In our study, novel mycosynthesis of ferromagnetic, monodispersed, spherical, crystalline iron oxide nanoparticles (IO-NPs) of 73.05 +/- 15.47 nm were biofabricated using manglicolous fungi Aspergillus tubingensis (STSP 25) isolated from rhizospheric sediment samples of Avicennia officinalis which was sustainably utilised for the removal of Pb (II), Ni (II), Cu (II), and Zn (II) from wastewater. The elemental and XRD characterisation had shown Fe2O3 (hematite) nature of the IO-NPs which were aqua stable due to deposition of extracellular fungal bio molecules onto them. Initial batch adsorption studies revealed that at pH 6 in 313 K temp, 1 g/L of IO-NPs could able to remove > 90 % of heavy metals from the aqueous matrix. This was further confirmed through muti-factor chemometric approach which involved RSM and ANN module. RSM and ANN analysis inferred that 98.0037 % of Pb (II), 96.4502 % of Ni (II), 92.1984 % of Cu (II), and 93.9913 % of Zn (II) ions were adsorbed from 9.66 mg/L of heavy metals on 1 g/L concentration of IO-NPs in 308.25 K temperature at pH 6. Adsorptive dynamics indicated the process of adsorption was kinetically spontaneous and thermodynamically it followed endothermic reaction, where metallic ions got chemisorbed on the monolayer interface of IO-NPs. The overall process followed the Langmuir isotherm model and Pseudo-second order kinetics. The Adsorbing potentiality of IO-NPs for Pb (II), Ni (II), Cu (II), and Zn (II) was found to be 9.206 mg/g, 9.666 mg/g, 8.335 mg/g and 9.106 mg/g respectively. Reusability study showed IO-NPs had high regeneration capability till five adsorption/desorption cycle.