Metodi di rivalorizzazione della scoria da acciaieria da Forno ad Arco Elettrico: rimozione del fosforo dalle acque di scarico e materiale riempitivo per polimeri

The steelmaking industry generates significant amount of wastes every year, among which Electric Arc Furnace slags are particularly abundant, being their production in the range of 6-9 billion tons per year in the world. These slags are usually disposed in landill, contributing to environmental pollution and wasting potentially valuable materials. In the last decades, the slags coming from Electric Arc Furnace have been considered as potential materials for future upcycling pathways, converting them into useful secondary products. The literature reports different recycling methods as additive for concrete, asphalt in road construction and fertilizers. This Thesis investigates innovative methods for the upcycling of this slag with a dual focus: phosphorus removal from wastewater and the application of slags as reinforcing fillers in polymer composites, both contributing to the circular economy by transforming industrial waste into valuable resources. To achieve these research objectives, a systematic experimental approach was adopted. For phosphorus removal, from model wastewater solutions, various slag/P-solution w/v ratios were tested to determine the most effective conditions, with batch experiments conducted over a 24-hour period, by increasing the phosphorus concentration in the solution. The experiments were designed to identify the optimal slag/P-solution w/v ratio that maximizes the phosphorus removal efficiency. In parallel, the research explored the application of Electric Arc Furnace steelmaking slag (EAF-slag) as fillers in different polymeric matrices: polypropylene, polymethylmethacrylate and polystyrene. Various weight percentages of slag were introduced into different polymers to assess their impact on mechanical properties, such as tensile strength, elasticity, and brittleness. The polymers were then subjected to tensile tests to evaluate the reinforcing effects of the slag. Different analytical methods were performed to investigate first the slag properties, such as X-ray Fluorescence (XRF) and X-ray Diffraction (XRD) and then to explore the type of phosphate adsorbed onto the slag surface, such as Attenuated Total Reflection (ATR), X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Analysis (SEM-EDX). Furthermore, in order to get deeper insights into the polymers reinforced with the slag, also X-ray Tomography Imaging and Digital image Correlation (DIC) were employed to investigate the role of the slag inside the polymeric matrices, focusing on the stress propagation and cracking formation into the composites during the tensile tests.