Sustainable Waste Flow Management: Utilization of recovered carbon black (rCB) from end-of-life tires (ELTs) pyrolysis for activated carbons (ACs) production

Licentiate thesis, 2024

The escalating problem of end-of-life tires (ELTs) represents a significant challenge on environmental, economic, and health fronts globally. The issue is reconceptualized within the framework of a circular economy, advocating for a shift from a traditional linear waste management approach to a circular one. A preliminary market analysis sheds light on the current dynamics of waste tire accumulation, such as the economic impacts, environmental hazards, and the policies governing ELTs management, with a focus on the European Union's regulations. This emphasizes the necessity for recycling strategies, demonstrating the potential of ELTs not just as a waste problem, but as a valuable resource. In view of this, conversion of ELTs into activated carbons (ACs) is a promising sustainable solution. ACs are highlighted for their multifaceted applications, especially adsorption, which could be potentially useful for gas cleaning and addressing the CO2 emissions challenge in small-scale units. The production of ACs can be effectively achieved through pyrolysis, which transforms precursor materials into carbon-rich char. The subsequent activation step, particularly alkali activation, is widely applied to further enhance textural properties. The research aims to explore how the alkali activation process can be finely tuned to optimize the performance of ACs in practical applications.

At the heart of the thesis is a characterization of rCB/ACs. This analysis is pivotal to understanding the inherent properties of the materials, such as their textural, chemical, and morphological properties, which are critical factors influencing their performance in sorption processes. Moreover, a significant portion of the thesis is dedicated to investigating the activation mechanisms of rCB using potassium-containing agents (KOH, KCl, K2CO3, CH3COOK, and K2C2O4). This process is crucial for enhancing the textural properties of the ACs, such as increasing their surface area and developing an optimal pore structure conducive. Through systematic experimental set-up, the research seeks to optimize the activation conditions and evaluate the factors influencing the development textural properties, including the physical state of KOH during the activation process, and the influence of changing KOH to NaOH to explain the distinct effects of the type of selected alkali ions. Finally, the research investigates the CO2 adsorption mechanisms of rCB-derived ACs, along with assessing their CO2 adsorption capacity and selectivity, as potential application. Moreover, the study examines the regeneration potential of these ACs over multiple adsorption-desorption cycles.