Potential role of engineered nanoparticles as contaminant carriers in aquatic ecosystems: Estimating sorption processes of the cyanobacterial toxin microcystin-LR by TiO2 nanoparticles

Abstract

Abstract In the present study, the adsorption of a cyanobacterial toxin, microcystin-LR (MC-LR), onto titanium dioxide nanoparticles (TiO 2 -NPs) was investigated in aqueous solution. TiO 2 -NPs with different crystalline phases (anatase, rutile, anatase-rutile mixture) and MC-LR in an environmental relevant concentration for German water bodies were used to make results more applicable to environmental conditions. To investigate the adsorption mechanism as well as to determine the rate-limiting step of adsorption, analysis of the adsorption kinetic was performed and common kinetic models were applied to the experimental data. Additionally, the influence of nano-TiO 2 dosage (0.01–10 mg/L) and particle size on adsorption capacity was examined, the latter by comparing the adsorption data of TiO 2 -NPs to a bulk sized counterpart. The analysis of the adsorption kinetic indicates a complex adsorption mechanism and the involvement of pseudo-second-order chemisorption in the adsorption process. While only anatase TiO 2 showed a variation of MC-LR adsorption at different adsorbent concentrations, the particle size of the adsorbents appears to be the most influencing factor on toxin adsorption. All TiO 2 -NPs exhibited higher adsorption capacities compared to the bulk TiO 2 counterpart, which was statistically significant for the environmental relevant concentration levels of TiO 2 -NPs. The obtained results emphasise the potential of TiO 2 -NPs to act as carriers for environmental contaminants such as the cyanobacterial toxin MC-LR, and thus to influence its fate in aquatic ecoystems.