Assessment of de-toxicity of treated dye solution via seed germination test: Photocatalytic treatment by Morinda citrifolia leaf extract mediated ZnO:Mo/g-C3N4 nanocomposite

Abstract

Molybdenum doped zinc oxide (ZnO:Mo) nanoparticles and ZnO:Mo/g-C3N4nanocomposites were prepared via green synthesis by using Morinda citrifolia (M. citrifolia) extract as the reducing agent. Another set of ZnO:Mo and ZnO:Mo/g-C3N4 nanomaterials were prepared using NaOH as the reducing agent and their photocatalytic efficiencies against methylene blue (MB) and methyl orange (MO) were evaluated and compared with those of their green synthesized counterparts. The degrading efficiency of green synthesized ZnO:Mo/g-C3N4 was 99 and 96 % against MB and MO of dyes, respectively, whereas the respective values in the case of chemical synthesis are only 95 and 90 %. The mechanism lies behind the photocatalytic activity of the nanocomposite was elaborated. The enhanced charge carrier concentration caused by Mo doping and the synergistic advantages of the composite partners, like band gap reduction and reduced recombination rate are discussed with relevant references. The water samples photocatalytically treated by the nanomaterials were applied to green gram seeds and the growth process is evaluated and compared. The powder XRD, field emission SEM, TEM, FTIR and EDAX results and the related analyses are presented as corroborative evidences for the composite formation and enhanced photocatalytic activity. The prepared green synthesized ZnO:Mo/g-C3N4 nanocomposite will be a promising material for de-toxification of dye effluents to make it conducive for seed germination and plant growth.