Hybrid materials for wastewater treatment: synergistic coupling of <i>Neochloris oleoabundans</i> and TiO₂ nanoparticles

In this work, we combined microalgae's sorptive properties with titania-based nanoparticles' photocatalytic capabilities to develop technologies applicable to wastewater treatment while also providing valuable insights into the innovation of adsorption technologies. The coupling of <i>Neochloris oleoabundans</i> biomass with an inorganic nanophase enables the formation of hybrid materials integrating heavy metal adsorption with photocatalytic action. To prepare the samples, we employed a water-based colloidal method followed by a spray freeze granulation treatment. The preparation process was followed by comprehensive physicochemical characterization from the wet precursors to the final hybrid granules. Key performance indicators, including adsorption and photocatalytic activity, were assessed using two model contaminants: copper ions (for heavy metal adsorption) and Rhodamine B (for photocatalysis). The results revealed a synergistic effect of the hybrid nanomaterials, significantly enhancing the Cu²⁺ adsorption capacity of the biomass, which increases from 30 mg g^-1 to 250 mg g^-1 when coupled with the inorganic phase and is likely due to the supporting and dispersing role of the inorganic nanoparticles on the biomass. The adsorption experimental values followed the Freundlich isothermal model and pseudo-second-order kinetic model, indicating that the adsorption occurred primarily through a multimolecular layer adsorption process, consistent with chemisorption mechanisms. The photocatalytic performance of the inorganic counterpart was preserved when coupled with the microalgae, with TiO₂-SiO₂/biomass achieving complete Rhodamine B degradation within 1 hour.