This thesis evaluates the leaching characteristics and environmental impacts of conventional and rubberized porous asphalt mixtures subjected to tidal flooding conditions. Given the increasing vulnerability of coastal infrastructures to tidal floods exacerbated by climate change, the research investigates explicitly the release behavior of metals, metalloids, and anions from both crumb rubber-modified and conventional porous asphalt immersed in tap water and seawater. The study aims to provide insights into the environmental implications of utilizing crumb rubber, derived from recycled tires, in porous asphalt formulations, balancing its mechanical benefits against potential environmental risks.

Through systematic laboratory experiments, leachates from compacted cylindrical asphalt samples were collected and analyzed using Inductively Coupled Plasma Optical Emission Spectrometry (ICPOES) for metals and Ion Chromatography (IC) for anions. The results demonstrate that crumb rubber significantly affects the leaching behavior of asphalt mixtures by acting as an adsorbent for several contaminants. Thus, generally reducing their leaching potential compared to conventional porous asphalt. However, elevated concentrations of certain elements, such as zinc, aluminum, and magnesium, originating from the crumb rubber itself, were observed, highlighting the complexity of the environmental behavior of these mixtures.

The research identifies critical differences in leachate release patterns between two different conditioning methods, with an initial rapid release of surface-bound contaminants followed by slower diffusion-controlled processes. Elements such as nickel and cadmium displayed unique delayed release behaviors, suggesting potential long-term environmental implications. Additionally, the study highlights the significant role of material composition, particularly tire-derived crumb rubber and structural additives, in influencing the leaching profiles.

The environmental risk assessment performed using the Heavy Metal Pollution Index (HPI) further emphasizes that crumb rubber-modified porous asphalt generally presents lower environmental risks compared to conventional mixtures. Nevertheless, specific metals and ions exceed regulatory thresholds, underscoring the importance of considering local environmental standards in the implementation
of these materials.

Overall, this research contributes valuable knowledge regarding the sustainable application of crumb rubber-modified porous asphalt in coastal regions. Recommendations for future studies include the investigation of long-term leachate dynamics under diverse environmental conditions and the exploration of effective mitigation strategies to enhance the ecological compatibility of asphalt pavements. ... Read more

Pharmaceuticals in wastewater are an urgent environmental concern. Many emerging technologies, such as advanced oxidation processes (AOPs), are being explored for their removal. One promising AOP is Photoelectrocatalysis (PEC), which combines photocatalysis with electrochemistry to enhance pollutant degradation by suppressing electron-hole recombination. Bismuth vanadate (BiVO₄) is a promising visible-light-responsive photoanode material due to its narrow bandgap and chemical stability. However, its overall performance is limited by poor charge mobility and rapid recombination of photogenerated electrons and holes. To overcome these limitations, surface modification strategies have been applied, including the use of surfactants to alter and enhance its surface properties. Quaternary ammonium compounds (QACs), widely used for their surfactant properties and structural flexibility, have shown potential in enhancing the photoelectrocatalytic performance of BiVO₄. This study evaluated the effect of six commonly used QACs on BiVO₄ photoanodes. The modified photoanodes were synthesized and comprehensively characterized using several techniques: X-ray Diffraction (XRD) to determine crystal structure, Scanning Electron Microscopy (SEM) to examine surface morphology, Energy Dispersive X-ray Spectroscopy (EDX) for elemental composition, X-ray Photoelectron Spectroscopy (XPS) to analyze surface chemical states, Ultraviolet-Visible (UV-Vis) spectroscopy to assess optical absorption, and Linear Sweep Voltammetry (LSV) to evaluate electrochemical behaviour.
Photoelectrocatalytic degradation experiments were performed using real secondary treated effluent collected from the Horstermeer Wastewater Treatment Plant (WWTP), which was spiked with 20 pharmaceutical compounds. The QAC-modified BiVO₄ photoanodes were tested under simulated solar irradiation. Characterization results confirmed that the monoclinic phase of BiVO₄ was preserved after QAC modification, with minor shifts indicating changes in surface properties. SEM images showed that the structural integrity of BiVO₄ was maintained, while EDX and XPS results revealed an increase in oxygen vacancies, suggesting improved charge transport characteristics. LSV confirmed that photocurrent generation occurred only under illumination, as expected in PEC systems. Among the modified electrodes, the BiVO₄ photoanode modified with DADMAC C18 exhibited the highest pharmaceutical degradation efficiency over a 120-minute PEC run, outperforming even the unmodified BiVO₄ electrode. The ATMAC C18 variant demonstrated rapid initial degradation within the first 15 minutes, while the BAC C18 variant showed relatively poor performance. Kinetic analysis indicated that sulfamethoxazole was the most persistent compound in the pharmaceutical mixture, with the longest half-life. To assess real-world application potential, full-scale PEC reactor designs were reviewed. A circular reactor configuration with annular electrodes was identified as the most suitable due to its balanced light distribution, effective photoelectrocatalytic surface area, and ease of operation. A conceptual full-scale design was proposed to replace the existing UV oxidation system at WWTP Horstermeer, targeting a treatment capacity of 25,000 cubic meters per day. Based on preliminary calculations, the estimated treatment cost was €0.24 per cubic meter, highlighting the potential economic feasibility of implementing PEC technology in municipal wastewater treatment.

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