Removal of Green 6 Direct Dye from Aqueous Solutions Using Immobilized Laccase Enzyme on Zinc Ferrite Nanoparticle

Manufactured wastewater management of industrial units containing toxic pollutants is essential for environmental protection. Considering the great applications and effects of using the nanomaterial and nanotechnology in the field of environmental protection, the nanoparticle of ZnFe2O4 has been used as a basic particle. On the other hand, enzyme processes, due to their low costs and cheapness, can be used as the new and efficient processes for decolorization from wastewater. Therefore, the aim of this study was to evaluate the efficiency of removal of green 6 direct dyes from aqueous solutions using immobilized laccase enzyme on zinc ferrite nanoparticle.
First, the magnetic zinc ferrite nanoparticles (ZnFe2O4) were synthesized using sol-gel method. Then, by immobilizing laccase enzyme onto it and enzyme activation of the nanoparticles, it was used to remove green 6 direct dye from the aqueous solution. Long-life catalytic converters have been used to immobilize the enzyme on the surface of nanoparticles. In order to study the physical properties of the synthesized nanoparticles, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) pattern and scanning electron microscopy (SEM) were used. The investigated conditions included contact time (120-160 minutes), adsorbent dosage )0.1-1mg/l(, pH (3,4,7,8,9) and initial color concentration (10 to 100 mg /l).
The results of the study showed a spherical and even crystalline structure of the enzymatic nanoparticles, with an average size of approximately equal to 23 to 40 nm. Photometric studies of the immobilized enzyme on zinc nanoparticle (IZFN) spectra at 1199, 1284, 2956 and 1714 peaks confirmed the CH2 group of triethoxymethylsilane, the peptide bond c = o group, as well as the S = O and C-N groups of the SO group in the Lacas enzyme. Therefore, the nanoscale composition of the enzyme immobilizing layers was confirmed. The maximum removal of color was 95% with the adsorbent dose of 0.2 mg/L, at the initial concentration of 10 mg /L, pH = 3.4 and the contact time of 120 minutes
The combination of the immobilized enzyme layers made in this study with immobilized enzyme on zinc nanoparticle can be a suitable adsorbent for the removal of dye contamination, especially the green 6 direct dyes from fabric dyeing wastewaters, as compared to the other similar nanoparticles.