## 1 Introduction  
Plastic pollution is one of the most challenging environmental hazards. The fast rate of plastic consumption and very short time of use before disposal overwhelms the ability to manage them after disposal. Currently, over 350 tons of plastics are produced by developed countries annually, and this number is expected to quadruple by 2050 due to more demand in the market [1]. Plastics frequently end up in natural ecosystems due to inadequate collection and disposal. Larger plastic debris, known as macroplastics, degrade into microplastics that pollute aquatic ecosystems, mainly oceans [2]. The recycling rates of plastic are very low even in developed countries, i.e., around 10% [3]. Furthermore, only 15-20% of all plastic waste is recycled using conventional mechanical methods such as sorting, grinding, washing, and extrusion [4]. The rest add to the burdens of landfills, filling them to their limits. Therefore, non-recyclable plastic fractions have been proposed as a source for tertiary technologies such as pyrolysis, in which polymers become lighter monomers under an inert atmosphere at high temperatures [4, 5]. This technology aims at the circular management of plastics' life and transforms them into gaseous substances, liquid, and solid products [6]. The gas product can be used as an energy source to provide the energy required for the pyrolysis process. The liquid product is an important renewable material for the generation of chemicals and fuel [7]. The solid residue is made of coke and ash, also known as char, and has little value as fuel. Recently, the possibility of using char from pyrolysis of the plastic mixtures has been explored as a potential adsorbent [8]; however, the limited porosity compromises the potential of this solid as an adsorbent of metals in water, e.g., lead [9], among others [10]. Upgradingthe char by activation has proven to be an attractive strategy to prepare porous carbonaceous materials with outstanding adsorption properties for a wide range of pollutants in water, such as dyes [11], anthropogenic organic contaminants of emerging concern [12], or metals [13]. Physical and chemical activation has been demonstrated to be an extraordinary strategy for producing porous carbonaceous materials. The most efficient activation agents include the CO\({}_{2}\) atmosphere [14] as a physical method and NaOH or KOH under an inert atmosphere [15,16] as a chemical procedure. Lead pollution in water can be ascribed to natural or artificial causes. Lead is one of the most hazardous contaminants, and its presence in drinking water is still a recurring problem around the world, especially in those countries that still use lead plumbing materials for water pipes or have not completely replaced them, such as the USA [17]. Lead pipes require careful corrosion control to prevent leaching into the aqueous media. Natural groundwater can also be polluted with lead due to close contact with ores [18]. In addition, lead can be present in the wastewater of many industries, including metal plating, paint, or battery storage industries [19]. Lead remediation can be performed using separation methods such as osmosis or adsorption. The use of adsorption is a convenient and affordable technology, accessible in many water treatment scenarios. Adsorption has been widely used due to the high efficiency of the removal from aqueous effluents and the diversity of materials to reach that purpose. Some examples of materials with high metal adsorption ability include carbonaceous materials [20,21], silica [22], zeolites [23], treated biomass [24], or metal-organic frameworks [25]. Using chars recycled from waste is a useful strategy to revalorize waste into a valuable material with metal adsorption properties [26]. The available data to date applied to lead adsorption is focused on the revalorization of biomass residues [27, 28, 29, 30, 31, 32] or other wastes rich in carbon, such as tires [33, 34, 35], or mixtures of both [9,10].