Impact of alginate concentration on the stability of agglomerates made of TiO2 engineered nanoparticles: Water hardness and pH effects

The stability of engineered nanoparticles in natural aquatic systems is of high interest for environmental risk assessment since an already important quantity of these reactive species is entering aquatic systems. In the present study, an important issue is addressed by investigating (i) the influence of divalent cations and water hardness (Mg 2+ and Ca 2+ ) in agglomerate formation and (ii) alginate concentration effect on the stability TiO 2 agglomerates formed in environmental freshwater conditions (pH and total hardness) representative of Lake Geneva, France/Switzerland. Our results indicate that the presence of alginate at typical natural organic matter concentration strongly modifies the stability of TiO 2 nanoparticle agglomerates by inducing their partial disagglomeration. Significant TiO 2 nanoparticles redispersion and formation of small fragments are expected to be induced by alginate adsorbed layer formed at the nanoparticle surfaces within the agglomerates. Graphical Abstract