Individual, co-transport and deposition of TiO2 and ZnO nanoparticles over quartz sand coated with consortium biofilm

The transport of TiO2 and ZnO nanoparticles was assessed using column experiments in a porous media containing biofilm. In order to understand the influence of bacteria encountered in the natural aquatic environment when nanoparticles are introduced in the surroundings, nanoparticles transport has been studied through quartz coated with a biofilm composing of a consortium of Pseudomonas aeruginosa (Gram-negative), Bacillus alitudinis and Bacillus subtilis (Gram-positive). The influence on individual and co-transport mobility and deposition kinetics of TiO2 (10, 15 mg/L) and ZnO (5, 10 mg/L) nanoparticles based on variations in ionic strength was also determined. Various environmentally related ionic strengths were studied for the experiment using NaCl (0.1-10 mM), by keeping the pH fixed to pH 7.0. At pH 7.0, TiO2 NPs transport declined, when the ZnO nanoparticles were present, whereas, enhanced ZnO nanoparticles transport was observed in the presence of TiO2 nanoparticles. The solution chemistries of the nanoparticles can be inferred from the breakthrough curves (BTCs), wherein an increase in ionic strength results in a decline in the BTC plateau. The inverse of BTC plateaus provided the retention profiles, which could also be anticipated from the mass balance contemplation. Altogether, the upshot of this work explains the transport behavior of both the nanoparticles in biofilm coated sand depends on suspension chemistries (pH and ionic strength) are likely the primary factors that control. Further research could thus be focused on enhancing our knowledge of the basic mechanisms governing nanoparticles transport and fate in typical biofilm containing aquatic environment.