Biosynthesis of silver nanoparticles by cell-free extracts from some bacteria species for dye removal from wastewater.

OBJECTIVES: To investigate the biosynthesis of silver nanoparticles (AgNPs) using extracts of some bacterial isolates Bacillus pumilus, Bacillus paralicheniformis and Sphingomonas paucimobilis. The formation of AgNPs was detected by the change in color into yellow and confirmed by the UV-Vis spectroscopy. The nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). RESULTS: The obtained AgNPs were spherical to oval in shape with particle size ranged from 4 to 20 nm and surface area 118 m2/g. The AgNPs have been used as nanocatalyst for the removal of malachite green dye (MG) from aqueous solution. The dye was chosen as a model dye released in wastewater. The AgNPs showed excellent nanocatalyst for the removal of MG. The dye removal process was observed by the continuous decrease in dye absorbance at 617 nm until it vanished over 160 min. The removal kinetics followed closely the pseudo-first-order kinetic model. CONCLUSION: The B. paralicheniformis strain KJ-16 was the most effective isolated bacteria to give extract for biosynthesis of AgNPs and dye removal. This method may be considered easy and eco-friendly, and could be applicable for large-scale decontamination of wastewater from harmful dyes.

The role of silver nanoparticles biosynthesized by Anabaena variabilis and Spirulina platensis cyanobacteria for malachite green removal from wastewater.

In this study, biosynthesis of silver nanoparticles (AgNPs) using two species of cyanobacteria, Anabaena variabilis (Kütz) and Spirulina platensis (Gomont) was investigated and evaluated for dye removing capacity. The formation of AgNPs was detected by the change in colour using UV-Vis spectroscopy and further characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR). The obtained AgNPs were spherical to oval with average particle size of 17.9 and 26.4 nm for S. platensis and A. variabilis, respectively. These AgNPs were applied as bio-sorbent for the removal of malachite green (MG) dye released into wastewater. Within the tested initial concentration range of MG, the reaction exhibited first order kinetics model as monitored via UV spectroscopy. As the dye concentration decreased, the removal efficiency increased to reach 93% for S. platensis and 82% for A. variabilis AgNPs. The results also indicated that increased AgNPs concentration enhanced the MG removal with an efficiency up to 88% and 81% for S. platensis and A. variabilis AgNPs, respectively. The smaller particle diameter and larger specific surface area of S. platensis AgNPs enabled boosted catalytic activity for dye removal than those of A. variabilis. After the treatment with AgNPs, the resultant dye- AgNPs-free effluent proved non-toxic to Triticum aestivum L (Giza 171) seedlings, implying their safety for cultivation practices.