Potential role of Spirulina (Arthrospira) platensis biomass for removal of TiO₂ NPs -MG hybrid nanocomposite produced after wastewater treatment by TiO₂ nanoparticles

Biosynthesis of titanium dioxide nanoparticles (TiO₂ NPs) by Sphingomonas paucimobilis B34 bacteria was successfully achieved and followed by UV-Vis spectroscopy. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and fourier transform infrared spectroscopy (FTIR) techniques. The biosynthesized TiO₂ NPs were spherical in shape with an average particle size of 15.6 nm. These TiO₂ NPs were used as nono-catalyst for removing of malachite green (MG) dye (at 103 mol/L) from wastewater solution. As indicated by the results, the biosynthesized TiO₂ NPs represented a capable approach for MG removal with up to 83 % efficiency. The removal process was found to follow a pseudo-fi rst-order kinetics. Furthermore, the developed TiO₂ NPs-MG hybrid nanocomposite was efficiently removed from the medium by using Spirulina platensis cyanobacterial biomass after wastewater treatment. S. platensis biomass was able to remove up to 89.43 % of the hybrid nanocomposite by a biosorption process. The resultant water effluent, after TiO₂ NPs-MG removal, showed no toxicity towards Vigna radiate L. seedlings implying its safety for agriculture purposes. According to the obtained results, S. platensis living biomass could play a dual re-cycling role, as natural biosorbent for removing both nanoparticles and dye (TiO₂ NPs-MG hybrid nano-composite) from solution after wastewater treatment for healthier environmental management. (author)