Assessment and reduction of the environmental impact of civil and industrial waste by innovative treatment, separation, recovery and degradation processes

Per- and polyfluoroalkyl substances (PFAS) are ubiquitary persistent and mobile contaminants increasingly detected in landfill leachate, posing a significant challenge for water treatment systems under tightening regulatory constraints. This issue is particularly critical in Northern Italy, where widespread PFAS contamination and stringent regulatory limits on drinking water and environmental discharge have intensified the demand for effective and scalable treatment solutions. Starting from real samples, this thesis develops an integrated treatment framework specifically oriented to PFAS removal in landfill leachate, combining adsorption, electrocoagulation (EC), and photocatalytic degradation, with emphasis, also using model solutions, on mechanistic understanding and process optimization under realistic conditions. Adsorption onto powdered activated carbon (PAC) demonstrated strong chain-length-dependent removal, with significant performance suppression in high-strength leachates due to dissolved organic matter (DOM) competition and pore blockage. To overcome these limitations, electrocoagulation process conditions were systematically investigated using a design of experiments (DOE) approach. The results show that EC performance is strongly governed by pH, treatment time, and matrix composition, with Zn/Al electrodes promoting robust removal of long-chain PFAS (>95–99%) and enhancing subsequent adsorption of short-chain compounds. A key contribution of this work is the identification and quantification of matrix-induced physicochemical and analytical effects. Solid-phase extraction (SPE) and mass balance analysis revealed that PFAS partitioning between aqueous, solid, and interfacial phases is highly sensitive to pH and DOM interactions. This behavior leads to discrepancies between nominal and measured concentrations, including apparent negative removal values, which are demonstrated to arise from adsorption–desorption-driven redistribution rather than experimental artefacts. Multivariate analysis further confirms that PFAS removal is governed by speciation (i.e. chain-length related) and interfacial (e.g. PFAS/DOM interactions) processes rather than a single dominant mechanism, particularly under complex leachate conditions, highlighting the limitations of conventional evaluation metrics. To explore subsequent destructive treatment pathways, innovative catalysts for a photocatalytic degradation of PFOA were investigated separately in water as a model system. Both nitride (C3N4) and oxide (Pt N-doped TiO2) materials showed a substantial degradation of PFOA under UV irradiation, though the evidence of an incomplete defluorination (41% after 48 h) underscores the distinction between transformation and mineralization, and highlights the challenges associated with achieving complete PFAS destruction. Overall, this work provides a systematically assessed protocol of PFAS removal from landfill leachate using a combined electrocoagulation–adsorption (EC–PAC) strategy under controlled matrix conditions, complemented by a DOE-driven mechanistic evaluation of the electrocoagulation process that explicitly accounts for matrix effects, analytical constraints, and regulatory performance requirements. The findings establish a mechanistic framework linking matrix composition, interfacial processes, and treatment efficiency, offering practical guidance for the design and optimization of PFAS treatment systems in regions facing stringent regulatory constraints.