Performance by design of TiO2 nanostructured granules exploitable in water remediation applications

Abstract

The development of advanced materials through safe and sustainable methods has become a priority in the field of material science. This study addresses this need by exploring how different design options affect the performance of nano-TiO₂ granulated powders exploitable in water remediation applications. The high-shear wet granulation (HSWG) process parameters have been investigated to produce nanostructured powders that are easy to handle, disperse, and remove from liquids, while preserving their ability to adsorb and photodegrade water pollutants or encapsulate and stabilize active ingredients. We systematically examined a range of key variables, including liquid-to-solid ratio, granulation time, and impeller speed, which were identified as the primary factors affecting the size population. The percentage of the > 1000 µm granules fraction reached 100 % by increasing the liquid-to-solid ratio up to 0.6 g_water/g_powder, while an increase in granulation time and impeller speed caused a reduction of the largest fraction by approximately 30 % and 20 %, respectively. Additionally, we investigated the addition of different binder agents, followed by calcination at 600 °C. We found a correlation between tapped density, open porosity, swelling ratio and compressive strength. Maltodextrin (MD) improved the degree of compaction resulting in the highest compressive strength (9.5 ± 0.2 MPa) and lowest release of titanium when redispersed in water, whilst micro acryl emulsion (MA) improved the sample porosity (80.6 ± 0.5 %) and its capacity to adsorb water (swelling ratio. The pro-oxidative potential of the granules was evaluated using an •OH radical sensitive probe. TiO₂-based granules showed a reactivity comparable to TiO₂ pristine nanopowders, consuming approximately 98 % of RNO after 4 h.