## 1 Introduction
These supports offer high surface area, mechanical strength, and active sites for adsorption and catalysis [15], while their porous structures prevent nanoparticle agglomeration, improving the reactivity and longevity of iron-based systems. However, the widespread application of nanoparticle-based catalysts, especially in the EF process, faces limitations due to the high cost of synthetic materials and concerns over nanoparticle release into the environment. To address these issues, researchersare increasingly turning to natural and waste-derived materials as nanoparticle support structures [16]. These alternatives provide a cost-effective and environmentally friendly solution, combining the benefits of traditional support materials with the sustainability of using waste-derived resources for enhanced catalytic processes. In the context of a circular economy, which seeks to minimize waste and make the best use of resources, the reuse of organic waste materials as catalytic supports has garnered significant attention [17; 18; 19]. In recent years, the use of agricultural and organic waste as a low-cost, renewable resource has been investigated for various applications, including water treatment. The incorporation of waste-derived materials into water purification processes not only aligns with the principles of resource recovery and waste minimization but also offers an eco-friendly alternative to traditional synthetic materials. Tea waste is one of the most abundant organic waste materials generated globally, with an estimated 3.5 million tons consumed annually worldwide. The Food and Agriculture Organization of the United Nations has estimated that the global production of black tea will reach 4.4 million tons by 2027 [20]. Almost 30% of the tea produced is discharged as low-quality and waste tea resulting from tea processing and garden maintenance [21]. Tea waste, typically discarded after tea consumption, contains a variety of bioactive compounds, including polyphenols, tannins, and polysaccharides, which can be extracted, generating value-added products from tea waste [21; 22; 23; 24; 25; 26]. Additionally, tea waste offers versatile properties and can be processed through various methods, including thermo-chemical and fermentation, for multiple applications, such as producing bio- oils, gases, and biochar. These technologies highlight tea waste's value as a resource for large-scale and specialized uses. Over the last few years, research on tea waste has focused on converting it into value-added products such as packaging materials, nanocomposites, supercapacitors, biochar, aerogels, and hydrogels [27; 28; 29]. These applications improve waste management and support sustainable economic growth, offering environmental and economic benefits [30; 31]. Tea residues are rich in cellulose, hemicelluloses, lignin, condensed tannins, and structural proteins, which possess a wide variety of functional groups, such as carboxyl, hydroxyl, and phenolic, as well as O-/heteroatoms-containing groups [32]. These functional groups, combined with the porous structure of tea waste, make it an ideal candidate for high adsorption capacity for several applications [33; 34]. Numerous studies have demonstrated the potential of tea waste as an adsorbent for the removal of heavy metals, dyes, and organic pollutants from water [35; 36; 37; 38; 39; 40]. [PERSON] and coworkers [38] prepared a low-cost adsorbent from waste green tea leaves for phenol elimination through the sono-adsorption process. A phenol removal of 92% was obtained under 60 min of treatment under optimal conditions. Similarly, [PERSON] and colleagues [41] prepared a tea waste/Fe\({}_{3}\)O\({}_{4}\) magnetic composite for the adsorption of crystal violet dye, achieving 98.7% removal using 1.0 g L\({}^{-1}\) after 90 min. Utilizing tea waste not only provides an effective alternative to virgin materials but also addresses economic and environmental challenges, promoting sustainable waste management practices.