# Unlocking the Detoxification of Phenanthrene from Water Using Alkali-Activated Slag Mortar
## 1 Introduction  
Portland cement is one of the most widely used binders in global construction, but its production has significant environmental impacts [1, 2]. The manufacture of Portland cement contributes approximately 6 to 7% of total global CO\({}_{2}\) emissions and consumes large amounts of raw materials like limestone and clay, as well as energy [3, 4]. Due to these environmental concerns, finding alternative binders has become crucial. Recently, alkali-activated materials (AAMs) have emerged as potential substitutes, attracting global scientific interest [5, 6]. These binders are synthesized by mixing aluminosilicate-rich materials (e.g., fly ash, blast furnace slag, metakaolinite, or pozzolana) with an alkaline solution [7, 8]. Ground granulated blast furnace slag (GGBFS), a by-product of steel manufacturing, is a popular precursor to AAM synthesis [9]. Compared to conventional materials from Portland cement, alkali-activated slag (AAS) offers higher early mechanical strength, lower hydration heat, better chemical and thermal resistance, but faces challenges like high drying shrinkage and rapid setting [10, 11]. Additionally, the main hydration product of AAS has been proven to be calcium silicate hydrate (C-S-H) with a much lower CaO/SiO\({}_{2}\) ratio compared to that of Portland cement [12]. Water quality has been continuously declining due to rapid population growth, urbanization, industrialization, and other environmental challenges [13]. Phenanthrene (PHE), a polycyclic aromatic hydrocarbon (PAH), is primarily released into the environment through processes like fossil fuel combustion and oil refining [14]. The US Environmental ProtectionAgency has classified PHE as a priority pollutant [15]. Consequently, various methods for removing PHE from water have been extensively researched and proposed. Various technologies have been proposed for the removal of organic contaminants from water, including chemical precipitation, ion-exchange, sorption, membrane filtration, and coagulation-flocculation methods [16]. Sorption, in particular, stands out as a highly effective method owing to its high efficiency, low energy consumption, and simplicity. Sorbents commonly used for this purpose include activated carbon, clay minerals, and organic-inorganic hybrid materials. By-products and residual wastes from steel manufacturing, such as blast fuel cokes, steel slag, and fly ash, have attracted attention as potential sorbent materials [17; 18]. However, raw by-products like steel slag and fly ash generally exhibit low sorption capacities for PHE, limiting their effectiveness in pollutant removal [17]. Therefore, it is essential to activate these by-products to enhance their sorption capacities. Activation processes significantly improve the physical and chemical properties of these materials, making them more suitable for use as sorbents in water treatment applications. Despite the potential of AAS as a sorbent for PHE removal, this application has received relatively less attention in the past. Given the promising characteristics of AAS, including its higher early mechanical strength, lower hydration heat, and better chemical and thermal resistance compared to traditional Portland cement, exploring its efficacy in PHE sorption is deemed crucial. Understanding the mechanisms and efficiency of PHE sorption using alkali-activated slag provides valuable insights and contributes to the development of more effective and sustainable water treatment solutions. Therefore, further research is necessary to investigate the sorption behavior of PHE using alkali-activated slag and to optimize its application in water purification processes. In this study, the aim is to demonstrate the applicability of AAS produced from GGBFS as a wastewater filter to reduce PHE content and achieve acceptable ion concentrations suitable for water reuse. Additionally, different ratios of Na\({}_{2}\)O are investigated to optimize the mechanical strength of AAS.